Do you have a short shifter? If you do, that is what caused the problem in the first place. Short throw shifters really screw up your synchros. My friend put one on his car, and now he grinds gears way more than he used to.

Synchros gone. Put some honda mtl in it and it might get better. Or else its going to need to be repaired

the cheapest/easiest solution/fix to a worn synchro is double-clutching

hpefully, I'll have the $30 cure soon.

Do you have a short shifter? If you do, that is what caused the problem in the first place. Short throw shifters really screw up your synchros. My friend put one on his car, and now he grinds gears way more than he used to.

I've been reading a lot of problems related to clutches and transmissions lately, and I thought I'd contribute some things I've learned. My day job as an engineer has me developing clutches and making them work with transmissions for major OEMs, so I have a fair grasp on the system. I am not a mechanic, however, so I haven't seen all of the problems and don't pretend to know how to fix them all. But hopefully this will help.
If you're driving down the road, and suddenly it's difficult or impossible to shift, it's probably the clutch, or the system that connects your left foot to the clutch. Here's what happens when you go to shift, normally, with the clutch:
1) You depress the clutch pedal, forcing hydraulic fluid through the pipes from the master cylinder to the slave cylinder. The slave cylinder pushes on a fork, which has the "release" or "throwout" bearing on its length. This release bearing actuates the diaphragm spring fingers in the clutch, which removes the clamp load holding the disc between the pressure plate and flywheel. The disc is now free from the engine.
2) You move the shift lever into the next gear. In order for the shifting to take place, your transmission has to match the speed of the "input shaft" (the shaft that the disc is attached to) to the speed of the "main shaft" (the shaft that the differential and eventually the wheels are attached to). This is where the synchronizer comes in. The synchronizer is a cone-shaped friction clutch that moves in and accelerates/decelerates the input shaft to match the speed of the output shaft in a given gear ratio. For example, say 2nd gear at 40 MPH has your input shaft turning at 6000 RPM and the main shaft turning at 2000 RPM. Now, if you shift into 3rd gear, for that 2000 RPM of the mainshaft, the input shaft only has to turn at 3000 RPM. So the synchonizer decelerates the input shaft AND DISC to the new speed.
3) You let the engine speed drop to the correct speed, and re-engage the clutch to allow torque to once again be transmitted through the system.

Now one cause of hard shifting is synchronizer wear. Each time you shift, particuarly a hard downshift (4th to 2nd or something like that) causes your synchronizer in that gear to wear slightly. In severe cases, downshifts can increase the surface temperature of the synchro to over 1600 degrees F. Also, old or poor oil can contribute, as it will not allow the shifting components (levers, synchros, gears) to mesh properly. However, both of these causes happen over time and won't suddenly appear, particularly in all gears.

Most of the time, it's caused by the clutch NOT RELEASING THE DISC when you depress the pedal. If the disc is still clamped, even just a little bit, when you shift, the synchronizer must not only overcome the rotational inertia of the disc to change its speed, but also the friction caused by the clamping! Effectively, you're asking your synchronizer to accelerate THE WHOLE ENGINE to the new speed, if the clutch is still engaged when you shift. Not only does this make shifting hard, but it also is terrible for the synchro!

What would cause a clutch not to release the disc? Usually a loss of hydraulic pressure in the system. If the master cylinder, slave cylinder, or piping develops a leak, or air gets in the system (just like brakes) then you could have a problem. Less common would be something in the clutch breaking and preventing the release from happening.

So if you're having trouble shifting in ALL gears, diagnose the release system first, then the clutch, then the transmission.

Hope this wasn't too long and someone learns something.

easy killer short shifters do increase the load on synchros. Just because you have been lucky (so far) don't go preaching.

Trying to find a supplier in the US for the synchro.

When I find the ($30) cure, I'll be semi-rich!

Would you be willing to try a Mazda synchro??????
Toyota??????? Nissan?????

Ever wonder if they share the same synchros???????

I have access to a warehouse full of parts.

From what I know (limited, OK!) 92-01 GSR all use the same synchros. Now I'm not clear on the differences between the 90-93 LS, 94-01 LS, and JDM trannies.

For now I'm only gonna concentrate on 3rd gear synchros as this seems to be the "weakest link"

IF ANYONE has old/worn 3rd gears synchros, message me. You have to know EXACTLY what tranny they came out of. If you send me old synchros, you get the killer deal on new ones, (like just pay 1/2 price + S&H).

I expect these synchros to be about $30 each. Won't know for sure till EXACT match is found.

We know you can get a rebuild kit from Transtar with or without the synchros. Well looking through the dealer catalog (not same as online version) you should be able to order the synchros one at a time.

I honestly don't expect much headway till early next year.


[Modified by Mista Bone, 8:32 AM 10/29/2002]