r154 gearbox help would be much appreciated

[88cameron88]

So i have an r154 gearbox mated to a 1jz with a 5 puck button clutch. the box has never been in the best condition since i got it, hardish at times to get into 2nd and 3rd.

Now all of a sudden since last monday, so a bit over a week, whenever you try to go from 1st to 2nd it CRUNCHES VERY LOUDLY into 2nd gear, it is very hard to shift from 3rd down to 2nd too. It only does this after ive been driving for 10 or 15 minutes and the box has warmed up. If the car is cold it will change gear fine as it did before.

Initially i thought it may be clutch adjustment due to the fact that it changes into 2nd fine if you double clutch or give the car a rev inbetween the shift... but this doesnt explain why the crunching only occurs once the box gets warm.

Im using a semi synthetic oil that has only been in the box for 10000kms.

Any ideas are greatly appreciated.

[mr75]

the fact that it does it once the box warms up suggests the oil is wrong. i have heard of a few people running the red line shock proof stuff. change the oil see if that helps

[88cameron88]

but the oil has been in there without issue for 10000kms, only in the last 300ks has it started playing up, i guess an oil change is cheaper then rebuilding/replacing the box so i guess ill do the oil when i get some cash

[allencr]

it changes into 2nd fine if you double clutch or give the car a rev inbetween the shift...

Clutch is dragging when warm.

[Tweak]

its your syncro's. There warn out more so then just "damaged".
When cold oil is thicker and compensates for warn tolerances. But when hot it thins out and its fubar

[88cameron88]

thats what i think is the main issue tweak but why did it do it nearlly instantly, one day its fine, the next day its a little bit harder to shoft, the next day it just starts crunching no matter what.

so allencr, do you think i should just adjust the clutch then to fix this?... its worth a try as itll cost me nothing to do, ill just make a slightly longer piston for my slave cylinder.

[MWP]

Redline MT90

[allencr]

why did it do it nearlly instantly, one day its fine, the next day its a little bit harder to shoft, the next day it just starts crunching no matter what.

... adjust the clutch then to fix this?...make a slightly longer piston for my slave cylinder.

The cushioned clutch hub, if it has one or even if it doesn't have one, can change in a second & drag enough so that worn syncros(HOW MANY Km/Miles- time on this stuff?) will not work as well as they used to, they're the ones that need to drag, not the clutch. A different lube may give them some bite.
There is nothing to adjust except free play. Much more then a few cm/in?
DON'T play with the piston or pushrod. It will only move as far as the amount of fluid from the MC pushes down to it, so the MC controls how much it will move, unless the bore size of the SC is changed.

[Hendo]

Bleed your clutch fluid, it's the easiest job in the world to do. Mine was black! dot 3 brake fluid is recommended if it's the same as mine

[mr75]

seems you have all the answers you need let us know once you have bled the slave if it is fixed

[88cameron88]

allen cr... the piston in the slave is the only way i can adjust my clutch, the motor and box is in a commodore.... I have adjusted my clutch in this way before, when i fitted a new clutch once before it slipped like crazy, so i cut a few mm's off my pistion and it fixed the problem, it is a commonly used way of adjusting clutches, its the only way you can do it in some falcons.

My clutch fluid is only a few months old and well bled.

To start with im going to use a longer piston then put some redline oil in. i will do this over the next week, i will let you know of the results, thanks very much for your assistance so far guys

[allencr]

So the clutch wasn't engaging completely and putting constant pressure on the release bearing & engine thrust washer/bearing. Yes, that is exactly the time to stop the piston from bottoming out in the SC, but I'd prefer shortening the rod instead or really, finding out what parts mismatch was causing the problem!!! Your cure to getting more travel from the slave piston by lengthening it may seem similar, but isn't. More fluid pushed into the slave(or smaller diameter piston) = more piston travel. Good luck.

[88cameron88]

okay so today i made a longer rod for my slave cylinder about 5 or 6mm longer.
I put that in, iam instantly finding it easier to select gears and the crunching has stopped when going into second, it is still a little rougher then it should be as obviously my box is fairly worn, so when cash permits i will put some redline oil in. But largely the problem has been minimised by lengthening the rod.
Thanks very much for the help guys