Reverse 'lost' - do I need to pull the transmission - how to best diagnose
 

The Turbo (77) seems to know that I like repairing it - just when I am done with the suspension rebuild it throws the following at me:

The reverse gear went from working without any issues to 'non existance'. This is the 930 4-speed gearbox. I researched on here and it seems that this issue does not occur to often, that the most probable cause is shift coupler alignment, and that people sometimes fix it by overhauling their transmission or just reajusting clutch and shift coupler.

My diagnosis so far suggests the following:
- Reverse feels completely 'blocked' and there was no gradual deterioration
- All other gears work absolutely fine and unchanged (suggesting it rather is not a clutch issue?)
- When disconnecting the shift coupler and operating the shift rod by hand I am able to easily get into 1/2 and 3/4 but I do not seem to be able to turn the shift rod from the 1/2 position in neutral (clutch depressed) to get into the reverse 'angle' of the shifter. I hear a metallic 'clang' on both sides when moving the shift coupler in neutral from side to side. To say it differently, it feels to me that the issue is not that I cannot push the rod back into the gearbox for reverse once the angle is correct but rather that I can't even change the angle to get to the reverse 'angle' in neutral.

I created a little video showing what I mean...

The big question now is what should I do / test before resorting to pulling the transmission.

The only upside of pulling the transmission would be a possible overhaul of it - the second gear bearing(s) are extremely loud which is quite annoying. In second rather than the motor and turbo I mostly hear the bearing :-)

That does seem ominous. From there I’d say you have a blockage keeping the shift selector from moving freely but that would seem to be a blockage inside.

Topo,

You could start buy draining the transmission gear oil. Then remove the Selector Cover With Fork. You can look inside to see if the Reverse Rod is engaged correctly and/or if there is any obstruction like possibly the reverse light switch pin or ???

Best of luck,

Rahl

Topo,

You can also do a search to find related threads.

https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/1001651-930-transmission-rebuild-early-1977-box.html?highlight=transmission+rebuild

See if this one helps. It is a rebuild thread but may give you a better idea of what is going on inside your transmission.

Rahl

I lost reverse in my 1986 930 today with very similar symptoms... did you find a resolution?

Check shift rod bushing first, under the hump in the floor behind seats. Mine was bad but did not feel sloppy, but car would not go into reverse, kept going into first gear.

I'd be looking at the linkage first. Make sure everything is moving as expected.

There is a critical bush below the shift lever. I just replaced mine - it was totally mashed. I still had gears, but the shifting was getting fairly random.
It is a bit of work to get in there, just to have a look. But way less work than pulling a gbox apart , to find it was a shift bush.
Alan

Lost reverse in mine once. For me it was simply the allen headed locating pin that centers the shift coupler with the shift rod under the access plate between the seats. It was loose, allowing slop. For you, wouldn't it be nice if so simple but from your description it sounds like something else is amiss.

+1 above. First place to look. In the tunnel housing - tapered allen screw. Can be quite troublesome. If not Tight Tight, fix. Usually needs some loctite.
I suspect if that is affecting reverse, then other gears would fail too. But def first place to look.
Alan

Stumbled upon this… I thought I remembered that reverse gears are 1st thing under the cover…

https://forums.pelicanparts.com/porsche-911-technical-forum/945596-930-turbo-no-reverse-gear-possiable-explanations-internal-transmission.html

Yep - not uncommon.
But try the other options first. At least , either way, not a complete g/box teardown.
Alan

Thank you to everyone that responded. I pulled the inspection cover today and allen screw was tight, but looks like the bushing shattered and there is lots of slop and side to side movement. I'll replace this bushing and maybe also have a look at the bushing under the shifter and replace it too.

If you replace the bushing under the shifter post a picture or two. This has been on my to-do list for a while. I have the part so all I need is the motivation.

The replacement shift coupler arrived from Pelican today and only took about 20 minutes to swap and the seems to have fixed reverse!

I purchased the entire shift coupler and also an extra set of bushings for the shift coupler. Replacing the bushings in the original coupler was also straight-forward and only took 20-30 minutes so now I have a spare coupler with new bushings.

I also ordered the ball cup bushing and the shift rod bushing which both go up at the shifter. Looks like the carpet needs to come out (which might mean taking the seats out?) so will save this for another day.

Online posts talk about removing the shift knob for this process, but I was able to remove the console with the shift knob in place, so looks like it might not need to come off.

I had to remove the knob but you may have got lucky.
I took the seat out . It will be a much harder job if you leave it in.
There are some screws hiding down low on both sides holding the console piece in.
Alan