1971 Jeepster Commando 231 V-6 and 700R4 Swap

[Mike M]

My Jeepster has the 225/3 spd and everything works quite well. However, to modernize it a bit and make it easier to drive for my wife, I scrounged up a 1984 Cutlass with a 3.8, and a 700R4/208. I also have (still on the truck) a 1991 Chevy 350 with TBI. My plan is to rebuild the 3.8 with buick 3.0 pistons and the Melling MTB1 cam. Add the TBI for easy starts and efficiency. The 700R4 is for my wifes bad knees. Any suggestions?

[Moses Ludel]

This is not a bad path.  The 700R4 would need to be from a 4x4 truck or adapted with an Advance Adapters kit to the Jeepster's Dana/Spicer 20 transfer case.  You mention the NP208.  Be aware of the drop side (right or left) to the front axle.  The Jeepster uses a Dana/Spicer 20 transfer case that drops to the right side at the front axle.  An NP208 drops to the left side.  The transfer case's front drop side must match the front axle's differential location.

I'm not clear whether you're rebuilding the Buick 3.8L V-6 from the '84 Cutlass?  You describe the pistons as "3.0".  Do you mean 0.030" oversized for a 231 Buick V-6?  

The TBI could work if you have the ECM and all of the sensors.  Many swap the entire 350 V-8 into a Jeepster.  Does the Jeepster have manual steering?  A GM/Saginaw rotary valve integral power steering gear is a popular conversion for these vehicles.  I have used the slower ratio GM "big car" (4-turns lock-to-lock) steering gears for this kind of application.

Advance Adapters makes adapters for mating the 700R4 to the Jeepster transfer case.  Most use the 700R4 overdrive (4-speed) transmission or a 3-speed THM350 or 400.  The Jeepsters of that era actually used a THM400 3-speed automatic behind the 225 (Buick) Dauntless V-6.  This was exceptionally strong for the vehicle's size, weight and engine output.  GM 4x4 pickups of that period got the lighter duty THM350.  The 700R4 would have the advantage of overdrive.

Anyway, I would like to know more about the parts you're considering:  the engine, transmission, transfer case and induction system.  If you do run a 231/3.8L Buick V-6, I would use a TBI system from a 4.3L Chevy V-6.  Howell (https://howellefi.com/) makes a wiring harness and other parts for GM TBI conversions.  You would need an ECM and all related sensors.  The Chevy 350 TBI V-8 with all of its sensors and ECM might be an easier swap if you want TBI.  Advance Adapters has motor mount brackets and other swap parts.  You would need exhaust system, cooling system, wiring harness and fuel supply system pieces suited for EFI/TBI and a larger output engine.

 

[Mike M]

The 700r4 is from a 86 chevy pickup, and the 208 is passenger drop. There were a couple of years when they did this on solid front axle trucks. I thought about adapting the Model 20, but thats another adapter to buy. Good case, I know, but the 208 has a lower low, and the weight of the Jeepster is quite a bit lighter than the truck it came out of, so I'm not worried. SO it'd just be a BOP to GM adapter ring and the flex plate thats native on the 3.8 (I think, havent found out yet if it will work, but its a 3 spd 200r in the cutlass.) Jeepsters are really rare in SE Wyoming, so I'll probably have to fab the crossmember.

I had also considered using the 350 that is in the other parts truck, but that opens up a lot more fab stuff that I don't want to do anymore. (three spine surgeries makes it rough sometimes) It is a running truck, so all of the sensors and whatnot are there. But I think you're right on the TB, it might be too large for the 3.8. I thought it was just the injectors that changed between the 350 and the 4.3? Not sure.

The 3.8 needs a rebuild, hence the idea of bumping the compression to 10:1 with buick 3.0 pistons. They're flat tops like with the 225, and the same bore and pins. I haven't run the Melling cam, but heard it was a good one for the most low end TQ. I noticed that you're fond of the 252 cam. I'll have to look at the specs on that. And if I can ever find a reasonably priced 4bbl manifold for the 3.8, I'll go with that too. Stock exhaust manifolds and a single 2 3/4" pipe. Now if I can figure out if the Electronic Spark Control of the Cutlass will integrate with the later TBI...hope that puts it together better! 

Awesome sight Moses! Thank you for your time! (and knowledge)

[Mike M]

Oh, the steering...picked up an open knuckle Dana 30 with 3.73's (matches my Jeepster), and a power steering gear from the Jeepster Guru (Russell Wiktop). I have a disc brake conversion ready to go on it and a brake booster and master. Just need a proportioning valve at this point and new U joints. (winter preps on everything got in the way of finishing that part). I actually picked up the entire Cutlass just for the power steering pump and brackets. The guy was very generous and wanted me to haul it off. Its actually in excellent shape body wise and would make a great hotrod if somebody wanted it for a LS swap. But I'm not that guy.

[Moses Ludel]

Mike M...Well thought out and researched approach.  Yes, the Model 20 is noted for its taller low range ratio (2:1), though there are aftermarket gear reduction kits available for a lower geared low range.  If the passenger drop 208 will work, it's much less expensive, and the 208 chain drive TC is plenty strong for this application...You've thought out the solution of a BOP to Chevrolet adapter ring, be sure that the stack height (crankshaft/flexplate location, transmission input shaft depth and converter fit) is correct. 

Yes, the Cutlass has a TH-200-4R.  Fab'ing the crossmember for the 700R-4 should not be difficult, I usually build-in a better skid plate at the same time.  If you need wiring for 700R-4 kickdown, etc., Painless has a popular kit with harness for these swaps.  Also, if the '86 700R-4 has never been rebuilt, there are some recommended upgrades.  Before the late eighties (1988-89), the 700R-4 underwent several changes, including a front pump seal fix to prevent the seal from popping loose.  Your unit may have these upgrades already.  Others impact the longevity of the unit.

Howell would be a good resource for confirming injector size compatibility between the 350/5.7L and the 4.3L V-6.  If the 4.3L injector is the only difference, and if it's a direct fit to the 350 throttle body, that would be simple enough.  (You could source a 4.3L replacement injector.)  Your will need a V-6 ECM and wiring harness, and the 4.3L could be a source.  Unlike multi-port/sequential fuel injection, throttle body injection would not create a problem as far as the cylinder firing order goes.  It simply needs to know the #1 cylinder TDC reference.  Regardless, both the Buick 3.8L and Chevy 4.3L use a 1-6-5-4-3-2 firing order.  (Confirm cylinder bank numbering.)...You will need to sort out the distributor/ECM interface, and this could be an issue.  If the ESC distributor won't work as a trigger, there are crankshaft trigger/sensors available from Edelbrock, Holley, MSD and others, though that's another cost.  You do need a crankshaft reference signal for TDC on #1 cylinder.

Confirm that the 350 V-8 sensors and wiring are compatible with a 4.3L wiring harness and ECM.  Howell does make a standalone 4.3L wiring harness, you'll need to confirm cost and such.  Harnesses can get spendy.

Ah, you did mean 3.0L pistons with this purpose in mind.  I like the later 231 for its even fire crankshaft and reliability.  The Cutlass 3.8L is the right source, it's rear wheel drive configuration.  10:1 may require higher octane fuel unless the knock sensor can offset the compression boost.  I build these engines at 8.7:1 to 9:1 maximum, which enables use of lower octane unleaded fuel.  Any camshaft choice should target low end torque and mid-range power.  4,500-5,000 rpm would be the maximum rpm you'll ever need, especially with overdrive.  Yes, my traditional choice was CompCams' 252H grind, which is now obsolete for many applications.  CompCams has re-profiled niche camshafts for bottom end power.  My goal in any case is more valve lift than stock with mild duration, a camshaft that produces high manifold vacuum at idle and lower rpm.

The 252 V-6 version of the Buick V-6 was available with a four-barrel (spread bore) manifold.  That's an OEM solution.  Otherwise, you'll be seeking an aftermarket performance alternative.  Be sure to use a dual-plane manifold.  The ESC distributor and ECM compatibility should be explored.  GM TBI functions from a combined fuel-and-spark management ECM.  Again, Howell may have insight into this ESC distributor.  (You'll keep the Howell tech line busy.)  Let us know how this sorts out.

I like your approach with the power steering and disc brake conversion.  Open knuckle is the only way to go from both a service standpoint and turning radius.  You'll have improved steering geometry, too, a smart approach. 

An OEM proportioning valve would be my approach, I've used aftermarket manual valves, they essentially damp down the rear brake apply pressure and lack the ability to apply the front disc brakes in sync with rear drum brakes.  (The OEM valves "hold-off" front disc pressure until the rear brake shoes' spring tension is overcome and the shoes contact the drums; this balances the brake apply.)  OEM valves also proportion the pressure front and rear to help reduce risk of rear brake lock-up or nose-diving with the front brakes.  A manual proportioning valve simply reduces rear pressure overall to prevent rear wheel/brake lock-up.  This reduces brake effectiveness.

An OEM combination valve will also signal a front or rear hydraulic system failure with a light installed at the dash.  I use an OEM combination valve for a vehicle with similar weight, wheelbase length and disc front/drum rear or four-wheel disc brake system—whichever you decide to run.  Disc front/drum rear is easier on your budget and works fine.  Water fording does require warming up/drying the rear brakes after a stream crossing.  This can be done by dragging your E-brake briefly at a slow speed.

Again, you've done your homework and will do a thorough job.  Please share photos, this sounds like a clean swap and build of a classic and popular Jeep 4x4!

Moses 

[Mike M]

What pistons do you use for your 9:1 CR? Also, we live at 5000 ft, which knocks down the actual CR a bit, but I cant remember the formula.

[Mike M]

Just going over all of this...not sure which swap would be easier to do. Just spoke to the mechanic that worked the heads and installed an RV cam in the 225 thats currently in the rig. He states that he thinks that the valve seats were replaced at some point. Which of course means that I could run unleaded fuel without worrying about seat issues. Dangit, I thought I had a plan. I would love to run FI of some sort, and an OD trans. Looks like I could use the 225 (48k miles) and not worry about the rest of it. Maybe pull the 3.8 and save it in the corner for future use. Heck, maybe pull both engines. Ive got 3 acres, why not?

[Moses Ludel]

Mike M...It's a 3-5% drop in horsepower per 1000 feet of elevation.  We live at 4,400 feet elevation, so I know your concern.  The good news is that lower octane fuel works just fine for us. 

I found what seems a reliable table for compression correction by altitude.  This is actually addressing cylinder pressure (PSI) rather than actual compression ratio.  (There is static and dynamic compression to consider as well.)  At 5,000 feet elevation, according to the table, you use a 0.862 factor to determine equivalent cylinder pressure.  If this approximates a compression ratio change, 10:1 x .862 equals 8.62:1. 

So, if you drive solely in your altitude zone, you could use 10:1 pistons on the 231 V-6.  I have traditionally used United Engine's Keith Black or Silv-O-Lite hypereutectic pistons.  Silv-O-Lite replacement pistons work just fine, Keith Black for high performance use.  At 10:1, you may need to fiddle with octane, though many GM TBI systems use a knock sensor that compensates sufficiently.  (The 1991 Chevy 350 engine may or may not use an ESC equivalent with knock sensor, you need to check whether it has the knock sensor.)  Here's the table, courtesy of www.TW200forum.com:

Altitude (ft)	Correction Factor		Altitude (ft)	Correction Factor
500	.987		3500	.907
1000	.971		4000	.888
1500	.960		4500	.880
2000	.943		5000	.862
2500	.933		5500	.853
3000	.915		6000	.836

 

Sounds like you're in a holding pattern with a 225 odd-fire V-6 that should last quite a while—especially with hard steel replacement exhaust valve seats.  Will you just keep the 3-speed manual transmission to ease the process?  The Jeepster was optioned with the THM400 behind the 225 V6.  Or you could adapt a 700R-4 (your BOP adapter or the OEM Jeep approach) to the Spicer 20 transfer case.  Length of the transmission would determine whether driveline resizing is necessary.  The torque converter and flexplate would need to match up and fit.  Your Jeepster parts source may have the goods for this automatic conversion.  THM400 to Spicer 20 was common with late Kaiser and earlier AMC/Jeep era vehicles.

Moses

[Mike M]

What about this thought...say I find an 86-88 FWD 3.8  and grab all of the SFI stuff and use that on my 84 engine? That way, its all OEM and designed specifically for that engine. No real conversion work at all, and I end up with a nice, reliable and somewhat economical rig. I havent seen this done anywhere on the net. Have you seen it done this way?

[Moses Ludel]

You'd need to break down the difference between the FWD and RWD versions of the 3.8L.  The SFI idea is sensible, a donor vehicle could even include the wiring harness if you like to sort through schematics and mate harnesses.  Many do this.  I recommend rosin core solder splices with double heat shrink tubing.  Butt crimp connectors are wholly unacceptable for electronic circuit wiring.

For openers, the FWD 3.8L intake faces the wrong way and cannot be "turned around".  An alleged workaround is a '96-2002 Camaro/Firebird 3.8L ("3800) intake.  You'd need to verify the fit.  There are block mount concerns.  I would research the block castings to see if that's an issue.  You would be fabricating engine mounts, but they still need to be at reasonable points on the block casting.  Verify the crankshaft configuration at the front/drive accessories end and the rear flange for the flexplate.  How will drive accessories fit?  Water pump?  Is the bellhousing pattern the same?  Would the Camaro/Firebird 3800 version be a more sensible engine for a swap?  Confirm this.

A good place to research is the long block offerings from engine rebuilders.  See whether a RWD 3.8L and a FWD 3.8L core is the same as a long block part number.  If the basic engine can be used in a RWD vehicle, the notion is sensible.  Otherwise, I'd look into the Camaro/Firebird V-6 3.8L.

Footnote:  I did a further search, and the GM 3.8L "3800" engine may be popular and relatively common.  There are numerous RWD later 3.8L V-6 applications that would have EFI or SFI.  Verify the bellhousing patterns and their fit to a 700R-4.  For a 4x4 application, the 700R-4's output shaft and tailhousing could be borrowed from your truck application of the 700R-4...You may have started a new swap engine trend.  According to one source, interchange is as follows on these RWD applications, and the common part number is supposed to be GM 89017861.  These donor cars should be abundant:

89017861 - 3.8L (L36-K) 1995-1996 Olds Ninety-Eight, 1995-1999 Buick Park Ave, 1995-2002 Chevy Camaro & Pontiac Firebird, 1995-1997 Buick Riviera, 1995-1999 Pontiac Bonneville, Olds Eighty-Eight, 1996-1999 Buick Lesabre, 1996-2004 Buick Regal & Century, 1997-2004 Pontiac Grand Prix, 1998-1999 Olds Cutlass Supreme, 1998-2005 Chevy Monte Carlo & Impala

Drill down on this prospect and see whether there is potential here.  The challenge would be the electronic interface and powertrain electrical wiring.  You need the donor car's engine and transmission wiring harness(s) and a detailed schematic for this one.  Let us know your findings and plans!

Moses

[Mike M]

OK, after having found a donor rig and thoroughly researched this SFI swap....it looks like it won't be a "cheap" junkyard swap. The biggest problem is the intake manifold. the TB is on one end, (the back side when turned longitudinally) and the water neck is on the other. No easy way to use it unless there is a lot of custom aluminum fabrication on the manifold. So that leaves the only other SFI platforms which were Grand National turbo setups. And as you may know are rare and expensive. So, unless you're willing to cut a hole in your firewall and run the air filter in your dash, this won't work. Haven't looked at drilling a standard carb manifold for injectors yet, but that might be an option. So, when it all comes down to the bottom of the pro/con list, the Holley sniper looks like the best option. The Dauntless I have currently runs well, a bit of valve train noise, but still tight and stout. Looks like the Holley Sniper is the proper route, considering I can rebuild the 84 core with the cam/pistons I want and the Sniper will convert over seamlessly. I've turned over every rock I could find, so unless someone has some secret knowledge, this is it.

[Mike M]

I found an 86 Buick Century as a donor (has RWD mount bosses as well as FWD mounts. You'd need the entire engine as there is a requirement for a cam and crank sensor)....the 89 up series 1 3800's have the 60 degree bellhousing. I have the 700r4 from an 86 chevy pickup. Yes, the tailhousing would convert to a 60 deg trans body, but I want to use the trans I have, and not spend more cash on the rare 60 deg variant. The newer 3800 variants would be an awesome swap if a fella hadnt already spent the coin on a 90deg trans. Does all of that make sense?

[Moses Ludel]

Mike M...I had mentioned the FWD engine design issues (intake position, etc.) in my last reply...According to the third link below, the late Buick engines do use a 60-degree (2.8L to 3.4L Chevrolet design) bellhousing pattern.  This would necessitate a different 700R-4 or a 200R-4.  A 2.8L/3.1L GM S-truck might be a source for a transmission.  Here are details on each engine, the 60-degree V-6 and the 231/3.8L V-6—plus the late series 3800:

https://en.wikipedia.org/wiki/General_Motors_60°_V6_engine

https://en.wikipedia.org/wiki/Buick_V6_engine

https://en.wikipedia.org/wiki/List_of_GM_bellhousing_patterns

If the 700R-4 is a deal breaker and "must keep", you'd be back to the older RWD 3.8L cars with SFI.  Rear wheel drive applications with the Buick (BOP) bellhousing pattern would work.  The 1986 Buick Century sounds like a possibility with your adapter ring to mate the Chevrolet 700R-4 to a Buick 3.8L V-6 block (BOP pattern).  Again, verify stack height if you use the adapter ring and 700R-4 transmission.

Moses

[Mike M]

MOses, with all I've researched, and your advice...(and back issues) I'm starting to think the 3.8 swap with holley sniper setup and just keeping the original 3 spd. I've seen hydraulic clutch setups that don't look too difficult. Finally got some heat out in the shop and will be able to get rolling on this project once again. Thanks Moses for all your help! If you're ever in Eastern WY, let me know! 

[Moses Ludel]

Mike M...If your wife can drive a stick, that's a solution.  There's no synchromesh on first gear, so keep that in mind:  Stop completely before downshifting to low.  For many of us, that was what we knew growing up.  Contemporary drivers find the non-synchromesh first gear unusual. 

Hydraulic clutch linkage is smart and available from Advance Adapters, Wilwood and others.  Your choice of design depends on how you want the pedal assembly to work.  You do want to maintain the dual master cylinder for brake safety.

The manual transmission is the easiest path.  As an option, a simpler manual "swap" transmission would be like the T98 four-speed that Kaiser offered in the CJs.  You have the Model 20 transfer case and can do this swap with the more common T18 and Advance Adapters pieces.  This swap can be so close to stock length that drivelines may not require work, especially with a mild suspension lift. 

The T18 (Ford pickup version) has a compound low gear (non-synchromesh) but allows starting in the synchromesh 2nd gear under most driving conditions.  This makes downshifting easier and eliminates the stigma of a T90, T86, T14 or T15 3-speed transmission.  The compound low is very handy for crawling off-pavement and slow speed, high torque chores.  Compound low does require stopping completely to engage.

Thanks for the invite to your incredible neighborhood.  You have a real incentive to own a Jeepster that is reliable and road/trail ready!

Moses

[Mike M]

Moses! 

Just an update on my rig...open knuckle Dana30 with a disc brake conversion, brake booster, power steering pump and gear, HEI dizzy, and they hydraulic clutch...all complete! Howell TBI, and Rocky Road YJ spring conversion on the way. I decided to go with a Hermtheoverdriveguy RTS 4 spd OD trans to replace the T14 since the hydraulic clutch worked so well. However, Herm can't source any more RTS transmissions, so I am on the hunt for one. (Once it warms up...-20 last week.) Looking forward to getting this finished! Oh, we also inherited a 1984 CJ7 that was front-ended. We'll see how that turns out. Merry CHristmas and a healthy, prosperous New Year!

[Moses Ludel]

Good to get your update, Mike M!  I know how cold it is at your area—our neighbors just arrived home from the Casper Area.  Winter. 

I like your equipment choices, lots of work done, on the home stretch now!  Share more about the RTS transmission.  I'm curious about this choice.  Share photos when you have time.  I'm sure the Members would enjoy seeing your work and how the Jeepster came together.

The '84 CJ-7, if the front axle is not bent, should provide good pieces:  a Dana 300 transfer case with helically cut gears, the front and rear axles (30 open knuckle with disc brakes front; AMC Model 20 rear, a very good axle once converted to one-piece rear axle shafts) and likely the venerable AMC 258 inline six.  Lots of value for either keeping or trading.

Have a wonderful New Year's Eve this weekend, stay warm and safe...2023 will be a good year!

Best,

Moses

[Mike M]

Freakin Winter....

So, the RTS has a very similar ratio set as the T14. At least the version that Herm rebuilds and sells. Very Close. Plus, he makes improvements where he can. From what I can determine, it's a drop in. No driveline corrections or anything. Since he can't source any, I am curious as to how difficult it is to adapt the Buick and the Model 20 to a WC T5? I didn't get a chance to get in touch with him today. So the project for tomorrow is to just remember to call him about it. I realized about two weeks ago that the original 37 amp alternator is and will be pathetically under powered for added electronics, so I ordered a 78 amp from an 84 Buick Regal. A bit of wiring, and it should be peaches. EFI, Winch, SEAT HEATERS.  .  I decided not to go full bore 94amps just due to added engine load. And I figure 78 ought to do it.

The new CJ7 project drove here just fine (with the hood strapped down. It has a 4cyl/4spd in place of the original 258/T5. ??? I know,, huh. Who would DO that? Anyway, many options on engine/trans combos. I do have that 210HP/275TQ 3.8 sitting there, but that's for the Jeepster when I need it. Any suggestions on a modernish engine/OD trans capable of interstate speeds? The wife likes the hydraulic clutch in my jeep so much, she has elected to stick with a manual gearbox.

[Mike M]

As far as cosmetics, and a bit of added function, I lightly trimmed the rear fenders and rolled the edge. The topless pic shows how the jeepster sat as I got it. The one with the top is trimmed. I have some fiberglass flares for totally trimmed rears, but decided to stick with a more stock look. The Rocky-Road YJ kit will lift it another inch.

[Moses Ludel]

See comments on your note below, Mike, thanks for sharing.  The Jeepster has tremendous potential—and you're finding it.  Readers will be envious of the rust-free body.  Wyoming and Nevada—high desert, semi-arid.

17 hours ago, Mike M said:

Freakin Winter....

So, the RTS has a very similar ratio set as the T14. At least the version that Herm rebuilds and sells. Very Close. Plus, he makes improvements where he can. From what I can determine, it's a drop in. No driveline corrections or anything. Since he can't source any, I am curious as to how difficult it is to adapt the Buick and the Model 20 to a WC T5? I didn't get a chance to get in touch with him today. So the project for tomorrow is to just remember to call him about it. I realized about two weeks ago that the original 37 amp alternator is and will be pathetically under powered for added electronics, so I ordered a 78 amp from an 84 Buick Regal. A bit of wiring, and it should be peaches. EFI, Winch, SEAT HEATERS.  .  I decided not to go full bore 94amps just due to added engine load. And I figure 78 ought to do it.

The new CJ7 project drove here just fine (with the hood strapped down. It has a 4cyl/4spd in place of the original 258/T5. ??? I know,, huh. Who would DO that? Anyway, many options on engine/trans combos. I do have that 210HP/275TQ 3.8 sitting there, but that's for the Jeepster when I need it. Any suggestions on a modernish engine/OD trans capable of interstate speeds? The wife likes the hydraulic clutch in my jeep so much, she has elected to stick with a manual gearbox.

 

 

The RTS sounds like the Ford F150 transmissions offered in the early '80s?  Three speeds forward plus an overdrive 4th, right?  The Ford units would be in the ballpark for a bellhousing pattern and such.  Is that the transmission Herm works with now?

Advance Adapters did a lot of work with the WC T5 when I was writing extensively for magazines in the eighties and nineties.  They were direct distributors for the B-W WC T5 and did a lot of adaptations.  Contact my friends there at 1-800-350-2223.  Ask about the approaches you are considering.

I like your rear fender roll work, a nice touch!  One thing I would do with the chassis is a shackle reversal kit at the front springs.  This would put your spring anchor ends to the front and the shackles at the rear of the leaf springs.  This makes a dramatic improvement in handling and control.  The stock front shackle setup (CJs and the Jeepster) has the frame pushing the springs and front axle forward from the rear (anchor) end of the springs.  The shackle reversal kits (available for CJs, presumably for the Jeepster, try a bit of searching) are common for CJs and YJ Wranglers.  For 1976-86 CJs, the shackle reversal is a must.  The frame brackets for the front shackles are notorious for folding and breaking.

Thanks much for the photos...Let us know where the transmission choice leads...

Moses

[Mike M]

Yes, the RTS that Herm uses has a few flavors...Tremec T170, SROD, RUG, etc. He only uses the truck versions. I haven't gotten over to AA yet, but Novak has adapters for AX15 and NV3550.  I will give AA a look as well. That YJ spring conversion uses frame mounts for the front hangers that look waaay better than the stock shackle/hangers. I'm kind of wary about doing a shackle reversal as I have had a bad experience with that long ago. Could've been the backwoods engineering...? I'll update as soon as a trans replacement is found. Thanks Moses!

[Moses Ludel]

Mike M...Thought it was the SROD or RUG, not a bad approach, these were used with light-duty pickups and moderate horsepower in league with your 231 Buick engine.  These transmissions have synchromesh on first through 4th/OD.  No gain in the ratios, but you get overdrive. 

Have you considered a truck box like the SM420 or SM465 Muncie four-speed?  The common version of the older SM420 transmission uses a non-synchromesh 7.05:1 compound low gear, and the SM465 has a 6.54:1 (non-synchromesh) compound low gear.  Either ratio would offset the taller low-range gearing of the Dana/Spicer 20 transfer case (2.03:1) if you plan to crawl off-road.  Many did this and ran taller axle ratios like 3.73s or 4.10s with 33" tires to compensate for no overdrive.  (Your tires look close to that size.)  3.73s or 4.10s and no overdrive would be tolerable on the highway.  What axle ratios does the Jeepster have? 3.73:1?

As you recall, the SM420 and SM465 normally start out in synchromesh 2nd.  To simplify, a Buick engine bolts to an SM420 or SM465 by using a stock Buick V6 passenger car three- or four-speed manual transmission bellhousing.  The SM420 (used from 1947 to as late as 1967/early-1968 in GM light trucks) and the SM465 (1968-up) have the typical GM front bearing retainer index diameter.  You could use either of these transmissions with a stock Buick V6 (passenger car) bellhousing and the correct crankshaft pilot bearing/bushing, clutch disc, cover, throwout bearing and release arm. 

You would need the transmission-to-transfer case adapter, which Advance Adapters can furnish.  They have the correct bearing(s) and adapter ring as well.  This approach has been a mainstay conversion for as long as Advance Adapters has been in business (1971).  These rugged transmissions are now getting older, and a "good used" one would need new bearings and refreshing. 

The beefier and heavier duty SM465 was my choice for higher horsepower applications.  I used one behind a 383 small-block Chevy stroker V8 in an FJ40 Land Cruiser magazine project vehicle...Either truck box would be overkill for the Buick 231 V6.  Even the vintage SM420 is much stouter than an SROD, T14, T176, T150, NV3550, AX15 or any other Jeep light 4x4 transmission.  The SM465 is much stouter than a T18/T19 truck box, more like an NP435.

Wider YJ springs are a popular upgrade for CJs.  The shackle reversal kit would need to be substantially built and well conceived.  If not, the front driveline, axle caster angle and other factors will be off.  The shackle position, shackle length and the spring arch must be correct to maintain proper axle/caster angle over the travel range and not force the front driveline through the transfer case.

Moses

[Mike M]

It's 3.73 axles with 31" tires. I hadn't considered the older 4 spds...hmmm. I don't plan to do any rock crawling, as there's not a lot of that around here. (Unlike western CO where I'm from) mostly trail riding to get to prospecting spots and hunting. My goal is to have this jeep as a daily driver/trail rig. Resto-mod sort of deal. Drive to Casper if I wanted to. (that's a crappy drive no matter what. Uphill both ways and ALWAYS windy  I will consider this option...! Thanks Moses!

[Mike M]

just a thought...I have that 700r4/208 case sitting there...it would almost be cheaper/easier to swap that in...if I can't source a trans from Herm. Crap. I thought I had it solved. It's only money, right?

[Moses Ludel]

Well, Mike, you'd be going full circle to the original plan, certainly an option.  The 700R4 with the correct drop side 208 is a prospect.  The 200R4 was common for Buick V6 models.  You have the BOP bellhousing pattern, which means V8 engine parallels.  There may be an early '80s Olds 307 or 350 V8 powered GM car that used the 700R4.  (350 diesel cars would have the Olds BOP pattern, too, and they used the 700R4.)  This could provide the front end of the transmission to mate with your V6. 

The output needs to be a 4WD application from a GM truck that used the 208.  A hybrid transmission could be built with those pieces.  GM upgrades make the late eighties (1988-up) units best.  Build the transmission with those upgrades.

3.73s with 31" tires would be okay for a truck 4-speed box, especially for your planned usage.  The compound low gear with your Dana/Spicer 20 transfer case would be a real asset and save clutch wear...Comes down to an automatic versus manual transmission.

Have a safe and Happy New Year as you contemplate the Jeepster project for 2023! 

Moses

[Mike M]

We will, and you do the same, SIr!