Started losing driveshafts

[merc123]

It's an '02 GRT with a standard Bert transmission. We have ran it several times with no problems. It had a used, 38.5" aluminum drive shaft and the yoke had about a 4 1/2" spline length and new 1310 u-joints. I felt a low speed vibration that smoothed out with speed but I thought it was the track. I let off the gas and was just turning into the corner and the driveshaft broke the ears off at the quick change. The yoke/drive shaft was still sitting in the transmission, dragging on the ground. The u-joint was still attached to the quick change, just missing the caps where the d/s was.

Put another used aluminum driveshaft in it with a different yoke that had about a 4 3/4" spline length and had put a new 1350 u-joint in it and 1310 in the back. There was another low speed vibration that smoothed out when I got up just a little bit of speed so once again didn't think anything about it. On the 2nd lap, on the gas in the middle of the corner the d/s came out again. It didn't break the ears off but warped one of them. Yoke was still in tranny with u-joint and u-joint on q/c still attached.

We're thinking it's because we're using used, aluminum drive shafts and maybe the locks aren't seating right. We did tap them in to the grooves with a screw driver. I also noticed the bushing in the tail shaft was pulled out about a 1/4" but the housing is a little worn as the bushing slipped in pretty easy when we replaced it. The yoke is pretty tight in the bushing though. It's pretty easy to push onto the shaft until you get to the bushing and it is a tight fit in the bushing. No marks on the yoke indicating any burrs or bad spots on the inside of the bushing.

What could be causing it?

[twisterf5]

It's an '02 GRT with a standard Bert transmission. We have ran it several times with no problems. It had a used, 38.5" aluminum drive shaft and the yoke had about a 4 1/2" spline length and new 1310 u-joints. I felt a low speed vibration that smoothed out with speed but I thought it was the track. I let off the gas and was just turning into the corner and the driveshaft broke the ears off at the quick change. The yoke/drive shaft was still sitting in the transmission, dragging on the ground. The u-joint was still attached to the quick change, just missing the caps where the d/s was.

Put another used aluminum driveshaft in it with a different yoke that had about a 4 3/4" spline length and had put a new 1350 u-joint in it and 1310 in the back. There was another low speed vibration that smoothed out when I got up just a little bit of speed so once again didn't think anything about it. On the 2nd lap, on the gas in the middle of the corner the d/s came out again. It didn't break the ears off but warped one of them. Yoke was still in tranny with u-joint and u-joint on q/c still attached.

We're thinking it's because we're using used, aluminum drive shafts and maybe the locks aren't seating right. We did tap them in to the grooves with a screw driver. I also noticed the bushing in the tail shaft was pulled out about a 1/4" but the housing is a little worn as the bushing slipped in pretty easy when we replaced it. The yoke is pretty tight in the bushing though. It's pretty easy to push onto the shaft until you get to the bushing and it is a tight fit in the bushing. No marks on the yoke indicating any burrs or bad spots on the inside of the bushing.

What could be causing it?
to much pinion angle or to soft 6th/braking spring. if it go's away on gas that is when you loose pinion angle let off gas then you are on 6th spring then hit the brakes and you can gain more angle. you may think you dont have alot but add in if the engine is in to high then you will brake them like you are. hope this helps

[merc123]

Why did it just start now? Car ran many races before I bought it with the same stuff (springs/shocks)


What's a good way to check pinion angle under braking or a good pinion angle to have?

[twisterf5]

Why did it just start now? Car ran many races before I bought it with the same stuff (springs/shocks)


What's a good way to check pinion angle under braking or a good pinion angle to have?
was it race ready???
ride highs
lot of factors more bite now, was the old driver heaver did some one raise left side if you are using your engine did you use spacers did they use them or not. i try not to go over 7 pinion angle at ride.lowes sells a cheap angle finder. make sure driver is in car slide under back find a flat spot on j-bar pinion mount and check it there. you can gain a few degree's or more under braking make sure braking spring is not worn out. unless you bought that car strait from the track race ready.most cars that are sold will end up having some older parts put on them. best way pull your door off look at the engine to the rear end and see if the drive shaft is going down hill should try to keep as level as you can.i would bet it is in you 5th and 6th springs back off 5th tighten up 6th a few turns then re set your 5th do that until you get 6/7 degrees

[merc123]

Only thing it didn't have was tranny/driveshaft. Other than that the ride heights are the same. Driver was lighter by about 30 pounds. All the engine spacers were still there and we used them. Basically all I did was drop in motor, tranny, driveshaft and scaled it and took bite out of the car from what they had. Also moved one bar up a hole on top birdcage.

We'll give it a shot and see what we come up with on pinion angle.

[speedbuggy]

"stock car driver
Senior Member

Join Date
Jul 2007
Posts
2,398

could be a bent pinion, use a dial indicator and check the run out on it.. "


What SCD said....pinion or yoke either one...


My "Reply with Quote" button don't work no more...anybody else having this problem?

[speedbuggy]

3 clicks to use quote now it used to be 2 I think.

three clicks worked

that's weird. thx

[merc123]

Guess I need to check the run out of pinion then. Apparently the pinion angle was checked at 6*. I didn't know it

[Spbulldog]

Check bushings and bolts on rear end. Sounds like rear end is rotating and pulling driveshaft out

[merc123]

Pinion angle was fine. Bought a brand new steel wiles driveshaft and fixed the issue. I was using used aluminum a and guess the lock channels weren't sitting right.

[mod watcher]

Check to see if the rearend is tight when you spin by hand , we had a pinion nut tighten up and kept breaking driveshafts .