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Trans popping out of third?

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J

Jimmy74

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Here's my stumper for the week. 1275 ribcase Transmission pops out of third, quietly, but often. The frequency of jumping to neutral can be reduced about 75 % if I rest my hand on the shifter. But even then it will gently but firmly push off third. Rarely under acceleration or engine breaking.

Any ideas?
 
Either broken spring behind the pin that holds it in gear or work selector forks I think.

Either way, due to the clever design of the Spridget tunnel, getting to anything to do with the gearbox is impossible without taking the engine and box out, so next time you're taking th engine out, rebuild the box at the same time :frown:
 
This is interesting- the 1098 rib-case unit had that same exact habit (popping out of 3rd) and that is why they redesigned the 3rd gear gear angle to prevent it and came out with the 1275 ribbox.
You MAY have a 1098 box or just a 1098box wannabe!
BillM
 
IMHO, You've got a combination of some worn parts. The engagement dogs on 3rd gear, the corresponding teeth on the 3/4 slide gear and likely a worn 3/4 shift fork. The extra room inside the 3/4 shift fork allows the slide gear to back off just enough to kick the trany out of gear. The detent on the shift rod can't hold it in gear after the slider has gotten some momentum being popped off 3rd's engagement teeth. Resting your hand on the shifter or holding in in gear will just postpone a terminal failure of the shift fork itself. The steel slide gear will eventually wear through the brass shift fork. When the shift fork gets thin enough, it will deform and the trany won't go into 3rd gear at all. Most likely 3rd's synchro/baulk ring is worn, as well as the cone material. Repairs unfortunately involve pulling the engine and gearbox to get to the gearbox itself. Don't be surprised at what you find. Usually opening up an engine or transmission involves finding more than what you went in to find. HTHs anyway.

Mike Miller
 
<span style="font-size: 11pt">Yeah, I'm thinking syncro and / or shift fork.

Either way, it's not a simple fix.

By the way, one of the worst things to do is to rest your hand on the shifter while the car is running down the road......after a while, the trans will start popping out of gear if that's done.</span>
 
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