Grinding shifting into 4th gear

[Dads gift]

1992 c2, slight grinding going into 4th, much worse downshifting from 5th. No grinding in other gears. Can almost not feel it if I hold in clutch and shift very slowly after being in neutral for a few seconds. If I try to shift fast, I will get a grind , but it will go into 4th. Stays in gear, does not pop out. Started with hot weather, and after I had a few people drive car that had never driven stick....never got out of 3rd, wife showing car to friends! Regardless, worried I might have synchro or gear or tranny problem. Not sure when last serviced. Clutch adjustment? Service? Synchro? Help.

[zedsn]

Sounds like a synchro problem to me. You might try and change trans gear oil to swepco or something similar to help with the issue.

[tkmoore]

Eliminate the easy and simple possibilities first. I'd begin with checking bushings on shifter ball cup, tunnel linkage bushing and shift coupler bushings then readjust coupler. So many times the culprit is in this linkage/coupler bushings and coupler adjustment. Good Luck. Tim

[spyerx]

964 g50 series tranny. I'd try changing oil first but this sounds like a synchro. Don't think you want swepco in a g50. I'm putting delvac in my g50. Try double clutching and see if it does it. (3rd, Clutch in, neutral, clutch out, rev, clutch in, shift to 4th)

[yelcab1]

If it goes away with double shifting and a slow hand in neutral, then it is 90% your synchro. Although it is somewhat unusual for the 4th gear synchro to go before the 1st and 2nd gears.

[Dads gift]

Originally Posted by spyerx

964 g50 series tranny. I'd try changing oil first but this sounds like a synchro. Don't think you want swepco in a g50. I'm putting delvac in my g50. Try double clutching and see if it does it. (3rd, Clutch in, neutral, clutch out, rev, clutch in, shift to 4th)

Ok Thanks. So if it does it, what do you think that means? Synchro? If no grind, service? Thanks again to all. Looking at getting this taken care of this week.

[gliding_serpent]

Originally Posted by yelcab1

If it goes away with double shifting and a slow hand in neutral, then it is 90% your synchro. Although it is somewhat unusual for the 4th gear synchro to go before the 1st and 2nd gears.

unless 1st and second synchros have already been replaced.

[Neilnaz]

Don't know much about g50 gearboxes but often grinding from 5th to 4th is 'touching reverse' which is due to poor adjustment of the coupler. It sounds like the coupler and bushes need to be examined to ensure that you are not 'touching reverse' on your way to 4th.

This may only apply to 915 gearboxes but I imagine it is possible for g50s too.

Cheers, Neil

[RedCoupe]

Originally Posted by Neilnaz

Don't know much about g50 gearboxes but often grinding from 5th to 4th is 'touching reverse' which is due to poor adjustment of the coupler. It sounds like the coupler and bushes need to be examined to ensure that you are not 'touching reverse' on your way to 4th.

This may only apply to 915 gearboxes but I imagine it is possible for g50s too.

Cheers, Neil

G50 has a different pattern than the 915. Reverse is to the left of 1st. The couple is different and doesn't have the same adjustability as the early transmissions.

[RedCoupe]

As mentioned earlier, it seems odd that the 4th gear synchro is the one that seems to be going. In addition to an oil change with fresh 75w-90 synthetic, I would flush and bleed the hydraulic clutch system. A bit of air in the system and it might not be completely disengaging.

[Neilnaz]

Thanks for the correction RedCoupe - I am now further edumacated...

Now back to my 'old-school' 911

Cheers, Neil

[Matt Monson]

What I have seen prematurely wear out 4th synchro is skip shifting. The owner jumps off the line, revs it up in 1 & 2, and then just goes to 4th once they are up to speed. 6 million ways to kill a gearbox, choose 1.

Nothing wrong with Swepco in a Borg Warner style synchro box. Just don't go the other way and put synthetic into a 915 or 930. I'd refresh the oil but a service inside the gearbox is likely.

[Dads gift]

Ok, update. Porsche mech believes synchro. Serviced, shift is better but still slight rub or crunch. Said synchro needs to be changed. So....can drive, he recommended not using 4th. Any opinions on that? I can shift into fourth with what seems to me as a very slight grind? Damaging? He said bushings and linkage not the problem. Car only has 38k on it since new, but he thinks dirty fluid led to issue. So, advice on how to best live with this, or how to get fixed most economically greatly appreciated.

[yelcab1]

Change the oil often and learn double clutching. That is the most economical.

[zedsn]

Why not just get it fixed?

[Dads gift]

Want to get this fixed. Best options? Cost estimate? Other work while we are in the gearbox? Thanks for the help.

[Jerome74911S]

A random thought - My car spends an awful lot of time in 4th gear, driving on the many 50 mph (80 kph) roads around here. Possibly for this reason, my 4th gear shows more wear, on the gear itself, than any other gear in my transmission. Although my trans shifts well into 4th, I imagine that this could be part of the picture.

[KTL]

Originally Posted by yelcab1

Change the oil often and learn double clutching. That is the most economical.

Agreed on the double-clutching. My former '87 has a sketchy 2nd gear and I had to learn to double-clutch it on downshifts when driving it at the track. Double-clutching "fixed" 2nd gear.

[Matt Monson]

Originally Posted by Jerome74911S

A random thought - My car spends an awful lot of time in 4th gear, driving on the many 50 mph (80 kph) roads around here. Possibly for this reason, my 4th gear shows more wear, on the gear itself, than any other gear in my transmission. Although my trans shifts well into 4th, I imagine that this could be part of the picture.

Not generally related. Guys get this same issue with 915 cars that were used to commute early in their lives. It's pretty hard to wear out the gear itself but it dies happen with many miles when the particular gear is used the same way for a long long time.

[Spumato]

Not sure what the expense is on the G50 rebuild, but for an idea... the 915 can run upwards of $2000 for a full rebuild done right. As these transmissions age, one should remember that they are not made for quick shifts. A former racer told me that the pattern should go from 1st - Neutral - 2nd and so on. You must train yourself to pause while in neutral. Fast shifts will kill the gearbox. And do not let people drive your car who cannot operate manual transmissions. The day and age of cheap, replacement parts is gone. A simple test drive can break something that can break the bank. Just my opinion, but feels to be sage advice given the current market for 911's.