you know what grinds my gears???

when my gears grind....... specifically first and fourth.
I wanted to know what exactly causes this because im not to knowledgeable about transmissions. i would also know how to fix the grinding. just trying to learn a bit more about this sour patch Z that we all love

as always,

Thanks NICO

Sometimes gears grind because the clutch doesn't fully compress due to faulty clutch system.

Or your transmission is not happy with the fluids inside it.

Or the sycros are shot and time for the transmission to be rebuilt.

4th gear grind is very common on these cars. The syncros wear out and you will feel a gear grind when shifting, especially 5th to 4th gear. The simplest thing to do to fix this is to drain your transmission and fill it with Redline MT-90. This has reduced and sometimes stopped gear grind. However, it will over time, get worse. When I swapped my transmission, I had horrible grind in 2nd and 4th whether up shifting or down shifting.

My 4th grind on hard shifting, until the entire 4th gear was gone one day..so i replaced the tranny with a 96+ one.

i replaced the fluid with royal purple but the grinding is still there.... i have a feeling my syncros is the issue...

My transmission only grinds downshifting from 5th to 4th at speeds above 40mph. Even then it's not TOO bad, just enough to notice it though.

Mine doesn't grind at all anymore thanks to NEO synthetics

i hate that grinding! what is the purpose of the syncros?

jona300zx wrote:i hate that grinding! what is the purpose of the syncros?

The synchromesh lets the shift fork to engage the gear you wish to be driven by the input shaft.



In the picture the sychronizer hub is the only thing connected to the output shaft. The sleeve wraps around it. When you shift a fork that surrounds the sleeve slides the assembly onto a dog drive that is permamently attached to the gear. The gear is constantly driven by the input shaft gears. So when the sleeve connects to the dog drive, the output shaft moves.

Video is simple, it's for a FWD car, but it's all the same.
[[youtube]http://www.youtube.com/watch?v=vzYGcDZXgWQ[/youtube]

You don't really grind gears, you grinding synros. Unless it's reverse, which is actually a gear on gear engagement. And also why you hear a whine when you are reversing very fast.

You can even play around with an animated manual transmission

http://auto.howstuffworks.com/transmission4.htm

Awesome!!! so there are more than one syncro?

jona300zx wrote:Awesome!!! so there are more than one syncro?

One for each gear, minus reverse. You also have a sleeve that mates with the synchro's, one for each pair of gears.

IIRC, 1st doesn't have a syncro on the Z32 tranny. That's only IIRC.

Redline MT-90 flushed every 15K or so will keep an old tranny happy.

Revmatching when downshifting helps more than any fluid ever will though. That makes the synchronizer's job much easier when the new gear speed matches with the engine speed.

BigTDogg (MA) wrote:IIRC, 1st doesn't have a syncro on the Z32 tranny. That's only IIRC.

Redline MT-90 flushed every 15K or so will keep an old tranny happy.

Revmatching when downshifting helps more than any fluid ever will though. That makes the synchronizer's job much easier when the new gear speed matches with the engine speed.

I realize I am necroing this thread like crazy, but what is the ideal RPM in this case?

The only way I know how to explain it is the difference in Rpm's when you downshift. Each gear is a specific size, so the difference between a gear (1st to 2nd, 2nd to 3rd, 3rd to 4th, 4th to 5th) should be fairly easy to find if you drive your car enough and pay attention. Usually if you rev your engine in between the gears when down shifting it's enough to get close to rev matching. I don't know what the exact difference is but I can find it when I'm driving. If you pay close attention to it when your downshifting you'll get the hang of it

Excellent info, I always had a basic understanding of how the manual transmission works but the little animated picture on howstuffworks was pretty sweet.