Gearbox upgrade

[gerryeddie]

Regarding the notoriously weak 4th gear in the Evo 1/2 in particular, what is the easiest and most budget friendly gearbox upgrade that can significantly strengthen the gears?..especially if the work was to need to be done by mechanics that aren't familiar with Evo's (read country town).
Would need to handle 2.4L E85 levels of torque with power goals up to 350ish atw.

Do any of the newer model gearboxes fit easily or are there any good upgrade options or is simply a matter of custom gearsets?

 

[DOUGMO]

you will need an upgraded 3/4 gear for sure, I smashed mine on a 2.3 with e85

looks like rob might be sending some bits off to be upgraded


http://www.4gtuner.com/topic/25233-double-synchro-3rd-and-4th-gears-broken/?hl=%2B4th+%2Bgear

 

[DOUGMO]

more info here

http://www.4gtuner.com/topic/21982-upgraded-evo2-gearbox/page-8

 

[gerryeddie]

Thanks Dougmo. So it's typically a matter of getting dog gears made up for 3rd and 4th? There is no straight bolt in replacement box options? Ie later model 5 speed Evo boxes (CP, CT's) seem to handle that sort of power no worries at all but are any of them potential replacement options or is it simply not possible?

 

[EVO-00X]

Unfortunately not that we nor the transmission gurus in the US know of GerryEddie.
I'm sure TMZ, TeamRip and Jacks Transmissions have worked on all the later EVO stuff and if there was any way of doing it with newer evo gears they would have done it by now.
Other than going dog gears, the alternative is to fit an automatic transmission.

 

[blackvr]

It is sort of the reason why us gravel rally guys HAVE to run a dogbox in our VR4's/ Evo 1-3 rally cars if you are half serious. The CP/CT gearbox is MUCH stronger and my gravel and tarmac rally customers can run a lot more torque thru a standard set up with out busting equipment. Unfortunately, it's not a simple case of adapting or bolting that gearbox up to earlier EVOs or VR4s !

 

[EVOCPE]

Another option is doing a EVO4+ engine/transmission swap, but involves a fair bit more work

 

[Dave_GSR1.8]

Hm... problems are relative, I wish I had enough power for this to be a problem for me!!

 

[gerryeddie]

Thanks for the info guys. We have all heard stories of 4th gear being munched and I understand it is a biscuit compared to the other gears but out of interest, how strong would you say 3rd gear is? Has anyone ever done 3rd gear? What power/torque levels have people seen it hold on the early evo's? Just wondering how much we could safely wind up the wick on the motor and just use 1-3 only for a while until I get the box sorted.

 

[evo-gsr]

In the link posted above matthias does 3rd and 4th gear upgrades.

 

[gerryeddie]

Yeah I know, that will be something I will look at before long, just in the short term I'm wondering how much 1-3 can stand up to.

 

[evo-gsr]

I have 300awkw and mines holding up so far....for how long though is the ?

 

[EVO-00X]

1-3 gears will handle 500hp atw no problem.
I've only ever seen 4th gear strip on cars making around 300kw atw + or running a RWD setup.
Where I found 3rd gear teeth broken it was due to another problem that caused it. It either was a case of the 4th gear stripping and metal chunks jamming the centre diff/ intermediate shaft/ 3rd gear teeth and damaging them, or the centre crosshaft and spider gears breaking inside the centre diff which locked the centre diff and break the teeth off 3rd gear and the intermediate shaft.
Anybody bordering around 300kw atw should be investing in a 4-spider centre diff in my opinion if they plan to do launches.
I have a friend who is making 500hp atw on E85 and stroker with a stock gearbox. I don't know how he hasn't killed it yet, but he doesn't launch, doesn't have LSD's and doesn't shift too hard.

 

[evo-gsr]

Yeah I don't launch mine....probably why its still holding out!

 

[4piknup]

1 big uphill overtaking maneuvere in 4th gear (past 3 trucks and a bus and a hilux with a boat trailer) away from a gearbox rebuild.

 

[ENGINR]

My 4th gear just failed on a 3rd-4th shift on the track. Was a nice and gentle shift (no point trying to beat synchros) and as soon as I loaded up the gear with full throttle it stripped the teeth.

I don't launch at silly rpm and always treat the mechanicals of the car with a "mediocum of consideration".

 

[DOUGMO]

Yeah I smashed 4th at peak torque in 4th

 

[Cranked]

I had a gsr box with welded centre diff stand up to 300kw, that was banging it down the 1/4 and Jamo u know how I drove that.... Centre diff destruction is only a matter of time though.

 

[Matthias boldt]

have ripped 5-6 times the oem 4th gear one time the 3th and twist 3 times the inputshaft.
at the moment my gearset is 2 years old and one year driven complete 1/4mile saison.
with the qm hd-geardrive clutch i sorted out the imputshaft twisting.
the other gears still working fine and have seen over 15k km hard streetdriven and quatermile.
you can see many videos about my car at youtube.
900+hp/880nm
oem 3th gear is strong and can hold over 650nm

 

[evo-gsr]

I had a gsr box with welded centre diff stand up to 300kw, that was banging it down the 1/4 and Jamo u know how I drove that.... Centre diff destruction is only a matter of time though.

Indeed...it wasnt babied.