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Dodge Dakota 4x4 With Frozen Front Axle Disconnect Actuator Motor

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I'm looking at buying my friend's 1991 Dodge Dakota with a frozen front axle switch motor. At least that's how my mechanic friend has diagnosed it.  Unfortunately it seems that part is particular to the 1990-91 Dakota.
 
In my search around the net looking for a solution I came across a post from biggman100 and contacted him to see if he could help out at all. He then said I should sign up for your forum as you might be able to offer a solution.
 
If you know of anything that could help me track down a way to replace or bypass the switch motor I would appreciate it.
 
Thanks...Luke

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Hey Luke, welcome. Is the pic i enclosed the piece you are looking for? We touched a little bit on this in another post, which is here: http://forums.4wdmechanix.com/topic/460-dakota-4x4-pickups-have-the-same-glitch-when-turning/#. If that is the right part, it looks like they use that same one in some of the older Dodge Rams, as well as a couple different Jeeps. This is where hopefully Moses can supply part numbers, and confirm if they did use the same one across different models.

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First off. Thanks biggman100 and moses for helping me get on the board. That is the part in the left of the picture. From what I've been able to find, the 90-91 part is unique to those two years, my friend was able to pull a part # 4338578.

 

I did find this post on another forum that presents a possible solution. http://dodgeforum.com/forum/1st-gen-dakota/345534-1989-dakota-frnt-axle-actuator.html#post2988536.

 

Any thoughts on swapping out the guts of the actuator with a new one? If the internals are identical as he says it seems like a viable solution to me.

 

Thanks again!

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Luke, the part number you found doesnt seem to be for the 1990-1991 Dakota, only for the full size Ram and Ramcharger. One site shows it for the 1992-1996 Dakota, but after having several of those trucks apart down to bare cab and frame, i have never seen a vacuum motor on those for the front axle. I did find a system called the 4x4 posi-lok, that seems to replace the vacuum motor with a manual system, but, so far all i find it for is the full size trucks and jeeps. If Moses, can find the original part number for the vacuum motor, and it does show the same part number for the Dakota and the Ram, Ramcharger, and Jeeps, then you might be able to use the posi lok kit.

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I've looked at the posi lok kit and would love to just put that in but they say in their FAQ that they're working on Dakota support. If you then google around on that you'll see that they've been making the claim of future Dakota support for a couple years.

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Luke, my thought on that is, I wonder if the posi-lok couldn't still be used on the Dakota. Being that it looks like the rod in the kit is threaded, if the plate can be bolted in where the Dakotas original vacuum set up is, then I don't see why you couldn't just use it with the existing arm for the Dakota, instead of the one in the kit.

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Pleased to have you join our forums, fnordo.  Glad you've "met" Biggman100 and broadened the discussion on your '91 Dakota front axle disconnect motor/actuator assembly. 

 

For openers, the parts involved with this front axle disconnect make for a very "busy" system.  It's interesting that the Dakota still uses the disconnect in 1991, and this could have something to do with the IFS front end and the axle half-shafts.  By 1990, the Jeep XJ Cherokee had discontinued the use of a disconnect at the front axle, although the YJ Wrangler stubbornly adhered to the setup. 

 

Here is the complete disconnect system for the Dakota 4x4, referred to as the "N5" model. One page in this PDF has "D5, D6 and D8" model references, and these are the full size trucks, not the Dakota:

 

1990-93 Dodge Dakota Front Axle Disconnect.pdf

 

If anyone is curious why there is no parts interchangeability between the Jeep 4x4s and the Dodge Dakota, here's my take: Unlike the full-size trucks and the Jeep models, the Dakota uses a Chrysler 7.25" front axle.  The Jeep lighter 4x4s since WWII have used the Spicer 25 and 27, and later the Dana 30 front axles. 

 

Full-size Jeep J-truck and Dodge trucks also use Spicer/Dana axles, although these would be the bigger Spicer and Dana 44 type front axles, and even the larger Dana 60 type on heavy duty chassis.  More recently, Dodge Ram full-size trucks have used the AAM front and rear beam axles.  While Jeep and full-size Dodge trucks have each used Chrysler type rear axles, the Dakota 4x4 uses a Chrysler axle at the front as well.

 

That leaves the Dakota with a unique front axle disconnect motor or "actuator".  Here are 10 components with OEM part numbers for the Dakota front axle disconnect vacuum motor assembly.  (See the PDF for more parts and illustration details.):

 

1) 04169634 SWITCH, Hub Lock Indicator (Blade Conn.)

     04289880 (Pin Conn.)

      04338554 GASKET, Switch

 

2) 04338654 VENT, Fitting

 

3) 04338648 COVER, Disconnect Housing

 

4) 04338570 GASKET, Cover

 

5) 181088 SCREW, w/Washer

 

6) 04338578 MOTOR, Vacuum Disconnect

     04338792 SHIELD, Stone 1990

      53008828 1991-92

 

7) CLIP, E-Type (Serv. w/Motor)

 

8) 06023878 1 CLIP, E-Type

 

9) 04338573 1 FORK, Shift w/Pads

 

10) 04338589 2 PAD, Wear

 

Now we'll compare the actuator found on Jeep XJ Cherokee and YJ Wrangler front axle disconnect systems.  These were found on 1987-95 Wranglers and the Cherokee from '84 until Chrysler/Jeep eliminated the actuator.  Note on the Jeep YJ Wrangler that there were years when the axle has no front axle disconnect system or actuator.  The XJ Cherokee shifted to this non-disconnect front axle approach by 1990.  For whatever reason, the Dakota 4x4 kept the front axle disconnect system with the vacuum actuator motor.

 

Note: Wondering why this elaborate vacuum disconnect system was there in the first place?  The whole point to front axle disconnect is that by splitting one axle shaft when the system is in 2WD, the drag from the front driveline and axle differential case/ring gear assembly is eliminated.  (I've given thought to this, and the net result is that the front differential side gears and pinions get a major workout with this design, spinning twice as fast as normal while the ring gear, differential case and front driveline remain stationary.)  The disconnect takes effect while no power flows from the transfer case to the front axle.  One objective is reduction of driveline and differential/ring gear drag or frictional loss...There would be no drag if Jeep and Dodge had simply kept the earlier style full-floating front axle wheel hubs with free-wheeling hubs at the outer ends.  Unfortunately, this was the era when marketing took precedence over sensible design:  It was assumed that consumers did not want to get out of the vehicle to turn a free-wheeling hub.  There were automatic locking hubs used by OEs and available in the aftermarket; however, these tended to be less predictable and were not trouble-free.  Chrysler elected to use axle shaft splitting with a vacuum disconnect mechanism rather than stick with full-floating front axles and encouraging the development of better automatic locking hubs.  One drawback with automatic locking hubs is that they remain locked after shifting back to 2WD mode until the vehicle stops completely and is backed up.

 

Here are the Jeep YJ Wrangler parts.   Compare the design, layout and part numbers.  See what, if anything, will interchange, as the Jeep application parts should still be available.  Otherwise, either the Posi-Lok (if that company wants to get involved) or piecing together used parts to restore the OEM Dakota system may be necessary.  Sounds expensive if you need to buy a complete Dorman actuator just to replace the vacuum diaphragm:

 

1987-95 YJ Wrangler Front Axle.pdf

 

For a quick overview, here are the front axle disconnect actuator/motor part numbers from the Jeep YJ Wrangler parts listing:

 

 

1) 83503113 1 MOTOR PACKAGE, Front Axle Vacuum

 

2) J8133708 1 CLIP PACKAGE

 

3) 83504813 1 COLLAR, Axle Shaft Shifter

 

4) 83503695 1 FORK, Axle Shift

 

5) J8133618 1 RING, Snap

 

6) J8133619 1 RING, Snap

 

7) J8133709 1 GASKET, Cover

 

8) 83500195 1 COVER, Axle Shift

 

9) J8133624 4 WASHER

 

10) J8133623 4 BOLT

 

11) J8133620 1 O-RING

 

12) SEAL, Rt.

     83500199 1 2.290"

     83503504 1 2.125"

 

Compare the part numbers.  Look at the schematics.  (Zoom-in for details on the PDFs.)  We'll go from there...

 

Moses

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Luke, after what Moses said, and using the part numbers he posted, i did an extensive search, and, like you came up with nothing. I did however look more into the posi-lok kit, and i dont see where it would actually be that hard to install on your dakota. The jeep kit, not the dodge kit, looks like it would work on your truck. You might need to modify your existing cover a bit to fit the cable set up from the kit, but, being that the jeep kit is adjustable, you should have enough room to play around with it until you get it adjusted right. The only downside to that would be, if you ordered the kit and then found it definitely wouldnt work, but, using the pics i attached, and going by what i see in the pics, i dont see where it would be that hard to do.

 

Moses, as for why they used the vacuum disconnect setup, that is because when the Dakota was first built, they just sourced major parts, such as the engine and transmission from what they already had, and the transmission, from what i have found out, was basically the same as what they used in v-6 Dodge Rams at the time. The only thing in the 1990-1991 Dakota that doesnt seem to match the Ram from that era is the 7.25 front axle. That seems to be unique only to the Dakota. They still use that same axle, only they did away with the vacuum disconnect after 1991.

 

Luke, another option, although a slightly more involved, as well as possibly a bit more pricey one, would be to source a 1992-1995 transfer case and front axle. That way you can eliminate the vacuum system completely. I did that swap on my 1991 Dakota, but, at the time the frame and cab were separated, so it was a lot easier for me to do. I am pretty sure i didnt have any issues with the transfer case mating up to the 1991 transmission. According to the pdf Moses posted about the front axle disconnect, the vacuum is controlled completely by the transfer case, and has nothing to do with the transmission. So, that leaves the only issue being that any wiring on the transfer case might be different. I did that whole swap so long ago, i honestly dont remember what all i had to do to make it work. I just remeber the axle and transfer case came from a 1995 Dakota.

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The switch for controlling the front axle disconnect is at the transfer case.  It's signaling the 2WD to 4WD mode change within the transfer case.  The transfer case shift triggers the vacuum shift at the front axle.  The idea is not bad, although many of the parts involved will wear out or fail over time, especially all of the hoses, which will deteriorate at the underside of a 4x4.

 

Given the number of Dakotas running around with this vacuum system (through the 1992 Dakota 4x4 models according to the parts listings), it would make sense to encourage Posi-Lok to build a manual shift kit for this application.  I'd suggest contacting Posi-Lok.  Share this forum topic thread and also note the other forums where owners are clambering for a solution. 

 

As a stop gap and immediate solution for your 1991 Dakota, see if Posi-Lok will determine which parts can be reused from the OEM Dakota actuator assembly and blend with Posi-Lok controls.  Like Biggman100 shares, there may be a way to mate off-the-shelf Posi-Lok pieces with your existing parts to make this work. 

 

If the vacuum diaphragm is the issue, another alternative is to identify the vacuum diaphragm maker (look closely at the canister).  See if this Dakota diaphragm has any other application in the industry.  The canister may be available as a replacement part if that's all you need.  There are even ways to rebuild or retrofit a canister...For other hard parts, the Jeep versus Dakota schematics and parts listings that I provided might help.  If the shift fork is unique to the Dakota, that's another story.

 

Another approach, if all other parts are the same in a later Dakota front end, including half shafts, flanges and so forth, is to get a later Dakota front axle center housing assembly with the same axle ratio as your current truck.  (Ring-and-pinion gears could be swapped if necessary.)  The later non-disconnect axle center housing and axle shafts assembly would eliminate the disconnect problem without the need for a Posi-Lok.  Make sure all other parts are compatible and that these later front ends are identical to the 1991 with the exception of the vacuum disconnect feature.  Biggman100 may have insight here.  Some scrutiny of Dakotas at recycling yards could turn up answers, too.

 

For comparisons, here is the front axle and axle shaft arrangement on a 1994 (essentially 1993-up) Dodge Dakota 4x4 without an axle shaft disconnect:

 

1994 Dodge Dakota Front Axle.pdf

 

Note: What you need to confirm is that the later Dakota 4x4s without the front axle disconnect are entirely the same in other ways.  Make sure that the only change in the later Dakota is a front axle housing without a disconnect feature that uses a one-piece right side axle shaft.  If this all works, you can strip out the vacuum maze and cap off the transfer case vacuum fittings and switches with vacuum caps.  Confirm that you still have a signal for the dash gauge 2WD/4WD mode change lamp.

 

Explore the feasibility of this simpler solution:  Like the 1991 front axle, the later Dakota front axle uses an outer housing end seal for the axle shaft.  If the later right side axle shaft and later axle shaft bearing and seal will fit your 1991 axle housing, consider using a later non-disconnect right side axle shaft in place of the OEM two-piece disconnect right side axle shaft.  Make sure the later (1993-up) axle shaft's splines, the later axle housing outer seal and the later axle shaft outer bearing will work with your 1991 front axle housing.  The overall axle shaft lengths and half-shaft drive flanges must match, too.

 

If the later right side axle shaft will fit and seal properly, you have "converted" to a non-disconnect front axle.  The Actuator assembly could be eliminated completely, you can make a cover plate for the actuator hole in the housing, install a new gasket or use RTV sealant, and mount your new homemade cover plate.  A piece of 0.120" steel sheet metal would work well for the cover plate, easy to cut, form and drill the mounting holes.  If all this works, strip away the vacuum maze and make sure you still have a dash signal lamp for 2WD/4WD mode.  Please share your findings here, and if this will work, document the installation with photos.  Many reading this forum topic would benefit from the photos, fit-up steps and part numbers involved!

 

Biggman100, I'm curious what the parts view in the right photo represents.  The vacuum canister and shaft look new, the housing and fork, too.  Are these Posi-Lok parts for a full-size Ram or a Jeep?

 

Moses

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Moses, the image with the new canister and fork are an old pic from a friend who did a ton of upgrades and custom work on a 1991 Dakota about 10 years ago. He is also the one who helped me do all the work on my red and white lifted 1989 Dakota. His site is still around, but he doesn't do much with it anymore.

As for the shift fork, the one in the Dakota 7.25 for 1990 and 1991 trucks is unique to that axle. I know the parts listing say they used that axle into 1992, but they actually didnt. They only used the vacuum actuated front axle in the 1990 (august 1989) to august 1991 (1991) models, and, under Hollander interchange, that axle shows as 1991 only. As for doing the axle swap, the half shafts, mounts, front driveshaft, and all the little pieces are interchangeable from 1991 to 1996 Dakotas, which means the 1992 to 1996 non vacuum front axle is a direct bolt in to the 1991. The only difference may be gear ratios. The only reason I suggested a transfer case swap as well is because as far as i know, the front axle is activated by the transfer case in the 1992 to 1996 Dakota, but, a friend reminded me today, the 1990 and 1991 speedometer is cable driven, and he is pretty sure it is driven off the transfer case, whereas the 1992 to 1996 Dakotas are all electronic speedometer, so, you may be able to swap just the complete front axle, if you can find one in a salvage yard, and can be sure capping the vacuum lines won't cause issues. On mine, i just used a dash mounted gps, and left the speedo disconnected.

 

One thing i would like to clarify for anyone who does come across this in the future, and to dispell any illusions. The 1991 Dakota, which except for body panels, and a few other minor pieces, shares almost nothing with the 1992 to 1996 year Dakotas. Electrical, engine, transmission, transfer case, rear axle, ECM, wiring, fuel system, even the fuel tank is unique to the 1991 Dakota. I have had a lot of experience with the 1991 Dakota, due to building a frankenstien 1991 from the frame up, using the frame and cab for a 1996, wiring, engine, ECM, transmission, transfer case, and driveshafts from the original 1991, bed from a 1993, new, stronger front axles that were for the 1995-1996, Then swapping the front axle and transfer case from a 1995, the list goes on and on. I also just did a frame up build on a 1995 Dakota, that used the frame from a 1991.

 

And, at least for now, the last thing i would like to clarify, the axle gears from the 1991 wont work in the 1992 to 1996 axle, due to the slider and shift fork set up for the vacuum disconnect, unless i am really missing something there.

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The 1991 axle's ring-and-pinion gear sets are likely the same as later axles.  (Compare the part numbers in the parts listings.)  The right side axle shafts within the front axle housing would be distinctly different between the 1991 axle with disconnect and any later models without axle disconnect.

 

Moses

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Sorry it's taken me so long to get back to this. It turned out there were a few other issues with the truck that took precedence over the 4wd.

I was talking with my mechanic last night and he brought up the idea of just locking the front axle in 4wd and just using the transfer case to enable/disable it.

The idea was just to see if he can manually actuate the disconnect.

 

This seems similar to the idea of swapping the front axle with a non-disconnect model.

Do you guys see any issues with this?

 

Luke

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I don't know if having the axle locked at highway speeds would be a good idea. It may cause damage to wheel bearings, and possibly axleshafts. I have never done it, though, so I can't say for sure. Moses or one of the other guys, especially the guys that build dedicated off road trucks may be able to weigh in better on this one.

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fnordo and biggman100...Wouldn't locking the right side axle shaft at the disconnect be the same as the later axle with a one-piece right side axle shaft?  The front axle shafts would both spin, the differential and ring-and-pinion would spin, and so would the front driveline, although there would be no power flow in 2WD mode.

 

This is the same as a later Jeep XJ Cherokee, a TJ Wrangler or a ZJ Grand Cherokee.  There is some additional drag but consistent with an OEM system like the later XJ Cherokee or TJ Wrangler.  The ZJ Grand Cherokee front axle shafts can be either single Cardan outer joints like the XJ Cherokee or Wranglers, or they have a CV type outer axle shaft joint at the steering knuckle (like the Dakotas).

 

The CV joint is to reduce NVH and to function with independent front suspension movement like on your Dakotas.  The single Cardan axle shaft joint works well on a beam axle with steering knuckles pivoting at its ends, like the XJ Cherokee, YJ Wrangler and TJ Wrangler or full size Dodge Ram non-IFS 4x4 trucks including my late Dodge Ram 3500, all of which have a steering knuckle mounted at each of the axle beam's ends.  Your Dakotas use CV inner and outer joints at the front axle because these front axle center sections are rigidly mounted, and the steering knuckles are part of the moving suspension—like a 2WD truck or an FWD passenger car.  Your front axle shafts are exposed half-shafts like a FWD car.

 

Are the CV joints lighter duty on the disconnect models than the later non-disconnect type axles?  Other than the added wear of some moving parts and increased drag from the differential/ring gear/pinion gear and front driveline, what would make the 1991 Dakota with the right side axle shaft locked at the disconnect member any different than a later Dakota front end with a one-piece right side axle shaft?  Are the outer half-shafts the same stamina between the 1991 and the later Dakotas?  Does the later Dakota without disconnect have issues with premature half-shaft CV-joint or front driveline failure?  It is assumed that the transfer case is a "part-time" unit, likely an NP231 or NP231J.  You'll be in 2WD mode of the transfer case unless 4WD is needed, right?  That means no power flow to the front axle or CV-joints unless 4WD is required on a loose traction surface with slip.

 

Moses

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Moses, actually, the 1991 to 1996 non-abs Dakotas use the same half shafts in the front. Since Luke's is a 1991, it won't have front abs. They do make a custom chrome-moly shaft, but, unless you are doing severe off roading with a Dakota, it isn't worth the expense. One thing I would do, as recommended by a friend who has his front axle locked,on a 1991 Dakota that had the same issue as Luke's, was to make sure the engine\front axle mounts are in really good shape. He said he knows when his mounts soften up, because the front end will bind at the end of its turning radius. I forgot all about his truck until I saw him today. His front end has been locked for at least 4 years. He did say however, that gas mileage will suffer a bit, but, it was a tradeoff he was willing to live with.

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That's some great news biggman, I always like to know I'm not the first when it comes to things like this.

 

Would you know if he's taking it on the highway or just offroading?

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Luke, it is his daily driver in the winter, and has been for a few years now. He drives it all over the place, including the highway, back roads, city streets, and even occasionally off road. He even tows a car trailer with it sometimes. So far,from what he said this morning, he hasn't done any damage to it, but, his highway trips usually aren't more than 30 miles round trip.

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Luke, i also found out something interesting on the 1992 to 1996 Dakota. The front axle is always locked, or at least seems that way, because when the front end is jacked up, if you spin either front wheel, the front driveshaft will spin, if the transfer case is in 2WD mode, but, if the transfer case is in 4HI or 4LO, the front wheels wont spin, because the transfer case locks. I found this out while checking something on my 1994, so, just to make sure of what i saw today, i also checked it on the 1995 with the same results, so, that tells me if shouldnt hurt anything if you lock your front axle.

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As I shared, this is "normal" for the later XJ Cherokee, the ZJ Grand Cherokee, the later 4x4 Dodge Ram axles and many other vehicles that do not have a front axle disconnect system.  The frictional losses from rotating the differential case, ring gear and front driveline apparently are worth tolerating—rather than suffering with the added parts and complexity found in a vacuum actuated front axle disconnect system.  For Jeep, concepts like vacuum shifters date to the Borg-Warner Quadratrac system of the 1970s.  Engineers at AMC/Jeep apparently had a fascination with vacuum motors and switches.  These same engineers might have influenced the early Dakota 4x4 pickup designs as well.  Makes sense, the Jeep MJ Comanche was in production with a vacuum disconnect front axle at the same time Chrysler bought AMC/Jeep (1987).  Dodge was building the Dakota when the first "Chrysler" YJ Wrangler hit the showrooms in 1988.

 

All of this vacuum disconnect stuff was because the full-floating front axle disappeared.  The introduction of "unit hubs" spelled the end of full-floating axles.  Jeep used full-floating axles through the CJ era, and full-size trucks featured full-floating axles well into the 1990s.  In my view, it's much more practical to have free-wheeling hubs than an axle disconnect system like the Dakota, full-size Ram, Jeep YJ Wrangler and other vehicles have used.  The argument is that consumers do not want to lock and unlock free-wheeling hubs. 

 

Note: Experiments with "automatic" locking hubs were not productive, either.  Automatic hubs are troublesome, require backing the vehicle up to free them, and generally are not reliable.  Full-floating front axle applications with automatic locking hubs were offered as OE in the '80s and '90s.

 

Today, we can consider the internet volume of discussion around the YJ Wrangler, XJ Cherokee and Dakota 4x4 pickup front axle vacuum disconnect systems.  Many aftermarket suppliers have created "full-floating" front hub conversion kits to replace OE unit hub systems on models like the Jeep TJ Wrangler or full-size truck beam axles like my '05 Ram 4x4.  For 4x4 trucks and SUVs, a factory full-floating front axle with free-wheeling manual hubs seems due again.  Is it really that difficult to turn a free-wheeling hub from "Free" to "Lock" when 4WD is needed?

 

Unfortunately, vehicle manufacturers often do not consider the high mileage (or duty cycle) troubles associated with complex engineering.  The front axle disconnect system was not a practical replacement for the full-floating front axle and free-wheeling hubs.  For the record, a half-century ago, even as late as the 1986 Jeep CJ-7 and Scrambler, it was common ritual to lock the manual hubs before leaving home on icy roadway days—or when leaving pavement on a 4WD trip.  Hubs locked, the front axle turned the differential and front driveline, but the transfer case was placed in 4WD Hi or Lo only when needed. 

 

These systems may have created slight increases in fuel consumption, but they worked quite well.  Well enough to help win WWII:  The original MB Jeep, Power Wagons, Deuce-and-Halfs and all other live front axle military vehicles had no axle disconnects or free-wheeling hubs.  Even the postwar Jeep models had "live" front axles without free-wheeling hubs or any kind of axle disconnect system.  

 

Free-wheeling hubs were invented by Arthur Warn.  He came up with the original detachable needle bearing "hubs".  Yes, the very first free wheeling hubs were installed by removing the 6-bolt splined drive plates from the front axle's wheel hubs.  The drive plate was replaced with a bolt-on plate that allowed the axle shaft's end to turn freely.  As the tire/wheel and wheel hub rotated, the axle shafts, differential and front driveline remained stationary...This was a lot more complicated than Warn's later free-wheeling hubs with a twist handle and "Free"/"Lock" modes!  

 

Moses

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Moses, i actually have a theory as to why manual hubs and solid front axles have dissapeared. The manufacturers say IFS makes a vehicle safer to drive, which, it may, but i think it is more for comfort than anything else. People use trucks more and more as everyday vehicles, but, they want their truck to ride like their car does. Ford used manual hubs on at least the F-150 into the mid 1990's, so they had to be a worthwhile idea. Ford stopped using them though, from what i have seen, when they started making IFS trucks.

 

Anyway, to continue the original discussion, according to a Dodge press release, from around late 1991, that i found on an obscure Dodge site, having the front axle locked on the 1992 and up Dakota was supposed to only have a very minimal impact on fuel mileage, but was somehow supposed to decrease wear and tear on internal front driveline parts. I cant see how, unless maybe with the disconnect system, the gears didnt rotate when the front end rotated, and therefore the gear oil didnt move around as much, maybe. Im lost on their way of thinking, but, either way, it seems a good bet that locking the axle on Luke's truck definitely wont hurt anything.

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Here's the capper on the "saving wear" on front axle parts when in 2WD axle disconnect mode...The left side axle shaft is turning the left side gear in the differential.  That turns the two small pinions within the "open" differential.  The opposite axle shaft (the inner shaft in the Dakota front axle, not the outer half-shaft with CVs) is "disconnected"; so it does not turn and only freewheels in disconnect mode. 

 

This means the left side gear and two small pinions spin inside the differential housing.  The differential housing and ring gear remain stationary; the front driveline does not turn because the differential housing, ring gear and the pinion shaft are not turning.

 

What does that leave turning?  On the Dakota, both outer axle half-shafts and CVs continue to turn, the unit bearing wheel hubs turn, and the two differential small pinion gears are spinning at a high rate of speed.  So, there's no "drag" from the differential housing, ring gear, pinion shaft or front driveline...But there's still wear at the two small pinion gears, the small pinion thrust washers and the left side (inner) axle shaft side gear. 

 

As for IFS and full-floating front wheel hubs instead of unit bearing hubs, think 1986-up Toyota 4x4 Pickup/4Runner with manual or automatic front locking hubs, or the Isuzu, Suzuki, Nissan or Dodge (Mitsubishi) Ram 50 trucks and SUVs.  Why not the Dakota?

 

Moses

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