9 replies to this topic

[foodboy]

Hi, How much power can the gearbox really take? iv got a 1380cc last dynoed at 109 bhp iv done some more work on it an it will be pushin out more power and torque. the car will be on the road and will be on the track, hill climbs etc. will a std box hold or do i really need to go straight cut??

cheers Ben

[Paul Wiginton]

The gears themselves will probably be fine but the diff and drop gears ought to be upgraded as theyre the weak points

Paul

[foodboy]

Its got a LSD i was thiking of getting straight cut drop gears.

Ben

[Jammy]

Straight cut gears by design aren't any stronger than helical. If the materials are of a higher spec then they will be stronger. By design they simply reduce transmission losses, resulting in marginally higher engine output at the wheels.

[blacktulip]

i reckon a well built standard gearbox can handle IRO 80-90ft/lbs of torque before problems occur.

[mk1leg]

Tran-X gears are about the best can take around 130bhp ..........

[Sprocket]

Thats crap as the gearbox does not transmit power, it transmits torque and its the torque that kills them.

Metro turbo box took 87lbft, so recon on another 50% before it becomes a real problem. Usualy when you have an engine that puts out 120+lbft you will be rebuilding the box a little sooner than 80k anyway

[T.Harper]

Straight cut gears just eliminate side loadings caused by helical gears. This is where you often see first signs of gearbox failure, as the idler gear munches its way into the housing.

[foodboy]

ok but, in my case will i be having problems, will it brake on the start line, swift tune says that unless im careful it will brake.

[Ethel]

As Sprocket said. Torque is a force and it's force that shears cogs 'n shafts. doubtless if you revved the mamories off it and dumped the clutch in 1st you could break something but it's not likely to be track records as you disappear in a cloud of tyre smoke. Don't think of gearbox modding as being just for reliability ratios that keep you in the power band will be as much use as extra HP.