How to inspect and rebuild your Dana 44 Trac Lok positraction unit.

Obviously first thing is to get the D44 center section out from under the car and on to a workbench with a big vise so you can work on it. I’m not going to cover removal of the center section from the car as it’s already been done on this forum.

Now how do you know if your Trac Lok Positraction is even in need of re-build??? That’s a good question…. The Spicer Manual 5313-3 states that the Trac Lok should hold a minimum of **25ft lbs**. Now you can check that a number of ways but I do it with a 36mm socket and a beam type TQ wrench on the outer stub axle nut. Jack one wheel off the ground put the car in neutral and start pulling on the TQ wrench until the Posi clutches break away…. That’s your initial reading or “break away”…. As you continue to pull the wrench you’ll notice it requires about 5ftlbs less to maintain clutch slippage…. This reading is your “constant”. BTW you’ll want to check both sides so you have an accurate read of both clutch packs.

**I want to note that for a high performance car like the Corvette - IMO 25ft lbs is woefully inadequate. For comparison a new Spicer Trac Lok unit will take 75-85ft lbs to break loose and a hand built, properly built unit can take over 150ft lbs. For a lot of racing use with most cars I’d suggest a rebuild when it gets under 65-70ft lbs. When these things blow up they do some MAJOR damage.**

Once it’s out of the car the best way to work on it IMO is to turn it upside down and clamp the C Beam attachment point in the vise.

The first thing your going to inspect is the inner stub axle end/side play. Use a feeler gauge to check the stub axel against the spider gear cross pin shaft. On this one the drivers side measured .007 and the passenger side measured .011…. indicating something is bad wrong, which I already knew since it required barley 15ft lbs breakaway. Write the measurement down.



Next remove the axle-retaining clips…. Your going to need a REALLY good set of snap ring pliers, a helper and some patience. Use the pliers to open the axle-retaining clip up while your helper pulls the stub axel out. There is no need to mark the axles as they are different lengths and can only go back one way.



Optional step - Next (if your going to) check the ring gear backlash. You’ll need a strip of meatal bolted to the housing since it’s alum. Set up the dial indicator on the drive side of the gear (the convex side). Hold the pinion still with your hand and rock the ring gear from one end of it’s free movement to the other. The measured distance is your back lash. On this particular gear set for the D44 the Spec is .005-.008 - These gears measured right on .005, which is better for drag racing.



You’re going to need to remove the bearing caps. Be sure to mark them so you can put them back in correct position… I have always used “D” and “P” (Drivers & Passenger).



Once the caps are removed you’re going to need to remove the ring gear carrier/Trac Lok unit. Sometimes they are in there tight so a pry bar is needed…. Just use a ring gear bolt to pry on



And have your helper hold his hand in a protective manner to keep it from flying out and on the ground. The bearing races are going to want to fall off so store the bearing races with its respective sides bearing cap so they don’t get mixed up.

On to the good stuff. You going to need to take the housing out of the vise and use the Miller tool PN (or you can use one of the stub axles) to hold the Trac Lok on it’s side. Remove the ring gear from the carrier with a 5/8 socket. They are standard right hand, fine thread, grade10 bolts… nothing special. Be careful removing the last few ring gear bolts because on the D44 the ring gear will fall right off the carrier. Set the ring aside as we won’t need it until re-assembly.







Use a straight flat nose punch to knock out the cross pin shaft retaining roll pin. Notice that there is a long side (ring gear flange) and short side (cut out) to the carrier where it’s located - Be sure to knock it out the short end (from the long end) using a long punch… You can’t drive it out thru the ring gear flanges end as the hole tapers down too small.



Now remove the cross pin shaft. Sometimes you’ll have to put the punch in the end and twist it around to get it to come out without beating the crap out of the end of it.



(Optional step) Insert the Miller spreader tool PN (you can also make this tool with a piece of 1” threaded rod, 2 nuts and some heavy washers) and tighten it to compress the clutch packs. I say this is optional because worn out Trac Loks don’t need the clutch packs compressed to break them loose.



Using the Miller Tool PN (or a correct side piece of pipe) turn the carrier so that the spider gears rotate around…..


Use your hand or your helper’s hand to grab the spider gears as they fall out of the carrier...



You can now remove the spreader tool and remove the side gears and clutch packs. (I didn't need it on this one)



I didn’t get a pic but there are (4) little half-moon machined sections (cut outs) in the Trac Lok carrier’s case where the clutch floater plates get held in place using these little wear washers/shims. Inspect the case in this area for wear or stress cracks. This is important and I can’t believe I didn’t take a pic for you but it’s self explanatory where these areas are once you have it apart.

I did manage a pic where you can see the grooves that the ears on the floater plates caused by hammering into the wear shims, which protect this critical part of the carrier.



There are 3 pieces that make up the spider gear assembly. Side gears, pinion gears and pinion gear washers. Inspect all pieces for damage. Anything that looks like it’s been welding together needs to be replaced. Keep in mind that these gear surfaces (all of them) are machined very rough from Spicer and as long as they are not welded/galled up or have any broken/chipped/worn sharp teeth - they are probably serviceable.

There are 3 different pieces that make up each clutch pack. Bevel washer, floater clutch plates and splined clutch plates. Inspect the clutch plates, bevel washer and side gears for wear/galling. This one is screwed up as the bevel washer is welded to the side gear and will need to be driven off with a hammer and a punch.





Check out how bad it galled up the side gear.



Notice there is no “bevel” left to the bevel washer and check out all the wear on the clutch plates as well.

The bevel washer is a big part of what controls the pre load on the clutch plates and therefore how much force they can hold before slipping. Another thing is the grooves on the plates…. They should be sharp but these are worn almost smooth and have no “tooth” to the grooves edges. Notice the floater plates have straight grooves radiating outward and the splined plates have spiral grooves.



Pay attention to what order the clutch plates come off the side gear. The Bevel washer is first then a splined clutch plate, then a floater clutch plate and then alternating splined clutch plates and a floater plates and so on till the last floater which goes against the inside of the carrier case.

New clutch plates. Spicer PN…



Time to re-assemble everything... Notice the new Bevel Washer is definatly cupped/beveled. It goes on like so, with the convex edge against the side gear and the concave edge towards the clutch plates...



Use some gear oil to lube the plates as you assemble them.


Our new side gear with the clutch pack assembled on it. Install the floater plate wear washers/shims.



The clutch pack assembled on the side gear with the floater plate wear washers/shims as it should be.

Reserved.

That is all for tonight guys.... I'll hopefully finish it up tomorrow night.

Can everybody follow along OK and does everything make sense?

I know I need to get the PN's off my Miller SPX clutch pack tools and put them in the thread and I'll take care of that tomorrow as well.

Any other suggestions?
Will

looks cool!

Will you have to do any adjustments to the fit of the ring/pinion? Or will they be ok cause they are being reused?

Are you replacing the bearings?

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As long as you keep the stock bearings/races there is absolutely no adjustment to the ring/pinion needed.

I'm just showing the optional step to check the ring gear backlash so everyone can see how to monitor it.

During the tear down I inspect the bearings/races for wear. You have the carrier bearings, pinion bearings and the stub axle bearings. I would replace any bearings if they needed it...

Which brings me to the carrier bearings/races... If one of them needs replacement it COULD result in the back lash changing. It would probally still be in spec but it might not be and then I'd have to show how to press the bearings on/off and swap side shims around.....

Same thing with the pinion bearings... It's pretty easy to rotate the pinion around and check to see it's smooth or put a TQ wrench on it to check the bearing pre-load.... The specification is 14-20in lbs.... However actual replacement of the front bearing could result in a need to re-shim the pinion for pre-load and replacement of the rear bearing could result in a need to re-set up the pinion depth.... both of those topics would need alot of explaining and to add fuel to the fire, some Dana 44's use a shim style pinion and some use a crush sleeve to set bearing pre-load....

I was afraid that talking about the bearings too much, could get me off topic from focasing on the rebuild of the Trac Lok itself and this thread would spiral out of control into a unreadable, totally uncomprehendable mess about everything there is to know about differentials....
Will

Nice, concise writeup Will.

Andy, this should be a Sticky when Will gats done.

Will, thanks for clarifying the point on bearings.

And Bill - this WILL be a sticky!

I almost feel this is a doable project.

One last bearing question - what are their life span???

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Different application (no launches) but the Dana in my Chev van ran 290k towing trailers before it went.

that would imply I have another 100k left... but with the clutches more then likely toast after 185k... ick...

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Oh yea.
Besides, the van wasn't posi.

Great write up!

Once you have both side gears and clutch packs assembled you need to get out the Miller Tool PN C4487-5 (or your stub axle) and install one side gear/clutch pack assembly in the Trac Lok carrier. Set the other one on top of it like so...



Insert the Miller clutch pack spreader Tools PN C4487-1, C4487 –2, C4487 –3 (or the tools you made from threaded rod) in between the 2 side gear assemblies and tighten to compress the bevel washers/clutch packs.



Assemble the Spider "pinion" Gears with their washers using a little gear oil.



Insert the 2 smaller Spider "Pinion" gears with their shims attached into the Trac Lok carrier. Try to get them across from each other. You'll also want to try to get them as close to the sides of the carrier's opening (of the direction you plan to turn the carrier to get them place) as you can so you don't have to hold them and pull on the bar all the way across the opening.



Next use the Miller Tool PN C4487-4 (or correct size piece of pipe) to pull the spider gears in place, lining them up with the cross pin shaft hole. You may have to tighten or loosen the Miller clutch pack spreader Tools (C4487-1, C4487 –2, C4487 –3 ) in very small increments to find the “sweet spot” for getting the pinion gears in the case and still being able to turn the carrier.



**A little trick I use - Because the Spider Pinion Gears almost never line up perfectly with their wear shims on the cross pin shaft hole. Once they are in place really close, tighten up the spreader tool to take all the tension off the Spider Pinion Gear and you can then line the shims up perfectly with your finger.**

Once the Spider Pinion Gears are in place, remove the Miller clutch pack spreader Tools PN C4487-1, C4487 –2, C4487 –3. Lube up and insert the cross pin shaft into the Trac Lok carrier. Note that I again use the punch as a guide to keep it aligned with the retaining roll pin hole.



You will have to tap it in place with a plastic dead blow hammer. On the last couple of shots take it easy and make sure everything is lined up so putting that roll pin in is easy. Action shot… Hammer Time!



Place the cross pin shaft retaining roll pin in place.


Drive the cross pin retaining roll pin in place with the punch… Notice that I drive it in from the short end, where the cut out is cast in the carrier…. Do NOT attempt to drive it in from the other direction… You cannot do it, without totally destroying the roll pin due to the hole tapering smaller.



Re-Install the ring gear on to the Trac Lok carrier. Use Loctite on the ring gear bolts and TQ them to 55ft lbs.



Re-Install the Trac Lok Carrier into the case. You will need to put the bearing races on the bearings (use a little gear lube), hold them in place with your hands and slide the carrier and ring gear assy in place… It won’t go all the way in. Once it’s started use the plastic dead blow hammer to drive it all the way down by striking on the bearing races with the end of the handle.

Once the Trac Lok carrier and ring gear assembly is in place, re-install the Bearing Caps and TQ the bolts to 55ft lbs.

Slide the Inner Stub Axles in place. This is where you set up the end play in them.

I could never find a specification for the stub axle end play, but it’s well known with old style Corvette diffs to set it to as little as possible (without being bound up). This is so the stub axles don’t slam into to cross pin as the suspension compresses under acceleration.

For racing I set them up at .0005 to .003 (yes that’s a half of a thousandth to three thousandths of an inch). Most good working stock units that I have taken apart to rebuild were in the .003-.005 range.

Now if your stock axle retaining rings get you in the above ball park and your happy that’s fine but if you want to set it up for racing or just want it the best it can be…. You can buy a set of different thickness axle retaining rings from TOMS Differential for about $35.

The easy way to set it up is to take the correct size feeler gauge and insert it between the axle and cross pin shaft. Then take the back edge of the axle retaining rings and try to slide them in the Axle’s groove until you find the one that just fits snug. Because of the previous damage - This diff took a .065 ring on the Drivers side and a .090 ring on the Passenger side to get the end play down to .0005 on both sides.



Once you have both sides figured out, install the correct retaining rings on to the axles. With the clips installed the axle should have a very slight amount of movement, and it should feel free. If the retaining rings are too thick they will apply pressure on the side gear, it will bind the axle up and that could put undue stress on the retaining ring.



At this point you are done… except for installing the batwing/cover and putting it back in the car.

I would be alot happier, to see you take the same car and do a write up on how to install a solid axle!! But at any rate, we will see how well this one holds up!!

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Well I know the owner of that car pretty good and he's got a couple of Corvette's....

If this one breaks, he'll just go race that turbocharged 93 Vert he's got in the driveway..... rear end is fine in that one.

Thats about the only thing that is fine in that car!! Besides, if he goes to race that one, you got a lot more to rebuild then just a rear end!!

You look like a magician doing all that work. Well done.