Tranny trouble :(

[Dr. Righteous]

Was driving my Ramcharger around today and as I slowed down to make a right turn onto a street that was up hill I noticed a bad vibration. It was more like a slipping, rubbing sound. I never heard that before so when I stopped again I nailed it from a stop and there it was again! A loud RRRRRRRRUP accompied by a rattling vibration. It will not do it if you accelerate moderately. (NO IT ISN'T A TIRE SLIPPING)
It seems to be coming from the tranny but I am not enough of a transmission expert to say what it is.

Otherwise the truck runs fine and shifts smoothly.
If I nail it from a stop it seems to slip a bit between gear changes will full power applied. But, moderate acceleration it shifts chrisply and smoothly. Only in a taxing situation does it seem to act up. Now, this truck has a rebuilt 360 and it was originally a 318 truck It had 120k miles when I swapped to the 360. The torque converter is the original. It was built back in the summer and I have only just noticed the problem. The fluid is nice and red without a burned smell. I added a tranny cooler last summer because I planned on doing some towing. As far as tranny service there has been none since I have owned it. It seemed to be in good shape so I didn't suspect any problems.

Any ideas???

[cuda367]

Dr. Is it a 4x4 and if so full time? If yes to these questions, it may be the transfer case chain jumping. It has been a long time, but I think I pulled the frt drive shaft and then locked the transfer case to check for this. Hope I helped.

[Dr. Righteous]

The transfer case is a NP 208T which is a part time case.
Been thinking about the fact that the tranny on this beast has NEVER been look at most likely.
I think I will change the fluid and filter and eyeball things and look for metal particles int the pan. It wouldn't be a bad idea to go to a deeper pan with a drain plug but if someone knows of one for a more reasonable price than $50+ let me know.

[deadhorse66]

Not that this will have anything to do with your noise, but did you have the butterfly weight welded onto the converter? The 360 needs it to balance the reciprocating assy. Might want to check for metal near the rear of the case. Sounds like the sprag in the back of your trans might be letting loose or coming out of the case. They have been known to pull right out. Try putting the truck in manual low, and then subject it to the same conditions. If it doesn't make the noise when in manual low range, then it is probably the sprag. If not, it is probably the transfer case.

P.S.--if it is the sprag, the tranny will have to be dissassembled for repair. You can buy a bolt in sprag that is much stronger.

[Brian Mills]

Check your throttle pressure kick down rod from the carb. Mud and crap gets on the lever at the trans and won't let it move, can cause a similar situation depending where the lever stuck.

[Dr. Righteous]

The sprag is a thought.
Are the symptoms of a worn sprag driveline slop? I mean when going from forward to reverse you get a BANG! I know that isn't the u-joints, rearend, slipjoint or drive shaft. I have checked all those. The slop is at the output of the xfer case, but can it be the sprag. I tried to notice what gear I was in when I heard the RRRRMP noise and vibration and it is 2nd gear. But I also noticed when leaving relatively hard (but not WOT) from a stop it seems the tranny is hesitation putting the torque to the ground.