87zjeff

iTrader: (4)

anybody know what might cause a 700r4 output shaft to crack without high torque from the motor???? no wrecks....no neutral drop.....the second time it has happened.

KrisW

iTrader: (5)

yep

This would seem to be an engine mount/transmission mount/torque arm problem.

Also check all of the mounts at the rear end. The rear end moving up and down causes the driveshaft to move in and out on the output shaft splines. If the rear end goes too far up into the car too many times it really pushes hard on that shaft.

performabuilt

Thats a highly irregular failure. Usually I only see it in very very high HP aplications or in cases where someone completely blocks the accumulator for second . Has a shift kit been installed

87zjeff

iTrader: (4)

all of the above mentioned mounts are poly mounts and in good condition. all rear bushings are in good condition. has done it with the current 4th gen rear and the factory 9 bolt rear. i am also using a 4th gen aluminum driveshaft with the balancer this time. first time was with the factory driveshaft.

according to the dyno, the torque was about 330ft/lb....hp wasn't even that high. i have run a transgo shift kit for years. it is the only kind i will run.

Pro Built Automatics

How firm are the part throttle shifts? How firm are the WOT shifts?

87zjeff

iTrader: (4)

the only times the shifts were harsh was if it was a real slow take off like i was behind the proverbial little old lady. regular to aggressive acceleration was firm and quick but not harsh.



this current build has been in service for over 2 years and has been in two different cars since the last build. it was put in the current one last summer.


i was getting off the interstate were i had been going about 85mph and came to a stop. when i went to take off again, it wouldn't shift out of first. there were other things destroyed this time but i figure it started with the output shaft cracking. right before i got on the interstate, my shifts felt higher than normal but that was the only "warning sign" that i got.

Dr. Pepper

Post a picture of the cracks. Seeing where the cracks were formed and where they are running may gave insight as to how they were formed.

Maybe the bushings supporting your driveshaft and output shaft are loose and causing the shaft to bend. Is is possible your case or tailshaft housing are cracked and stressing the output shaft?

87zjeff

iTrader: (4)

the case and tail housing are both crack free. the crack started at the lube holes for the reaction shaft bushing. straight through both of them and down into the splines for the rear ring gear hub. i had to knock it off with a hammer.



i finished the rebuild last night so i'll have to see how it goes. gonna try to put it back in tonight.

Pro Built Automatics

The 1-2 shift being harsh at light throttle openings can do this. I would fix this asap if you do not want to do it again. The modified TransGo Performance Shift kit can solve this. Let me know if I can be of help?

87zjeff

iTrader: (4)

i appreciate it. i'm hoping it was something wrong with the valve body i was using. the first transgo kit i used didn't do this. i haev a different valve body, pump, and seperator plate and reworked all three of them so hopefully that will have solved the problem.

Pro Built Automatics

If you still have it apart, give me a call (909 7951876) and I will help out on the correct way of doing this. Dana

87zjeff

iTrader: (4)

the harsh shifts had to have had something to do with the valve body i was using. i got the tranny installed, took it for a test drive and it is smooth as silk. the shifts are smooth, firm, and quick without being harsh and jarring.

Dana, i appreciate the offer but i already had it together when i last posted. i had already scrapped the valve body i was using at work so it wouldn't make it into production so i can't go back looking at it. i may still give you a call monday to discuss your indidiual kits just for my own curiosity. i'll prolly call from work so don't think it's a sales call