OK friends, I had great luck getting help with the brake problem I had, let's see how this one goes.

1981 Corvette completely stock. Rear spindle replacement.
Issues: According to everything I've gathered off the internet, the castle nuts are 3/4, but the castle nuts on it ARE NOT 3/4" on mine. Don't tell me they are, they aren't. They haven't been replaced. All of them on the rear arm are the same size that is LARGER than 3/4" and is not 3/4". What socket fits these? It's driving me nuts, lol.

The brackets to remove axle shafts in the rear are 1/4" 12 point bolts instead of 9/16" hex bolts like every other Corvette from this generation. So I know there was some generational differences between older C3 and the 1981. There is no diagram of this part in the GM shop manual for this car, every other part of it, but not his part. Is there anything else I should be ready for when doing this job?

Thanks in advance for your help. This forum is a great resource. There are ZERO mechanics in Fresno, CA that know anything about this car. Several have told me they can't even look at it, as it is older than all of their techs, so I can't take it anywhere. Two mechanics have made the car worse or not repaired what they said they would, or left the car broken and told me it was my fault. I have to do all this myself, so any suggestion to take it somewhere won't work.

THANKS!


The axle shaft bracket to be removed to remove the axle shaft. Then I'll be able to get to the castle nut and knock the spindle out of the trailing arm.

 

The bolt holding the flange on is NOT stock.
Unclear what castle nut you are referring to that is supposed to be 3/4" but the next size up is 13/16.

 

The castle nut question: what socket goes on it. Everywhere says its a 3/4 with a 20 thread, but I can't find anywhere that says what socket goes on it.

I have to disagree about the u-joint bolt. The area that its tightened to is not big enough for a larger bolt to seat to. It's right up against the bump where the u joint is. That's why I posted a pic. I agree that it is unusual. All the other C3 videos and forums do NOT have this bolt. It is the same bolt on every single u joint on the car though. Unlikely that someone would change every single one on the car, and the car is 100% stock in every other part of the car, it's essentially un repaired un restored. It's not the first time that the 1981 has been very different than the earlier C3s, like the computer controlled carb situation.

Thanks for your post though!

 

I had a mix of pieces when I removed the half-shafts on my 80. The 80 and 81 4-speed use 1350 U-Joints, so they are a bit bigger than the ones on the auto cars. Some were 12 point (likely original), some were Allen key (likely replacements). Since I was sending the half-shafts to be rebuilt anyway (I had to specify and pay extra to get Spicer non-greasable 1350s), I ended up cutting some of the straps.

I used new bolts and Spicer straps when I replaced everything. I sent my trailing arms out to be rebuilt so I didn't have to deal with the hub bearings.

EDIT: Here's the bearing strap kit I used. Spicer 3-70-28X. It includes new 6-point bolts, and is specific to the 1350 U-joints.

Before and after:

 

Awesome, so it is the stock bolt...It's an auto car. What size it he castle nut socket that you have to use to remove it.

 

Just want to know which socket to use, I don’t own one large enough so I have to buy it, would rather not buy a whole set for one socket.

 

I updated my post since you read it, though it sounds like you have 1330 U-joints if you have an auto.

Do you mean the castle nut circled? I never touched that. Both arms, with hubs and rotors, got sent out to be rebuilt. Perhaps you can measure it with calipers.

 

Starting at Post #84, here's a thread on a DIY hub rebuild. I don't know if it calls out the socket size.

https://www.corvetteforum.com/forums...-thread-5.html

 

Hi, I’m rebuilding my trailing arms on my 81 as we speak. The size of the spindle nut is 1 1/16 and the flange bolts are 12 point 1/4. I have an automatic trans on my car. I hope this helps.

 

Correct, the thread size is 3/4-20 and you won't find that die or tap at a local store if you want to dress them. All 63-82 axles have the same size threads.

 

The final answer, for anyone following along, was 1 1/16 for the spindle nut, and 15/16" socket to take off the castle nuts elsewhere, they are different for the 2 positions. The bolts for the u-joint on a 1981 automatic are 1/4" 12 point socket.

 

Yes those are the correct u-joint straps and 12 point bolts for the 81. The difference on the manual cars and automatic cars is the size of the u-joints on the half shafts, the size of the straps, the 12 point bolts, the spindle flange and the side yoke. 1980 and 1981 auto cars used the 1330 u-joint for the half shafts and the 1/4" 12 point bolts but the manual cars used the 1350 u-joint for the half shafts and a 5/16" 12 point bolt. The exception to this was the 1982 cars, they actually used the 1350 u-joint for the half shafts and the 5/16" 12 point bolts.