NV3500 Keeps cracking bellhousing

[Gerardo Soto]

I have 1996 Cheyenne 2wd. When I bought it, it had a sm465 4 speed but I decided to put a Nv3500 for some more top end. I have gone through 2 so far and the problem is that the bellhousing keeps cracking. 1st one got stuck in 3rd gear and bellhousing cracked, Picked the 2nd one up at a scrap yard bellhousing cracked open aswell but would not go into gear when the truck is on. OFF every gear would go in. It has the same flywheel as when it had the SM465 since flywheel I bought at Autozone had a different bolt patter. If anyone knows how to help please comment!

 

[JWOK]

What portion of the bell housing is cracking?
Does the truck have a bad vibration?
Did you change driveshafts with the swap and/or verify enough travel in the yoke?
Did you verify the proper pilot bearing/bushing was in place?
What engine does it have, has it been changed? - the replacement flywheel having wrong bolt pattern brings up that question.
Are the dowel pins still in place between engine and transmission?
The trans not going into gear when running after the bellhousing cracked would not be unusual. It is caused by a dragging clutch or pilot bearing/bushing which could definitely result from misalignment.
There are a number of possibile causes for a cracked bellhousing, just throwing out some questions that might help reach a conclusion.

 

[Gerardo Soto]

What portion of the bell housing is cracking?
Does the truck have a bad vibration?
Did you change driveshafts with the swap and/or verify enough travel in the yoke?
Did you verify the proper pilot bearing/bushing was in place?
What engine does it have, has it been changed? - the replacement flywheel having wrong bolt pattern brings up that question.
Are the dowel pins still in place between engine and transmission?
The trans not going into gear when running after the bellhousing cracked would not be unusual. It is caused by a dragging clutch or pilot bearing/bushing which could definitely result from misalignment.
There are a number of possibile causes for a cracked bellhousing, just throwing out some questions that might help reach a conclusion.

Thank you for your reply! i had the drive shaft lengthened and slip yoke changed so it would fit the new transmission. My truck has 350 5.7. first time bell housing cracked where starter is partially covered second time it cracked all around! I have not verified about the pilot/bushing placement.

 

[JWOK]

Any major vibration?

 

[Dropped88]

I actually had one busted all the way around bellhousing few months back I changed.

And it was a vibration from bad u joint. But a missing bellhousing bolt and nut missing on trans Mount didnt help

Like stated above do you have a vibration and also do you have any missing bolts

 

[Gerardo Soto]

Any major vibration?

there was vibration when i would go into 4th gear and 5th gear.

 

[F4U-1A]

Not that this may help. But I have been hammering my 96 2wd 5.7 Cheyenne for 24yrs. No injuries other then the F-ing mice my clutch grinds up and pukes out the bell housing every spring. Could it be harmonic motion issues? Drive shaft mating error. Point, mind came from Indiana it this configuration.

 

[Hipster]

What year 350/5.7 and what flywheel? Tbi and vortec engines are not internally balanced. An out of balance or the wrong flywheel is really hard on engine bearings and can make for lots of broken parts.

 

[JWOK]

there was vibration when i would go into 4th gear and 5th gear.

Was the vibration present with both transmissions that cracked? That may well be your smoking gun. A vibration in 4th and 5th gear suggests it is coming on with vehicle speed which would likely be an issue in the driveshaft. You should definitely look over the driveshaft to make sure the u-joints are centered and in good shape, clips are in place, you have the proper size u-joint for the rear axle, and get the balance checked. I have seen new driveshafts that were not balanced properly. If you bring it back to the same shop that built it and they say it is good, I would consider checking with another shop. Before having it balanced, make sure you have enough free travel in the yoke so that it is not bottoming out with suspension travel. While checking all this, you better check your rear axle yoke to make sure it is not loose.

You can usually narrow down a vibration as being engine/trans related vs driveshaft related by slowly revving engine up to normal cruise rpm while sitting still. If you pick up the vibration doing this, it is engine or trans. If not, it is usually driveshaft, u-joints, etc.

 

[Supercharged111]

How about the aforementioned dowel pins? The first thing that came to my mind was bell housing alignment.