Rb20det Gearboxes

[Roy]

Has anynone taken the time to strip down their RB20DET gearbox when it has failed. Im tryign to get an idea of what component/s fail. Im reluctant to throw an RB25 box in my car due to the expense and the weight when my RB20 bos has done a pretty good job holding the power im making

So if i can get an idea of what parts fail, and whether they can be economincally strengthened then i would like ot beef up the lighter RB20 box.

Any help would be greatly appreciated!

[Bl4cK32]

Cubes smashed 3rd gear loaded it in 3rd gear....hes got pics somehwere too...

Weight isnt really an issue. I can easily lift a rb20 box by myself, and can still lift a rb25box. It is heavier, but not anything u would notice while driving id think....wind in another 2psi and u wont

[AzzurrA]

i'm wondering the same thing, as my gearbox seems to be dealing with my power okay (only 170rwkw, and i don't think i'll be chasing more) however it is whining like a biatch, and if its worthwhile, i might just get it rebuilt (anyone know a rough price for a gearbox rebuild?)

Frankly, i don't see the point in doing an RB25 box conversion, when the RB20 box seems to be handling the power okay, and for the same money as the conversion with the 2nd hand rb25 box, i could have a brand new RB20 box?

thoughts?

[dangerous_daveo]

Already told you about the weight issue Roy, start exercising that and you can change your drive shaft to a 1 peice, that will shave some weight.

But bearings, syncros. The quotes I got, with the 'warrenty' they offered, I couldnt justify the money of fixing it. I do plan on going an RB30 at some stage tho, so that did infulence my decision.

Do it once and do it properly.

[Roy]

So its the gear themselves that let go? A friend is a transmission engineer with Ion and he is a boffin to boot....so was talking to him and he suggested its not rocklet science to beef up the box, secret is findign what the weak part is...im thinking close ratio 5 spd box whislt we are in there

LOL...if i had the money id buy the spare gearbox a friend has, close ratio 5 spd Hollinger with magnesium bellhousing to bolt straight up to the almighty RB20

[Roy]

Ok the latest is I need to get my hands on a cheap 2nd hand gearbox, be it running or broken.

The plan is to strip down the RB20 box and do the following

- replace synchros if needed

- micro bead blast the gears, concentrating around the root of the gears

- Phospate coat the gearset.

If the money doesnt add up too fast we will be:

- replacing the 2nd driven gear, depending on how much it costs to manufacture one form EN36 bar stock. Im guessing way too much.

- Will also look at enduction hardening the gear surfaces.

Fingers crossed it will be a tough gearbox that weighs a lot less then the RB25 box

[AzzurrA]

what about cryo-treating the gearsets? possibly cheaper.... don't know the 'real world' benefits though, as i haven't seen any back-to-back comparisons of before/after, only the 'claims' of what it does...

[acsplit]

Well hopefully soon PPG will be making some nice changeover rb20det gearboxes. but they will certainly cost more than an rb25det one

[Roy]

My friend advises me this is the way to go about reliably toughening the gears….whether that’s the main mode of failure in the RB20 gearbox im still not too sure…So if ppl have broken gearboxes and are in Melbourne or Sydney, then id be keen to get my hands on them. Not that i know what im looking at but my friend will

And are you hopng or you know that PPG will be makign something for them shortly? Because that would be ideal, a close ratio box that weighs no more then std and is strong...id be happy to pay the money

[R31Nismoid]

I almost shredded mine.

The whine that the box gave out was amazing.

Although i think its the added torque of the RB25 at the time (and 330rwkw) that kinda pushed it to the edge

Mine was syncro's as far as i could tell as it didnt want to go into gear in the upper RPM when it came time to replace it

[acsplit]

roy a friend of mine is in the process of sending over a CA box and rb20det so should be a goer

[Roy]

Ash, still go the the 20 box?

Also i have read that the itnernals of the CA and RB20 box are similar...and the Jpas do make gearsets for CAs...or use to?

[browny]

Hey Roy & others,

There's a topic come up on Performance Forums lately where one of the guys has come across a RB20 box with some sort of custom close ratio gearset in it.

Basically they are trying to figure out who might have done the work and whether it's worth the effort of trying to sell it off.

Have a look:

http://www.performanceforums.com/forums/sh...php?p=839536283

[Roy]

Thats interesting...and seriously, if a PPG RB20 gearset is going to be available in before end of August then i will grab one, as im really what Dutton will do to the std 180,00km gearbox

This would be dreamy, and great for the peaky RB20...

http://www.ppgearbox.com.au/images/content/SCDOG.wmv

[T04GTR]

i have blown 11 of these. (fs5w71c)

each one failed on the gear teath. all due to abuse and mashing through the gears.

one other problem,apart from the shiet synchros is the small bearingfor the countershaft.

if heavily loaded the bearing race cage can let go. this leads to a knocking sound at idle. with the noise getting quieter as you go up through the gears.

good quality oil can prevent this from happening.

the main problem with these gearboxes is they get "crunched" through the gears. this shock loads the gears and causes them to crack then fail.

the counter shaft has less durable metal for the gear facings. its the counter shaft that is always the culprit.

so a 25 or fs5r30a box upgrade is highly recomended as the metal used is of higher quality.

not to mension much bigger gears and synchro rings. also the bearings are much bigger.

so basicly it would be much less stressed.

[R31Nismoid]

Dont have the box anymore... well.

I doubt Benno would have kept an RB20 box in his workshop

i'll ask, but un-likely.

Otherwise you could have it for free

[Roy]

i have blown 11 of these. (fs5w71c)

each one failed on the gear teath. all due to abuse and mashing through the gears.

one other problem,apart from the shiet synchros is the small bearingfor the countershaft.

if heavily loaded the bearing race cage can let go. this leads to a knocking sound at idle. with the noise getting quieter as you go up through the gears.

good quality oil can prevent this from happening.

the main problem with these gearboxes is they get "crunched" through the gears. this shock loads the gears and causes them to crack then fail.

the counter shaft has less durable metal for the gear facings. its the counter shaft that is always the culprit.

so a 25 or fs5r30a box upgrade is highly recomended as the metal used is of higher quality.

not to mension much bigger gears and synchro rings. also the bearings are much bigger.

so basicly it would be much less stressed.

Thanks for that...With regards to crucnching gears...im pretty easy on gearboxes so thats probably the reason why it still lives.

So based in what you have posted, micro bead blast the gears will help with the strength (or at least relieve the weak/stressed point) . And good quality oil (i use Castrol Castrol Syntrax 75W/90 ) combined with the phosphate coating may help the bearing race cage problem you mentioned

[sproosy]

my gearbox had some slight "death whine" when i purchased the car in Nov 2004. Now its starting to sound like a Cat on heat!

Very interested!

[FATGTS-R]

Hi Roy

Just to add, the gearbox on the 31 sounded fine when I first got the car with about 150rwkw.

It still sounded and drove the same all the way to 235rwkw untill I did a windout in third gear on a rare occasion that it didnt break traction and then it instantly had a very loud whine.

This whine lasted for over a year and also when power upped to 285rwkw. I decided to drive up to PI to see the group A racers and cruised all the way up at the speed limit and as soon as I slowed down to 60 as I came to the island a loud,grinding rattling noise started. It grings in neutral and if I press the clutch it goes away which seems like a bearing. I also never was an aggressive shifter.

[Cillham]

whats the weight difference between rb20 and rb25 boxes?