What causes gear griding......??? your opinion

[meet07]

Ok I have noticed in the last 2 weeks that 3-4th gear im getting a grind. The only thing I have done to the car in the last month or 2 dealing with the transmission is.....

1) Changed the transmission fluid to Royal Purlpe Syncromesh2) tore the clutch slave cylinder apart,cleaned and put back together.

Does any one have any ideas of what could cause the problem.

[eh?]

I would dump the synchomesh as it made made my transmission grind. I believe it's a GL-5 lube which you are not supposed to use. Make sure you get a GL-4 lube.

[meet07]

da##it......I kind figured that could have been the problem. I would almost say that the fluid could be to slippery as well. I guess Ill invest in some liteweigh shoock proof and mt90.

[Booztd 3]

Mechanically, the insert springs that align the syncros break/snap and fall apart into the case. With these missing, grinding is more apparent

I tore down a Z32 and an RB25 transmission here

http://www.rbz32.com/viewtopic.php?f=2&t=57

You can see what the inserts and the syncros look like after the inserts have gone missing...

FYI - I use redline 75-90 in my trans

[Carl H]

granny shifting, not double clutching like you should have been...oh, wait not that kind of grinding.sounds like typical nissan box issues especialy prevalent in the z32 and other 'big box trans' cars/trucks...follow the advice above but it most likely is the syncros, also oil will have lots to do with it.

[meet07]

well im running that royal purple synchromax......it was required for the gm guys that uses the gm synochromesh. I figured it would be a great fluid but im not sure about that now.

hey booztd3- where did you get the adapter plate for your th400 transmission?? i dont know much about them but i may start looking more into it if the transmission goes out on me.

[20DET]

can be alota things...could be clutch travel.could be worn clutch.could be play in syncros.could be play in bearings inside the box.i found on my old r32 skyline wen i rebuilt the box that the thrust bearing was worn creating end float on the shaft wich made it grind.....but basicly mostly all nissan boxes grind.....just keep grinding em hahaha they last forever grinding

[meet07]

i have a act pressure plate and spec clutch disc. Thats interchangable right??

[Carl H]

should be fine.

[20DET]

is the clutch plate worn??? that can make it grind if the clutch plate is too thin....u might wana check with the manufactures specs for the clutch and make sure it is interchangable cos i know some clutchs arent interchangable because of the pressure plate diaphram going over the center point (or some s*** like that...some one will know)

[meet07]

its so weird....it didnt grind today??? im stumped. I may pull the motor back out when it starts to cool down and check everything out. I left the supports off on the side of the transmission/block. will that do anything??

[LSDrift]

Any solution come of this meet07? I'm having the exact same issue and I'm using Valvoline 75w90 full synthetic...ever since I've had the engine/trans in the car(which is about two weeks) if I leave it in 4th gear and decelerate, it pops out of 4th. I thought it was grinding because I just wasn't getting the clutch all the way to the floor fast enough because I'm not used to having the damper deleted yet. I think my 4th may be toast now though...

[Cjmartz2k]

Mechanically, the insert springs that align the syncros break/snap and fall apart into the case. With these missing, grinding is more apparent

I tore down a Z32 and an RB25 transmission here

http://www.rbz32.com/viewtopic.php?f=2&t=57

You can see what the inserts and the syncros look like after the inserts have gone missing...

FYI - I use redline 75-90 in my trans

This is 100% dead on. Happened to 2 of my RB25 trannies over time. Worn synchros and little clips coming out with fluid change. MT90 is best for trannies IMHO. Royal Purple sucks for manual trannies. MT90 will *help* worn gears, but it can't replace your worn snchros for you.

A lot of gear oil people use includes the additive for an LSD (friction modifier) and this can be very slick for synchros. Removing that friction modifier can help spin them up quicker, but again, fluid can only do so much. Also, mine didn't grind typically until I got the fluid heated up and thinned out a bit.

[LSDrift]

Funny you say that, about the heating up, I noticed on my way to work this morning that 4th wasn't grinding, even with a midrange rpm shift. It dawned on me that it was probably because it wasn't warmed up yet. And the valvoline stuff I'm using right now has the LSD additive haha. I know jack about transmissions in the great scheme of things so I thought it might even be a good thing to have in there...clearly it's not haha. Guess I'll have to switch oils and watch for bits of clips on this next change.

[Kevin.A]

When you put the slave back in, did you bleed it properly?

Since this has started happening, did you rebleed it?
I had a similar problem in an sr20-s13 and a 87 MR2
both times, the slave cylinder wasn't engaging the clutch all the way.

[LSDrift]

Are you asking me? I never had the slave off...but I did bleed it properly and it's disengaging all the way for sure. I thought that might be the problem at first but 4th is the only one that does it, no matter how slow I shift if I'm in any rpm above 4500ish. I'm still waiting on my MT90 to show up because UPS destroyed it in shipping somehow so it's still another week out now probably.