1G 1ga 90 gsx 1st and 2nd gear grinding

[VampireVr4]

I have a 1990 GSX. I'm confused about the whole shimming/fork vs syncros thing.

My 1st gear grinds while rolling almost all the time, unless I go super super slow. At a complete stop it is fine. 2nd grinds below 4k rpm. I have a little bit of play from shifter bushings I presume.

At first it, 1st gear would grind no matter if I was stopped. I adjusted the clutch pedal near the gas pedal, and it helped but it's basically all the way adjusted out already.

My question is, what do you think this closely resembles? Syncros? Fork needs shimming? Replacement of pedal assembly? If it's the pedal assembly, can I use a 2g? Some say the 1990s have issues with being different than the 1gbs and up. Trying not to break the bank here or else I would start replacing everything.

I'm from central California if anyone knows of a good DSM gear head nearby. Thank you

 

[pauleyman]

You've listed all the fixes for problems you dont k now you have yet. You have to find the root cause first. Do you understand what a synchro ring is how it functions?

 

[bastarddsm]

Its simple. If the trans grinds, it's wore out and needs rebuilt.

 

[pauleyman]

Its simple. If the trans grinds, it's wore out and needs rebuilt.

Not necessarily true.

 

[bastarddsm]

110% wrong.

 

[pauleyman]

110% wrong.

I've seen plenty that grind when clutch is midadjusted.
Back on topic. OP needs to figure out if clutch is dragging. If it is then find out why. Pedal assmebly is likely if it had not been addressed already. Also what clutch is in it. Lastly how old are the synchros?
Yes it could be a rebuild needed.

 

[twicks69]

Think of it this way....if it's a 90, and has never been rebuilt, it is like saying you have 30 year old brake pads that have never been replaced. The early synchros were organic lined and very finicky to gear oil selection and were notorious for glazing or burning out. You could be dealing with a wear issue. Secondly, the intermediate shaft bearings are a notorious wear issue with these transmissions and it can get excessive bearing endplay (should be under preload), causing the shaft to move and put excessive wear on the 1/2 fork, and will wear down the engagement teeth on the 1/2 slider and gear engagement teeth causing shifting issues or pop out issues.

You likely need a complete teardown and refresh. As well, if it is 90 components, the gears and shafts and hub/slider assemblies are also more difficult to find new or used spares.

Good luck,

TMZ

 

[1990TSIAWDTALON]

Thanks Tim!
I'm glad I have these odd ducks for some reason.
And spare parts car(s).

 

[twicks69]

You could still be dealing with a clutch adjustment/hydraulics issue, pedal assembly bushings worn out, or improper step height or out of spec flywheel or a failing clutch, or a clutch fork that is out of spec, etc.

If you are going to look further into clutch stuff first, start with where the clutch fork placement at "pedal up", and then what distance the clutch fork travels when the pedal is fully depressed. With holding the pedal fully down, does the slave cylinder maintain continuous pressure or does it not? You should see the fork initially in the center of the window or towards the driver side slightly from center. When fully depressed, the fork should be about midway from middle towards the passenger side. It should not move at all with the pedal held down (bleeding pressure). You can also have an issue with over adjustment of the master cylinder rod causing dragging issues, as well as being overadjusted and causing fluid bypass so you are not using the full cylinder fluid capacity to make it properly work.

Back out the adjustment rod like 10 revolutions if you are maxed out, then bleed the clutch hydraulics several times slowly with fresh quality synthetic DOT3/4 fluid and start there. Then adjust in or out depending on where the disengagement range is.

What flywheel and clutch assembly are installed? Has the flywheel ever been machined? OEM or parts store clutch master and slave cylinders? Stock hydraulic lines or upgraded to braided stainless? How fresh is the fluid being used? What specific fluid are you using?

Also for the gearbox, what specific gear oil type, viscosity and brand are you using?

Have you checked the condition of the shift cable bushings, shift cable bracket bushings, front and rear motor mount bushings , shift cables, shifter base and shift lever bushings, etc.

 

[bastarddsm]

I've seen plenty that grind when clutch is midadjusted.
Back on topic. OP needs to figure out if clutch is dragging. If it is then find out why. Pedal assmebly is likely if it had not been addressed already. Also what clutch is in it. Lastly how old are the synchros?
Yes it could be a rebuild needed.

By the time it grinds from a miss adjusted clutch, the synchros are shot. The only job of the synchros is to prevent grinding. They physically block the slider from moving onto the gear until they are synchronized. If the clutch is dragging, synchronization can not occur, and the synchro blocks the slider from getting onto the gear. I mean if you are really really determined, you can force the slider by the synchro, but 9/10 times you end up breaking something doing that. If it grinds during casual driving, the transmission is junk. I've had my hands in hundreds of these. Just this last weekend I took 5 apart for a customer. All of them "had a slight grind at high rpm", and guess what, all of them needed , 2nd,3rd and 4th synchros.

 

[pauleyman]

By the time it grinds from a miss adjusted clutch, the synchros are shot. The only job of the synchros is to prevent grinding. They physically block the slider from moving onto the gear until they are synchronized. If the clutch is dragging, synchronization can not occur, and the synchro blocks the slider from getting onto the gear. I mean if you are really really determined, you can force the slider by the synchro, but 9/10 times you end up breaking something doing that. If it grinds during casual driving, the transmission is junk. I've had my hands in hundreds of these. Just this last weekend I took 5 apart for a customer. All of them "had a slight grind at high rpm", and guess what, all of them needed , 2nd,3rd and 4th synchros.

I will agree. I just thought your statement was very broad. I haven't been through hundreds but dozens for sure.
Back to the original post.