R154 Issues

[Quadcob]

I have a R154 gearbox bolted to a a stock standard 1UZ in a car that weights about 1150kg that is not wanting to stay in first gear. As soon as I take off it comes out of first gear. Even when I hold it in first gear it still wants to spring out of gear when I drive off. Before I pull out the gearbox(which involves pulling out the motor as well) I would like to eliminate any problems that it might be.
If anyone has any ideas what could be the problem they would be greatly appreciated.

Thanks
Warren

 

[sideshow]

does it vibrate abit
could be bent centre shaft pushing the 1st gear back out of selection
i doubt its and syncro or detent springs cause u should still be able to hold it in with
your hand
can u hold it in 1st if u accelerate slowly
and does it do it in any other gears which id say no as u might have said it does it in all gears
but to me it sounds like something as it spins is pushing the 1st gear back

 

[Quadcob]

There is no vibration, all the other gears appear to be OK although there was a rattle when in 3rd gear, but did not sound like a gearbox noise. I havn't used any excessive force to hold it in first gear.
I was thinking maybe the first gear thrust washer, but no noise from the gearbox. I will drain the oil and see if there is any thing in the oil or attached to drain plug magnet.

Warren

 

[AutoLuxLexES]

During my research on r154, I've heard that if the thrust washer goes, then you will have gear pop outs like you've explained. But I remember hearing that it will do this on 1 2 and 3 gear.
Have you found out your issue yet?
Charley

 

[stevieg]

1st/2nd shift fork is weak, pirate4x4.com sells a billet one, common failure point for r151/154

 

[4U2QUIK]

yup it's a fairly common problem and you can get them directy from marlin crawler.

 

[stevieg]

Sorry, marlin crawler is correct

 

[Quadcob]

After looking through the internet I came to the same conclusion as everyone mentioned. I have already ordered a new thrust washer, a heavy duty bearing cover plate and billet 1-2 shifter fork from Marlin Crawler. It appears the standard bearing plate flexes and the design of the oem thrust washer contributes to its failure.
I will getting the rebuild kit from Driftmotion at this stage.
So by the time it goes back in the car the gearbox will be rebuilt to a point that it should not be a problem again, well I hope so as am about to install a Opcon supercharger on the motor.

Thanks everyone for your input.

Warren