Flushing gearbox?

[Greg]

I recently changed my gearbox oil (manual) for some synthetic shell oil (75w90). the box is a lot worse to use now. i can't change into 2nd properly when cold (grinding noises) and every gear is a bit 'notchy', sometimes even when warm.

now i read in some thread that when changing from mineral oil to synthetic oil in the gearbox, sticky deposits can be formed on the gears which make the gearbox hard to use. i think this is my problem.

I was considering putting half a bottle of the engine flush stuff into the gearbox before draining it to see if that helped...is this safe to do? or is there a more conventional method of flushing the gearbox?

or am i completely wrong and something is wrong with my clutch (ie not fully disengaging)?

thanks

Greg

[_turtle_]

Hey greg, maybe coz the oil grade is 75-90? its slightly thicker than the old stuff u had in there? I wouldn't put any of that engine oil flush into ur gearbox, dunno if it does any damage or not but i don't think any ones tried it before. not too sure what kinda crap is in that flush fluid.

are you changing the fluid urself? or taking it to mechanic? lol, coz i need to change mine.

I think that you should drive the car for a few more k's, and then after that change the oil again with that synthetic stuff.

[Genesis®]

try using Nulon G70 instead. its great stuff! i had the VMX80 in mine but felt alot smoother with the G70 in it 3 weeks later.

if that fails, then do the flush but i wouldn't recommend it though.

[Greg]

Hey greg, maybe coz the oil grade is 75-90? its slightly thicker than the old stuff u had in there? I wouldn't put any of that engine oil flush into ur gearbox, dunno if it does any damage or not but i don't think any ones tried it before. not too sure what kinda crap is in that flush fluid.

are you changing the fluid urself? or taking it to mechanic? lol, coz i need to change mine.

I think that you should drive the car for a few more k's, and then after that change the oil again with that synthetic stuff.

hmm the owners manual say to use 75w90...but i get what your saying, an older/worn gearbox needs thicker oil. changing fluid myself. its easy to to do, GenesisR32 posted a great thread DIY thread, its in the FAQ section or i can show ya if you want. thanks denny

try using Nulon G70 instead. its great stuff! i had the VMX80 in mine but felt alot smoother with the G70 in it 3 weeks later.

if that fails, then do the flush but i wouldn't recommend it though.

yeah i put a tube of G70 in...it made a bit of difference but its still really crunchy when cold. i might try this VMX80, everyone seems to speak highly of it. if that doesn't work then its redline time. if that fails then gearbox rebuild time lol thanks mate

[Greg]

i might end up buying cheap oil to flush the gearbox with...i admit it is a bit dodgy using engine flush in the gearbox

[Genesis®]

Vmx80 + G70 =

redline oil = :thumbsup: but expensive

the VMX80 takes a while to run in when you put it in the gearbox and i noticed that its highly effective only warmed up properly but like you, i did experienced some crunching when cold. when i added the G70, it became a whole lot smoother regardless of hot AND cold.

dun you feel your arms muscles tightening up everytime you do the filler and drain plug??

i used the redline stuff in my diff instead.

[Greg]

lol yeah i reckon! i need to buy a longer socket driver to get better leverage...i struggled for at least half an hour to get the plugs undone! thanks for your help

[terry.m]

Sorry GenesisR32, I disagree. Nulon G70 is the biggest load of crap I have ever put in my gearbox. The shit is TOO slippery. My synchros started behaving in ways that resembled a slipping clutch.

I too had Shell Synthetic 75w90, which I feel comes along side the Nulon additive as being the crapiest gearbox oil on the market. As soon as I changed the oil to Shell, the shift from 1st to 2nd was hell worse. I then added the Nulon additive, the shift was still crappy and I started having synchro problems. I drained the crap (Which now looked like cows milk thanks to the Nulon additive) and replaced it with VMX80, bled the clutch...Perfecto! (well nearly) The 1st to 2nd change is significantly smoother, even in the cold. Oh and so far, no more synchro problems...touch wood! The stupid thing is that the money that I have spent so far in this little episode, I could have used RedLine Shockproof for the same money...oh well...you live and learn.

[Greg]

thanks for that terry...you had the exact same problems as i'm having now. i'm going to change to vmx80 ASAP

[Genesis®]

terry - i guess the result varies with the different types of gearbox oil. i had vmx80 with G70 in mine and it works great.