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Author Topic:   Broken Drive Train
Robert Carson
posted October 15, 2002 01:42 PM           
Trying to figure out what happened: Limited Late Model, stock front clip actually full frame car, multi-leaf, solid engine mounts, engine-to-tranny mid-plate, T350, rear tranny brace (brace is constructed out of square tubing with 2 rubber “doughnuts” that the tranny rests on), stock drive shaft, 9” rear end. Been running this set-up for 1.5 seasons. Have cracked bell housing twice now. 1st time thought it was fluke (my mistake for assuming maybe uh?).

Last weekend was last points race of season. 1st time out since recently rebuilding tranny (new pump & planetary). Started on pole in heat race, race went green, made it to flag stand when loud “CRACK/POP” & I coasted to stop all the way around track to pit exit.

Results: bell housing cracked totally in 2 from driver to passenger side, drive shaft twisted in two, pinion gear snapped in two behind yoke, went from finishing season 6th in points to 7th.

Any ideas as to where to start looking?

posted October 15, 2002 02:55 PM
Ive seen tranny's blow apart because there was not enough slip yoke left on the drive line yolk. when you car gets a bite, it will try to drive the drive shaft thru the tranny. I run 1 1/2 inches of slip.

Robert Carson
posted October 15, 2002 03:01 PM           
It's a possibility that I've been considering. I tend to discount it 'cuz I've basically been running the same set-up for more than 25 races.

BUT, maybe I shouldn't (discount it that is) due to the fact I recently made a change: heavier left leaf.

Appreciate the reply & I'm still researching

posted October 15, 2002 04:11 PM
I have had the same situation happen to me and was not able to pin point the exact culprit. I talked with my trani guy and he said because of the mid plate the stock dowel pins do not locate the trani very well.
He suggested that I remove the pins and replace with longer 2 inch. I have done this but still question it because as you I ran a full season with no problems. I still think installing longer dowel pins makes sense.

posted October 15, 2002 04:23 PM
did you change your pinion angle when you added the leaf? that might have lessened your slip

posted October 15, 2002 11:49 PM
How much of your yolk is showing? I'll bet 311 is right on.

[This message has been edited by Wauge28 (edited October 15, 2002).]

Robert Carson
posted October 16, 2002 11:02 AM           
Appreciate all the replies. Taking everything into consideration.

To "Car311": when I changed the leaf, I replaced the whole multi-leaf, didn't just add a leaf. And I measured the eye-to-eye length & arch and compared to the leaf I was replacing. They were the same. As far as yoke length, it's been the same for 20+ races; however, I'm dropping the tranny off at tranny sponsor to be thoroughly checked out. Plan to have them check for evidence of the drive shaft driving through tranny.

To "Leftturn73": will bounce that option of the tranny sponsor. Fortunately, he's been involved in dirt track racing (driver & owner) for 30+ years, so I'm hoping he can come up with the reason. But as far aslining the tranny up to the dowel pins and mount, I try to take my time and do it in such a manner as to not put anything in a bind.

Also, the shop that built(and is now repairing) the 9" suspects the driveshaft failed & initiated the failures.