Dana 44 Swap Questions

[Minuit]

I have an '88-'90 MJ D44 that I'll be swapping into my '91 MJ in the relatively distant future. I have plenty of time to get my ducks in a row on this project, but I want to get as many questions out of the way as possible. I have the what the parts manual calls the "axle assembly" plus most of the drum brake setup. I do not have the u-bolt plates, u-bolts, parking brake cables, or load sensing valve that go with this axle. I have not taken the axle apart yet, so I do not know what condition the shafts or bearings are in.

 

My plan is a limited slip differential of some kind, most likely 3.73 gears, and disc brakes. I will be doing all of the setup work.

 

1) As I mentioned, I don't have the u-bolt plates. Are these going to be difficult to find? Am I correct in assuming I will not be able to reuse the u-bolt plates from my '91 D35?

 

2) I have a complete ZJ rear disc setup on my current D35 that works great. I'm aware that this will not be a direct swap to the D44 due to differences in the tube diameter and brake backing plate retainer. I'm aware that they can be made to work with significant modifications. Does anyone know of anything that will let me use at least some of my ZJ disc parts, WITHOUT drilling or elongating the holes in the ZJ backing plate and retainer? What about the aluminum ZJ D44?

 

3) Am I correct in assuming that the driveshaft will need to be shortened by roughly 1"?

 

4) My axle has 3.07 gears and an open differential. I'd like neither of those to be present on the final product. I'm strongly considering the Eaton TrueTrac as my differential. Does anyone have any experience with these in either an on or offroad use? Driving is 95% on paved roads, with occasional driving on wet grass or mud (why I want the LSD). Am I correct in assuming that the Trac-Lok is not worth messing with at any price?

[DirtyComanche]

1) I believe you can reuse the D35 plates if you slightly slot the holes.  I have never tried this, but the difference in the diameter of the axle tubes isn't a ton and there is already some wiggle room in the holes, so I believe it is plausible.

 

4) I would recommend the Truetrac.  The only issue with them is they revert to being open if there is zero traction on one wheel, this is easy to combat in a rear application by gently applying the parking brake a few notches in the event you get stuck and it refuses to lock.  They are seamless on road, and will help a lot offroad.

[MeanLemons]

Axle tube diameter are the same on the 35 and 44;  2.75” wide.

 

so the plates should still fit.

 

 

as for LSD. I bought an AUBURN geared LSD. 

[Strokermjcomanche]

The plates(at least the 90 and older ones )  have different dimensions 80mm (d35) and 85mm (d44 ) , on the old two part plates I was able to slot the holes the 5mm no problem when I did my swap . The newer plates are much more stout and appear to be slotted for the d44 

 

I never had had to shorten my driveshaft. 

[schardein]

I have much the same project in mind.

 

Currently have a factory MJ D44, complete, 3.07 and open diff.

 

Plan to put in 3.73 gears and a Detroit Trutrac (have both on hand).  Planning to run 235 or 30"s, possibly 31's.  Converting to 4wd at the same time, so will figure out driveshafts then.

 

I have the original spring plates for the axle.  I also have the original load sensing valve rod and bracket that bolts to the diff cover.  These are shaped differently than the D35 parts.  As far as I know, the load sensing valve itself is the same.

 

It's been a while since I messed with these parts.  I could post some pics later if interested.

 

Here is most of my axle collection, except the MJ D44...

[Limeyjeeper]

The truetrac is a great locker. They are surprisingly strong and quiet as they are a gear locker not a clutch locker. I am putting them front and back on my new build. The backing plates for the ZJ brakes will need some surgery. You have to change the spacing and fill the old holes with JB weld or a real weld. You will also need some preload spacers which you can get fro Teraflex

https://teraflex.com/shop_items/528ffa7fead962f416e73011

 

The MJ Auto rear driveshaft is 1" shorter for the D44. You can get replacement plates and u bolts here:-

 

https://www.rustysoffroad.com/rusty-s-u-bolt-plates-mj-comanche.html

 

 

 

[DirtyComanche]

6 hours ago, MeanLemons said:

Axle tube diameter are the same on the 35 and 44;  2.75” wide.

 

The D35 is only 2-5/8" tube diameter.  But close enough.

[MeanLemons]

28 minutes ago, DirtyComanche said:

 

The D35 is only 2-5/8" tube diameter.  But close enough.

I had a few d35s.  They are 2.75

[schardein]

1 hour ago, Limeyjeeper said:

The truetrac is a great locker. They are surprisingly strong and quiet as they are a gear locker not a clutch locker. I am putting them front and back on my new build. The backing plates for the ZJ brakes will need some surgery. You have to change the spacing and fill the old holes with JB weld or a real weld. You will also need some preload spacers which you can get fro Teraflex

https://teraflex.com/shop_items/528ffa7fead962f416e73011

 

The MJ Auto rear driveshaft is 1" shorter for the D44. You can get replacement plates and u bolts here:-

 

https://www.rustysoffroad.com/rusty-s-u-bolt-plates-mj-comanche.html

 

 

 

A while back I replaced the front u-bolts and plates on the front D44 in my CJ-7.  I used parts from Barnes.  The u-bolts are 5/8" diameter (two sizes up from the stock 1/2").  The plates were also much thicker than the stock CJ ones.  The stock plates were bending at the recommended torque of the 1/2" u-bolts.  They 1/2" u-bolts would lose their clamping force and I would get creeking sounds from the front end after hard off road trips.  The thicker plates and 5/8" u-bolts (with higher recommended torque specs) solved this issue.  I am strongly considering using something similar when I put the D44 in the rear of my MJ.  5/8" u-bolts are basically 3/4 ton truck sized hardware.  I wonder if the Rusty's plates are designed for stock, or larger than stock u-bolt diameters?

 

[WahooSteeler]

2 hours ago, Limeyjeeper said:

The truetrac is a great locker. They are surprisingly strong and quiet as they are a gear locker not a clutch locker. I am putting them front and back on my new build. The backing plates for the ZJ brakes will need some surgery. You have to change the spacing and fill the old holes with JB weld or a real weld. You will also need some preload spacers which you can get fro Teraflex

https://teraflex.com/shop_items/528ffa7fead962f416e73011

 

The MJ Auto rear driveshaft is 1" shorter for the D44. You can get replacement plates and u bolts here:-

 

https://www.rustysoffroad.com/rusty-s-u-bolt-plates-mj-comanche.html

 

 

 

 

Jeremy, you can also get just the backing plates from Teraflex for your D44 and require no drilling. I have not done my disc swap yet but I have these parts. Link to thread below where I list the part #s for the individual backing plates, i.e. not the full kit. 

 

 

[DesertRat1991]

11 hours ago, Minuit said:

I have an '88-'90 MJ D44 that I'll be swapping into my '91 MJ in the relatively distant future. I have plenty of time to get my ducks in a row on this project, but I want to get as many questions out of the way as possible. I have the what the parts manual calls the "axle assembly" plus most of the drum brake setup. I do not have the u-bolt plates, u-bolts, parking brake cables, or load sensing valve that go with this axle. I have not taken the axle apart yet, so I do not know what condition the shafts or bearings are in.

 

My plan is a limited slip differential of some kind, most likely 3.73 gears, and disc brakes. I will be doing all of the setup work.

 

1) As I mentioned, I don't have the u-bolt plates. Are these going to be difficult to find? Am I correct in assuming I will not be able to reuse the u-bolt plates from my '91 D35?

 

2) I have a complete ZJ rear disc setup on my current D35 that works great. I'm aware that this will not be a direct swap to the D44 due to differences in the tube diameter and brake backing plate retainer. I'm aware that they can be made to work with significant modifications. Does anyone know of anything that will let me use at least some of my ZJ disc parts, WITHOUT drilling or elongating the holes in the ZJ backing plate and retainer? What about the aluminum ZJ D44?

 

3) Am I correct in assuming that the driveshaft will need to be shortened by roughly 1"?

 

4) My axle has 3.07 gears and an open differential. I'd like neither of those to be present on the final product. I'm strongly considering the Eaton TrueTrac as my differential. Does anyone have any experience with these in either an on or offroad use? Driving is 95% on paved roads, with occasional driving on wet grass or mud (why I want the LSD). Am I correct in assuming that the Trac-Lok is not worth messing with at any price?

 

 

1)  I moved up to 5/8 u-bolts on the D44 and can confirm that 1/2" D35 u-bolts and 5/8 D44 u-bolts both fit into the +91 plates just fine.   But a test fit using the older two-part plates from an '86 yielded interesting results.  The 5/8 u-bolts were a tight fit through the primary plate, but they made.  However, the holes in the reinforcement plate would not line up.  The holes in the reinforcement plate would need to be oblonged to fit 5/8 D44 u-bolts.  I see now why this issue gets so muddled.

 

2) No info. 

 

3)  In my case, the stock driveshaft barely fit with about ~3.5" of lift in the rear.  The truck is totally driveable on the street, but I feel the fit is too close for comfort off-road.  I have about 1/4" of slip yoke showing.  I'd feel better if it was around 3/4-1" so I'm planning to shorten it.  Actually, I'd love for someone to post a pic of how much driveshaft engagement these trucks are supposed to have when on the ground at stock ride height.  Haven't been able to find that spec online so I actually don't know how far off the fit is.

 

4) Trac-Lok is a fine system with a good reputation among those who know it's not a locker.  The main down side is the maintenance that it requires every ~25-30k miles which works out to about $100 bucks and a half day of work for a DIYer.  Both TrueTrac and Trac-Lok provide improved traction, but they work differently.  A TT does nothing for most of its life (open diff) and only engages to transfer torque when it detects a loss of traction on one wheel. Even then, there are conditions where it fails to do its job.   The TL system is engaged all the time (power to both wheels) and is designed to slip when going around corners.  It's always working and has wear components.  Both do their jobs transparently, neither is infallible.  If what you really want is a locker, don't get either because you will be disappointed.   If you put a lot of miles on your truck, get the TT to save yourself on maintenance costs.  The toughest call is if you found a D44 with a TL already installed.  For a weekend cruiser that doesn't see much off-road use, I'd say go ahead and rebuild it with confidence. 

[WahooSteeler]

40 minutes ago, DesertRat1991 said:

4) Trac-Lok is a fine system with a good reputation among those who know it's not a locker.  The main down side is the maintenance that it requires every ~25-30k miles which works out to about $100 bucks and a half day of work for a DIYer.  Both TrueTrac and Trac-Lok provide improved traction, but they work differently.  A TT does nothing for most of its life (open diff) and only engages to transfer torque when it detects a loss of traction on one wheel. Even then, there are conditions where it fails to do its job.   The TL system is engaged all the time (power to both wheels) and is designed to slip when going around corners.  It's always working and has wear components.  Both do their jobs transparently, neither is infallible.  If what you really want is a locker, don't get either because you will be disappointed.   If you put a lot of miles on your truck, get the TT to save yourself on maintenance costs.  The toughest call is if you found a D44 with a TL already installed.  For a weekend cruiser that doesn't see much off-road use, I'd say go ahead and rebuild it with confidence. 

 

What maintenance is involved every 25-30k miles? I have a D44 w/TL and I've put about 20k miles on it since I bought it years ago. Very little off-road use, but would like to have it maintained for when that occurs and during the winters. Recently changed the fluid but have never had it serviced in any way otherwise. 

[mjeff87]

1 hour ago, DesertRat1991 said:

 

 

 

 

3)  In my case, the stock driveshaft barely fit with about ~3.5" of lift in the rear.  The truck is totally driveable on the street, but I feel the fit is too close for comfort off-road.  I have about 1/4" of slip yoke showing.  I'd feel better if it was around 3/4-1" so I'm planning to shorten it.  Actually, I'd love for someone to post a pic of how much driveshaft engagement these trucks are supposed to have when on the ground at stock ride height.  Haven't been able to find that spec online so I actually don't know how far off the fit is.

 

 

 

Ideally (for me, anyhow), you want about half the length of the yoke engaged in the tailshaft.  Take a sharpie and mark where your tailshaft seal lands on your yoke, then pull the driveshaft off.  Make a center mark on the yoke and then measure the distance from it to the first mark you made....that would be the amount you need to shorten the driveshaft by.  At least that's what I've always done.  But I did almost destroy my entire garage trying to swap out a simple U-joint on my KJ rear shaft a couple days ago, so there's that.

 

edit:  if you are re-using your original slip yoke, you should be able to look at it and see how much of it was originally engaged in OEM configuration.  The non-exposed portion of the yoke (inside the tailshaft of the TC) should be nice and shiny clean.  That would show you what "normal" once was.

[DesertRat1991]

1 hour ago, WahooSteeler said:

 

What maintenance is involved every 25-30k miles? I have a D44 w/TL and I've put about 20k miles on it since I bought it years ago. Very little off-road use, but would like to have it maintained for when that occurs and during the winters. Recently changed the fluid but have never had it serviced in any way otherwise. 

 

Eventually, the clutch packs will begin to exhibit signs of wear.  Meaning the engagement becomes less aggressive and the Trac-Lok begins to function more like an open diff at all times.  If you begin to notice an uptick in open-diff behavior (one wheel spinning under low traction conditions), this can be a sign that it's time to replace your clutch packs.  Your maintenance interval can vary based on your driving style, but all clutch pack style LSD's eventually wear out.  This is not the kind of failure that will leave you stranded, so don't worry yourself too much -- like I said, it just slowly defaults to open diff.  To replace the discs, you will need to pull the axle shafts, diff carrier, remove the spider gears and swap out the clutch discs which can all be done with basic tools.  You don't typically need to have your gears re-set after doing this job.   

 

1 hour ago, mjeff87 said:

 

Ideally (for me, anyhow), you want about half the length of the yoke engaged in the tailshaft.  Take a sharpie and mark where your tailshaft seal lands on your yoke, then pull the driveshaft off.  Make a center mark on the yoke and then measure the distance from it to the first mark you made....that would be the amount you need to shorten the driveshaft by.  At least that's what I've always done.  But I did almost destroy my entire garage trying to swap out a simple U-joint on my KJ rear shaft a couple days ago, so there's that.

 

edit:  if you are re-using your original slip yoke, you should be able to look at it and see how much of it was originally engaged in OEM configuration.  The non-exposed portion of the yoke (inside the tailshaft of the TC) should be nice and shiny clean.  That would show you what "normal" once was.

 

Thanks.  I've got some new u-joints on the way so I'll check that out next time I'm under there. 

[Eagle]

On 7/26/2019 at 11:20 AM, schardein said:

A while back I replaced the front u-bolts and plates on the front D44 in my CJ-7.  I used parts from Barnes.  The u-bolts are 5/8" diameter (two sizes up from the stock 1/2").  The plates were also much thicker than the stock CJ ones.  The stock plates were bending at the recommended torque of the 1/2" u-bolts.  They 1/2" u-bolts would lose their clamping force and I would get creeking sounds from the front end after hard off road trips.  The thicker plates and 5/8" u-bolts (with higher recommended torque specs) solved this issue.  I am strongly considering using something similar when I put the D44 in the rear of my MJ.  5/8" u-bolts are basically 3/4 ton truck sized hardware.  I wonder if the Rusty's plates are designed for stock, or larger than stock u-bolt diameters?

 

 

Factory rear spring U-bolts were 12mm for the XJ and 14mm for the MJ. 14mm is roughly 9/16"

[Minuit]

Good info all. I can't quote everyone, but thanks for the good info.

 

1) I went and looked at my u-bolt plates. The holes in use appear to be slotted, and there are four extra holes, one at each corner of the plate. So this would mean that I can reuse the '91 plates?

 

2) Teraflex appears to have the solution here. My axle has the "early model" flange bolt pattern. So Teraflex part numbers 86311 and 86312 are the backing plates, 86262 being the required preload spacers.

 

The only question left is whether their kit uses ZJ or Ford Explorer parts, and I can't really tell because the parts are practically identical between the two. I'm leaning towards ZJ. The pads and calipers seem to be the same between the "early Jeep" and "late Jeep" kits, and the "late Jeep" kit instructions from the 2010 catalog, not the new one (sneaky sneaky!) specify that the parts are interchangeable with ZJ parts. Not a huge matter as long as they're from SOME type of OEM installation, since I'll probably assemble another disc brake setup so that the axle truly is bolt-in when I'm ready and I won't have to rob parts from my D35. As long as Teraflex will sell me their backing plates separately and I can determine a source for everything else (or just use the calipers, rotors, and pads I have on my D35) I think we're set here.

 

3) Alright, sounds like I'll be shortening my driveshaft. Or getting a new one made 1" shorter than stock. Or waiting until the inevitable 4WD conversion and doing all of it at once.

 

4) So the Truetrac comes highly recommended. I don't hate the TracLok, but at the prices I was seeing for new parts, there were too many downsides for it to be an option. The maintenance every so often is a downside, as is the price (more expensive for new parts than a Truetrac!) - if there is a situation where I come upon a used Traclok for dirt cheap and it works out to be at least a couple hundred bucks less than the Truetrac, that's fine with me, but it seems to me that the Truetrac or other geared LSD is the better system. I do want to be clear here - my truck is at stock height on highway tires with no plans of any true offroading. Ever.

 

Anyone see any holes in this?

[Eagle]

21 minutes ago, Minuit said:

Anyone see any holes in this?

 

Nope. Sounds like a solid plan. I have a TrueTrac in the Dana 35 under my red '88 MJ and I think it's "the bee's knees" (whatever that was supposed to mean).

 

One other point: in your opening post you wrote that you don't have the height sensing valve "for this axle." The height sensing valve is mounted to the frame and it isn't axle-specific. Since you're converting to disc brakes, you should probably look into making the connecting rod for the height sensing valve adjustable, and that will allow you to dial in your rear brake bias with the discs.

[Minuit]

1 minute ago, Eagle said:

One other point: in your opening post you wrote that you don't have the height sensing valve "for this axle." The height sensing valve is mounted to the frame and it isn't axle-specific. Since you're converting to disc brakes, you should probably look into making the connecting rod for the height sensing valve adjustable, and that will allow you to dial in your rear brake bias with the discs.

I did not get the LSV that went to the truck the D44 came from, but the LSV is present and working on my truck, and I do intend to keep it with the D44.

 

The '91 LSV is adjustable without an adjustable rod (although it's kind of a pain to do) and I have it adjusted for slightly more rear braking than stock. Still, your point is well taken - I have not verified my brake bias since the disc conversion and I need to do that.