Why do you have to dial in an aftemarket bell housing? I didn't think GM dialed there factory bell housings in did they?

It helps keep the centerlines of the crankshaft and transmission in alignment. GM probably didn't 'center' the bellhousings on assembly.

The General's manufacturing process allowed the b/housing to be made in one 'sitting' on the machine therefore keeping the production tolerances to a mininum. Most aftermarket processes have the b/housing being moved from its original clamping to machine other surfaces. Hence, the machinist has to relocat the b/housing.

It certainly doesn't hurt to "dial-in" an OEM b/housing.

You don't have to, just be ready to take the consiquences (sp) if you don't. I just did mine and it was a major pain but I felt it was well worth it when I was done. It has to be much better for the entire drive train if everything runs true. Just bite the bullet and do it...besides you will learn a lot graemlins/thumbsup.gif

Dan.

Thanks for your replies.
I was just trying to figure out why the aftermarket b/housing wasn’t made with more accuracy. I do know the consequences. graemlins/clonk.gif I Installed an aftermarket b/housing a number of years ago only to get about 500 miles out of the clutch. At that time I had no idea that the even made offset pins. I now plan on using the original one.
graemlins/beers.gif

Jerry

If you need pins, make sure you use the Moroso pins. The Lakewood pins are to short. Ask me how I know. graemlins/clonk.gif

Dan.

Dont naturally assume that the aftermarket bellhousings are entirely at fault, ever think about what happens when you line bore or line hone a block? As only the caps are cut on the parting line, when the block is align bored or honed it moves the crankshaft centreline up towards the camshaft, also i have seen blocks were the rear flange is not 90 degrees to the crank centreline ( harder to repair as the block must be machined in a mill ) Makes a big differnce on the 4th gear ( input) dog teeth when they are centered. GM bellhousings are usually very close. Hope this helps.

rszmjt, you bring a couple good points, you must have been there at one time.......

Hello Everett, Yea i have been there ( at the drags ) for about 31 years, and still am. I have Blown up Lots of manual trans stuff, and i learned about bellhousing alignment 20 years ago after breaking lots of Liberty Pro Shifted gears. I now use a Lenco, but i still check the bellhousing alignment, trust me its worth it. ( $$$$$$$$$$$$$$$$$ and FRUSTRATION )