As the title says, I was mapping mine last night, got to 1.1 bar with a 2.5 with a .70 commpressor ,.63 exhaust housing. An hour in to mapping and the box was very noisy on lift off (layer shaft bearing??? any idea) ok when it is on power. Is it worth rebuilding the 6 speed? Or is a dog box the only option? hoping to run it at 1.6 bar max (for play time) and 1.2 for every day thanks for any help John...

 

I Beleve the guys in the u.s are running the six speed well over the 500/500 mark not sure how long they last at that. Only real issue i hear is oil temps. That's why a few are using oil coolers for the box but this is for extreme power. . what sort of power are you running ?

 

It should be OK for your playtime if you are careful with the changes - the selector fork bushes on some examples can be easy to wear.

Mine was rebuilt after 23000 miles with est 395 to 450 lbft on a 2.5 (up to 1.7bar on GT30R, 0.82AR, headgaskets didn't like that though).

 

With that turbo @ 1.1 EST 400bhp ish spools really low though about 3400 RPM low down torque is massive. Done a five speed already (skin head on 3rd) expected the 6 speed to be better ( although I know its second hand) don’t want to waste money on a re build to break it again!.

Does it sound like the layer shaft bearing to you guys? like an electric milk float on lift off? if so will it last on reduced power say 0.9bar? till i can afford a dog box

thanks for your quick responses

 

Think youll be okay if its rebuilt, judging from what other cars ive seen with standard 6 spd boxes they seem to hold on to the grunt pretty well

 

David Wallis' 6 speed stood upto some serious abuse, with in excess of 550bhp and 490lbft. It now suffers from a slightly dodgy synchro on fast changes from 2nd to 3rd, but thats it.

My own 6 speed stood up very well to the abuse i put it through with an EJ257 and GT30R-LP at 1.6bar, and is still running well on an ej257 producing roughly 400bhp and 400lbft.

 

as steven says, Its had around 600+ bhp through it (hard to tell since last RR session..) they aint going to appreciate the abuse.. apparently the syncro's dont like thick oil.

David

 

In the 80's Porsche added spray bars and an oil pump to force lub the gears/bearings 'stratigically'. Same small mechanical pump fed a simple copper tube oil cooler strapped to the side of the box.
This allowed a significant increase in torque rating over previous designs.
Does the latest 6 speeder have these tweeks or similar?

Maybe I am wrong, but a synchro 'dog' (straight/semi helical) gearbox is as strong as a true Dog change box, just slower to change gear as you need to use/dip the clutch.(?)
Graham.

 

Thanks guys for the help, so looks like the box has had some hammer before i bought it ! any idear's on the price of a re-build for the 6 speed? cheers

 

Call David at www.apiengines.com
Graham

 

Ask John Banks he had his done,

 

How much did it cost m8?

 

I paid £1100 for a rebuild including replacing all the selector forks, synchros and bearings that could possibly need changing and were available. I could have done it cheaper, but I don't like removing 6 speed boxes!

 

removing my 6speed was p1ss easy yesterday , could not have gone better. must have been something to do with you not being there dropping spanners on my head when doing down pipe , spilling oil everywhere and moaning about tight nuts and bolts

 

LOL. You're really encouraging me to crawl under some mad project car aren't you ?

 

where did this mad bit come from ? , I was just talking about a decent 5speed and seeing how close to bob's time we can get with the unopened uk engine.

 

Well we can start with that

 

Still remember putting the 6 speed in pig of a job and very heavy

 

Wasn't that bad for my dad and I to do...mind you we had speant an hour beforehand making a cradle for the gearbox that rested very nicely on three trolley jacks so we could position it easily and slide it into the engine bay...worked a treat

 

Me and steven never seem to struggle, unless we are hungover..

But then a 2 post lift does make it easy..

David

 

I've just seen a house for sale in my price range, near where my new job is, with large garage and a pit...granted it's no 2 post lift, but it beats lying under the car at least

 

So i need to save for a two post lift and a gearbox re-build lol

just hope it dont break again if i go for it

 

my six speed is handling about 500 at the moment with no worries yet. other things tend to go in the drive train like driveshafts etc