All you need to know about the M90

[15A]

Originally Posted by Mr.Borrie

you dont happend to have a pic of that

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

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?

[foggyjames]

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

[15A]

Got a major malfunction with second gear. See here:

http://forums.turbobricks.com/showthread.php?t=181919

Any thoughts?

[Janspeed]

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?

[Fivehundred]

Originally Posted by Janspeed

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?

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.

[Janspeed]

good info! Thanks!

[foggyjames]

Interesting comment about the bolt lengths...never noticed that...

cheers

James

[Janspeed]

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.

[ZVOLV]

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....

[Janspeed]

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.

[Asleeper]

I believe the front and rear halves of the driveshaft are seperately balanced. I haven't had any vibration issues with mine at highway speeds.

[ZVOLV]

It's been about 100 miles and so far it's wonderful!

2.4 flywheel, 850 aftermarket unsprung clutch disc, 740 pressure plate, 740 release bearing, M46 pivot pin.

Also used 850 pilot bushing from FCP.

Clutch disc was only about $80 from clutchnet. Everywhere else, including dealer, only sold complete fwd clutch kits for $300-$500.

6 m46 driveshaft bolts and nuts. All same length....not sure why above poster had probs.

Driving is so much better with 5 real gears!!! My OD would only work after 50 miles of driving and it was getting old driving to work at 4500 rpms.

Hoping mpg has gone up drastically from the prior 15mpg.

I found a cracked egr pipe and then capped of the system by installing a Miller High Life crushed bottle cap between egr flange and manifold.

Also spaced wastegate actuator with a nickel for 5psi more boost!

Rpms are about 3000 at 65 mph so a 3.3 axle might be better than the stock auto 3.73

I'm loving it so far!!!!

[Captain Bondo]

Originally Posted by ZVOLV

Rpms are about 3000 at 65 mph so a 3.3 axle might be better than the stock auto 3.73

I'm loving it so far!!!!

+1
I find the same thing w/ 3.73's and M90, it's not a very good diff ratio for the trans. 3.31's would be the gears to have with an M90 IMO.

[foggyjames]

Glad to hear you're getting on well with it, Zach!

3.54:1 is good too...but I agree that the 3.31 is probably best.

cheers

James

[Janspeed]

Originally Posted by foggyjames

Glad to hear you're getting on well with it, Zach!

3.54:1 is good too...but I agree that the 3.31 is probably best.

cheers

James

IMO longer ratio is not always better...

i have the 3.54:1 + m90 + K-cam on my car.
The annoying thing with regard to this setup is that the revs drop to about 2000rpm when doing 100kmh/60mph and when you want to speed up again quickly you need to drop down a gear because the boost only starts to develop at 2500rpm. Really annoying when you are just cruising and not in hyper-attack mode. Pick-up below 2200rpm is just weak sauce when running a K-cam in a turbo engine. (8.7:1CR)

Conclusion:
- if you want to use a highish reving cam, take the 3.73:1.
- if you keep on using the low rev torque cams (T or M) you can use the longer ratio's without having to drop gears for decent low rev acceleration. This setup will also give you good mileage.

[foggyjames]

That's what the gearbox is for, isn't it? I don't see there's any way around it. You want big power from low displacement, you're going to need the use the gearbox. If not...put a V8 in?

Having said that, Ryan's car runs an M90, a 3.54:1 axle, a K cam and a T3/T4 hybrid, and it still picks up from 60mph faster than a standard 740 Turbo. It's weak compared to pick-up from 80mph, but it's not as bad as you might expect. To be honest, I've been surprised by how good it is.

cheers

James