5 Speed gearbox safe power limit?

[Davie M12]

Anyone on here running big power on the 5 speed box?
My GTO3 is currently at jetstream getting some upgrades and as part of the work I'm getting the box sent off to gerboxman for a freshen up & uprated bearings etc.
I have the Quaif ATB diff and as far as I understand its the old open diff that is the weak part in the 5 speed boxes?
I'm aiming for 450 bhp and around 420 lbft question is will the box take this OK?
Is it worth the extra cash to add a cooler or is this overkill?
I'll be doing occasional trackdays no racing or endurance events!
Any info or real life figures would be greatly appreciated!
Cheers

[andygtt]

lot of people have run up to 500bhp with the 5 speed box... just make sure you run a good oil cooling and have an LSD

edited to add that its important to have cooling IMO

[TuxMan]

Hi Dave , I ran 490bhp and 420ftlb through my uprated 5 speed for 2 years with no problem , box is now running in Devils car at the same power and is still running well .

Tux

[mgbond]

Is gearbox cooling a big issue for road?

So far my gearbox temps arnt getting that high. Will be interested to see how high they go at Silverstone.
What temp is regarded too high. I was informed 105 deg is when I prob need to back off?

[The devil]

TuxMan said:

Hi Dave , I ran 490bhp and 420ftlb through my uprated 5 speed for 2 years with no problem , box is now running in Devils car at the same power and is still running well .

Tux

Yep, its running 500 BHP and 440 ft/lb and so far so good,,,,,fingers crossed

[Davie M12]

Thanks guys, good to hear there are a few boxes holding this power with no issues!