Hi all, just finishing up with a 12 bolt swap into my 72 Skylark. The pinion yoke position is slightly farther away from the trans output shaft with the 12 bolt (vs my 10 bolt), so my driveshaft doesn’t seat quite as far onto the trans. Might be about a 1/2” shorter. Is this within acceptable tolerance? I have a photo of the driveshaft engagement on the trans.
I would personally switch to a longer driveshaft. Will it work as is, likely but you will have much less engagement on the splines. I think you can buy a longer yoke, that would fix your issue with less cost if that’s an option.
Your car original came with an 8.5” 10-bolt. That rear has the longest pinion snout of all the GM rears of that era. The result is that is takes the shortest driveshaft to reach it. If you swap FROM the 8.5” TO a 12-bolt Chevy or any 8.2”,you will need a longer shaft. What is your current driveshaft length? I might have something that will work.
Thanks Brian, what’s the proper way to measure it? It’s installed currently. Also, I’m up in Canada so it might be a bit of a beast to ship
i LIKE TO MEASURE CENTER OF U-JOINT HOLE TO CENTER OF U JOINT HOLE FOR LENGTH. BUT make sure both of you are on the same page for measuring or is will be a disaster.
It is close you do need to have some slide in to the trans to get the drive shaft in and out of the car. BUT to me yes looks like another 1/2 is going to be in a better position as you do want more on the output shaft for a better support of the slip yoke from wobble .
Thanks Jim, I figured as much. Sean’s suggestion of a longer trans yoke might be a better option than an entire drive shaft. Any insight into that for a possibility? I cruised around Summit and saw they have a few different lengths/u-joint types, but I’ll need to pull my yoke out and measure first before I know if that’s an option. If I can find one about a 1/2 longer, that sounds like a good solution.
Make sure the spline INSIDE the yoke slip tube goes the complete length. Or it is not solving the problem
i would call a 4x4 shop and ask them about the minimum spline engagement length. That’s a common issue with lift kits.
Well,in my GS 455 I have a longer yoke.You might find those in one of the big cars,like Electra or any other big GM cars.Bruno.
