Manual transmission slipping out of 5th gear



I hvae a friend who owns a 1999 Infinity G20 and I said I’d find the answer for him. When the car is in fifth gear, he has to hold it in gear (and I’ve had to do this too - just cause I’m a nice friend). If we don’t hold it in 5th gear, eventually it will slip out and go into neutral. When it’s doing this, it makes a very light popping/grinding noise.

My question, I’ve been reading online that it could be the synchronizer (how would we replace that?) and I’ve also read it’s just a bad clutch.



It’s not the clutch. If the transmission is slipping out of gear, it’s an internal mechanical problem. Big bucks!


Exactly; it’s an internal transmission problem. The synchronizer is not the problem. Everyone always blames the synchronizer because it’s the only word they know that is associated with a manual transmission.

It’s either a worn shift fork or worn synchronizer hub, sleeve, and inserts. This would involve a complete transmission teardown and rebuild since there is no way one would go through all of this and do a piecemeal repair.

If the synchronizer sleeve and/or shift fork is worn, this could point to your friend driving around with their hand resting on the gearshift lever. You might ask them if they have a habit of this. It’s not unusual.


I suspect this is a high-mileage car… These symptoms usually mean the bearings that support the two shafts spinning inside the transmission are getting worn and loose, allowing the shafts to move out of position which pops the tranny out of gear…The transmission is no doubt a Mitsubishi unit and 5th gear (overdrive) is the weakest part…Rebuilding them is not THAT bad…It’s a job for experts only…


Depending on how long your friend is planning on keeping this car and its overall condition, I would probably not fix this. You can just use 4th gear as your top gear. You will burn a little extra gas, but it will be much cheaper than a transmission rebuild.


Thanks for all your thoughts. How long could he keep driving like this… holding it into place? Will it do any damage to keep driving like this? Thanks again car lovers!


It won’t hurt anything at this point. Chances are the trans will outlast the car, although it can be an irritating situation.


Constantly holding the gear clutch sleeve in gear will continue to wear the fork and the clutch sleeve groove. Eventually they will wear enough that you won’t be able to hold it in fifth. All the while metal particles will be getting into the oil doing who knows what damage to the fine bearings holding the shafts and gears. The way most transmissions are designed the forks do not do much to hold the clutch sleeve on the gear dog teeth. The sleeve and gear teeth are designed to pull themselves together once engaged – on accelleration, drive, and deccelleration. There is not a constant contact between the sleeve groove and the fork except when synchronizing and engaging.

If you want to use this car a while longer, just use fourth. Your gas mileage will suffer but the cost will probably be way less than a replacement transmission.


If it’s already worn then microscopic metal particles are already in the oil, and probably have been for a long timne.
Any particles will be so microscopically fine they are not going to hurt anything at this point.