neat

I broke the drivers side rear spindle last night at the drag strip. I don't really understand how I broke it. My car is basically a stock L98 with a 100 shot. On the juice it is making mid 300's for HP and high 400's for TQ at the wheels. I have a McLeod twin disk clutch, stock black tag ZF6, spicer U-joints that were cryo'd by a local company back when I lived in Utah, half and main shafts are Jeb Burnett cryo'd, stock D44, and the spindles are Jeb Burnett cryo'd. I am running 275-40/17 M/T ET street radials. The car has been to the track twice on the MT tires, and never gone sub 1.9 sixty foot times. Tonight was the second night on the M/T tires. I made my first pass on motor, after a lengthy burnout I slipped the clutch to a 2.2 sixty foot time. I pulled around again, backed into the water, did a 1-2 rotation spin, and pulled out of the water box. When the car infront of me got to about the 330 foot mark the starter gave me the signal to do my burnout. I ran it up to about 3k and dropped the clutch while flooring the throttle. The McLeod bit hard, and there was a loud clank, crunch, crunch, crunch sound. The tires never even spun. Maybe 1/3 a rotation, no more.

Could wheel hop cause this? I don't beleive I am experiencing any wheel hop, but I've never had the launch videod or anything. What about rear alignment?

Anyway, after I broke the spindle the car would not move. If I eased the clutch out it tried to move slightly, then stopped and made another crunching noise. That leads me to believe the posi unti has failed.

I got it towed home and discovered that both half shafts were turning when I spun the drive shaft, but the drivers side wheel would not turn. That makes sense with the broken spindle. I am afraid that the posi-traction unit has let go and it transferred all the torque to one wheel, and that's why the spindle broke. I pulled the batwing tonight and all the gears inside look fine. There were no chipped or missing teeth on the ring, pinion, or spider gears. There was no metal filings or chunks in the fluid or the bottom of the case. The diff turns pretty easily when I turn the drive train, and it seems to be operating smoothly.

Is there a way to determine if the posi unit is functioning properly? I dont' have a problem replacing it if it is bad, but I don't want to replace parts that I don't have too.

Thoughts?

CFI-EFI

I don't see it in my 1984 FSM, but in other FSMs, I have seen a procedure that involves noting the amount of torque required to turn one wheel, while the other wheel can't turn, such as when it is on the ground. If, with one wheel locked up, you can easily turn the other, I'd say the posi clutches need replacing.

RACE ON!!!

anesthes

A stock L98 and a 100 shot put's you in the "11 second club" ?? Dang.. I'm glad I bought a vette.

The procedure calls for the vehicle to be in gear, one wheel on ground, and using a tool that slips over the wheel, then a torque wrench (beam style). You measure how much torque it takes to rotate. I have the specs at the shop I can post later if noone else does.

-- Joe

CentralCoaster

If I recall its more than your standard torque wrench can handle. Remember, the car is putting down about 3,000 ft-lbs of torque onto the rear axles on launch.

neat

The other car in my sig went in the 11's not the 91. 11.88 @ 121 MPH 4400 feet above sea level, over 7,000 elevation if you use density altitude. Back to topic now...

So with out special tools that attach to the wheel, and a special ultra heavy duty torque wrench, it can't be done?

C4DC

I do know that if there is no toruqe on one axle, it will spin freely if the clutch is released. There needs to be a certain amount of resistance on the slipping side to engage the lsd clutchpacks. Same thing happened to another member here when we were at the track. Tried to do a burnout and the tires deadhooked and broke a spindle. Had to push the car off the track. Now if you have a true positraction, none of this will apply, but you didn't say this in your original post. I'd think you could just replace the spindle and go from there.

neat

I have the drivers side half shaft out. I am going to put the car in gear and set the brake, then put a strap wrench on the output yoke of the D44 on the drivers side and see if it'll turn.

New spindle is on it's way, thanks Jeb Burnett.

I think I may have found the culprit. The spindle nut was only finger tight. Do you guys think that could cause the spindle to twist like this?

neat

Here's some pics:

neat

Another...

neat

Last one...

anesthes

Heavy duty? No way. The spec for the auburn in my '91 was 35lbs. I havn't been to my shop yet, but I can't imagine the unit in the dana44 having much more.

http://www.thirdgen.org/techboard/tr...+torque+wrench
http://www.thirdgen.org/techboard/tr...+torque+wrench

Seems like 35-40 foot lbs to break it loose seems common on the GM/auburn posi's.

I'll scan the page from the service manual in the AM if noone else will.

-- Joe

anesthes

Finger tight when the shaft was 1 pc, or finger tight now that there is no load on it because it's broke in half? If I recall, those nuts are non locking and will go all the way on with a pinky. The torque comes from loading up and stretching the axle.

ANyway, I've broken a ton of halve shafts just like you did in various 4x4s from bad wheel bearings. Hows the bearing?

-- Joe

neat

Doh, finger tight now that the shaft is broken.

The wheel bearing is shot. There's 1/2 inch of play or more in the hub. That could be what killed the spindle for sure.

anesthes

They always seem to break the same way, no matter what car they are in.

Good luck with it!

-- Joe

DVNCI

neat - busted my passenger side spindle friday night at drag strip - first pass

But I'm pretty much sure it was because my wheel bearings were shot, I bet your posi is fine