Gear grinding but... not every days
 

Hello !
It's been a while I come here on this forum. Usually I found answer to my questions, but this time it's really weird.
Since I have my 86 (more than one month), I sometime get gear crunch when going 3th->4th over 4000RPM, or 5th ->4th.
It really feels like a bad synchro. (CRRRRRR....)
There a lot of topic about that here.


BUT, some weeks the problem disappear completely (I can shift very quickly at 7000RPM with no problems)... And some other weeks it goes back, grinding even at 4000RPM. Some days it's only at 6000RPM. Bother people here have the problem ALWAYS.
If I change shift very slowly, no problems.


The dealer said me it can not be a synchro if it's not everyday. Any idea ? Thank you !

Welcome to posting, there, lludo .......... :clap:

You may consider replacing the oil in your car's transmission with an aftermarket brand (like Motul - your countries oil ..... ;)).

Meanwhile, I suggest you just shift slower ......... besides, what's the big hurry, if you're not on a track ....... :D


humfrz

The synchros have been known to go on these transmissions, but I'd look at getting your transmission fluid changed as @humfrz suggested before exploring the possibility of needing a new transmission.

Like he said though when sychros go they don't recover for weeks at a time. Intermittent stuff like this can be tough.

So, is it a fairly new transmission or just new to you..??

Are you new to manual transmissions..??

Either way, here's my prescription:

Remember, a warmer transmission is a happier transmission.

I would suggest that when shifting, wind up the last gear pretty tight (4-5,000 rpms) before shifting into the next higher gear.

Also, when shifting, pull (or push) the shift lever slowly and firmly into the next gear.

It's not a toggle switch ..... the lever is moving heavy transmission parts.

I suggest you NOT "lazy leg" it ……. be sure to push the clutch pedal all the way to the floor when shifting.

If this technique doesn't help, you may consider changing the transmission oil (as discussed).


humfrz

Sorry I forgot to precise.. the car has 4 years, 20 000 km. Previous owner never noticed something like that. He changed the fluid with Motul Gear 300 (I think it's the best) one month before selling it.
I'm driving since ten years manuals, I've got sports cars, and here there is one thing I am sure : it's absolutely not normal. I know how works modern transmissions : even when you push the lever very hard, the shift should not pass until the synchro are at the same speed than the gear. It's just that I can't understand how one day it can work, the day after it doesn't work anymore. The dealer also don't understand.

Hum sorry my English is not perfect. What are you meaning when you say intermittent stuff like this can be tough ? You mean that it should not be possible ?

I mean when the problem comes and goes it can be hard to figure out what the real cause is. When something breaks and stays that way it is easy you can see what is broke and fix it. When broke then not broke then broke again you have to look at many more things to see what is really wrong. Much harder unless you hit right thing first time.

OK, @lludo , so now we know the transmission is "broken in" and you are "broken in" (know how to shift a MT .... :cool:).

So, I reckon a strategy for finding out what's wrong with the transmission would be to try to determine what is different from the times it works good and the times it doesn't work good..... ??

Like, maybe:

* transmission temperature?

* air temperature (air in the hydrolytic clutch lines)?

* road surface?

* payload?

* phase of the moon ......:D

OK, what I would do is to drain and replace the transmission oil (I wouldn't care what the previous owner said). That, of course, will make sure the fluid level is up to full.

Next, I would drain and replace the clutch fluid and bleed the system (you may have air in the system).

You may wish to re-check the clutch adjustment.

So, if those things don't "fix" it, I reckon it's time for a new transmission (since people don't rebuild things anymore ..... :().


I hope you get it sorted out.


humfrz

Thank you.
It's not the clutch, I'm absolutely certain. It would grind at other shifts, especially the reverse gear. Definitely not that.
There seems that when I bump on a hole on the road, then it goes better or bad. But not sure...

Maybe the transmission mounts are lose ...... :iono:


humfrz

OK, si it's definitively "bump" related.
Also, it seems to get better when the oil is really cold (0°C).
I went back to the dealer today, they test drive the car and they agreed it's really, really not normal. They are waiting an answer from Toyota, If they have to replace the transmission, or just repair it. I really hope they will just repair it because I still don't know if it gets under warranty (the tech said me that my warranty was broken because one of the motor oil change was made with one month delay :-( ) Even if it has no links with the transmission, it breaks the warranty.

I'm not sure about Toyota in France, but that wouldn't be the case in the US.

I'm thinking the tech that told you that is wrong. I suggest you take up that question with the service manager or the general manager.



humfrz

Ah yes! That could certainly lead to weird shifts.