915 stuck in reverse - but why?

[Kidasters]

Real bummer of a day yesterday.

Was running errands in my 84 Targa. Was leaving the bank, and car was acting funny. Shift lever in R, car would just bog down. Shift lever in N, Car drives in reverse.

Got a tow home and it turns out this happens on 915 gearboxes. I've done a lot of reasearch on the fix, ordered gaskets and transmission fluid and will tackle the problem.

The question is - why? The last two times I've driven the car, it was shifting funny. Like, I would shift into 1st, but it acts like it's in 3rd. Or can't find the right gear. But, eventually that would clear up and it would run like normal.

Some info on my car. 84 3.2. I'm the second owner. Approximately 140,000 miles, 5000 by me. I bought the car in 2008 from the original owner's widow. He had the transmisison rebuilt at some point. When I got the car - all plastic and rubber goods were a mess all through the car. So - the first thing I did was completely go through the shift linkage and replace all of it. Installed the factory short shift kit, the Seine Systems gate shifter and a Wevo coupler. Until a few weeks ago, it was shifting fine.

I'm sure I'm due for a fluids change, and this will force that issue. But what else should I do while I'm under the car that can keep this from happening again?

[MBAtarga]

Is the shift coupling still connected at the tunnel?

[Kidasters]

Good question. Yes - the coupler under the access cover is fine, and moving like it should.

[917_Langheck]

Make sure the shift rod holder right behind the shift mechanism is still attached, under the plate. If it's loose you get those symptoms.

[Kidasters]

Rod holder is fine. I'm certain the problem is inside the transmission.

[959swede]

Shiftfork for the reverse has cracked.

Hans,

[917_Langheck]

Shift lever in R, car would just bog down. Shift lever in N, Car drives in reverse.

Reverse and 5th are engaged at the same time. I've seen this movie.

[gled49]

The usual culprit (if the gearbox was rebuilt recently) is the lockout pin ends up on top of the 3-4 shift rail, defeating the lockout function. 5th and reverse are on the same shift rail so cannot be in those gears at the same time. It’s possible thru the backup switch hole to get the trans out of reverse. If trans has not been rebuilt, adjustments outside or internally could solve issue.

[Flat6pac]

Your swivel in the back seat access is too worn out and needs replacing.
You might need to open the access on the right side of the trans and locate and align the selector
Bruce

[shoooo32]

99 times out of 100 it's shift linkage. I mark the coupler with a paint pen once it's adjusted. Then it's easy to tell if it's inadvertently moved during operation.

[917_Langheck]

[john walker's workshop]

Remove the reverse light switch on the nose of the trans and push the activating pin inward to pop it out of reverse. Probably an assembly error way back when. Got the detent above the shaft rather than under it. Gotta be sure of it's position before installing the center housing.

[jbscheff]

Exact same thing happened to me several years ago when my transmission was rebuilt. Just as others said - lockout pin / detent not aligned properly when rebuilt and after a while it shifted and car was stuck in reverse and a forward gear.