rb20det gearbox problems

[kwazza11]

my gearbox is starting to play up, if i rev the motor over 4500 rpm in 1st then change to 2nd it crunches severely, if its over 5500 rpm it wont go in at all and will just grind until the revs drop below 4000 or you double clutch it again.

gives me the shits as you gotta rev this motor out and if you cant rev 1st then by the time your into boost in 2nd the other cars i'm playing with are like a car length infront of you....

just wondering if anyone else has had this problem as this is the 2nd gearbox the importer has given me with this problem and my warranty has just run out so i'm rooted.

anyone know if the rb25 box is any stronger and will it bolt up?


not happy. :mad:

[tandy ass]

Can you get it into reverse without gears crunching? If not then you need to adjust your clutch.

If you can get it into reverse without any gears crunching then you have broken synchro rings on your gearbox. If it's just started happening all of a sudden then you will need to revise your driving habits because all of the NA RB30 gearboxes seem to have ultra-weak synchro's. A mate broke 3 gearboxes in 3 weeks due to him snap-changing the gears. Remember there is a neutral between first and second, use it :p

The RB25 NA gearbox is just as weak as the RB30E and RB20DET gearboxes. The only super dooper strong gearbox is the RB25DET one (which I've fitted and cant kill it :))

[kwazza11]

its been gradually getting worse since i've got the box.. i shoulda took it back the first signs of it but i was sick of changing boxes (got 3 duds before this one). plus i crunched it pretty severly dragging a soarer on saturday and i think that made it abit worse.

oh and i'd revise my driving habits but that'd kill the point of having a quick car.. :D

[fast31]

its the synchro's mate
im in the same boat at the moment

[kwazza11]

ok guess i gotta take an extra 500-1000 out on my loan... mabye try track down a vl turbo box if i cant get a rb25det box.

just got my cooler core and the materials to make my exhaust, i guess the brakes will have to wait now...

[tandy ass]

If you have trouble getting an RB25DET gearbox for under $1300 in SA, let me know, I may be able to get one here and shipped to you for less.

[tandy ass]

Oh, furthemore, you need the slip yoke from the RB25DET gearbox and the clutch slave cylinder and a crossmember from an R32 automatic GTSt Skyline which needs to be welded to fit the R31. Then you need an electronics genius to work out how to connect the speedo up. Then you need a single piece tailshaft made up which will cost between $250-$400 depending on where you go. Been there done that :)

[BEV11S]

Im having exactly the same problem with my FJ20ET gearbox
too many revs and it crunches into second

waiting to hear back from someone in regards to a reco box (BUZ11T)!

[2JZR31]

My RB30E R31 has a crunchy box too.

[kwazza11]

well for all the trouble to fit an rb25det box mabye i'll just keep buying rb20det boxs then throw em out after a year.. hehehe

seriously though it'd probably work out cheaper considering i can get rb20det boxes for $300

[fast31]

if its only the synchros, and you can pull the box out yourself, ring around a few mechanics and see what they charge to just fit new synchros. This may be better than buying another box and having it fail after a month.
From my experience, they are a pretty strong box, with only the synchros letting it down

[GTSBoy]

If he has been driving it around with crunches then it will need more than just synchros. All the tips will be buzzed off the gear teeth and it will never shift right even with new synchros.

My advice echos Bozz's. Drive the thing correctly and you will not destroy it.

You will not go much slower to make your change 1 - slight pause - 2, rather than just banging it through.

cheers

[Angle]

GTSBoy,

These gearboxes are constant mesh so the gears will be fine. You may find you have to replace the syncro hub and the syncro ring tho.

[GTSBoy]

Angle,

I'm not talking about the gear faces (helical teeth etc) . I'm talking about the engagement "dogs".....the little pointy ones on the side of the gears and on the selectors. AFAIK there is no way to keep them in constant mesh!

[Angle]

Yeah, that is the syncro hub / cone assembly. You can replace them (and are supposed to replace the cone by the Manuafacturers recommendation every time you replace the syncro ring, they are matched pairs), dunno what they are worth though. Saying that, most people only replace the ring itself.

[RB26DETT]

i took the torana out yesterday and 2nd, 3rd, 4th & 5 where sweet, but i found it real hard to get it in to 1st i dosent crunch but stiff, will it loosen up, or is if FU(ked, to make matters worse the pivot for the cluch, the one that the arm from teh thrust bearing to the slave cyl sists on snaped off now i have to pull the gear box out, to replace that arrrrrrrrrrr

are rb20det boxes expencive to rebuild??

[kwazza11]

actually you loose a hell of alot of distance when draging an auto if you take long changing gears... thats one of the major reasons people go to auto for drag cars.

i would of thought it would be rather hard finding new synchros for a import box like this.

[Angle]

I am not absolutely sure but I think they are a Type 71 nissan gearbox, so the parts are most likely the same as 240K, Bluebird, Skyline etc.

[GTSBoy]

Depends on the year. The later ones (I think like 1993 or thereabouts) have double synchros on 2nd, but the earlier ones don't.

[gtst4]

Originally posted by kwazza11
oh and i'd revise my driving habits but that'd kill the point of having a quick car.. :D That's what racetracks are for:mad:

[kwazza11]

theres a line between dangerous driving and f*cking around with ya mates, you just gotta have the common sense not to do anything stupid.
not to mention open days at mallala are $80! thats alot for an apprentice.

but lets not get into this age old debate!

[tandy ass]

Not to mention the most basic speeding ticket is 30% more than an open day at Mallala.

[kwazza11]

yep. but everyone speeds. i doubt anyone here trying to lecture me can say they've never sped... :p

plz dont judge my driving just cause my gearbox has started crunching..

[tandy ass]

I'm not judging your driving, I'm suggesting you revise your gearchange habits or get the RB25DET gearbox which will handle more torture but even it is still breakable. Remember the RB20DE, DET, RB30E and RB25DE gearboxes are just as weak as one another. I've seen bad driving break gearboxes, I was in the car at the times as a passenger. You simply have to learn how to use neutral in between first - second, the gearbox should slip itself into gear without it being forced.

[kwazza11]

i do pause before changing gears, the only time i crunch it is when i'm having a drag or drifting, drifting its not so bad to pause when changing, you just gotta fry the clutch abit more if you pause. but when dragging i care not about doing damage.. so yea your right, i should get a strong box. but its gunna take time to get that sorta money, so in the meantime i'll have to try make this box last aslong as i can.

[meggala]

do you depress the clutch when changing :D
seriously I can change very fast using the clutch
but for thebest time at the drags you do need to flat change but I dont do that very often at all my box is fine I did have some issues with my clutch which made me thing the box was stuffed.
but I got the pedal adjusted and its fine now.
while the rb25 box is blessed there are options a guy is sell an supra box with an rb bell housing now thats interesting.
good luck kwazza glad to hear your enjoying your car now its done :)
meggala