reidry

Seems every project I start (Corvette or otherwise) develops a few projects of it's own.

Pulled the D44 out of my '85 to clean, inspect and reseal (had a small leak). Got it out and apart, cleaned it, resealed it and went to reassemble only to find that someone had over torqued these bizarre differential bolts and stripped 3 of the 5 holes holding the batwing to the differential case. Anyone who has held one of these bolts will understand the "bizarre" comment. Instead of the shank being a round threaded cylinder, it's triangular. My only guess is that the design was supposed to be torque limiting since the bolts were being threaded into the tapped aluminum differential case.

I promptly helicoiled all the holes - better to do it now while the whole thing is out of the car. When reinstalling the bolts one stripped just before the proper torque. What luck!

So I ordered a set of replacement bolts from ARP, figured I might as well use fully threaded bolts. Bolts arrived and I'm ready to install ... Only one question remains. The bolts from ARP came with washers. The washers are no larger than the shoulder on the bolts and I'm leaning towards not using them - any opinions? The originals didn't have washers and I don't think I've ever seen washers used on diffs.

Thanks,

Ryan

CFI-EFI

If the ARP bolts are for that specific application, I'd use them. I believe the original bolts were self tapping and that the diff housing wasn't tapped.

RACE ON!!!

Corvette Kid

If they came with the bolts then they are designed to be used with them. I think ARP knows what they're doing when it comes to critical hardware. My ARP rod bolts torque beyond stock spec. Does that mean I should have assumed they were full of crap and only torqued them to stock? ARP is an improvement over stock. That's why we use them.

reidry

These are high strength chromoly however they are not specifically intended for the D44 differential. I spoke directly with ARP about using these bolts for this purpose and they agreed with the selection as far as strength but did not mention the washers.

I don't really think I could go wrong either way, just wanted to see what the general concensus was.

Ryan

Corvette Kid

I noticed in your original bolts the description of the bolts. I installed an '85 D44 in my car and the bolts did not look like that. They looked just like the ones in my '95 D36 only larger. The ones you described sound like self tapping bolts for sure. Either way, do they have a round flange under the hex where the bolt contacts the cover? Both sets of mine did and if your ARP bolts do, fine. But if they don't, use the washers so the hex doesn't dig into the soft aluminum. I'm sure if they came with ARP bolts they are hardened washers and should not cause a problem.

Corvette Kid

I noticed in your original post the description of the bolts. I installed an '85 D44 in my car and the bolts did not look like that. They looked just like the ones in my '95 D36 only larger. The ones you described sound like self tapping bolts for sure. Either way, do they have a round flange under the hex where the bolt contacts the cover? Both sets of mine did and if your ARP bolts do, fine. But if they don't, use the washers so the hex doesn't dig into the soft aluminum. I'm sure if they came with ARP bolts they are hardened washers and should not cause a problem.

reidry

Yeah they have the round flange under the head. The only real difference in the head is that the ARP is a smaller socket size with the same diameter flange.

Ryan

Corvette Kid

Okay, I don't think you'd need them in that case. I'm still curious about the bolts you removed. I'm wondering if they're something someone installed because they had screwed up the holes already. Anyone know for sure if any such bolt was ever used? As I mentioned before, my '85 diff had the conventional flanged bolts just like my '95. Just curious.

reidry

Interesting. I assumed that they were original but I may be mistaken. The stamp on the bolts is:

31.2
5

My car has had some pretty extensive mods. The codes are missing from the storage compartment area, it has a Richmond 6 Speed Trans, some engine mods, etc. I don't doubt that the whole rear could have been transplanted.

Now I'm really curious if the bolts are original. My first attempt at a replacement was GM but the bolts were not readily available, they quoted a week to get just one. Since I had helicoiled the holes I figured I'd just get an ARP fastener and forget about it.

Ryan

Corvette Kid

Helicoil is a GOOD thing in aluminum castings. I was glad to see that the rocker stud holes were all Helicoiled in the new heads I got from Precision Porting & Coating. With the good bolts too, you're in good shape now.