803 Gearbox

[jaguar68]

Hi Chaps,

Is the 803 gearbox man enough to handle the power of the mildly tuned 948cc engine with a 4.22 diff?

Cheers

John

[ampwhu]

i am running an 803 box with a 948 engine and 3.9 diff. works fine.

[bmcecosse]

It will take the power - it's the syncro that is v weak, but if you double de clutch it will be fine. However - do start looking for a good 948 box!

[jaguar68]

Double declutching is fine, I became accustomed to it when my 1098 had the standard 4 speed box.

[mike.perry]

The higher the diff gearing the less likely the 803 box will fall apart. A 3.9 diff will be easier on the box than a 4.55

[ampwhu]

The higher the diff gearing the less likely the 803 box will fall apart. A 3.9 diff will be easier on the box than a 4.55

i sort of understand what your saying, however..... in 4th, it won't effect the box as the power is going from the engine straight through to the axle. the box is sort of 1/1 if that makes sense?

[liammonty]

It's the "power" of the engine that will risk damaging the 'box, not the diff ratio. I guess very low diff ratio (high for BMCecosse ) would increase the torque at the wheels, which would be harder on the half shafts, but not the 'box.

Ampwhu- does your car go OK with that set-up?! I've got a modded 948 on a 4.22 diff, and that feels like it's enough tbh. My 1098 is good with a 3.9, but even standard it's got much more torque than the 948.

[ampwhu]

It's the "power" of the engine that will risk damaging the 'box, not the diff ratio. I guess very low diff ratio (high for BMCecosse ) would increase the torque at the wheels, which would be harder on the half shafts, but not the 'box.

Ampwhu- does your car go OK with that set-up?! I've got a modded 948 on a 4.22 diff, and that feels like it's enough tbh. My 1098 is good with a 3.9, but even standard it's got much more torque than the 948.

fine. i live in a flat area, but have driven the car up a steep hill and it's always made it ok.

i had a 4.2 diff with the box and engine and it was fine. i decided on the 3.9 so i could cruise at a higher speed without the engine screaming. mine goes along nice at around 70-75mph now.

[liammonty]

Sounds good! 948s are much happier at those revs than 1098s which always sound to me like they are going to self-destruct when you rev them too much. Unfortunately, there are a few too many hills round by me I think, though as you say, it must be good on the motorway.