C4 Dana 44 question

Hi all, this is my first post here, although maybe some of you might recognize me from other places. :hi:

I'm in the middle of checking over a C4 dana diff for a friend. He had it "professionally" rebuilt just recently and it lasted about 100 miles (and was grinding and moaning from the start). The rebuilder is maintaining the gears obviously weren't hardened, yeah right. We can soon put a stop to that BS as I intend to get them hardness tested at work. But in the meantime I've measured the pinion depth to see if I can figure out why this unit failed so prematurely.

So can anybody tell me what the basic pinion depth should be for a C4 D44?
I know that for the C3 unit it's supposed to be 2.625". Did that value carry over to the later models?

I'm kind of hoping not, because the pinion depth on this one is 2.580", or 45 thou closer to the pinion than the C3 unit should be!

If it IS supposed to be 2.625 then I think I might have found out why it grenaded so soon!

cheers
Theo

theo said:

Hi all, this is my first post here, although maybe some of you might recognize me from other places. :hi:

I'm in the middle of checking over a C4 dana diff for a friend. He had it "professionally" rebuilt just recently and it lasted about 100 miles (and was grinding and moaning from the start). The rebuilder is maintaining the gears obviously weren't hardened, yeah right. We can soon put a stop to that BS as I intend to get them hardness tested at work. But in the meantime I've measured the pinion depth to see if I can figure out why this unit failed so prematurely.

So can anybody tell me what the basic pinion depth should be for a C4 D44?
I know that for the C3 unit it's supposed to be 2.625". Did that value carry over to the later models?

I'm kind of hoping not, because the pinion depth on this one is 2.580", or 45 thou closer to the pinion than the C3 unit should be!

If it IS supposed to be 2.625 then I think I might have found out why it grenaded so soon!

cheers
Theo

Click to expand...

This is sort of related, so I thought I would post it. Did you do a pattern check of the gears before you pulled it apart? That will tell you a lot about how the gears were set up.

It was delivered to me with the diff removed from the casing (but the pinion still installed), so yes, I will spread the case, put the diff back in and do a pattern check before we strip it to hardness test it.

But the teeth are so polished up from the failure that there probably won't be much to see, except perhaps on the coast side! (Which would still be useful)

I need to have a good look at the R/G tooth damage (that in itself is essentially a "contact pattern"!) to see what it tells me, just interested for the moment to see how far off that basic pinion depth setting was......

theo said:

It was delivered to me with the diff removed from the casing (but the pinion still installed), so yes, I will spread the case, put the diff back in and do a pattern check before we strip it to hardness test it.

But the teeth are so polished up from the failure that there probably won't be much to see, except perhaps on the coast side! (Which would still be useful)

I need to have a good look at the R/G tooth damage (that in itself is essentially a "contact pattern"!) to see what it tells me, just interested for the moment to see how far off that basic pinion depth setting was......

Click to expand...

I have never rebuilt a c4 diff before, so I don't want to give any bad/wrong info. I know Mike Dyer (tracdogg2) rebuilds every type of diff imagineable, so he'll probably be able to help you out. Send him a PM with your concerns, or a link to this thread.

The correct pinion depth should be marked or engraved on the pinion face.

The depth is around 2.625 yes, I've got a set with 2.620 depth engraved on them. Whining is usually a too tight pinion depth, if the gears are all "polished' they're messed up. What brand is the gear set? Might want to try and find a dana gearset, the vipers use those too. It's aD44 sized ring and D60 sized pinion for the super dana 44 setup.

The pinion depth is easily changed, the preload is also done with shims. Only very late diffs (94?? up??) have a crush sleeve.

They're apparently Dana gears, and yes they're totally shot! My job is to try and see what this builder's done to cause the problem.

They don't have an actual depth engraved on the nose, just a VERY hard to decipher "squiggle" which is obviously supposed to be the +/- number. I needed the "basic" setting so a) I can see if the guy's installed them to the correct depth and b) I can set up new gears in it.

I've found out a bit more info now, having got a look in a GM manual. Apparently, according to the book, the basic pinion depth is measured from ring gear centreline to the BACK edge of the pinion, rather than from centreline to pinion front edge/nose. So I'll need to pull the old/knackered pinion and add the thickness of the gear to what I've already measured to get the "basic" depth. Then add/subtract whatever's on the new set. BTW, the GM spec I've now found is 4.312", from ring gear centreline to Pinion back face/shoulder.

Actually, thinking about it, that way of doing it might make the setup easier, I guess you could install the pinion bearings in the case, preload them with a bolt/nut/washers through the centre (ie without having the pinion pressed in) and then just measure down to the shoulder face of the inner pinion bearing cone. I'd do the fine tuning by contact pattern though.

It's a ZR1 (1990?), by the way.

All aftermarket ones are measured from the cap mating surface to the nose.
No need for super fancy tools even. If you don't have a depth gauge you can simply use a straight machinist rule and a vernier caliper and clamp the 2 together and take a measurement that way. It'll be close enough for initial setup. Also, you'll need a case spreader to preload the side bearings, without one it will never have proper preload and you'll get wavy wear patterns on the carrier side bearing races.
The GM setup uses a special tool, which is one of those J numbers and next to impossible to get (Kent Moore Tools...spent moore )

According to Tavia Dana/Spicer 44 pinion depth is 4.312" indeed.

One thing, the pinion depth is a guideline! It's not gospel. You shim it to the proepr depth and then you pull a pattern and adjsut from there. In fact, it's pretty common for the suggested pinion depth to be off, it'll need fine tuning afterward.

Might want to contact member GEE (George), all I know about these differentials, I got pretty much from him years ago. He might know the numbers off the top of his head.

Pressuing the pinion bearing on/off isn't that hard at all (you'll need a good blade puller so you don't mess up the cage) but also not necessary. . I have a set of bearings that I slip fitted for setting up the diff. I have a set for a C3 D44, a C4 D44 and the iton eaton posis.

Yep, made myself a case spreader when I did my first diff a while back.

the first measurement I took today was pretty much as you describe, using a depth micrometer off the bearing cap machined pads. That's where I got 2.580" from, but as we now know that figure has to have the thickness of the pinion gear itself added to make sense as per the manual.


I see what you're saying about the pinion depth not being gospel, and indeed I'd always dial it in with the pattern anyway, but you see the reason why I wanted a "spec" here is to just see how close (or far away!) this particular setup is - as I said this diff was "professionally rebuild" (haha) and was knackered after 100 miles, so I'm trying to do some detective work before repairing it, so the owner has some ammunition for the builder, who is apparently being far from courteous about it all!


And also yes, I was going to grind up some slip fit bearings for the pinion like you say. Never did this on previous builds but I can see it would make the setup much easier.

A point to note there: Did you know that the Timken tolerance on the installed height of their taper roller bearings (ie the width in the axial direction) is something like +/- 7 thou?! That's going from memory of their catalogue, but something to bear in mind when you see how that kind of change could affect what you "think" is going to be a good pattern when you press the final bearing on. No idea what kind of tolerance they have in practice, but I guess the best thing to do is measure the difference between your new bearing and your setup bearing (preloaded, obviously) and then make shim changes accordingly when you do the final fit.

Cheers for your pointers :thumbs:

DANA 36 vs DANA 44

The C-4 Dana 36 was the only axle available in 1984 Corvettes. In 1985, Chevrolet brought out the Dana 44 which was similar to the 80-82 Corvette axle, but not interchangeable. The Dana 44 axle is considerably stronger, but not indestructible. The Dana 36 and the Dana 44 (44's in some autos and all manuals) axles were used through 1996.

The Dana 44 is much larger than the D36. The 44 has a larger, "beefier" carrier/components to handle larger (lower) ring and pinions, and increased torque. NOTICE THE LOCATION OF THE TOP CENTER BOLT HOLE ON THE DANA 36 THATS NOT ON THE DANA 44 REAR, thats a QUICK WAY TO TELL THEM APART

603967 GM 44 REAR 1980 CORVETTE
605172 GM 36 REAR 1984 CORVETTE
605180 GM 36 REAR 1984 CORVETTE
605220 GM 44 REAR 1985-87 CORVETTE
605239 GM 36 REAR 1984-86 CORVETTE
605260 GM 36 REAR 1985-87 CORVETTE
605321 GM 36 REAR 1988-90 CORVETTE
605322 GM 44 REAR 1989 1/2-90 CORVETTE
605365 GM 44 REAR 1988-89 CORVETTE
605417 GM 44 REAR 1990-90 1/2 CORVETTE
605490 GM 36 REAR 1990 1/2-96 1/2 CORVETTE
605491 GM 44 REAR 1990-96 1/2 CORVETTE
605492 GM 44 REAR 1990 1/2 CORVETTE


Look at the size difference, especially at the case above the yokes:


Dana 36


Dana 44

And visit

ikerds.com

Who were kind enough to supply the pics