The Getrag transmission on my '92 Dodge Cummins 250 4x4 has just recently started slipping out of 5th gear – usually while decelerating, but occasionally under light load or when re-accelerating. It started a few days ago while pulling a light RV trailer a few miles, but had been fine before. Now it slips out when pulling trailer or not.

I have put only a couple thousand miles on the truck since purchasing it (my 4th First Generation truck) with 133,000. It is a real sweetheart – closer to “cherry” than anything I have owned.

Slight forward pressure on the shifter will keep it from slipping out, but there is movement in the shifter even then. Once in a great while it does the same thing in reverse or second.

I drained the oil and there was a little “gold” dust and some really tiny steel that was attracted to a magnet. The total amount couldn’t have been more than the material in a common office staple ground very fine.

The PTO covers / inspection plates had been removed at least once judging from the blue gasket sealer. Opening them didn’t tell me a thing – couldn’t see far enough up and forward to see the 5th / reverse shifters or gears.

I refilled with Rotella 15 – 40 engine oil (though the manual recommends 5 – 30 – I live in warm climate) and overfilled by one pint.

My efforts didn’t make any difference.

What next?

 

It might be a synchro wearing out.

 

In my humble opinion, I would pour out the 15-40 and refill with 5-30. One of the reasons the g360 is so loathed is the input shaft bearing doesn't get proper lube--especially on an upgrade. This leads to premature wear and noise. While thicker oil will quiet things a bit, the tranny life may actually be shorter yet because the tolerances throughout the rest of the tranny are set up for a viscosity of 5-30---15-40 may, in some cases, starve the bearings even in a wam climate. I just got my truck in December on the understanding that the tranny needed rebuilding. So far I have 2000 miles on my rebuild. Mine used to pop out of 3rd and 5th under similar circumstances as you describe---new syncros solved that. My core had the same problem---I'm begining to see a trend. I guess I could've shortened this down to ''get ready to build that tranny'' but I think it's worth mentioning that 5-30 will prolly let it live what it's got left to the fullest. hope this helps

greg

 

My dad's 90 would pop out of 3rd when he decelerated. Took it to the dealer and they "lost" the record of the problem when the tranny failed just out of warranty. Understand it is out of warranty but get the thing looked at soon is my .02 worth. Better now than when towing a good load and away from home.

 

As others have said, you need new synchros. And also, the 15W-40 is too thick. The Getrag is assembled with preload instead of clearance, thick oils do not make the bearings happy.