Sunday, August 22, 2010

Refurbishing the 1963 Differential

OK, lets recap. This is a picture of the 1975 differential currently installed in our Corvette. When we tried to install the drive shaft we found out this differential uses a 3.7" diameter universal joint but we need one that accepts a 3.3" universal joint. Since we have a 1963 differential on the shelf, and it accepts the smaller universal joint, we decided to swap them out. But first... We need to remove a broken bolt, one of four hardened bolts that hold the leaf spring assembly in place. It's in the lower right of this picture and this is going to be a bear.
A small pilot hole was drilled through the entire length of the bolt in order to get penetrating oil on both ends.
The hole was enlarged, heat was applied, then I grabbed an Easy-out.
A few whacks with a hammer to seat the Easy-out and we are ready for extraction.
Looks simple doesn't it? Trust me, it's editing magic.
With that repair behind us, the differential was cleaned as best as possible before heading to the sand blasting box. Pre-cleaning is done to keep the blast media from becoming contaminated with road grease and grime. It took 3 hours of picking, grinding, wire brushing, and wiping with solvent before it was ready. Just before blasting, kite string was wrapped down behind all 3 yokes to protect the seals.
After sand blasting the strings were removed, primer was applied...
followed by a couple coats of cast iron colored paint.
It looks nice!
Next posting should be the swap out the 1975 rear end for the 1963. Thanks for watching.
Update! After running the numbers it turns out the 1963 differential is really a 1965. Use the Poll in the upper right of this blog to help decide which differential we want to use.


  1. Hi Ausy Pete here again
    that finish comes up great, what paint are you using? what gear set are you running in the diff?

  2. Hey Pete!

    The 1975 rear end, the one currently installed in the Corvette, is a 3.70 positraction. The 1963 rear end, the one we just extracted the broken bolt from, is a 3.36 positraction. I've got to tell you though, after running the numbers I found out the 1963 differential is really a 1965. Although both bolt up with no issues, neither one is from 1963. So I have 3 choices, leave the 1975 3.70 in the car as installed, swap out the 1963 3.36 and get a little better MPG, or start looking for an original 1963 differential. I am still considering my options. Maybe a survey is in order. Yeah, that's it, maybe a survey...

  3. Ausy Pete here
    I have a 66 3.7 in my 64 . 3.7 was common with the FI. Are you intending the stop light Grand Prix or just some cruising? Cruising is more the 3.36 I think

  4. Pete,

    Probably more cruising than anything else. But since we're trying to assemble a period correct, era modified fuel injection Corvette the 3.70's might be the better way to go. And as far as the 3.36's go, I am not sure you could get a fuelie in 1963 with those gears. We'll figure it out though.