Breaking bell housings

[jbt352]

1977 Chevy Malibu,stock rear supspension with urethane control arm bushings.
Small block running 13:60/13:80's(1/4 mile)
4:11 gear.
turbo 350.
leaves nice.
Rubber trans mount.
Solid motor mounts.
Car does not twist when it leaves(not enough power).
No vibrations, car feels smooth.
I have not checked the pinoin angle yet.
Why would this thing break the bell housing????
Any ideas would be great.

[HandOverFist]

How long have you owned the transmission? Possibly was cracked in another application?

[Mike Pearson]

Get rid of the rubber mount. cut the broken bell housing off and put an ultra bell on your trans.

[Alan Roehrich]

I would never use a steel or solid mount on a transmission. I've put in dozens of race car transmissions.

I use an ordinary stock replacement mount, with two radiator hose clamps around it as a safety device. Or a urethane mount. In 30 years of working race cars, including a lot of years as the person in charge of race car work in a well respected transmission shop, I have never seen a properly installed rubber or urethane transmission mount cause a broken case. But I have stopped several cars from breaking cases by replacing a steel mount with a correctly installed rubber or urethane mount.

If I'm not using motor plates, I use urethane mounts, or one steel mount on the driver's side and a urethane mount on the passenger side.

You do have flex, a vibration, or a misalignment. You may not have it identified, but it is there.

Adding a bolt on bellhousing merely moves the weak point to the case behind the pump, and when it breaks there, it will dump fluid under your tires.

[Jim B]

Another item to check would be to make sure the driveshaft slip yoke is not bottoming out against the output shaft splines. (Manually move the driveshaft forwards and backwards from the rear u-joint and make sure the driveshaft is not too long or too short) Make sure there are no broken/damaged rear suspension components that would allow the rear to move forward or rotate on the leave. I also assume the shaft length to tubing diameter/wall thickness combination and straightness are not causing a harmonic whip. (mostly seen in an insufficient driveshaft length to tubing diameter relationship) Also any history of cracked flex plates? It wouldn't hurt to check the pinion angle.

[Jim Kaekel]

Personally, I would ditch the steel motor mounts and replace them with stock units. I believe either all steel, or all rubber mounts. Then, install a torque strap on the left front of the engine.

[Alan Nyhus]

Another culprit can be the bellhousing dowel pins, if they've been changed. Some of the after market extra length pins are a bit bigger i.d. than the factory ones, causing the case to be stressed when bolted to the block. -Al

[Jeff Niceswanger]

Rossler has told me many times, that too much pinion angle breaks transmissions more than anything. He must see a lot of that.....

[jbt352]

Originally Posted by Jeff Niceswanger

Rossler has told me many times, that too much pinion angle breaks transmissions more than anything. He must see a lot of that.....

Jeff I agree .


This is my sons car, I ran a full body 69 Chevelle with a big block and turbo 400. The car went 12:00-12:30 with stock suspension. The car would twist and pull both wheels,and I never broke a tranny in all the years I ran it.
It had solid mounts up front and rubber at the trans.
This car should not have an issue going mid to high 13's.
Talked to the old owner of this car and he had the same problem.
We put the tranny in 3 years ago.
We need to keep looking.

[Lee Valentine]

Broke 4 TH-200's in my son's 85 Camaro, had solid motor mounts and rubber trans mount. Tried different driveshafts ,solid trans mount,new renforced crossmember,different transmission, brace on case etc. Finally put all stock mounts on engine and trans and never broke another case in 7 years.