How you got burned, or what expensive mistakes you've made

[ronh72c10]

I was inspired by a recent thread (TH400 Tailshaft differences? ) to start this topic in hopes that it might go into the faq to help people avoid common (or uncommon mistakes) you've made putting vehicles together, parts differences, etc.

Here's what I learned today. TH400 trannys come with at least two different kinds of tailshafts, the slip yoke kind and the bolt on kind. The bolt on kind of tailshaft will accept a slip on yoke but the yoke won't go all the way into the tranny because the splines aren't cut as deep. Thus messing up your driveshaft length and maybe leaving you without enough of the splines engaged when the suspension is at full droop.

Bring it on, some thoughts of things that might have burned others, short and long water pump related accessories, carb differences, headers...