Any luck straightening bent mainshafts?

[ChrisBennet]

Hi everyone,
I think the mainshaft is bent on my 915. The input shaft seal started leaking a few hundred miles after an accident. I replaced the seal and a few hunder miles later, it's leaking again. Does this sound like a bent mainshaft or something else?
If it is bent, can I wack it straight? Should I have a machinist do it?
I understand that if the runout is too large I'll need to replace it but I'm hoping that's not the case.
-Chris

[BGCarrera32]

Oy, excuse the ignorance, but how would it have gotten bent? I'm assuming you put some oil on the o-ring seal before you reinstalled it...spinning it up dry might have torn it?? Just a thought...

Pulling it out and slowly spinning it in a swept in lathe while running a dial indicator across would tell you for sure. I can't imagine hammering it back straight if it was bent...and turning material off obviously isn't an option...

Any possibilty of in/out (fore/aft) excessive play that could be screwing up the seal?

-BG

[Jim Sims]

I seem to recall the factory shop manual described a straightening procedure for this shaft. Another possibilty is that the area on the shaft where the seal runs is excessively worn. One could possibly move the seal slightly so it runs of a different part of the shaft. Cheers, Jim

[ChrisBennet]

BG,
Frankly, I don't see how the shaft could get bent by the accident but it started leaking soon after so I thought I'd throw that in.
-Chris

[Formerly Steve Wilkinson]

Gary Fairbanks, in Norwalk, Connecticut, straightened mine (915, '83 SC) and he said it was "the worst one he'd ever fixed." Went out and bought a huge bronze mallet of some sort and I think he simply put it on a milling surface and gave it one mighty whack. Send it to Gary. He's the best. Been working perfectly for the last 4,500 miles, street and track, and the modified engine just dynoed at 280 hp at the flywheel.

Stephan

[ChrisBennet]

Stephan,
Thanks. I used to by my transmission parts from Gary. He's quite the people person on the phone.
-Chris

[BGCarrera32]

Chris, did you ever get the "bearings spinning in the case" issue resolved? If so, what ended up happening?

-BG

[ChrisBennet]

Originally posted by BGCarrera32
Chris, did you ever get the "bearings spinning in the case" issue resolved? If so, what ended up happening?

-BG

(Transmission bearings tend to pound the races loose in the case and I've seen this in a few transmissions I've worked on.)
There is no inexpensive cure for this AFIK. The Wevo/Windrush bearing retainer would seem to be a solution but Wevo actually posted that it isn't a fix. You can replace the tranmission case diff case ($4-500) or have Wevo fix it ($900).
On the plus side, the bearing races are fine in my own transmission.
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-Chris

[Geary]

It's a pretty common procedure to straighten in a hydraulic press, and check runout on a pair of V-blocks. (There should be a ground area on the shaft specifically for the dial indicator.)