T150 jumping out of first

[78blue5er]

Well hi everyone, I am having a pretty disappointing issue with my jeep. Me and my dad acquired a 78 CJ5 with a AMC 258 i6 / 4.2l /T-150 /Dana 20 and the po had the everything out. They said the Transmission needed synchros because it was jumping out of first, so we ordered a rebuild kit. We didn't notice the anything about the synchros wore so we were wondering why they said thats what it needed. After rebuilding it by the book, we decided to take the bellhousing off, and gosh it was messy. The clutch had fallen apart! So we ordered a new one and installed it.

We get everything back together and get the jeep running. I get in and put it in first and all seems well, but as I start to get going the Transmission jumps out of first. The jeep will drive fine if you hold down on shifter, and it only happens in first. After driving it some we put it in first and listened and it kinda sounded like the gear may have a flat spot in it, because you can hear a thump as you have the clutch in at a stop.

Sorry for the long post but we would like to know for sure what it could be. Thank you all for reading and have a good day

 

[jp360cj]

Could be something in the shifter housing...Maybe a bent shift fork? Does it have detent balls/springs?

 

[Posi]

The kit only has the blocking rings (besides bearings and some part).
As you know that didn't fix your problem
This is what I would recommend
Remove the top cover and rebuild it.
Reinstall it check to see if that corrected your problem
If its still popping out of first you need to pull the Transmission
Inspect the first gear, and first-reverse sleeve and gear (some call it synchro assembly).
Check where the two gears slide into each other, chances are those two pieces are your problem.

 

[78blue5er]

Could be something in the shifter housing...Maybe a bent shift fork? Does it have detent balls/springs?

Yes it does have them


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[78blue5er]

The kit only has the blocking rings (besides bearings and some part).
As you know that didn't fix your problem
This is what I would recommend
Remove the top cover and rebuild it.
Reinstall it check to see if that corrected your problem
If its still popping out of first you need to pull the Transmission
Inspected the first gear, and first-reverse sleeve and gear (some call it synchro assembly.
Check where the two gears slide into each other, chances are those two pieces are your problem.

I was hoping that wouldn’t be the case.


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[Mbuckley]

Hey there!

I just got finished solving this EXACT problem with my T-150 . It would not stay in first gear--popping out under load when accelerating. The gear itself was the problem--worn and beveled. I rebuilt the tranny with a kit, and also replaced the first gear as well (along with the first/reverse syncronizer assembly. I hope this helps.

 

[Posi]

Inspect the first gear, and first-reverse sleeve and gear (some call it synchro assembly).
Check where the two gears slide into each other, chances are those two pieces are your problem.

Good to hear it worked out for you.