Two different sized Half shafts on my 66

[Nick M.]

I was working on my 66 vert this weekend. The project was to simply lower the back end of the car as it sits approx 2" higher than the front. 28" vs 26 1/4" floor to inside lip of wheel well. I used longer spring bolts, grade 8, 8" long bolts and new washers and cushions replacing stock originals. Changed it out and the hight of the rear didn't move one bit.

But I digress.... looking at the rear end, assembly I noticed that the left Half shaft was 3" in diameter and the right is 2.5". Any idea why this would be? what years used 3" half shafts?

The car runs well, tracks well, running two differenct half shafts can you see any issues with this?

Now that I know this want to also change out the 3" shaft for the correct one, just another thing to add to the list.

Also any suggestions on my issue with lowering the rear of the car?

Thanks in advance for any help.

[Greg L.]

Re: Two different sized Half shafts on my 66

Nick I think the 3" half shaft started in or around 74. I can't see there being any real issues with the two different sizes because I drove my 69 like that for about 20k miles and only noticed it after I took the body off!

I believe that you need to roll the car ahead and back a ways to let the rear spring settle. Either that or use a grease plate under each rear wheel.

[Nick M.]

Re: Two different sized Half shafts on my 66

Thanks Greg,

Good to learn about the different use of the shafts and that it is not an immediate issue that will require changing.

I will try and move the car around to settle the spring.

Thank you very much

[Joe L.]

Re: Two different sized Half shafts on my 66

Thanks Greg,

Good to learn about the different use of the shafts and that it is not an immediate issue that will require changing.

I will try and move the car around to settle the spring.

Thank you very much

Nick----


The 3" OD half shafts were first used in PRODUCTION for the 1975 model year. However, shortly thereafter they became the SERVICE half shafts for all 63-74 Corvettes. So, they are, consequently, approved by GM for use on 63-74 Corvettes regardless of whether they are replaced in pairs or as a single unit. I expect that at some point in your car's history, it required a half shaft replacement and, by that time, the 3" shaft was the one being sold by GM.