Gregs928

My "new to me" of five months with 100884 miles 84 runs great but this past Saturday I first noticed the issue with shifting into 5th and it not staying in gear. I had to hold it in place and release the clutch. Not the normal smooth transition. My clutch is a little softer than my friends 87 and the fluid level is good. The issue then happened when I geared down into 3rd. Yesterday it did it in 1st. 2nd and 4th are no issue oddly. Any ideas out there?

Mrmerlin

You might need to re adjust the rear shift coupler or replace it

Gregs928

MrMerlin, could you give me a little more info. Not sure what part your talking about.

rjtw

Having just been in there, here’s a picture. The coupler is located at the top and front of the transmission, over the torque tube. You’ll need to remove the rear heat shield to access it, and it should be covered by a large boot which you’ll need to (carefully) slide over the bulky joint to the rear.

First slide back the boot and have someone shift into various gears while you observe the coupler. The coupler uses phenolic (?) bushings between the input shaft and the output shafts which are known to disintegrate over time. A small amount of play is built in. If there is more than a small amount of play, or telltale plastic-like crumbs falling out, then time to replace. There are a number of how-to threads here on Rennlist you can find.

PS 1st, 3rd and 5th are all served by different shift rods, shift forks and most importantly different shift rings, so I agree with Stan that the good news is that it’s probably not a problem with the transmission itself. There are also plastic bushings under the shift lever and also a front ball cup that can wear but probably wouldn’t explain the 1/3/5 issues. A worn rear coupler though could explain that the transmission input selector rod (that’s what is bolted to the coupler) is not getting moved forward far enough to go into gear fully. R/2/4 require pushing the rod back and for whatever reason (only partially disintegrated bushings) the coupler may still be able to do that, for now!

Or, maybe the coupler has worked itself loose from its front or rear coupling or something is getting blocked in the shift rods... maybe the rear coupler shifted to the rear on its splined shaft, that would cause your problems too and as Stan said that can be readjusted... clues to all these causes if there's some extra play in the gearshift lever and/or if its position has changed.

Let us know what you find!




PS here’s a photo of an old coupler where the bushings have completely disintegrated.

Gregs928

Thank you for the description and the pics. Hopefully this weekend I will have a chance to get under it. I had an 86.5 21 years ago in which the ball coupler, under the shifter, came apart. I was able to replace that on my own, hopefully the same can be said for this.

Mrmerlin

loosen the 13mm bolt,
then have a helper push the stick forward a bit,
till you see the shaft move into the rod then retighten the bolt and test the shifter for position,
it should stand centered in neutral.
and easily go into all the gears without hitting any of the surrounding console.

soontobered84

During the 4 years that I worked on my first 928 (Pre-Rennlist and pre-928 knowledge days), one of the things I did was replace the worn-out front ball cup. Unfortunately, I did not measure the threads for the one I replaced, so I did not position the new one correctly. In effect, the new one was either screwed in too far or not far enough and the result was that the transmission would not go into 1st gear and would not stay in 3rd and 5th gears.

rjtw

Yeah, misadjustment of the ball cup or rear coupler would definitely do it. Good point for anyone replacing that front ball cup. Just to avoid confusion to the OP and others in the future encountering this issue, wear of the front ball cup seems to result in popping the cup and disabling ALL gears not just some! LOL! I guess the other point worth making is that the front cup can't go out of adjustment, or at least is unable to rotate on the threads, once installed, so it wouldn't account for the OP's issue. I think Stan's right, it's gotta be that rear coupler sliding on the splines.

In my '83 the front cup failed just a few years ago, and the rear coupler failed about a year later. I'd recommend that once any part of the system fails, just go through and replace BOTH couplers, and the bushings under the gearshift lever all in one go. Otherwise you'll just be digging into the system repeatedly as parts fail until they're all renewed anyway! Now that I've replaced all the "wear" components in the shift linkage, shifting feels as solid as brand new!

Gregs928

RJTW, would you be willing to assist me in getting all of the linkage that you mentioned. I really would like to have everything in hand and not take additional time figuring out what all I will need.

rjtw

Sure -- here are the parts in PET -- with the caveat that you may not "need" ANY of them (yet) as you probably just need an adjustment. Recommend you inspect first, but of course if you want to replace these before they break, then... welcome to 928 ownership!!! :-)

Recommend you order from Roger (928sRus) to double-check all the below and to catch any updated part numbers:
928.424.005.01 - front ball cup, need 1
999.924.002.40 - gearshift lever bushings, need 4 (may want to pick up a couple spares in case you damage any during install)
928.424.029.00 - rear coupler, need 1
(Optional) 928.424.229.00, lock screw for rear coupler, these sometimes corrode
(Optional) 928.424.209.00, rubber bellows covering the rear coupler -- these are often missing or split open
(Optional) tube of Dow Corning Molykote DC-111 silicon grease, spread this on rubber bellows to preserve (and use on virtually all rubber parts throughout the car, get on Amazon)
(Optional) ratcheting tie-down strap or big worm screw clamp to install front ball cup -- see threads

Please do some searching here on the list before tackling the front ball cup, that's the hardest part, and there are also some threads on the shift lever bushings which have little springs which can also be a little challenging. I did it all though, and it's really not bad -- and totally worth the effort!

PS PET is an awesome resource, they're on the Porsche website. Here's the one for our cars: https://www.porsche.com/all/media/pd...86_KATALOG.pdf