915 problem after a 1st gear repair

[wesayso]

After reading a lot of 915 threads including the 915 wiki I'm still puzzled what happened to my recently repaired 915 gearbox. First a little background;
In december 2009 I was driving my '82 SC to work and wanted to pull away from a stop sign and heard a dreadfull rattle when selecting first gear. The car didn't move much and I pulled to a stop and checked the axles and they looked fine. I managed to select second gear and coasted home.
About a month and a half ago I send the gearbox out for a repair. My first gear dog teath had sheared off and the repair shop replaced quite a few pricy parts. All of them related to first gear. They inspected the rest of the gears and decided those parts where good enough to leave them untouched.
I took that time to replace my old rusted heat exchangers for SSI's and a complete clutch/pressure plate replacement and a reground flywheel, replaced all CV's and when the gearbox returned reassembled the engine/gearbox.
The gearbox worked fine and I drove it to work for 3 days without a problem.

On the last day I selected first gear, drove off and while still in first gear the gearbox froze up, leaving the impression that the axles where about to explode! I stepped on the clutch and parked the car at the side of the road. When I gently let go of the clutch the engine was about to die so I tried to select neutral. I noticed I was still in a gear and tried the lever in second gear. It felt the same as neutral, the car would move instead of the hang up in first gear.
I couldn't get it in neutral, but I could move the shift lever in different directions.
I was able to coast home in the gear the car was in (don't know what gear as I limped home) and haven't been able to free up the hung gear using the shift lever.
I checked to see if the shift lever was still connected to the gearbox. As I move the shift lever I see the selection shaft move freely.

The shop that did the repair suggested to collect my car and remove the bottom inspection plate to free the stuck gear. However I'm not convinced that it will solve the problem I experienced. After all, the gearbox froze up while pulling away in first gear. I can think of two reasons for that.
One beeing the gearbox somehow selected another gear while driving off in first gear. a misplaced detent??
The second reason I'm able to think of is a lock up of debris between the gears freezing the gearbox. But that wouldn't explain beeing stuck in a gear afterwards.

Can any of you make sense of this? I hope my story is clear enough to read, English is not my first language.

I suggested to the shop that did the repair that I wouldn't be satisfied without a complete disassembly of the gearbox to make sure this couldn't happen again. I'll wait for the answer from them but would like to figure out what happened here...
I hope one of you can shed some light on this.

[0396]

sub.. good luck

[GaryR]

If the shop is any good at all I find it hard to believe the shop didn't want the car right back to fix correctly. You drove the car 3 times since a costly repair a few months ago and they tell you to pop the inspection plate off??? How about the $50 worth of Swepco 201, who pays for that every time this happens (if the transmission just doesn't explode 1st).. I would let the shop know that they need to make this right.... a 915 just doesn't jam up driving down the road.

[Peter Zimmermann]

Sounds like the car has to go back to the shop, that is the strangest symptom that I've ever heard. Unless, of course, during the install the forward, outboard, trans mount bolts were left loose, and the trans has dropped onto the shift rod/coupler at the tunnel.

[pcar9119]

This might be a silly question, but, is the coupler loose on the shifting rod. Sounds like it may have lossened up and rotated. It happened to me thats why I ask, LOL.

[john walker's workshop]

very typical problem caused by not paying attention to the internal detent position on assembly. requires disassembly to reposition one or both of the detents.

[wesayso]

Thanks for the replies...
To answer some questions: the trans mounts are not loose, the shift coupler is propperly connected to the shifting rod (first thing I checked).
I'm glad I got these replies as I've read a couple of the threads where you, John Walker, commented and that's what made me think it could be the internal detents. I'll try and convince the shop to disassembe and check them.

[Flat6pac]

The shift coupler is worn out, replace new, not just the bushings but new complete.
Bruce

[Flieger]

Originally Posted by john walker's workshop

very typical problem caused by not paying attention to the internal detent position on assembly. requires disassembly to reposition one or both of the detents.

I agree based on past expert inputs on similar issues. You got two gears selected at once.

[john walker's workshop]

there are two flathead plugs on top of the trans. one towards the top of the diff housing and one towards the top of the center housing. they plug the bores for the internal detents. they pry out, or tap out with a hammer and screwdriver under the lip of the plug. if you can see the rounded end of a detent down in the bore, or if you can get it out with a skinny magnet, it's in the wrong place. if you see the curved side of a shift rod, you're ok. kind of tight to do a mirror and flashlight inspection with the trans in the car, but it can be done.