Rb20det Gearboxes

[phunky_monkey]

I've just gone through my second SR box (same as RB20), and both times it has been teeth chipping/snapping.

First from a 3rd gear clutch dump, and second from a combination of abuse/power/iffy clutch

Any solutions let me know Troy!!

[nsta]

Im thinking of going the rb20 box route in my r33 gts25t, currently auto, i have around 220rwkw, and may aim for around 240 very soon, i know the rb20's are much cheaper use, whihc is the main reson for considering one.

I'll be getting a twin plate clutch, and lightened flywheel at the same time, should i be okay with this setup, or go the rb25 route, also do i lose any power in going the rb20?

[Sydneykid]

We killed an RB20 gearbox at Bathurst, broke the 5th / reverse selector. It happened on the up change coming up to the kink just before the Chase, hit the rev limiter in 4th and went to change into 5th. Nasty little bang and then no 5th or reverse engagement. So it has an RB25 gearbox now. I haven’t pulled the RB20 box apart to see exactly what broke, must do that one day.

cheers

[predator]

I'll be getting a twin plate clutch, and lightened flywheel at the same time, should i be okay with this setup, or go the rb25 route, also do i lose any power in going the rb20?

Twin plate will kill it very quickly I reckon. Anything with too much bite on it, will destroy the box pretty quickly as it sends the vibration right through the box.

I specifically chose my clutch type to give a longer span to my rb20 box until i can afford the 25 box when changing to manual. Seems to be holding up ok at mild power levels anyhow.

[Sydneykid]

Twin plate will kill it very quickly I reckon. Anything with too much bite on it, will destroy the box pretty quickly as it sends the vibration right through the box.

I specifically chose my clutch type to give a longer span to my rb20 box until i can afford the 25 box when changing to manual. Seems to be holding up ok at mild power levels anyhow.

The R33GTST has a 6 puck paddle, sprung centre clutch plate with a high clamping force pressure plate and a lightened flywheel. The R32GTST has a race (not road) OS Giken twin plate. I don’t believe that there is any difference in the shock loading they send though the gearbox. I think the driver has more influence on that than the clutch being single or twin plate.

cheers

[Ben D]

I have had both in my car (S12 gazelle) and the RB20 DET box was fine for drag racing up to around 500 wheel HP, when the output shaft broke. This was the weakest link in my experience, as its the same diameter as all the early series gearboxes, while I note the RB25 box I have now has a much larger output shaft. The input shafts on either box seem to be strong enough in my opinion (the car 60 fts in 1.33 sec, so its not like i'm taking it easy), but you can break anything if you abuse it for long enough or are determined to break it. I have had no troubles with the RB25 box down to low 9 sec passes with 730 wheel HP, until the last meet where the ignition interrupt for the flat change was switched off, I was trying to flat change with the limiter set at 8500 rpm, and hence damaged the synchro on the 3rd to 4th shift. The car was still driveable, but the 3 little springs fell out of the 3/4 synchro assembly and got munched up - I'm now looking for replacements for them (they're hard to find - can anyone help me with locating a new set of these little buggers ?).

Ben

[T04GTR]

interesting. thats all the proof i need mr ben d

try nissan. youd be suprised at what you can get through them.

if not pretty much any gearbox reco shop will help you out.

[T04GTR]

go the mighty fj. makes me wish i still had mr dr30

[underground32]

Please be gentle with me as I am only new at this but can I ask some obvious (code for dumb) questions.

1. Are the R34 boxes any better than the R33

2. Would an S15 box fit the R32, and if it is not a direct bolt up is it possible. (I race the car at the track a so six speed box is on the wish list)

Any help wpuld be appreciated.

UG32

[Emancipator]

Just for the record..

I spun the input bearing with 170rwkW RB30ET on an RB30 (same as RB20) gear box. Mind you it was a 300K Km box and my spiggot bush failed.

Hyper31 (R31POWER) smashed 2nd gear teeth off with his 200rwKw RB20DET.

Seeing how this second one holds up to 212kw.

[DCIEVE]

Damaged synchro's in my hr31 rb20 box, I doubt the power was a factor.. it just didnt like being rushed through the gears. 2nd went then 3rd before I bit the bullet and installed a r34 25box.

The rb20box behind the 26 (yes its definantly a 20box..) has survived a few years with approaching 400rwhp.. and im yet to make it crunch, it has better shift quality than the r34 box in the rb20 powered r31. Treating it like glass though!

[Fabio]

Any one know what Nissan rated the RB20 and RB25 gearbox as? My understanding is that it is the torque that will kill a gearbox quicker that the KW's, but it is obvious from reading this, that driving style also is a large cause of failures

[CEF11E]

I have killed 2 rb20 boxes.

box 1# the input shaft bacame worn and started to whine. I left it in and kept driving it untill I had a new box. Pulled it apart and the shaft had massive grooves worn into it. and bearings were still in good condition.

Box 2# Lasted for 3 months and wend BANG in a big way. I was in second at mid range RPM, kiked the clutch in and let it back out at 6000 RPM. it gave a mighty crunch crunch BANG!!!! Once AGAIN!! input shaft was rooted and the 2nd gear was stripped and the case was full of crunchy metal bits.

Both boxes were killed with a shade over 200rwkw the first was killed with normal driving on the street and the second was killed drifting on a dry track with crappy rear 225 tyres.

The last box I put in I was very gentle with it.

[underground32]

2nd went then 3rd before I bit the bullet and installed a r34 25box.

DCIEVE, PM sent

Do you have the R34 box behind your RB20? How difficult was the conversion (shortening tail shafts/mounting etc)?

UG32

Edited June 16, 2006 by underground32

[R31 POWER]

As Emancipator said i blew second.Nailed it while in second and then bang lol. I could'nt engage second at all and when i tried it crunched and carried on. About 4/5 teeth were missing and mashed.

One thing i noticed was 5th or reverse had chipped one side of the gear.

Roy go the rb25det box and be done with it

[johan.p.g]

are the gear ratios different between the manual box for the rb30 and rb20

[Cubes]

old thread.

I broke third gear by simply holding the gear out with light throttle.

The acceleration prior was half throttle up on boost in third.

Taking good pics of the teeth I was told by GTRgeoff I think it is that the teeth stripped due to fatigue. Similiar to that of bending a coat hanger until it finally breaks. As the 3ltr torque was constantly pushing hard up against the teeth they were slightly bending then one day just bang.

I've still got good maco shot pics if u want to see Roymiester.

[Roy]

Well new drag radials and 1.5 bar through the TD06 at the end of the month

Grabbing an RB25 box next week so i can stop worrying about blowing it. After 3 days of use with 2 different drivers at Dutton it is a bit noisey, a whine. Cold its a bit stiff, warm it feels fine. Funnily enough shifting at speed and in anger its fine. So will see how it goes if i actually launch it as hard as i can at the drags next Friday.

Will strip the thing when its done, as i want a close ratio box one day and hopefully PPG will release one that i can put in the guts of the thing

[Cubes]

Good stuff Troy..

Can't wait to see the results of 1.5 + drag radials...... or the lack of.. heheh

Joke... lol... I'm sure it will do very well.

[Roy]

Honestly, i will be surprised if i run any quicker then a 12.6...which i will still be happy with...but im betting i wont kill the gearbox. Mine just does not want to seem to die