Jeep CJ Axle Gearing with T176 and Stroker 4.6L Engine

[Tawanda]

Moses, thank you for your great cam and motor information. I finally got the cam thing figured out. Comp said they would do a custom grind for either of those cams. I ordered it but like everything these days I am waiting for them to get cam cores in.

On to gears. I am rebuilding front and back differentials and while I am at it changing gears from 3.08s. See below what I posted on a forum and refresh of my build. Would love to get your opinion. 

I have seen many suggestions on gear set up and I am at a cross roads to make a decision. First here is the build I'm working on.
Frame off restoration 1980 CJ7 - I bought this not running so I have never driven it before to know its characteristics.
1980 CJ7 Renegade
3.08 gears
Building 4.6L Stroker with T176 4sp trans, Dana 300 transfer
Dana 30 front(narrow) AMC20 rear (narrow)
2-2.5" lift
31' tires (would like to stay 31's but if the lift is too much and I need to fill in the wheel wells a bit I would be open to go 32's or 33's)
Any opinion on tire size to lift?

This is fun weekend Jeep that will mostly cruise around town, camping, beach driving ( some highway driving to get to destinations) and would like it set up so my wife and kids will enjoy driving it as well.
All charts point to run 3.73 - 4.11 gearing however the break point of having to switch the front carrier is 3.54.
1) With the added power and torque with the stroker would 3.54 ratio be sufficient with 31's?
2)What is I need to go up to 32 or 33's -
3) if I need to switch carriers is it a straight swap that I can just get a 3.73 and up case and switch internals?
4) is there a different carrier or locker that I should look into based on my application

Thanks for your input, Unfortunately I was not able to drive it prior to know the characteristics so I would like to hear personal experiences.

Thanks,

Kevin

 

 

 

[Moses Ludel]

Hi, Kevin...A 2-2.5" chassis lift (only) has historically been a 31"x10.5"x15" or equivalent metric tire size on 8-inch negative offset rims.  With the non-overdrive T176, highway driving would benefit from 3.73s.  The 4.6L stroker motor will easily pull this gearing with a good clutch (Centerforce or similar) behind the engine.  You have a Dana 300 low range ratio for decent off-pavement trail running.  If the vehicle were driven primarily off-pavement, 4.11s would be a consideration with this tire size.

33" tires would dictate 4.11 gears plus a chassis lift (only) of 4" for that tire diameter.  I'm not a fan of body lifts, they create body, radiator, steering shaft and other alignment issues, so I think in terms of a chassis lift.

If not worn (41 years old?), you could use the internals with new ring-and-pinion gear sets.  I like a manual locker at least at the rear, historically running an ARB Air Locker.  Front and rear lockers are generally for hardcore wheeling.  A rear only locker will make a world of difference under most driving conditions. 

I prefer a manual locker for more control and safety on off-camber trails where a locked axle can cause both wheels at an axle to spin, and the vehicle slides sideways to the low side of the trail.  Here, I run open differentials front and rear for better directional stability.  I address this in my Jeep® books.

Moses

 

[Tawanda]

Great thanks. Yeah I want to stick with 31's just was not sure about the lift height, so that is great news to know. If sticking with 31's was just wondering since I had the stroker if I could get by with a happy medium 3.54 so I wouldn't have to change the front carrier. ( internals look pretty good) Not the biggest of deals though, I would rather have the best set up for all around use.

Funny you mentioned your book. My father mentioned he had a couple Jeep books for me and one was yours. I have not had a chance to check them out yet but definitely will. Is there a book in particular that my build could benefit from?

 

[Moses Ludel]

Kevin...3.54 gears would "get by" if you were primarily highway driving.  The T176 gearing is respectable despite no compound 1st or overdrive.  If that transmission is your future, 3.54 gears with 31" tires would be approximately what the Jeep feels like with stone stock tires (225/75SB15 or 28.3" diameter) and 3.08s.  Here are the 65 mph engine speeds in 4th/direct gear for each axle ratio, including your current 3.08s and 31" tires:

1) 2,320 rpm with near stock tires (29")and 3.08s

2) 2,170 rpm with 31" tires and your current 3.08s

3) 2,494 rpm with 31" tires and 3.54s

4) 2,628 rpm with 31" tires and 3.73s

If seen this way, and if near stock tires (28.3"-29") and 3.08s were livable, your idea of 3.54s on a budget build is not bad.  The 4.6L stroker motor would be a happy camper below 2,500 rpm and not eat as much fuel.  Highway driving looks a lot better with the 3.54s if your new camshaft is a torque grind for bottom end and mid-range performance (idle to 4,000 rpm). 

31" tires and 3.54s would be a sweet spot for the engine, at peak torque on the highway in 4th gear.  (3.08s would feel like a modern "overdrive" in 4th/direct gear.)  Here are the transmission ratios for the T176, courtesy of our friends at Advance Adapters:

• 1st gear 3.52:1
• 2nd gear 2.29:1
• 3rd Gear 1.46:1
• 4th Gear 1.00:1
• Reverse 3.52:1

You have a reasonably low first gear (not compound, though) with 4th direct.  Without overdrive, this is a juggling act, balancing between performance, fuel efficiency and engine rpm.  You might leave the axle gearing alone until after you get the engine together and have a chance to drive the vehicle with the lift, 31" tires and stock gearing.  The axle ratio choice would then be based on a real world "feel" for how the Jeep performs.  With a strong clutch, you could drive the Jeep and evaluate its performance and loads in each gear before making an informed choice about the optimal axle gearing.

As for books, the one that would serve you well at this moment is the Jeep® CJ Rebuilder's Manual:  1972-86 edition (Bentley Publishers), available from a variety of sources, including Amazon and Bentley.  It's hands on and in-depth on axles, the transfer case and other mechanical service work.

Moses