I live in a small town in SC, and don’t have a lot of shops here or close by that I know of that could or works on corvettes,so after a few months of trying to find someone,although have never messed with rear ends and although I wouldn’t say I’m a mechanic I do and have worked cars a little the last say 40 years,so,I am comfortable working on them,so,I already have a new aluminum differential in a box with 3.54 gears,has 2.87 now,so that shouldn’t be to hard,just a swap,but plan on replacing trailing arms also,which is where things might get complicated,so what to expect if I do it,oh and I don’t have a lift,so will be on jack stands,what kind of special tools would I need? Any issues getting old bearings out of trailing arms.



Thanks

 

Saw from your profile you are working on an 81. I have done trailing arms on a 72 and 73 and presume they are the same. I know new trailing arms are advertised as fitting all C3s. In any event trailing arm removal ranks up there with the most challenging disassembly chores, especially without a lift. Getting the bearings out is not the problem. Usually the trailing arm end in the frame paocket with shims held in with the large cotter pin are rust fused to the bolt and frame. I ended up cutting off a sawz all blade so it would fit in the pocket and then spent hours hacking away through the shims and bolt (like many here hammered on that bolt forever and didn't budge it; heated it; used every penetrating oil available, no dice). And I have a lift. If you are having your trailing arms rebuilt or doing it yourself then you have to take some care. If the arms are toast alot of people hack it in two in order to make it easier to get to get to the shim pack. Search the archives for many posts on the subject. Good luck.

 

You'll need a carbide blade to cut the trailing arms out. You will burn up regular metal blades, so don't bother with those. Since you'll be rebuilding the half-shafts with new U-joints, don't hesitate to cut the U-joint straps, too.

I hope that aluminum diff works out for you. Though it requires shortening your driveshaft, you can bolt an iron diff to the aluminum batwing rear diff housing.

 

I have new trailing arms,with all new hardware,and all new u joints,I’m just assuming all bearings are good,and yes it is a 1981,80k miles,and is been well taking care of,and as for the pin,I don’t see by looks of course,not rusted or anything,but have not tried yet either,but cutting would be know problem.and I ordered the rear differential from Duntov in TX. But from what you’re saying the pin getting out is the problem then.

 

You don't have to remove the trailing arms to get the bearings out and serviced. If the trailing arm bushings and shims are good, remove the half shaft, remove the caliper. remove the rotor. If the rotor is still riveted, drill them out and remove the rotor. Remove the parking brake assembly and remove the four nuts. Once the nuts are off, the bearing hub will slide out from the inboard side. You may have to spray some penetrating oil between the trailing arm flange and the bearing housing. One last thing, It is easier to remove the large nut on the inboard side with the rotor and brake caliper on the car. Just put a large screw driver through the top of the caliper and into the rotor. That will anchor the shaft and keep it from spinning. That said, if you have never done a bearing replacement on a C-2 or C-3 vette, it can be challenging. There are specialized tools required to get the runout and end play tolerances correct. Look up posts by GTR 1999 for more information. Once the bearing hub is removed, it can be sent out and rebuilt. For a few extra dollars, have your rebuilder supply a new rotor with runout at or below .002. Good luck. Jerry

 

If you are replacing the trailing arms, you gotta get the old ones out. A carbide blade on your Sawzall is your friend.

Perhaps you'll get lucky. Or perhaps you'll need to cut the trailing arm bolts, as well as the strut rods. If the inner steel sleeve has rusted to the bolt inside the trailing arm bushing, you won't get it out.

 

I don't see a spring pack in that diff, so I assume Duntov is trying to copy Gary's work. If I were you I'd check every clearance in the unit before I installed it.

 

I would suggest getting yourself a Quickjack. I have my 78 up on one now and everything you will be doing will be much easier. Just lifting the car a foot or two off the ground will make your projects a lot easier.

 

The Dana didn't use the spring pack like the Eaton or earlier DANA. I agree 100% checking things though especially given the past history of the rebuilder.

 

Yea,I have several 3 ton floor jack,and plenty of jack stands,and that’s when I’m out of my comfort zone,with tolerance and all that,I have already replaced with new rotors,pads and replaced old seals in calipers,and there again putting bearings into new trailing arms.I will see about some help with a friend that would know more with the rear end as far as the tolerances.

 

Oh sorry canvasman you mean Quickjack,like a air lift,or fluid lift,no because of where my garage is,and I’m renting it,but if I buy or build my own garage,shop.I will definitely have to have one.

 

So the quick jack is totally portable. No permanent structure to the building. If you get to the point where you aren’t comfortable with all the jack stands I will offer up my quickjack to you for 2:or 3:weeks if you come down to Summerville and pick it up. I used to do everything with jack stands but as I got older I needed something easier and my garage is too low for a lift. Like I said I have one if you want to use it. Good luck on your project.

 

Dont reuse your old bearings.. buy new and swap everything out, bearings bushings etc. You shouldnt have to cut anything out. The onlything you should be able to reuse is the trailing arm cross bolt adn th eshims. Mark the shims for inner and outer shim packs and do it for both sides so you dont screw up the rear alignmment. Go to you tube and look at videos of how to get the batwing out. THe older cars had sombrero mounts that were a bitch to pop out but you should have and easier go

 

Update,I found someone that’s a lot more familiar with it than me,so taking it to him next week after Memorial Day,and canvasman,thanks for the offer,maybe when I get finished with it,would love to take a trip to Summerville,hadn’t been in years,like 20.lol,it seem I went to a festival then,my memory isn’t what it use to be,but seems like the festival was after the name of some flowers 🌺. Is that correct,and do you have any corvette shows that way.

 

Sorry for the delay, kid's KIA had issues that dad had to fix! The dreaded harmonic balancer falling apart ( I thought that was only on C6 corvettes?)Yes, the Azalea Festival turns the whole town into a parking lot. You haven't missed anything in 20 years. And yes, there was a great all corvette show here last month DOIN THE CHARLEStON. They have that every year and there were a few cars from Myrtle Beach. Actually we are heading up to the Myrtle Beach Corvette club show on Broadway next Saturday for a few hours. Went there last year and could not get over how many cars were there. THis year they are trying to get over 800 I believe. If you are going to that one, PM me and we can share contact info and maybe meet up for a bit and match faces with names!

 

I’m assuming this Saturday the 8th,I have a golf tournament that day,but would have loved to if I didn’t.and hadn’t been to broadway in a long time.

 

Hi all,

A diff related topic ...

I have an issue mounting the leaf spring to the differential cover using the four 7/16-14 bolts. In one of the two rear facing bolt holes, the thread in the cover is gone. The previous owner has solved this by using a longer bolt going all the way through + a locking nut on top. Looks secure enough. I did the same for the other one next to it just for conformity & looks, even if strictly speaking not necessary.

The problem is with one of the two other bolts holes that go into the cover but aren't protruding anywhere so I can't put a nut on them but in one of them, the thread is NOK too. I'll try rethreading 7/16-14 but if that doesn't help I had the idea to use a slightly larger 1/2-13 and for that, drill the hole out with a 10.8mm drill and rethread for the slightly larger 1/2-13 (if that works do the same for the 2nd hole too).

However, I wonder if there's material enough in the cover to do that? Looks solid enough but just don't know for sure. Looks like a workable way to attach the leaf-spring securely after all without replacing the cover & all the work that goes with it. Just a 1/16 thicker bolt, should work. No? WDYT?

Any help is appreciated
GL

 

Golferdad, you can play your tournament and completely focus on your swing , the vette show was LAST Saturday the first of June! It was a great show and the weather made it even more fun. Spent about 3 or 4 hours there and could have spent more if I wanted to look at a lot of C7's and 8's. No worries, there will be another next year.

 

Make sure he is familiar with Corvette C3 IRS and not just diffs in other cars.
There are some major important differences, since our diff acts as part of the suspension, others don't.

Have him check these and report back to you:

1. Make sure the new trailing arms have rubber bushings on the front,- poly will not last
2. Rotating TQ on the pinion before install
3. Gear backlash measurement
4. Pic of gear pattern - (I don't trust anyone except GTR)
5. Side axle stub backlash in/out - this is the main item that is C3 vette specific
6. Spring bolts and hole length going into diff - very specific lengths, and will crack the diff if too long
7. Tighten spring mount bolts AFTER the car is back with it's weight on the wheels, or diff will crack
8. Outer stub axle bearing endplay - GTR1999 likes .001" endplay - vette specific - bearing runout setup here is very C3 specific and should be done by a C3 specialist
9. Measure endplay on new rotors and shim until .001" runout on rotor - again c3 specific due to solid mount calipers - brakes will get air and leak if you don't
10. Buy a set of front trailing arm shims ahead of time, and have him get toe-in alignment close during install - c3 specific - PITA for alignment shop
11. Many tips tricks on here to bleeding rear calipers to get all the air out to get a solid pedal
12. Adjustable rubber bushed lower strut rods make alignment easier - again poly will not last due to twisting motion

PLEASE HAVE HIM MAKE A NOTE OF ALL THESE MEASUREMENTS AND ASK FOR THEM TO BE HANDED TO YOU FOR FUTURE REFERENCE
(This way you know he actually did them - most WILL NOT)

 

Start your own thread for better responses!!

Not an expert, but helicoils might solve the problem....