M10 Gearbox Strength - 4 or 5 Speed????

[sleeperviva]

Greetings chaps!

Currently building up a turbo'd M10 1.8 for my current E21 but might be obtaining an earlier vehicle for parts which happens to have a 4-speed box

My question is.....which is stronger? standard M10 4-speed or overdrive 5-speed?

Dont fancy blowing up my 5-speed as it might take awhile to find another

Cheers
Steve

[e21-Mark]

I've always been led to believe 4 speed is stronger but have never blown either as the diffs gave way first.

[Danny043]

I believe a 5 speed overdrive box is nothing but a 4 speed box with an overdrive housing bolted to it. So I reckon there's no difference in strenght.

[sleeperviva]

Thanks for your replys gents!
Looks like I will just go with the 5speed for now

[Sav]

Has anyone had any more experience of M10 Turbos and the 245 overdrive? A place near me said the limit is 200ft-lb torque, but I'm sure I've heard of them standing more.
Did the 5 speed hold up well for you? and at what Bhp/torque level?

[Wilmo]

Probably the clutch is the weakest link. If you do not beef up that too much, it will protect the gearbox.

I have a NOS clutch with an E30 five speed overdrive gearbox. With my M10 I put about 160hp through it.

[sleeperviva]

10yrs ago

Car never received its lovely, well assembled M10 turbo engine as I got bored with the car and flogged the lot!

Sorry guys I have nothing else to add