Churchill

Six months ago while puttering down the road I tried to shift into 2nd and got grinding -- wouldn't go into gear. All the other gears felt perfectly normal. Drove it for a couple of days before garaging it until last week, just haven't had time to deal with it. Been driving it the past few days and the gearbox seems to be deteriorating, which has me wondering if I don't actually have a bushing or linkage problem rather than something internal with the gearbox (my car's got 150K miles, so anything is possible).

The shifter feel for the other gears, especially 1st, is getting sloppy and weird. I wouldn't think that 2nd gear syncros disintegrating or something like that would cause other gears, and the shifter feel in general, to get progressively worse. That sounds more like a bushing that broke and is now getting mashed into little pieces with each shift. Then again, the inability to shift into one specific gear is not a problem I've ever seen attributable to a bushing.

I'm going to get the car in the air this weekend and take a look at the linkage but I'm curious if anyone has thoughts on this before I dig in. Sure would be nice if it turns out the gearbox doesn't have to come out....

911F1

Sorry to hear your issues. Before my transmission was rebuilt I had similar issues. Except I couldn't shift into any of the gears toward the back of the shifter box. No 2nd, 4th or 6th.
The problem was the stock differential was falling apart. Chunks of metal had lodged themselves into the shift rod shaft inside the transmission. Blocking the movement.

So it's possible something internally has lodged itself.
I would start off by looking over your shift linkage outside of the transmission and then changing your fluid and take a look at what comes out. I found larger metal shavings than the usual fine dust you see on a normal fluid change. I knew right away something was wrong. Good luck

Churchill

Thanks -- good idea re draining the fluid. Why hadn't I thought of that? I think I'm mentally slipping!

71-3.0-911

Interesting situation. Does the behavior present itself if the engine isn't running? Could eliminate the synchros as a cause that way. I am assuming the obvious has been fixed (bushings, cups, lube, etc...). On my 100k car, I had to replace all of those wear devices, shifting was terrible. I know you've been around a while, I am figuring you've already done this and eliminated those possibilities.

MarinS4

Shift forks are known to break on these transmissions. You won't see any metal flakes from the failure.

I agree with 911F1, disconnect the linkage at trans and take it from there. While it's great to be hopeful I just don't expect a simple outcome from what you described.

Churchill

Yeah, agree -- I'll be genuinely shocked if it's just a bushing that fell apart. Just doesn't seem possible. Am gonna try to inspect the linkage and drain the fluid tonight.

Meenrod

I broke my shift fork on 3rd and it presented issues exactly like you have described.

pp000830

Usually, worn synchros fail very slowly over a long period, starting with
--Only shifting without a dig or two once the transmission is warmed up.
--Followed by grinding with each shift into that gear.
--Usually, it shows up in the first to 2nd gear shift first as that gets the most use.

A clutch that does not fully disengage causes poor shifting into all gears, dings, grinding, won't release.
-- Due to the hydraulic in the master or slave needing bleeding
-- Problems internal to the clutch

I would think a worn shift linkage would make it hard to select a gear but unrelated to grinding.

This suggests you have a combination of issues.

On the upside, the transmission can be removed and serviced on a 993 without removing the engine lowering your cost in investigating what you need.

Here is a page listing the parts needed to service the shift linkage:
https://993servicerepair.blogspot.co...-key-part.html

Here is a page on having a 993 transmission serviced:
https://993servicerepair.blogspot.co...nsmission.html

Good luck with this,
Andy

cscrogham

Good advice to try draining the fluid and look for any big chunks that might plop out, but I would recommend doing a fluid flush and giving Redline 75w90 NS a shot before committing to a rebuild.

Churchill

I don't think any gear oil, no matter how special, is going to make it possible to shift into 2nd gear. Something is broken, most likely inside the gearbox but possibly in the shift linkage. Gear oil can't fix broken metal parts.

os993

Good opportunity to regear??😄?

pp000830

Funny you should mention this. It is very common for big chunks of metal to show up at the drain plug due to chips from the differential gear from aggressive starts where one of the wheels lets go and upon hooking up put jackhammer-like forces on the diff gears. This is for cars with the standard diff. Even with the chunks missing the diff will work properly.

The synchros take the form of a ring and have teeth all around them where all the teeth engage at once during a shift.
So for one tooth is to break off and show up as a chunk at the drain port I would think this would require some rather catastrophic failure involving all the teeth to some extent if it could even happen.

I would think the sign of excessive synchro tooth wear would be bronze-colored fine metal dust at the drain plug as all the bronze teeth on the ring would be worn to the same extent and it would probably be accompanied by possibly the tranny wanting to pop out of gear on its own as the profile of the teeth gets worn down. The primary part that is subject to wear is the clutch surface on the synchro, not the teeth, as synchros reach the end of life they fail to provide friction for synchronization and shifting moves from an occasional ding for worn synchros to full-on grinding with every shift.

Andy

Churchill

I like where your head is at -- but in my case, already done.

os993

Then perhaps a closer study to when you regeared and whether this introduced an anomaly. My shift fork was replaced when I regeared, even though the fork looked perfectly good. If done recently, I would get the shop who did your work in the loop.

abiazis

Synchros most probably a part of the issue as Andy states above......