[sherpa]

I am in the process of installing a borg warner st 10 4 speed into a 73 firebird which was originally an auto trans. I have been reading how important it is to use a dial indicator or the special purpose tool to center the bell housing with the crankshaft. If this is done what happens to the perfect alignment when the transmission is mated to the bell housing. Specifically, the 4 bolt holes on the trans are bored larger than the attaching bolts, doesn't this extra space between the bolt and bolt hole throw the alignment off again since the allowable tolerance is so small. It seems like the bell housing and crank are aligned but the trans is not aligned with the crank due to the play between the 4 bolt holes and the transmission. Comments welcome to help explain this question.

[TedRamAirII]

I believe the front bearing retainer centers in the bell housing for alignment. Critical alignment of components do not rely on the dimension of bolt holes. Of course I do not know how a T10 and that bell housing pair up. It should be a slip fit.

[sherpa]

You are correct, I completely overlooked the fact that the front of trans fits into center bore of bell housing which removes the bolt hole play from any impact on the alignment issue. Thanks for the reply.

[Tom Vaught]

Agree, the bolts just apply a clamping load to the trans and bellhousing, the input shaft collar registers the trans in relation to the bellhousing and crank centerline.

Tom V.

[fiedlerh]

It can be a pain because the input shaft splines have to go into the clutch disk splines, the nose of the input shaft has to go into the pilot bearing hole, the tranny front bearing retainer has to go through the throwout bearing and lastly the outer diameter of the front bearing retainer has to go into the hole in the bell housing. If all goes well, it all just slips in.

If you screw 4 pieces of all-thread (or long bolts the the heads cut off), it helps guide the transmission into place. This will help prevent accidentally hanging the weight of the tranny on the clutch disk.

[TedRamAirII]

Originally Posted by fiedlerh

It can be a pain because the input shaft splines have to go into the clutch disk splines, the nose of the input shaft has to go into the pilot bearing hole, the tranny front bearing retainer has to go through the throwout bearing and lastly the outer diameter of the front bearing retainer has to go into the hole in the bell housing. If all goes well, it all just slips in.

If you screw 4 pieces of all-thread (or long bolts the the heads cut off), it helps guide the transmission into place. This will help prevent accidentally hanging the weight of the tranny on the clutch disk.

One thing that may help is to have a yoke on the output shaft and have the trans in gear. Thay way you can turn the input shaft to line up the splines of the disc if needed, fine splines seem to just fall in while coarse splines sometimes need a little help.

[sherpa]

Thanks to all for the helpful comments.

[fiedlerh]

One thing that may help is to have a yoke on the output shaft and have the trans in gear.

Yep that helps. Also keeps you from getting gear oil all over yourself if you put the lube in ahead of time.

BTW, if you decide to add the lube later, an enema kit works well, but it takes a few hours to fill. Why the hell did I have an enema kit? It was supposed to be for a sigmoidoscopy, but I swear I never used it.

[sherpa]

Thanks for the tip on filling the trans. By the way, what is the best fluid to use and what is the proper amount.

[ANDYA]

The only gear oil you should use is a GL-4 rated oil. Brad Penn as well as some other manufacturers still make it. Stay away from modern GL-5 rated oils. They contain chlorine and sulphur which will dissolve the brass syncros in old manual transmissions.