colesdad

After reviewing the previous owners repair records I see the tranny was installed at 181K The truck now has 256K but according to the old owner the tranny has had this problem (jumps out of 5th gear) since somewhere around 225K. The mechanic who has maintained the truck for the old owner since 70K thought it was "the problem" he heard about with the Dodge trans jumping out of 5th gear and would get the repair kit and fix it when the old owner got around to bringing it back in. Problem was that the old owner only drove around town and never used 5th gear....... work went undone for a year and a half. THEN...... when it became important to get it fixed (so I could buy it) they discovered that the fix was for the NV4500. Apparently the mech went in and "re-tightened" a nut that holds 5th gear on and hoped for the best.

The tranny is a Getrag 360 and it jumps out of 5th gear upon deceleration, most of the time when the road is a little rough. If the road is very smooth and it is a gentle deceleration it stays in gear, but that is probably only 30% of the time at best.

Here is my question, (I know what the problems are caused from when the NV4500 jumps out of 5th gear but) what would cause a Getrag to do that? It even has a rivited tag on the trans that says "reconditioned" so I know the rebuild happened as claimed.

Does anyone have an idea of what it is going to take to repair this tranny so it doesn't jump out of gear?

CG98x

My 90 did this and it was due to a worn pocket bearing on the mainshaft. It allowed the mainshaft to move more than 1/8". I stuck new bearings in it and all was well.

colesdad

Thanks for the reply, I will mention that to the mechanic, I'm sure he is going to be talking to the business who rebuilt this tranny. Wouldn't it be nice if they repaired it under warranty...

stillsmokin

You might have a bad sliding sleeve or engagement teeth on 5th. Also detent springs/ball problems in the sliding sleeve. There might be problems with the shift rail/detents or a worn/bent shift fork in the top cover.

The bearing problem could do it too but I'd guess for the few above to be more likely in a hopout condition as you describe.

BearKiller

In 1991, driving a new 91 Dodge/Cummins D-350, pulling a big load of cattle out of south Louisianna to Kentucky, coming north on I-55 in Mississippi, the truck started popping out of fifth.

At first, only when hitting the rough transition on bridges, then, later, at the least little bump.

No big dramatic POP, no noisy CRUNCH, just quietly smoothly slipping into neutral.

Between Memphis and Nashville, fifth quit pulling, entirely, and we came home on four gears.

This was in the "disposable/un-servicable" Getrag days.

The transmission was replaced under new-truck warranty and we never got to see, or know, just exactly what was wrong.

Chrisreyn

My older truck was doing this in third and second, it was worn-out synchros to blame. The Synchros "hold tension" on teh gears to keep them in positon and if they are worn, the gear can slide out when the "load" is released from it, such as during decelleration.
Maybe a simplistic explanation, but this is how my tranny guy explained it.

colesdad

gettin ready to have the repair done, I'll post the results!