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All you need to know about the M90

They're just taking chunks out of the sides...? Sure, that'll work. A flat flywheel with LH2.4 timing marks and a suitable clutch would work too.

cheers

James
 
I'd be tempted to jump straight to a billet piece at that point. Isn't there that place that Fred got his from in Sweden that does them for quite sensible money?

cheers

James
 
yeah , i just need to chase him up again foggy !!

itll be a straight replacement for a dual mass flywheel with 850 r clutch for m90 cars .
 
really ? , thats gone up a bit .

the redblock price is a bit cheaper than that , well i suppose with shipping itll not be much cheaper than that .
 
Mr.Borrie said:
you dont happend to have a pic of that
Click to expand...

OMG no....I was just happy to get the @#!* thing in! :rofl:

But seriously.....IIRC, its either a black or white plug with 2 wires. Check out a wiring diagram and you'll see what colors to easily identify them. I was prepared to cut and splice but was happily surprised to see the AW71 and M90 both used the same plug. You did get the harness with it, yes?
 
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I believe the wiring is the same for the M46 as for the M90...except with the two extra pins (to a) give the "3rd/4th gear engaged" signal, and b) to actuate the OD solenoid) not connected.

cheers

James
 
my brother and i will be doing an M90 swap on his 780. My brother did get the front section of the driveshaft from the M90-car but not the rear section. He has the IRS suspention on his 780-IRS.
Now here are my questions:
- does anybody know for a fact if the IRS drive shaft rear section will actually slide in the M90 drivehaft front section? (number of splines the same?)
- does anybody know if these 2-section driveshafts are balanced together (as an assembly) or is each section balanced solo?
 
Janspeed said:
my brother and i will be doing an M90 swap on his 780. My brother did get the front section of the driveshaft from the M90-car but not the rear section. He has the IRS suspention on his 780-IRS.
Now here are my questions:
- does anybody know for a fact if the IRS drive shaft rear section will actually slide in the M90 drivehaft front section? (number of splines the same?)
- does anybody know if these 2-section driveshafts are balanced together (as an assembly) or is each section balanced solo?
Click to expand...

I've never tried it on a 780, but I tried it with the rear half of the prop on an auto MK II Irs from a V90 and the front half from a manual M90 940 and they fit together. Remember there is a master spline, and it isn't obvious.

The balancing on these props is strange, look carefully at the flange bolts, there are several different lengths, that's how they were balanced on first assembly.
 
past saturday we did the M90 swap into the 780 B204GT(no kat). Here are our findings:
- bolt lenghts: there are 2 lenghts holding the guibo between gbox and driveshaft. 6 bolts in total. the shortest 3 hold the guibo to the gbox flange.(the longer 3 don't fit between flange and M90 tailpiece.)
- both driveshaft sections have strips of material tacked on their tubes so we figured they were both balanced individually.
(this is also the case with the M46 front section, it also has separate material tacked on the tube of the driveshaft)
- master spline:female M90 driveshaft section has it, male 780 IRS driveshaft section does NOT have the master spline. yet they fit very snugly, no sloppyness, same total spline number. It just means one single male spline is not meshing any female spline. I don't think that's a problem.
- M90 is shorter and has more girth, but it fits inside the tunnel without mods.
- M90 shifter fits like it was meant to be, no mods needed
- lambda sensor does not clear the m90 so we will need to relocate that sensor.
we used: original single mass LH2.4 flywheel, 850-R frictionplate, original pressureplate, M90 throwout bearing, my'97 940 M90L gearbox + front section driveshaft, 5mm spacing rings behind clutch release arm pivot bolt, original rear section driveshaft, orginal clutch slave cilinder.

preliminary conclusion: easy swap. We still need to evaluate if the clutch actually releases and how the balance of the driveshaft is, how it feels once the car can be driven. watch this thread for a report.
 
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I just ordered a new pivot ball for M46 and here is what it looks like compared to the M90 pivot ball. Maybe you just need to run one of these instead of running spacers behind the M90 pivot ball....
 
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Good find! That would have been the more elegant solution. But i'm not taking it off again. ;-)

Last Sunday we took the 780-M90 for a cruise to a Volvo tradefair (VKB). it ran flawless, perfect light clutch action, the usual smooth M90 gearchanges and i must admit somewhat to my surprise, no drivetrain vibrations at all. We tested it to about 80mph. (it's not engine revs related, it is carspeed related). We figured if it's good enough to 80mph it will be good for all speeds.
conclusion: the M90 front section driveshaft combined with the IRS rear section driveshaft is plug-'n-play! each section must have been balanced separatly.
 
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