• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

All you need to know about the M90

I have just got the flywheel and diesel clutch to go on my car. The only things I forgot about are the flywheel to crank and clutch cover bolts.
The early flywheel has a thinner center on it so I guess I will need the bolts off an early car as well.

Part number for these is 946379.

This number is also listed for non turbo M90 cars, turbo ones should have 978271.

The clutch cover bolts are different as well, can anyone tell me what the differences are.

Thanks
 
frpe82 said:
The L2 has the highest gear of the M90 boxes you know... 0.7 on the L2 instead of the H and L which has 0.81

I chose the L2 because it has a better spacing between gears, and therefore you can also choose a different rear end ratio to get you both acceleration and good economy.
Click to expand...

I have to agree, especially for those of us in the states since suitable axle ratios are quite rare. While there are several ways around this, I'm going to focus on the most cost effective solution which is replacing the entire axle. If you have a 91+ 7/9 series it is nearly impossible to find a 3.31/3.54 1041 axle. A 3.54 1041 would have been in a 91 740 turbo manual(ubher rare, good luck finding one) or a 3.31 in a 93-94 960 wagon(also rare).

The L2 lets you run 3.73's and still get good mileage on the highway. I had been using 3.31's on my M90L but have since switched back to 3.73's since the 3.31's are dog off the line and give poor in gear acceleration. I like the 3.73's but highway rpm's are too high ~3100@70mph, ~3500@75mph.
 
Steve940Estate said:
I have just got the flywheel and diesel clutch to go on my car. The only things I forgot about are the flywheel to crank and clutch cover bolts.
The early flywheel has a thinner center on it so I guess I will need the bolts off an early car as well.

Part number for these is 946379.

This number is also listed for non turbo M90 cars, turbo ones should have 978271.

The clutch cover bolts are different as well, can anyone tell me what the differences are ?

Thanks
Click to expand...

Just to add that I've got a 3.91 diff on my car and with the 195/55 16 tyres it shows an indicated 3000rpm at 70mph. It's a bit high but not that much different from when it was auto, and it doesn't change down a couple of gears every time you touch the accelerator !
 
Well that's a fair point...the advice for people in the US is likely to be different, what with it being harder to find axles with manual diffs. A 0.81 5th box is fine for most use if you have a manual (and non-B200) diff, but I accept that it sucks if you're stick with a diff from a slusher. In that case, the L2 is the preferable option. It's just a shame they're so damn hard to find...

Rob - I think we got the answer to the part number question from Steve...but many thanks for the offer.

cheers

James
 
Asleeper said:
I have to agree, especially for those of us in the states since suitable axle ratios are quite rare. While there are several ways around this, I'm going to focus on the most cost effective solution which is replacing the entire axle. If you have a 91+ 7/9 series it is nearly impossible to find a 3.31/3.54 1041 axle. A 3.54 1041 would have been in a 91 740 turbo manual(ubher rare, good luck finding one) or a 3.31 in a 93-94 960 wagon(also rare).

The L2 lets you run 3.73's and still get good mileage on the highway. I had been using 3.31's on my M90L but have since switched back to 3.73's since the 3.31's are dog off the line and give poor in gear acceleration. I like the 3.73's but highway rpm's are too high ~3100@70mph, ~3500@75mph.
Click to expand...

The point though is that if we assume a 3.73 axle and 195/65/15 tyres, which are common on a turbo then using an L2 box, ie .71 5th gear ratio, means the car is geared for 168 MPH at 6000 rpm, with an H2, ie 0.81 5th gear, it is geared for 147MPH.

Given this is a performance forum I fail to see the point of theoretical gearing for a speed the car will never attain.

There have always been more than one ratio, it isn't simply a post '97 L2 thing.
 
Last edited:
I have been investigating the flywheel and cluch cover bolts and I think these are the ones to use.

Flywheel Bolts - 946379 x8

Clutch Cover Bolts - 959220 x6

This isn't a problem if you are fitting an M90 to an early car with a solid flywheel as these are the standard bolts. I am converting a car fitted with a dual mass flywheel and the flywheel bolts (on the Turbo at least) are different.

From reading what others have done I understand it's necessary to space the pivot out. How do the pivots fit to the casing ? I haven't stripped the car down yet so haven't found out. Is there any advantage in making a proper spacer or are washers really good enough ?
 
The pivot is on a stud, so you can pack washers underneath it. I didn't go that way because I decided it was pointless after having measured everything. That doesn't mean I'm right, but it is what I decided.

When I just put it all together the pedal bite was too near the floor, and the front of the slave cylinder piston poked out of its bore. I made it a longer pushrod to solve the problem works OK now. I think ideally it needs a taller release bearing. I have toyed with the idea if shimming the flywheel out slightly using the shim from an automatic flywheel, but I haven't tried it yet.


Steve940Estate said:
I have been investigating the flywheel and cluch cover bolts and I think these are the ones to use.

Flywheel Bolts - 946379 x8

Clutch Cover Bolts - 959220 x6

This isn't a problem if you are fitting an M90 to an early car with a solid flywheel as these are the standard bolts. I am converting a car fitted with a dual mass flywheel and the flywheel bolts (on the Turbo at least) are different.

From reading what others have done I understand it's necessary to space the pivot out. How do the pivots fit to the casing ? I haven't stripped the car down yet so haven't found out. Is there any advantage in making a proper spacer or are washers really good enough ?
Click to expand...
 
Cheers for that. When you say stud is it threaded ?

I might try and make a few adjustable bits. I did wonder about the pivot stud but it's probably hardened, but might make adjustable pushrods so I can adjust the pedal height properly. I was thinking about the spacers instead of washers as they could be made a bit bigger diameter if needed to spread the load.
I'm guessing a bit as I haven't seen it. Just want to get things ready so I can swap it all over as quickly as possible.

Is there any problem with the clutch plate coming off the end of the splines or is there more than enough spare ?

Thinking about the shim you might have problems with the starter motor engaging properly.
 
Fivehundred said:
The pivot is on a stud, so you can pack washers underneath it. I didn't go that way because I decided it was pointless after having measured everything. That doesn't mean I'm right, but it is what I decided.

When I just put it all together the pedal bite was too near the floor, and the front of the slave cylinder piston poked out of its bore. I made it a longer pushrod to solve the problem works OK now. I think ideally it needs a taller release bearing. I have toyed with the idea if shimming the flywheel out slightly using the shim from an automatic flywheel, but I haven't tried it yet.
Click to expand...

The Lh2.4 crank position sensor might not like dealing with a shimmed out flywheel. Stealthfti and Fredrik have said LH is picky about where those damned holes in the flywheel are.

The reason I'm cussing is because I had a flywheel lightened and balnced. Even after I told the machine shop not to eff with the holes around the FW perimeter, they drilled 3 to a larger diameter when balancing it. Stealthfti and Fred said I would be playing with fire using it in that condition.
 
Yes I hadn't even thought of that. It might be possible to put a spacer behind the sensor.

The enlarged holes on your one might be a problem though. I wonder if it would be possible to glue something light weight into the hole to reduce it's size and not effect the balancing much. I was thinking nylon or alloy but there might be too much heat unless you got some really good adhesive.
 
Steve940Estate said:
Yes I hadn't even thought of that. It might be possible to put a spacer behind the sensor.

The enlarged holes on your one might be a problem though. I wonder if it would be possible to glue something light weight into the hole to reduce it's size and not effect the balancing much. I was thinking nylon or alloy but there might be too much heat unless you got some really good adhesive.
Click to expand...

I had a thread about this about 6 months ago. The consenus was that hole restoration would have to be metal so as to not confuse the sensor. Your idea to space the sensor out an amount equal to the flywheel being spaced out is a good one.

On my soon to be installed M90, I put one washer behind the pivot ball after test fitting the M90, flywheel and clutch assembly to a spare block. 2 washers had the clutch fork pressing against the rubber dust boot in the transmission housing, which in turn pressed the release bearing against the clutch pressure plate a little too firmly to my liking. Also with 2 washers there was not much thread on the stud for the pivot to screw onto.
 
JW240 said:
I know, just different way of saying. lowest ratio. lowest rpm while cruising.
Click to expand...
Ah... yes, I kinda' got that after I made my post. I just didn't change it. I kow what you mean.

Steve940Estate said:
I have just got the flywheel and diesel clutch to go on my car. The only things I forgot about are the flywheel to crank and clutch cover bolts.
The early flywheel has a thinner center on it so I guess I will need the bolts off an early car as well.

Part number for these is 946379.

This number is also listed for non turbo M90 cars, turbo ones should have 978271.

The clutch cover bolts are different as well, can anyone tell me what the differences are.

Thanks
Click to expand...
Yes, the dog-dish bolts is what has to be used.

And the M90 was never fitted to NA cars.
 
Last edited:
MrSteve said:
I had a thread about this about 6 months ago. The consenus was that hole restoration would have to be metal so as to not confuse the sensor. Your idea to space the sensor out an amount equal to the flywheel being spaced out is a good one.

On my soon to be installed M90, I put one washer behind the pivot ball after test fitting the M90, flywheel and clutch assembly to a spare block. 2 washers had the clutch fork pressing against the rubber dust boot in the transmission housing, which in turn pressed the release bearing against the clutch pressure plate a little too firmly to my liking. Also with 2 washers there was not much thread on the stud for the pivot to screw onto.
Click to expand...
The clutch setup is hydraulic. It will never press too hard on the pressure plate.

And if you were not able to fit two washers behind the pivot ball, then how thick were those washers?
 
Fivehundred said:
I have toyed with the idea if shimming the flywheel out slightly using the shim from an automatic flywheel, but I haven't tried it yet.
Click to expand...
Like the others said: It will not get underneath the crank sensor.

You will have to space out the sensor as well.
 
frpe82 said:
You can use any of the bolts for the flywheel to crank. Both the dog-dish bolts and the dual-mass bolts fit just fine.

And the M90 was never fitted to NA cars.
Click to expand...

Thanks
I've ordered some new ones to be on the safe side. I thought the longer dual mass bolts would be too long for the crankshaft.
I keep forgetting that non turbo cars didn't get the M90, late ones had the M47 didn't they. That explains why the bolts are the same.

One other question was about the grease used. I have never been sure about using grease on clutch parts. I asked today (when I ordered the bolts) and they only do large quantities and one of the technicians recommended using copper based grease.
Has anyone got any idea what spec the Volvo grease is ?
 
Most new clutches (Sachs anyway) have a bit of grease supplied with them. I used Liqui Moli MoS2 high temperature/high load grease.

I bought the clutch cover bolts at a industrial hardware store, the size is M8x1.25x20mm. Stock is grade 8.8, i got them in 12.9 (thanks for the tip Wagner). That way the in-hex wont strip out as easily.
Flywheel bolts for the dig dish flywheel are M10x1.5X25mm, grade 12.9, make sure you get the right ones, you don't want one (or more) failing.
More sizes and tightening torques in the 740 buildup thread from Wagner.
 
Thanks.
I've got a Sachs clutch but no grease, oh well !

I had to order a new rear main oil seal from Volvo so got the bolts as well. They should be ok for what I am doing but the sizes you have listed will no doubt help someone else out.

I should be all set to change the flywheel and clutch, thanks for everyone's help.
 
frpe82 said:
You can use any of the bolts for the flywheel to crank. Both the dog-dish bolts and the dual-mass bolts fit just fine.
Click to expand...
Ding ding ding...wrong ;-)

The dual-mass ones are quite a bit longer, as the flywheel is much thicker at this point. You can't get DM ones to clamp a dished flywheel down...and dished flywheel bolts won't make it to the threads when used with DM flywheel. Learned that one the hard way...

cheers

James
 
foggyjames said:
Ding ding ding...wrong ;-)

The dual-mass ones are quite a bit longer, as the flywheel is much thicker at this point. You can't get DM ones to clamp a dished flywheel down...and dished flywheel bolts won't make it to the threads when used with DM flywheel. Learned that one the hard way...

cheers

James
Click to expand...
I am so sorry. That could have gone horribly wrong. :oops:

What I was thinking about were the bolts for the flexplate and the dog-dish respectively. I don't know why I wrote that the dual-mass bolts would fit. My head thought one thing and my hands wrote something else.
 
No don't worry about it Fredrik. I wasn't completely convinced but as I haven't taken it apart before wasn't sure how deep the threads in the crank were.

I picked up the bolts today along with a new crank seal and copper washers for the drain and fill plugs. I asked about the grease for the clutch splines and Volvo list a PTFE based spray in the consumables catalogue. I didn't bother with the number as thay want a stupid amount of money for it and I will only need the smallest amount.
 
You must log in or register to reply here.
Back
Top