Ok I'm a little confused on this topic. I have been told I need to find a specific one to match the 32 spline output shaft of the TH400 transmission that will match the smaller driveline of the 86' Cutlass driveline. Is there one that is made from a driveshaft or transmission website? Or does anyone on here have one for sale? The TH400 I have does not have a rear slip yoke on it but it was converted to the short tail. Just a little stumped on as to what I have to do to get it connected to the car. I know I have to shorten the driveshaft by .75" to 1" so this is my only hold up as far as tranny work goes. Thanks for any input I could get on this situation!!

 

Not sure if this helps or
will add to the confusion.

Years ago I put a drivetrain
out of a 75 Monte Carlo into
a 64 shortbed truck. I used the
64's driveline and had a bastard
U-joint made for it. It worked fine.

 

Well, since you didn't tell us if the trans was a TH400 or not, or what trans the driveshaft was originally set up for, or how that even applies to an 86 Cutlass, I vote for "adding to the confusion".

Now, to the original question:

Don't overthink this. The only part of your driveshaft that's "smaller" is the front yoke. Get a TH400 yoke - they are readily available. The TH400 yokes used different size U-joint cap diameters. Your driveshaft uses 1.125" OD U-joint caps. Just get a TH400 yoke with the same size and you can use the original U-joint. The 1971-76 full size cars with TH400 used yokes with this size, as one example. Alternately, get a TH400 yoke from an earlier car (68-72 Cutlii for example) and these have the 1.062" caps. In that case, simply get a conversion 1310 U-joint that has two large and two small caps.

This site has some useful U-joint info.

 

Good point Joe.
It was a 350/350 from the Monte.
replacing a 283 w/ pwrglide.