Im in the process of going from a 350/350 to a 455/400 in my 72 skylark...I got the motor and trans at the same time, and the guy I got them from said the transmission had been rebuilt...now doing some research on this board and online, I was thinking I was gon need a yoke with 32 splines but the old 27 spline yoke fits right on there...I measured the driveshaft (which is too long) but before I go have it cut I wanted to know ifanybody has gone through this before, and if so do you have the exact length that I need...
Exact length will be an iffy prediction over the intertubes. Your best bet is to measure the length. Put the yoke in, all the way forward, measure from back to back on the caps of the u-joints, and subtract 3/4 inch for axle windup. If I'm off with any sizing, someone else can pipe up, but that's how I did it when I put a 700-(4R) in mine.
CONFUSED??? 400th is not a 27 spline yoke...The rear end is 27 spline yoke the 400TH has a big 32 spline output shaft. If it does not have this YOU do not have a 400TH...??? As far as length goes. Install all the parts then measure the length you need WITH the assistance of the drive line shop that will perform the shortening of the shaft. That way both of you are on the same page and you will measure to the DRIVE LINE shops specs. That is most important. Good luck and recheck the 350th / 400th rebuilt rear you have...??? o No: JIM JD
Stock set-up with a 455/400 combo on a '71/'72 car with 8.5" rear is 54.241" C to C on the universals. A stock '70 set up with the 8.2" rear is 55.10". Stock also refers to a short tail TH400.
As stated already; TH 400 and TH 350 have different spline count yoke and diameter. Are you sure you have a TH 400? If so, is it a long or short tail shaft TH 400 behind the 455? Long shaft trans will work but pinion angle can get compromised in the A Body. I suggest using a short shaft trans. A long shaft can be converted to short shaft. I also suggest if using an old drive shaft that you find a solid tube / one piece drive shaft for this project and not use the two piece drive shaft if that is what you have. The biggest factory tubes were from full size - mid sixties Pontiac but the BUICK one piece shafts are fine. Keep in mind the stresses imposed on these old drive shafts over the years and a 455 is going to really put that old drive shaft to work. You may want to apply the money you are going to pay a shop to work an old drive shaft over toward the $300 bucks for a brand new, one piece shaft that you will not need to worry about. Keep us posted.
Without knowing where you are in the conversion process...Here is some useful reference material. http://www.buickperformance.com/conversi.htm
My drive shaft shop has me measure from the back of transmission (not spline) to the front of the rear. He builds mine to length based on that measurement.
It is also important that the vehicle is sitting level and on its own weight (suspension) when that measurement is taken. So, if on jack stands, be sure they are not under the frame but under the differential and the front are is on a wheel ramp or the lower control arm.
thanks guys for all the advice...I was wondering since the trans had been rebuilt, maybe the guy that did the work used 350 parts...I read online that sometimes people do that...is there any way I can I.D the trans for sure...its a short tail...
here is a link for trans pan ID http://www.nastyz28.com/chevy-transmission-identification.php another- http://www.crankshaftcoalition.com/wiki/Transmission_identification
