I recently pulled the differential out of my 80 Corvette. I originally just planned to replace the seals, however I started wondering if I should just rebuild the whole thing. As far as I knew it had never been worked on. That may not be the case after what I've found. When I pulled the pinion seal and the outer bearing behind it, I noticed that the bearing was slightly damaged, and it was a Timken brand. You can see the bearing has been deformed slightly in the pic below.




I'm guessing GM didn't use Timken bearings from the factory did they? This would have to be aftermarket.

I then decided to just pull the bearing caps knowing full well that I would't be able to get the diff out of the carrier housing without the case spreader. But what do you know? I was able to pull the entire differential out of the case with no problem at all after removing the bearing caps.





I can't tell on the installed diff bearings, but the races under the bearing caps are also Timken brand. I'm beginning to think the differential has been rebuilt in the past.

My big questions:
Were Timken bearings used from the factory?
Why the hell didn't I need a case spreader to pull out the diff?
Is there a way to verify that this is even the original diff for the car?

Any help would be appreciated. Thanks!

 

GTR1999 can help you and give you all the answers that you asked.....

 

Thanks, I'll see if I can get in touch with him.

 

I know 1 person that works on the dana 44 with the batwing. if interested you can send a pm and I will give you the contact information.
Dave

 

From memory the diff in my 81 had timkins in it when I opened it up. It's still at work so I could have a look tomorrow when I go in. Interesting that you didn't need a case spreader, as I didn't either. The posi fell out when I removed the bearing caps. Luckily I caught it before it hit anything.

 

You can reach Gary (GTR1999) by sending him a PM. He posts regularly here and has a current thread going specifically on 63-64 differentials in the C1-C2 Forum.
https://www.corvetteforum.com/forums...1-gtr1999.html

Good luck... GUSTO

 

Hi,
I just saw you contacted me. The 80-82's I had in did have Timkens in them.




The side of the ring gear will have a date code, DANA, and tooth count for the ratio.




43-14 = 307 ratio



The case bearing preload is setup by shims under the case bearings not in between the bearing and case like the 63-79 irons.


There is a date code on the housing



With all that said I do not take these in to work on. I literally gave away all the cores and parts I had for the 80-82 differentials. There are plenty of places like Van Steel, Zip, Bair's, etc that will rebuild them.

I don't like these diff's at all. GM went back to DANA & aluminum housing after running Eaton posi's in iron housings since 1965 and they just are not as good. The 63-64's were iron but had a lousy Dana posi in them. The open diff's were stronger. The same square shoulder pinion was brought back only smaller, the clutch retainer breaks, the bearing caps are aluminum, the spiders & clutches are smaller, the cross shaft is held by c clips, and the axles wear as bad as the mid 70's axles did.

While a steel cap & C4 posi can be added that cost would be better put toward a conversion to an iron diff setup - just my opinion on them, take it or leave it. If I had an 80-82 it would have an iron diff in it. Now there are those out there that run them hard and swear by them which is fine, I have seen them fail. The last one I had the housing was tweaked.

They are about 35 lbs lighter though.













I hope this helped you, good luck with it. If you want to convert to iron you should be able to find a complete 74-79 setup including diff, 1/2 shafts, strut rods, outer axle flange, front bracket and will have to mod or replace the driveshaft. The iron will bolt to the batwing and can be built to handle I would say 500-550hp but I wouldn't go beyond that( yes I know some do with 10 bolts)

 

Gary,

I appreciate your help. I think I'm going to go ahead an rebuild the DANA for now. I'm in a bit of a time crunch and need to get it back on the road. Maybe in the future I'll consider the 74-79 swap. I do have the 1980 Corvette Shop manual, but it appears that it's not exactly correct for my diff. GM must have forgot to update some aspects of the manual in 1980. Not needing the spreader was a big one.

The diagram in the manual also shows two sets of shims on the drive pinion. One set between the outer bearing and the shaft (#5 in the pic). The other set looks like it's between the inner bearing race and the bore (#4 in the pic). Is that correct? Although I haven't pulled the race yet, it doesn't look like there are any shims between it and the boar. I also don't seem to have what they call a SLINGER - Pinion Outer (#7 in the pic).



Maybe I missed it, but the lash is set by one set of shims between the bearing and the diff case? As shown in the pic you supplied?

I planned to reuse the ring/pinion and spider gears. They seem to be in good shape from what I can tell. I'm planning to just change the bearings and the clutch packs in the case. Do you happen to have a trick for removing the spider gears? I obviously don't have the slick tool that the shop manual calls for. I've been brainstorming trying to determine how to twist those gears around and get them out.

Finally, if I just reuse all shims exactly as they were when I pulled them out, the lash, pinion depth, etc should be fine correct? I shouldn't have to make any adjustments I wouldn't think.

Thanks again for everyone who replied. It's nice have a community that's willing to help each other out.

 

The Dana 44 ICA doesn't have a "crush sleeve" but instead uses shims to set the pinion depth and shims to set the bearing pre-load. The DANA differential cases used were poorly designed as they allowed the limited slip shim retainers to break and chew up the differential case. There is a later version of the case in which the problem was fixed by putting more material in that area.

 

Is there a reason you are replacing the bearings? If you need new bearings, you should probably be replacing the gears as well. The gears in there have been worn in to the shim setting that they were setup initially. Swapping out bearings will mean you likely need a slightly different shim pack, and you will very likely not get the gears meshed the same way they were worn.


Either replace the gears and bearings all together or leave them all in there. If it is just a seal issue, replace the seals and be done.

 

Tom at Toms Differential is trying to retire and has his business up for sale, but he has 80-82 Posi cases all polished, or I strongly recommend this be done! He had heat treated gear sets and stronger crossshafts! He also marketed a stronger outer Axles in his KA line. For inner Axles, it would be best to see if someone else has something better than stock!

 

You make great points. To tell you the truth, other than the outer pinion bearing that is damaged (see the pic in the initial post), I have no idea if the other bearings are good or bad. The car hasn't been seriously driven since I bought it 10+ years ago. Just spinning them by hand they seem fine, but I don't know for certain. I just don't want to get the whole car restored and find out the rear end is bad and I have to pull the diff back out later.

 

Does anyone know the Timken part number for the side axle bearings? The bearings that are in it are Torrington DB-43932 from what I can tell. I'd like to replace them with new Timken's but I can't figure out the part number.

 

I have rebuilt many rear ends - many "bad" bearings spin nice and feel great. But good bearings and races are cheap. Replace them all while you are in there. Why not? And no it won't totally screw the gear mesh. Reset all the backlash and check engagement pattern and it will be fine. I have never had a used gearset issue as long as there were no obvious problems (broken or chipped teeth).

 

I don't think my 1980 shop manual is correct. It says to torque the diff bearing caps to 70 ft lbs. That seems way to high for aluminum. Anyone have a better idea of the necessary torque for both the bearing caps and the batwing bolts?

 

Hate to say it again but ask Gary, GTR1999.....He is the diff expert and a professional....