Bellhousing Alignment Technique Question

[clm69z28]

Hi Jody, nice to hear from you as always with some good information on all things transmissions. You actually helped me rebuild my M22 a few years ago, it was my first transmission rebuild but you helped out with a lot of tech help and parts. Where I learned the importance of bellhousing alignment was that '69 Z that the M22 was in. Had a bad drivetrain buzz that I couldn't get rid of; checked drivetrain angles, balanced the driveshaft, shimmed the rear end, etc., etc. It wasn't until I checked the bellhousing and found out that it had been repaired-probably blew the clutch and welded it back together- that I found it was way off. Took a set of .014" dowels and some shims to straighten it out and, guess what, no more vibration. So I am a believer in always checking the alignment. If you don't have any vibration, lucky you. Chevy sure built a lot of cars without worrying about it too, but both of my Camaros have been out of alignment.

 

[bonedoc]

I am in the process of checking the alignment of my bellhousing and wondered what the appropriate technique for accounting for the end-play of the crankshaft? To reach a critical measurement for parallel alignment of .002" of less, how do you prevent the end-play from affecting that measurement as you rotate the engine to take the measurements?

And is there any accepted technique to measure the flywheel run-out on the car and the crank snout to determine if there is any run-out? This is being done while the engine is in the car. Thanks in advance for any responses.

what you mean, I believe is need to check if the transmission is exactly in line with the Flywheel. This is CRITICAL if your going to run a TREMEC transmission for the bearing in the input shaft is NOT conical like the old Muncie. If Tremec you need to check parallelism and run-out, both done with dial indicators and . Just go to Y-tube and look for Tremec alignment. Many good videos. If it a Muncie just bolt it up, especially if you running a stock clutch bell housing. If its an aftermarket scatter shield, many are not concentric, so I would do run out test and use if necessary off set dowel pins in the block.

 

[badazz81z28]

what you mean, I believe is need to check if the transmission is exactly in line with the Flywheel. This is CRITICAL if your going to run a TREMEC transmission for the bearing in the input shaft is NOT conical like the old Muncie. If Tremec you need to check parallelism and run-out, both done with dial indicators and . Just go to Y-tube and look for Tremec alignment. Many good videos. If it a Muncie just bolt it up, especially if you running a stock clutch bell housing. If its an aftermarket scatter shield, many are not concentric, so I would do run out test and use if necessary off set dowel pins in the block.

What are assembly lines doing for production vehicles? All the Mustangs, Camaros and Challengers?

 

[JodysTrans]

what you mean, I believe is need to check if the transmission is exactly in line with the Flywheel. This is CRITICAL if your going to run a TREMEC transmission for the bearing in the input shaft is NOT conical like the old Muncie. If Tremec you need to check parallelism and run-out, both done with dial indicators and . Just go to Y-tube and look for Tremec alignment. Many good videos. If it a Muncie just bolt it up, especially if you running a stock clutch bell housing. If its an aftermarket scatter shield, many are not concentric, so I would do run out test and use if necessary off set dowel pins in the block.

I was waiting for the Muncie alignment comment that so many post!

Yes, a Muncie front bearing is more forgiving on bellhousing mis-alignment than a Tremec install but, the pilot bushing doesn't care what transmission is behind it. If you're out of bellhousing alignment specs, you will have premature pilot bushing wear and shifting issues.

 

[Fbird]

What are assembly lines doing for production vehicles? All the Mustangs, Camaros and Challengers?

you might find it astonishing but even in MASS manufacturing the tolerances are quite small +/- .001 is NOT uncommon ...even in the masses!! and quite easy to maintain with the level of production inspection utilized.

 

[clm69z28]

I can only speak from personal experience, but both of my 50 plus year old cars needed to be adjusted to be within spec. One was probably due to a bad bellhousing repair and the other appears to be just out of tolerance, with what appears to be all factory parts. So I'm a believer, and the results in my '69 were dramatic. If you don't have any of the typical symptoms associated with this issue, then lucky you!

 

[badazz81z28]

I can only speak from personal experience, but both of my 50 plus year old cars needed to be adjusted to be within spec. One was probably due to a bad bellhousing repair and the other appears to be just out of tolerance, with what appears to be all factory parts. So I'm a believer, and the results in my '69 were dramatic. If you don't have any of the typical symptoms associated with this issue, then lucky you!

I have owned a handful of 4 speed cars, none of them had issues. I even ran a T56 behind a 454 with a 4 speed bell-housing and no issues. I don’t think it’s luck.

 

[C4Racer]

I skipped parallel alignment and went to runout - corrected everything and then checked parallel. It was pretty far off and Bowler recommended that I address it - so I added some really thin shims to the top few bolts of the bellhousing which brought the parallel alignment within spec. Of course then the runout was completely off so I had to redo that and it was tougher the second time. And luckily after getting that within spec the parallel hadn't changed. This is on a T56 magnum with a Quicktime bellhousing on a gen1 SBC. That bellhousing is supposed to be made to pretty good tolerance - I'm not so sure that's true or it could be my block - whatever the case.

I think with a LS motor you are better off as the factory block and bellhousing tolerance is much better than the old stuff - especially once you start machining the old blocks when building motors, etc.

I mean - you could get lucky - but my original set-up was really far off on both parallel and run-out - I mean really far off - I'm pretty sure it would have impacted the trans shifting or something. YMMV!!

 

[badazz81z28]

^^ it’s not the bellhousing, it’s the engine. I had my T56 Magnum on my LS6 and it required off-set dowels to move it up and to the driver side. When I put the whole assembly on the LS7 I needed more offset and moved it down. I think getting a steel bellhousing within a spec is way easier and consistency than that of a casted block. I have personally never checked parallel. I think the only way to do it right is to machine the face and back of the bellhousing to ensure flatness as I’m sure the powder coating thickness isn’t consistent nor perfectly flat. I haven’t experienced any shifting issues. Not saying right or wrong, just my opinion.

 

[C4Racer]

Ya - I agree it's the engine that's off. And I would expect these older blocks that have been machined a few different times to be worse than a new untouched LS block.

Parallel was easy to check - just use a dial indicator and take the reading at 12 - 3 - 6 - 9 on a clock.
My setup was good in the 3-9 direction but off on the 12-6 direction. The spec Tremec wants to see is pretty tight - no idea if that is really necessary. In my case I think all it took was 1 or 2 .005" shims on the top set of bolts between the bellhousing and the block. I just ordered generic shims from McMaster - didn't see anybody selling these specific for this purpose like they do the offset dowels.