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All you need to know about the M90

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.
 
M90 is in!

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!!!!
 
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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.
 
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
 
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.
 
That's what the gearbox is for, isn't it? :-D 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
 
Live of a M90 can be short when you're having fun. After my conversion I didn't expect my M90L2 to give me trouble this soon (after 2k mls). Rattling noise at idle (gone when disengage clutch), short squeaking noise when I pull up and shift down from fourth to third only goes smootly with a pause in the middle. Daily driver and absolutely no abuse. Full power only in third, fourth and fifth gear. One thing is clear by now: an M90 obvious can't handle 417/485 for long.
 
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Live of a M90 can be short when you're having fun. After my conversion I didn't expect my M90L2 to give me trouble this soon (after 2k mls). Rattling noise at idle (gone when disengage clutch), short squeaking noise when I pull up and without employing some force, shift down from fourth to third only goes smootly with a pause in the middle. Daily driver and absolutely no abuse. Full power only in third, fourth and fifth gear. One thing is clear by now: an M90 obvious can't handle 417/485 for long.

Did you weld the 3rd gear synchro stop ring?

The rattle might be normal - these transmissions came on cars equipped with dual mass flywheels partially to dampen that. Mine doesn't rattle w/ single mass but I have heavy fluid in it.


I put ~5000k on mine last summer with 350-380hp most of the time and it has been ok- but I think it may have developed a slight howl in 2nd gear. Next year will be a better indicator.
 
No welding yet. Box with dm flywheel (replaced by dogdish now) performed very smooth with 280/410 connected to my old B204FT. Rattle is just two weeks old.
 
I also hear a rattle at idle unless I push in the clutch....

Also 3rd, 4th, and 5th are very noisy when decelerating....

Whatever, I dont really care unless it blows up.
 
I believe the safe limit in a 2/7/900 (i.e. that weight class) is considered to be around 400lbft, so depending on what exactly 417/485 means (bhp/lbft?) that may well be no surprise.

Ryan's gearbox became quite a bit noisier this year. It coincided with the change to a Clutchnet 4-puck sprung disc...but that might be a pure coincidence. That's with a setup making around 300lbft and 300bhp. The box has done around 300k, so it's had a fair life.

cheers

James
 
I'm not too hot on doing the NM / lbft calculation in my head...so I thought 485 NM would be far too low to get 417bhp, but I just did the conversion (I make it 357 lbft), and see that my guess was wrong :rofl: That seems quite low to be causing a problem...we made 300lbft at 20psi, and we've had the car running 27psi before (which I would guestimate would push us halfway towards 357) with no issues...and that's with an early "weak" box with 300k on it. The noise I mentioned earlier...on reading it back, it sounds a little more damning for the gearbox than I think it actually is. We gained some driveline noise...from somewhere...specifically 'chatter' when getting on/off load in traffic. That could well be the clutch disc. It's quiet on-load, and under engine braking.

cheers

James
 
I'm not too hot on doing the NM / lbft calculation in my head...so I thought 485 NM would be far too low to get 417bhp, but I just did the conversion (I make it 357 lbft), and see that my guess was wrong :rofl: That seems quite low to be causing a problem...we made 300lbft at 20psi

417 hp/ 485 Nm at 12 psi on ron 95.
 
Ok, I'll be installing the M90 soon I hope, a few questions..

- The shifter is ugly/scratched. Replacing looks difficult (there even is a special tool for it...). If I get around to changing it, can I also put an 850R shifter on?
- What about ''running in'' the new clutch and flywheel to make sure I get maximum lifespan/grip?
- What bolts should I use to mount the pp? 8.8/10.9/12.9?

Thanks!
 
You mean the shifterknob ? thats a real bitch to take off without damaging it. And yes an 850 one will work. just a pain in the ass but looks real good with a fresh shifterknob !

I don't know whats the trick with running in a clutch, I just use it regularly without doing big burnouts :-P You'll love the 850R clutch set-up

I used the bolts that I got from an old 850 flywheel. Have no idea what strength they are...

Hope you can use this info
 
Yeah, I mean the shifter knob. I'll try to get some prices on new ones, or look on ebay.

In general, taking it easy with a new clutch seems the way to go then, I won't do any burnouts :grrr:

I'll just get some strong bolts and we'll see. I'll report back when the pp falls of:-P
 
That's really good to know. Makes me feel alot better about the M90. I've heard "around 300ish" for awhile, but never heard at what power someone actually has blown one up.
 
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