Gearbox internals

[capnmchl]

Out of curiosity mainly, is it possible to change the internals of the gearboxes between models?

For instance, could you take the shafts from the IS 240 box and use them on a normal 240 box? Or take the 260/s internals and use them on a normal 240 box? Can singular gears be interchanged or are they part of the shafts?

Just thinking on behalf of the track slags, the IS gearbox has a much shorter 3rd gear which must be way more useful on the track?

Does the M20 have a different bell housing pattern from the M40 and 42 engines? I take it the M10 has it's own bell hosing pattern, which is the same as the M30?

[Grrrmachine]

I'm no expert, but there are certain things you can and can't do by default.

For starters, the 260 box is quite a bit longer than the 240. For that reason, I'd expect the shafts inside not to be transferable, and therefore by definition the gears.

The 240 has two bellhousings; one for the M20 and another for the M40/M42 engines. Both will bolt to an M50 engine, but the M40 box will have a significant tilt to it, probably due to the different angles those engines sit at. Could an M40 box be redrilled to fit an M20, or the innards swapped over? Who knows - don't think anyone's been daft enough to go to all that effort just for 0.30 difference in the ratio of one gear.

[capnmchl]

I've never seen a 260 box, let alone side by side with a 240, so that's good to know.

Surely there are 3 bell housing designs for the 240? M10, M20 and M40?

Whats the deal with the M42 box when fitting the M50 engine then? Does it have the tilt and bell housing of the M20 240 boxes but with different internals? Or do you still get the tilt issue with them?

You're probably right in saying it's not worth stripping down a gearbox for .3 of a ratio, but it's interesting to know/learn these things. It's a shame they didn't give them detachable bell housings

[greg124]

For what its worth, the standard 4-speed slush box can be swapped from an M10 to an M40, which suggests that both of those engines will accept the same bellhousing.

[daimlerman]

M10/M20/M30 sit at a different angle to M40/M42/M50.

Therefore a Getrang 240 sourced from either M40/M42 will bolt straight up to M50/M52.

Getrang 240 sourced from an M20 will sit at an odd angle,ie with the filler plug too low,making it difficult to service,apart from the gear linkage issue.

With these 'boxes being so robust and in plentiful supply s/h,it's not yet been worthwhile finding out just what swaps into what regarding their innards.

Perhaps the OP would care to carry out some experiments and report the findings?

[capnmchl]

I think the bell housings are changeable on the autos anyway greg. I've got one sat around I'm taking apart from a transmissions assignment, so I'll be able to double check.

I'd wouldn't mind taking some apart, but it's finding cheap boxes. As you say, they're so robust you never tend to see any that are broken going cheap.

So the M50 sits at the same angle as the M40 engines?

[daimlerman]

So the M50 sits at the same angle as the M40 engines?

That's right!

This is one reason for it being the 'box of choice for M50/M52 conversions,I use one in my touring.
Other reason is that 4th is direct drive,5th being overdriven.

By comparision,the later ZF box used in E36/later E34 has a direct 5th,giving diff ratio difficulties.

From a personal POV,I feel that Getrang 240 is perhaps operating at it's limit with a tuned M52,remember that the 'box was first designed for E21 323i with about 150bhp,assume that it's design capacity is 150% of that and you are looking at about 225bhp...M52 with M50 inlet and a re-map shows around 220bhp..

I have had absolutely no issues with my set-up,though.

[capnmchl]

That's fair enough. I'd heard/read about the whole diff/gearbox combo's associated with the E36 and 318is boxes. I wonder if anyone has had a problem with the is box taking the M52 power.

Guess I'll just have to trawl ebay and find some cheap boxes when I have the money. Might have to pick up an is box when the inevitable M52 conversion happens.