Worn transmission mount

[johnJhicks]

I have a 1988 3.2 Carrera (G50) with little mileage (32k).
Since I got it, I switched to Wevo shifter & PSJ, and installed the Wevo engine mounts.

Now, I have noticed that when changing gears at high RPM, the gearbox “pops out”.

Could this be caused by worn transmission mounts? See below a picture of the mount - they are not cracked, but there is a small gap, unsure if this is expected or not.

What else could cause this?
I was thinking that it could be the clutch or the synchros, but ideally I could validate before changing those parts.

Thanks for your help!

[Bill Douglas]

When I renewed my engine and transmission mounts it made some weird gearbox issues go away. It's one of those things you do first. I think you'll be pleasantly surprised.

[KTL]

I suspect when you changed the shifter and the shift joint/coupler, you did not properly set the shifter. If the shifter isn't properly "calibrated" you don't always get complete gear engagement and it can pop out of gear.

Or, coincidentally the synchro teeth are worn and not holding a gear under heavy load. Probably pretty unlikely but is a possibility.

Excellence had an article in April 2002 that I scanned and the info/procedure they provided came from the factory service manual

G50 Shift

I also have the 84-89 911 manual pdf on my google drive if you'd like me to share it with you.

[Ok here we go]

Originally Posted by KTL

I suspect when you changed the shifter and the shift joint/coupler, you did not properly set the shifter. If the shifter isn't properly "calibrated" you don't always get complete gear engagement and it can pop out of gear.

Or, coincidentally the synchro teeth are worn and not holding a gear under heavy load. Probably pretty unlikely but is a possibility.

Excellence had an article in April 2002 that I scanned and the info/procedure they provided came from the factory service manual

G50 Shift

I also have the 84-89 911 manual pdf on my google drive if you'd like me to share it with you.

@KTL,

I had the same problem as OP where the shifter would pop out (1st gear only in G50 trans) more often than not, but since I changed out the transmission mounts, replaced the shift coupler and rebuilt the shifter with new bushings it would happen only once in a while. Could it be possible that I may have also inadvertently "calibrated" the shifter while doing the upgrades? Also, I do hear a lot of gear whine as I accelerate through the gears. I'm trying to narrow down the cause of the gear popping. The odd thing is that it doesn't happen when I have a full tank of gas, but when I'm at half or below the shifter pops out more often.

[KTL]

The synchro teeth are shaped in a way that they "bite" into each other when engaged and power is applied. But when the teeth wear out, that bite is lost and you can pop out of gear.

That said, driveline flex from worn bushings can make the shift linkage move and allow the gear to pop that way too.

It's possible that your installation of the shifter just so happened to fall into place properly. The G50 shifter assembly is a bit more simplified than the older shifters and there's not a lot of adjustment to it. Whereas with a 915 shifter, you can get it out of adjustment VERY easily and have all sorts of difficulty selecting gears.

The gear noise is directly related to the shift coupler. If you replaced the original G50 coupler with a WEVO style jointed coupler, the rubber isolation is gone. The first years of the G50 ('87 to '89) are notoriously noisy as they have aged. Bearing noise is really noticeable on high mileage G50s. Plus the replacement of the rubber centered clutch disc with a traditional spring center disc is a reliability improvement but the rubber disc was originally used for noise isolation as well.

[Ok here we go]

Originally Posted by KTL

The synchro teeth are shaped in a way that they "bite" into each other when engaged and power is applied. But when the teeth wear out, that bite is lost and you can pop out of gear.

That said, driveline flex from worn bushings can make the shift linkage move and allow the gear to pop that way too.

It's possible that your installation of the shifter just so happened to fall into place properly. The G50 shifter assembly is a bit more simplified than the older shifters and there's not a lot of adjustment to it. Whereas with a 915 shifter, you can get it out of adjustment VERY easily and have all sorts of difficulty selecting gears.

The gear noise is directly related to the shift coupler. If you replaced the original G50 coupler with a WEVO style jointed coupler, the rubber isolation is gone. The first years of the G50 ('87 to '89) are notoriously noisy as they have aged. Bearing noise is really noticeable on high mileage G50s. Plus the replacement of the rubber centered clutch disc with a traditional spring center disc is a reliability improvement but the rubber disc was originally used for noise isolation as well.

Thank you for the explanation - made a lot of sense with what I'm experiencing with my trans.