How does the T 10 compare in length to what you are taking out?

 

21 7/8 " same as the 3 speed i took out. should be no problem but drive shaft just wont go in. drive shaft was not in the car before. the drive shaft is 54 1/2 " center to center of u joints

 

Are you saying that the driveshaft YOKE will not go up into the T-10 tail housing all the way?
A bone stock driveshaft for a 57 3sp will be the SAME LENGTH as it would be for a T-10. If the yoke will go all the way into the 3sp tail housing, but the SAME yoke will not go all the way into the T-10 tail housing -------------- MOST PROBABLY ------------------ the T-10 tail shaft has been twisted. T-10 4spds with the 17spline tail shaft were quite common for having the tail shaft twisted. That is a main reason why transmissions went to the 27spline tail shaft in 63.
Unfortunately, I do not have a picture of a T-10 tail shaft that is twisted. The only picture I had of a twisted T-10 tail shaft was saved on Photobucket, and PB has hijacked all the pictures that I uploaded!!!!!!!!!!!!!!!!!!!!!! I wish someone would take the PB folks out behind the barn and give them a proper "education"!!!

 

Check to see if the yoke has the same number of splines as both transmission output shafts

 

^^^^ THIS

 

Transmission tail shaft splines UP THROUGH 62 were 16 (3sp, 3spOD, T-10, PG TG). In 63-later, the tail shaft splines were 27.
The Turbo 400, 71-later Muncies and Super T-10 had a larger tail shaft with 32 splines.

 

the yoke slides right in. same # of splines . drive shaft is too long. guess i will have to get it cut. stock motor and bell housing on stock mounts. i am confused but drive shaft just will not go in

 

Do you have the car sitting up on blocks like it will be at ride height makes a difference when the rear axle is at ride height especially on a lowered car also there are different length yokes I was able to change mine to a slightly longer yoke after switching from a t56 back to a 4l65e after thinking I was going to have to have a longer shaft made but the driveshaft shop reached up & grabbed a different yoke worked great but if all else fails & you have to have your shaft shortened usually Around $100 or so around here. Talk to the shop that’s going to shorten it ask how he wants you to measure.different shops have different ways

 

Just to clarify are you saying that the yoke will go all the way into the three speed but not the t10 if that is the case then 555mad I’m sure is correct I just a little confused if it’s going into the t10 all the way then your shaft is too long again if the car is at ride height is it possible this is the wrong shaft for the car or was this car together with the 3 speed & this driveshaft one other thing could the rear assembly been changed to something different than stock original. According to what (I just looked up the shaft appears to near the correct length it’s listed at 54” center to center of u joints)

 

this is my problem. stock engine stock bell housing stock rear all on stock mounts. drive shaft is just too long. not sure why. yoke will push further in but then there would be no free play. weight is on the rear wheels. i have put t10 in try 5s before with no issues. going to have shaft shortened i inch

 

That’s what you need to do simple enough if the car is lowered a lot that might be the difference ?

 

car has stock suspension but something has happened. just cant figure why the shaft is too long. oh well off to the drive shaft place tomorrow

 

is the car on jack stands with the rear end hanging free? if so that is part of the problem.