Even though the post is 4 years old I want to make sure that anyone searching for information in the future on this swap knows that you MUST use the original yolk from the T5.
As any transmission is used the yolk and tail shaft bearing wear together and must be used toghether from then on. If you take a used T5 and throw in any yolk but the original one, you will have leakage and vibration issues.
Ask me how I know...
For those that will flame me, go over to Mustang Forums and search for a thread by "Gun Jam" called Pinion or driveline angle.
He has the dreaded post T5 swap vibration issue, just like I do, and guess what solved it after trying everything else...a new tail shaft bearing and new yolk.
I agree that if your slip yoke is a worn-out, rusty POS it should be replaced. However, despite what many parts suppliers say, there is no such thing as a "T5 conversion slip yoke". The T5 uses the exact same 28 spline pattern with the same outside diameter as any 3.03 3-speed, C4 automatic, or 28 spline 4-speed transmission. There is nothing special about the T5 slip yoke.
No matter what trans you have, if you have the slip yoke out for any reason, and it's not in perfect shape, replace it. It's not like they're hard to find, new.
When replacing the slip yoke, you're doing it because it's worn or corroded, usually both. It is essential that you replace not only the seal, but the slip yoke bushing, too. As with the slip yoke, the 3.03 3-speed, C4 automatic, 28 spline 4-speed use the same seal and bushing. They are cheap, at most $25 for the set, so don't be stingy for a few bucks. Fortunately, with the right tools, this can be done in the car, in less than two hours. If your mechanic wants to charge more than two hours, and claims the trans has to come out or apart, find a more competent mechanic.
