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All you need to know about the M90

Thanks for that, I'm no expert reading the parts lists and there are lots of notes ! I might have got there in the end but it would have taken a while.

I used to have a Lockheed catalogue that listed bore sizes for clutch and brake hydraulics, could have had a look in that to see whats what. Not sure where it is now since I moved house.
 
frpe82 said:
8601785 (1330248) is the only master cylinder for the M90 gearbox.

6814719 is the only master cylinder for the M46/M47 gearbox.

And...

6843913 is the only slave cylinder for the M90 gearbox.

6843914 is the only slave cylinder for the M46/M47 gearbox.
Click to expand...

I can compare the last 2 as I have both.

Both pedal boxes I have have the plastic clutch pedal.
 
MrSteve said:
I can compare the last 2 as I have both.

Both pedal boxes I have have the plastic clutch pedal.
Click to expand...
I would also like to make a qualified guess here...

Since the master cylinders are different, the rods for them might also be of different lengths. That might also mean that the pedal boxes for both types are not fully compatible when it comes to the position and pedal stroke.
 
If it helps I can measure the length of the rods I have and the bore size as well. As far as I know they are correct for a car fitted with an M90. Will have to be tomorrow now though as it's late here.
 
Steve940Estate said:
If it helps I can measure the length of the rods I have and the bore size as well. As far as I know they are correct for a car fitted with an M90. Will have to be tomorrow now though as it's late here.
Click to expand...
I am thinking of the pedals as well. Specifically these points:

* Where the position of the hole is on the pedal in relation to the master cylinder (distance from the master cylinder and the angle).
* Where the hole for the rod is on the pedal in the relation to the axle on the pedal box.
 
I have a 240 master cylinder and a 700 series slave cylinder on my M90, everything engages/disengages as it should.

I wouldn't over complicate this part. Match the master cylinder to the pedal box and call it a day (in other words if your car already had an M46 and hydraulic clutch, I would try leaving the hydraulic components as-is.)
 
Probably better to try what you have as the standard set up doesn't seem perfect. You might end up with something better.
My pedal was sitting about 20mm higher than the brake which isn't much, just meant you had to lift your foot at a strange angle to get on the pedal. Unless I have the wrong master cylinder I guess all 940's with M90 are the same.


I have been measuring. I can't get in to measure the slave cylinder bore very well but the other dimensions are accurate.

M90 Master Cylinder

Bore - 19mm
Pin (measured from pivot pin center to face of the stop) - 95mm

Slave Cylinder

Bore - 23mm
Pin (overall length) - 80mm
 
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I'm off to the shop, and have 2 complete hydraulic set-ups in car, so I guess I'll get them out of the car and check it out.

If they look the same, I'll keep the M46 one. (because thats what's in the car where the M90 is going in already).

I'll report back tonight, hope I don't forget to make some pictures.
 
I have 3 slaves and they all have the same part number. One came on the M90 I have.

I have 2 clutch pedals and they look the same although one has a ribbed foot pad and the other has a 3-block foot pad.

I should measure the slave pushrods, though. 2 have plastic pads where they contact the clutch release fork. The other (which appears new) has a one-piece shiny metal pushrod.
 
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I had a look to, and both the master & slave cylinders have the same partnumber FAG6472 & FAG3592 or something like that. I'll take some pictures later.

To me it all looks like the same stuff.

I compared between a '85 740 Turbo & '96 940 LPT.
 
Do you guys like making life hard for yourselves...? :-P It's almost like you take some sort of perverse pleasure in making one of the easiest and most elegant swaps you can do for our cars as complex as possible! :rofl:

We fitted the M90 setup to an M46 car (with the dished flywheel and diesel clutch), and it just worked. At first, the pedal was super-heavy, as we didn't have an M90 fork, and didn't realise they were different. Once we fixed that, it's been no trouble at all. That, again, is a 300k mile old 1995 M90L (worst version?)...it's tight as a drum...and I believe I might be right in saying it's in the most powerful redblock M90 equipped car on the board...at least among regulars...?

cheers

James
 
foggyjames said:
and I believe I might be right in saying it's in the most powerful redblock M90 equipped car on the board...at least among regulars...?
Click to expand...
Too bad I never got a dyno sheet of my car then... It might have beaten it.

How much did the car make?
 
Think it was me that started it, I was born in England though !
My car is fine with this setup it's just the pedal height I didn't like. It was like it before and is just down to the stop on the master cylinder being where it is.
 
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