Dana 44--I found one. Swap questions....

[coolwind57]

I may have found my unicorn.  Tonight, I'm planning on picking up a MJ Dana 44 for fairly cheap, just an hour or so from my house.  It has the 3:55 gears that I need to match up to my whining D35.  An axle swap is new to me, so I have a few questions:

 

1.  The axle is from a 90 MJ.  Does this bring up any issues that you can think of?   Mine's an 89.

2.  Should I grab the driveshaft?  I understand that mine is likely too long due the the longer pinion of the D44.  I have only a 2-3 inches of lift if that matters.  He wants $80 for the driveshaft.  Also, it is from a short bed and my truck is a long bed.  I didn't think there were different driveshafts between the two, but I may be wrong.  Is shortening my driveshaft a better option than buying his, considering that I have a couple inches of lift?

3. Pardon my ignorance, but he says its a limited slip diff.  This doesn't really mean anything significant to me as i swap this over, right?  My front axle would match the 3:55 ratio.  I'm not really up on whether limited slip is a factor in any way, as I just figured all MJ axles were.  

 

Sure appreciate you guys' input.  Thanks for being a great resource of knowledge.

.    

[krustyballer16]

Driveshaft will not work. Lengths are totally different. Even if you were swapping from a d35 to d44, driveshafts are different lengths.


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[Pete M]

that driveshaft will be about 6" too short.    the 12" difference between long and short beds is broken up into 6" in front and 6" behind the rear axle. 

[coolwind57]

Just now, krustyballer16 said:

Even if you were swapping from a d35 to d44, driveshafts are different lengths.

I was aware of the 1" difference, noted in #2.  So, you're saying that shortening my driveshaft is my only option, then correct?

[krustyballer16]

I was aware of the 1" difference, noted in #2.  So, you're saying that shortening my driveshaft is my only option, then correct?

Probably a 1" difference. And with your lift, it might come out right. Gonna have to measure. Only way of knowing for sure

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[coolwind57]

2 minutes ago, Pete M said:

that driveshaft will be about 6" too short.    the 12" difference between long and short beds is broken up into 6" in front and 6" behind the rear axle. 

Cool, thanks for the schooling Pete.   Sounds like shortening my driveshaft to accommodate the D44 is in order then.

[Pete M]

maybe.  or it might be fine.  you wouldn't be the first to run it with the stock shaft.  I would probably try fitting it all up and see how close it is.

[coolwind57]

And where does one go for these type of driveshaft mods?  Muffler shops?  Some sort of specialists?  I'm hoping Krustyballer is right in that I won't need to shorten due to the lift.    

[coolwind57]

1 minute ago, Pete M said:

maybe.  or it might be fine.  you wouldn't be the first to run it with the stock shaft.  I would probably try fitting it all up and see how close it is.

And I shouldn't be concerned with splines not matching up, Pete?

[Pete M]

splines?  if you use your current driveshaft, it'll still fit to your current t-case.  

[coolwind57]

1 minute ago, Pete M said:

splines?  if you use your current driveshaft, it'll still fit to your current t-case.  

Oh hell, that's right!  haha   Brain fart.

[Pete M]

happens to the best of us.   that's why I always recommend asking questions.  the collective brain is a great resource. 

[89 MJ]

1 hour ago, coolwind57 said:

1.  The axle is from a 90 MJ.  Does this bring up any issues that you can think of?   Mine's an 89.

2.  Should I grab the driveshaft?  I understand that mine is likely too long due the the longer pinion of the D44.  I have only a 2-3 inches of lift if that matters.  He wants $80 for the driveshaft.  Also, it is from a short bed and my truck is a long bed.  I didn't think there were different driveshafts between the two, but I may be wrong.  Is shortening my driveshaft a better option than buying his, considering that I have a couple inches of lift?

3. Pardon my ignorance, but he says its a limited slip diff.  This doesn't really mean anything significant to me as i swap this over, right?  My front axle would match the 3:55 ratio.  I'm not really up on whether limited slip is a factor in any way, as I just figured all MJ axles were.  

No issues swapping it in. 

don't grab the driveshaft, a shortbed one doesn’t fit a long bed. 

A limited slip means power will go to bothe rear wheels, not just one. It is good for off-roading. 

[ComancheKid45]

With 3" or so of lift your driveshaft should be fine to use with no modifications. I'm sure the Trac lok packs are shot inside so if having Limited slip is something you want, I'd go ahead and redo the clutches before you install the axle. Watch the brake lines and maybe even replace them all on the D44. Otherwise is a straight bolt in process.

[Minuit]

If it was a factory limited slip, if the axle has more than 75k or so the clutches are worn and the limited slip is probably barely, if at all, functional.

 

The trac-lok can be rebuilt, but there are better maintenance-free options out there. There are a number of ways to tell if it really is a limited slip.

[derf]

Yeah, at this point the factory limited slip is probably an open differential.  Rebuild is not hard.  Just make sure not to mix up the shims when you pull the differential.

 

As far as the drive shaft, the different pinion length will mean you need to shorten the driveshaft.  The lift would let you shorten it less.  Have the truck on level ground and take a picture of the slip yoke.  Put the new axle in and hook it up.  See how much further in the slip yoke sits.  If it's too much, find a driveline shop.  They're in most significant cities.  They have the tools they need to balance the shaft after shortening it.  It's not difficult work but it is a niche and you want a professional with the right tools doing it.  You can have them replace the ujoints while it's there as long as it's out.

 

Any heavy equipment shop (truck, tractor, etc) would probably know a place they farm the work out to.

[schardein]

Even if the driveshaft fit, I'd be careful- I'd inspect it before handing over the cash.  Unless it was in pristine shape, u-joints looked fresh and caps were taped to stay on, slip yoke wasn't excessively worn, no excessive rust and especially no dents- I'd pass, or talk the price down, .  If it spent time in a junkyard, the rear shaft is almost always bent when they move the truck with a forklift.  A pair of Spicer u-joints run about $30, then you need to install them- straightforward job, but if they are the originals they might be a pain to get out.  Sometimes ponying up for a new shaft in a custom app (lift) is worth it in the long run.

 

I've had local machine shops shorten shafts for me before, even though they didn't normally build complete shafts.

 

If you plan to retain your factory rear brake load sensing setup, the bracket on the axle end is different for a Dana 44, make sure it is there, or you will be fabbing one.  I don't know if the connecting rod is the same or not, but I would assume not.  See if it is there also.

 

And I believe the spring plates are different, I would hope those were present and included in the price.

[coolwind57]

9 hours ago, schardein said:

Even if the driveshaft fit, I'd be careful- I'd inspect it before handing over the cash.  Unless it was in pristine shape, u-joints looked fresh and caps were taped to stay on, slip yoke wasn't excessively worn, no excessive rust and especially no dents- I'd pass, or talk the price down, .  If it spent time in a junkyard, the rear shaft is almost always bent when they move the truck with a forklift.  A pair of Spicer u-joints run about $30, then you need to install them- straightforward job, but if they are the originals they might be a pain to get out.  Sometimes ponying up for a new shaft in a custom app (lift) is worth it in the long run.

 

I've had local machine shops shorten shafts for me before, even though they didn't normally build complete shafts.

 

If you plan to retain your factory rear brake load sensing setup, the bracket on the axle end is different for a Dana 44, make sure it is there, or you will be fabbing one.  I don't know if the connecting rod is the same or not, but I would assume not.  See if it is there also.

 

And I believe the spring plates are different, I would hope those were present and included in the price.

The axle (and driveshaft) was from a short bed.  Mine's a long.  So I didn't buy the driveshaft.  I'll see where my driveshaft sits and adjust accordingly once i get my D44 in place.  

 

My truck has the load sensing valve removed.    

 

I wasn't aware that the spring plates were different---good thing I nabbed them while I was there.  He tossed them in for free.  

 

Thanks for the input, Schardein.  

[coolwind57]

15 hours ago, Minuit said:

If it was a factory limited slip, if the axle has more than 75k or so the clutches are worn and the limited slip is probably barely, if at all, functional.

 

The trac-lok can be rebuilt, but there are better maintenance-free options out there. There are a number of ways to tell if it really is a limited slip.

I spun the yoke by hand and the axle shafts spun in the same direction, so I suppose at least with hand-speed the LSD is working.  

 

I'll take a week or so cleaning the outside of this axle up, ordering new brake parts and getting some POR-15 on it.  Then, I'll likely take it over to a driveline shop and have them eyeball it.  

 

So if that LSD is worn or bad, what are the repercussions?  Just an open diff?  Noisy clutch discs?  Any harm running it like that?  I am diggin' what I'm reading about the benefits of LSD, so I have no intention of neglecting it or being without it.

 

I had asked him if he himself had driven on this axle and he confirmed he did and that there were no issues with it.  The reason he sold it was that he was converting to a more heavier duty off-road truck and he already had an 8.25 sitting around with the serious axle ratio he desired.   His truck was rough, man.  Looks like he's going for more of a off-road toy than anything. 

   

[ghetdjc320]

22 minutes ago, coolwind57 said:

I spun the yoke by hand and the axle shafts spun in the same direction, so I suppose at least with hand-speed the LSD is working.  

 

I'll take a week or so cleaning the outside of this axle up, ordering new brake parts and getting some POR-15 on it.  Then, I'll likely take it over to a driveline shop and have them eyeball it.  

 

So if that LSD is worn or bad, what are the repercussions?  Just an open diff?  Noisy clutch discs?  Any harm running it like that?  I am diggin' what I'm reading about the benefits of LSD, so I have no intention of neglecting it or being without it.

 

I had asked him if he himself had driven on this axle and he confirmed he did and that there were no issues with it.  The reason he sold it was that he was converting to a more heavier duty off-road truck and he already had an 8.25 sitting around with the serious axle ratio he desired.   His truck was rough, man.  Looks like he's going for more of a off-road toy than anything. 

   

Worn lsd will just mean an open diff. The oem clutch style lsd never was a great traction adder off-road anyways. Other thing to check out is that the axle is straight.

[derf]

I've seen individual clutches in the packs break inside of a D35.  All that does is make it whine a little.  It acts like an open differential when the clutch packs wear out.  The worn metal dust floating around in the gear oil doesn't help your bearings, which can also make some noise when they start to go bad.

 

While the axle is out, it's not a bad time to replace seals and the outer axle bearings no matter what you do.

 

A drivetrain shop should be able to figure out what's good and what's bad and get you set up.  If you really want a working limited slip, you can either get the unit rebuilt or spend a little more and get a better limited slip.  Eaton makes a TrueTrac that I use and it's great.  There's another company that started making one very similar in the last few years.  I forget the name.  It's less expensive than the TrueTrac but seems to be getting good reviews.

[DesertRat1991]

3 hours ago, coolwind57 said:

The axle (and driveshaft) was from a short bed.  Mine's a long.  So I didn't buy the driveshaft.  I'll see where my driveshaft sits and adjust accordingly once i get my D44 in place.  

 

My truck has the load sensing valve removed.    

 

I wasn't aware that the spring plates were different---good thing I nabbed them while I was there.  He tossed them in for free.  

 

Thanks for the input, Schardein.  

 

 

The spring plates are not different.

 

91+ spring plates are of a single piece design. Older spring plates are a 2-piece design (spring plate and support plate). The difference is not related to D35 vs D44.  Either style will physically fit either axle. 

 

One thing that hasn't been mentioned is that the D44 is designed to accept a larger leaf spring center pin.  If you are on stock, non-metric ton leaf springs then you will discover that your centering pin is too small to do its job properly.  But, the pins are easily replaced.

 

[schardein]

2 hours ago, DesertRat1991 said:

 

 

The spring plates are not different.

 

91+ spring plates are of a single piece design. Older spring plates are a 2-piece design (spring plate and support plate). The difference is not related to D35 vs D44.  Either style will physically fit either axle. 

 

One thing that hasn't been mentioned is that the D44 is designed to accept a larger leaf spring center pin.  If you are on stock, non-metric ton leaf springs then you will discover that your centering pin is too small to do its job properly.  But, the pins are easily replaced.

 

87-90 Parts Manual actually shows different part numbers for reinforcing plate for standard duty & heavy duty.  Whether they are actually different, I don't know.

Parts Manual also shows different U-bolts for standard and heavy duty, with heavy duty having 3 different part numbers depending on the year.  I would guess that to be a difference in bolt diameter (larger) and a length difference due leaf pack thickness variations and/or spring plate thickness variations.

 

For center pins, on several occasions I've used pins with a large locating head, and custom ground the head on a bench grinder and/or disc sander to fit its specific application.

[coolwind57]

2 hours ago, DesertRat1991 said:

One thing that hasn't been mentioned is that the D44 is designed to accept a larger leaf spring center pin.  If you are on stock, non-metric ton leaf springs then you will discover that your centering pin is too small to do its job properly.  But, the pins are easily replaced.

 

 

34 minutes ago, schardein said:

For center pins, on several occasions I've used pins with a large locating head, and custom ground the head on a bench grinder and/or disc sander to fit its specific application.

 

I'm assuming the centering pin is the pin sticking up from the center of the leaf springs, just under the U-bolts in the pic above.  

 

What's an acceptable fix for this if my spring's centering pin is indeed too narrow for the D44's hole?  Add some sort of adapter or shroud over my existing pin?  Modify the hole in the axle in some way?    What have other's done?

[schardein]

Yes, That centering pin actually locates the axle on the leafspring. The U-bolts and plate secure it.  Replacement pins are available with different shank diameters and head diameters. The shank diameter should match the hole in the leaf springs. The head diameter should match the recess in the spring mounting pad on the axle.   You should always check for a proper fit. If the head diameter is too small, it will allow the axle to shift on the leafspring. If the head length is too long it could bottom out in the leaf spring pad and prevent proper tightening of the U bolts.