Broken Bellhousings from the Alfa Digest v5-174

From: DRM dmiller@totcon.com
Date: Mon, 03 Nov 1997 22:34:46 -0500
Subject: Broken Bellhousings

In answer to the gentleman with the broken bell housings...

I'm surprised that, Steve Piantieri, hasn't jumped on this one yet. We have a whole pile of broken bell housings in the corner of his shop from his Spider race car. We are using the high HP starter with the earlier ring gear, but I think all it's doing is tearing up the starter drive. We tried bracing the starter with brackets, replacing motor mounts, polishing flanges, truing mating surfaces and even welding gusset plates all over the front of the bell housing. Still... hairline cracks developed everywhere (especially around the starter). Sometimes we'd catch them early, and other times he would lose the clutch during the race because it was trying to separate the engine and transmission. Bell housings are a pain in the a__ to change in the Ant infested grass at the track.

Getting to the point... I think we finally found the problem. The pilot bushing on the front of the drive shaft fits over a ball on the end of the transmission output shaft. There was a flat spot on one side of this ball and the drive shaft would only center at certain (lower) RPM's and really vibrate (high freq) at high RPM's.

Steve said the car felt incredibly smooth and quiet after this repair. It had worn so slowly he hadn't really felt it. We haven't broken a bellhousing since the fix. (knock on wood) I'm not sure how many races, but certainly more than twice as many as we were able to before.

I can't tell you the time spent "head scratching" and the untold hours wasted trying to modify and strengthen. Check it out. It's worth a try. Please post your findings.

Dave Miller dmiller@totcon.com Deltona, Florida USA

Taking a stab at the cracked bell housing on the spider:

Growing up in Portland, Oregon, I spent many an afternoon getting parts and advice from David Rugh (Rugh Engineering). I remember him showing me the cause of a chronic bell housing failure - the output shaft of the transmission.

Initial syptoms were loose fasteners between the bell housing and the engine. After double nutting these, I pretty sure the next symptom was cracking of the bell housing.

Anyway, the root cause was that the output shaft on the transmission. It has a ball on it. This ball allows the donut to be centered while the short part of the driveline and the transmission fall out of alignment (axial alignment). The short shaft has a hard steel "socket" pressed into it which is filled with grease and protected with a lip seal. After the grease goes away, the "socket" wears a flat spot on the ball end of the shaft (which is soft) and consequently sets up a vibration that leads to cracking and loose fasteners. Dave had found a way to fix the shafts and harden the area to give better life.

For most of use, the fix requires a new mainshaft (output section) for the transmission. Better yet, just buy a used transmission (with a good end!) and when you install it, make sure that this "socket" is greased and SEALED.

Thats my guess.

For those with Milanos or GTV-6's the ball end detail can be found at the input shaft of the transaxle. Same function, centers the donut. This one also has a lip seal and should be greased. The engine donut also has a centering feature (slightly different design) which is greased and sealed. If your front donut fails, you should replace this seal also and regrease. Else the car may never be as smooth as when Alfa shipped it out.

Erik Roe
Alfa Romeo Owners of Oregon

Capital page

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1997