Checking bellhousing runout

I know Richmond and Tremec require checking the bellhousing runout to prevent premature failure of the input shaft bearing. But it seems no one makes a big deal about checking it for a Muncie.
Are they that forgiving of slop?
I've corrected runout before, it's not that big of a deal, just kind of a PITA.
Should I check/correct it for the Muncie or not worry about it?

yeah, sloppy input but I would do it anyway, it's not a big deal and knowing where things at is a reassurance.

Automatic Transmissions Can Benefit Also...

I had a challenging problem last year with an automatic trans - when the trans was bolted to the engine, the torque converter was in a bind - not good! :smash:

After exhausting the normal solutions like ensuring that the pump halves were aligned, the pump was concentric with the case, the TC was fully seated and the snout of the TC was free of paint, nothing seemed to help so I resolved to measure the runout by attaching a dial indicator to the flex plate and mapping the radial measurement from the stator support. Here's a few pics to illustrate...







After inputting the data into Excel, here's what I found...



When I replaced the stock alignment dowels with offset dowels to effect a shift of .028", the TC rotated freely, and has survived very well in dozens of drag strip passes well into the 11 second zone.

Cheers!

larrywalk said:

I had a challenging problem last year with an automatic trans - when the trans was bolted to the engine, the torque converter was in a bind - not good! :smash:

After exhausting the normal solutions like ensuring that the pump halves were aligned, the pump was concentric with the case, the TC was fully seated and the snout of the TC was free of paint, nothing seemed to help so I resolved to measure the runout by attaching a dial indicator to the flex plate and mapping the radial measurement from the stator support. Here's a few pics to illustrate...


When I replaced the stock alignment dowels with offset dowels to effect a shift of .028", the TC rotated freely, and has survived very well in dozens of drag strip passes well into the 11 second zone.

Cheers!

Click to expand...

did you ever determine WHO was off kilter there?? someone was not home, obviously.....

engine or tranny??

I've made two Muncie installations using the stock bellhousing and stock transmission. Never made any tolerance measurements, just bolted them together- no problem.

I did bolt up a Muncie to a Lakewood scattershield without doing the tolerance measurement. ....results...one destroyed Muncie (input shaft bearing). This was 35 years ago!! When I bought another Lakewood scattershield in 2004 (?) the install instructions said to perform this measurement and weld in a dowel pin to align the scattershield with the engine. After all these years, why didn't Lakewood just manufacture their scattershield with accurate dimensions?

Am I correct in thinking that the McLeod bellhousings are dimensionally correct? At least more correct than Lakewood?

68/70Vette said:

I've made two Muncie installations using the stock bellhousing and stock transmission. Never made any tolerance measurements, just bolted them together- no problem.

I did bolt up a Muncie to a Lakewood scattershield without doing the tolerance measurement. ....results...one destroyed Muncie (input shaft bearing). This was 35 years ago!! When I bought another Lakewood scattershield in 2004 (?) the install instructions said to perform this measurement and weld in a dowel pin to align the scattershield with the engine. After all these years, why didn't Lakewood just manufacture their scattershield with accurate dimensions?

Am I correct in thinking that the McLeod bellhousings are dimensionally correct? At least more correct than Lakewood?

Click to expand...

WTF, if GM can stamp out 50 billion engines/tranny combos over 100 years and have a near zero on that off set thing....

what is so hard for others to do??

:hunter:

It's getting bolted to a new 621 bell housing, but they're probably made in china these days. I guess I'll measure it...dammit.
But I think even the chinese could do better than 0.028. I didn't even think offset dowels were available over 0.010

mrvette said:

did you ever determine WHO was off kilter there?? someone was not home, obviously.....

engine or tranny??

Click to expand...

I measured the distance from the rear crank journal (as it exits the block) to the edge of the dowel pins, but since it was greater than my dial caliper, it had to be done with an engineering rule. Could not determine any significant difference so I'm guessing that the run-out was the trans case.

Since I had just rebuilt the TH350, I didn't want to pull it apart again to dial-indicate the case with a dial indicator against the bore wall of the recess for the front pump. So... I figured out that checking the stator support would work as well.

I called a well-known trans engineering company for clues before doing the measuring and asked if the case could have been tweaked due to a previous failure of the intermediate sprag (but not the race) - they said that the case probably would have cracked instead of being tweaked.

I won't know for sure which is the culprit until I pull the trans and dial-in another bellhousing with this engine. Regardless, having the alignment right-on is sweet! I'm a believer and will do this in any future build-ups, auto or manual!

:drink:

50 years working on cars, I have HEARD of these troubles, but never had the experience personally....hence my questions....

:gurney::drink:

Garys 68 said:

It's getting bolted to a new 621 bell housing, but they're probably made in china these days. I guess I'll measure it...dammit.
But I think even the chinese could do better than 0.028. I didn't even think offset dowels were available over 0.010

Click to expand...

I believe the GM bellhousings were close to perfect, I was also told the Chinese CM bells were cast in China but machined here by different shops...I have a nice genuine GM #621 if anyone is interested, I also have a very clean #444 that needs a 1" weld..

Glad I checked, it was out 0.020. Guessing that's a lot for even a muncie. Thanks for everyones input.

Garys 68 said:

Glad I checked, it was out 0.020. Guessing that's a lot for even a muncie. Thanks for everyones input.

Click to expand...

don`t blame the trans, blame that offshore bellhousing. genuine GM bellhousings are remarkably close.