1997 M90 Clutch decision

[TonyS9]

Yes, its 2 masses sprung loaded together, what else is a 'proper DMF'? (M90 gearbox 940s, earlier M47 GB use a solid dogdish flywheel)

I didn't see any rubber, and was able to move the DMF about 5mm by hand.

All it is is moving the springs from the changeable clutch plate to the more permanent and heavier flywheel. I don't really get it, its not like the solid flywheels where a problem.

Mine does judder a little and as you bring the clutch out you can hear its not quite alighned/true.

The ball pin has a plastic hat to lubricate it, once that is worn away it starts to eat the metal.

[Laird Scooby]

Originally Posted by TonyS9

All it is is moving the springs from the changeable clutch plate to the more permanent and heavier flywheel. I don't really get it, its not like the solid flywheels where a problem.

I think the driven plate still has springs Tony, the idea behind the dual mass is to damp out vibrations apparently but i have to agree, i don't get the purpose of them on a petrol engine, i know of many other engines that are much more powerful than the B230 in stock trim (inc turbo versions) and they don't have (or need) a DMF either.

From what i learned when i looked online the other day, they were originally designed for diseasels that have a lumpy idle to start with, allegedly it reduces shock transmission to the gearbox and improves economy.

[classicswede]

Lets get some facts here

1) all petrol engined 940 with the M90 gearbox were fitted with a DMF ( as far as I am aware the diesel had a solid flywheel)
2) The DMF is internally sprung and not held togther with rubber
3) The clutch friction plate does not have the dampers springs fitted that you would find in a traditional clutch
4) the clutch cover works the same as a normal clutch/flywheel setup


DMF's coming into common use to help dampen diesel engines is correct.

(no proof of being fact but likely true) Volvo used the DMF with the m90 to stop the rattle at idle caused by the shaft layout. The m90 was based on the FWD gearbox (M56) and with using the same compents in the RWD box the gears could chatter out of gear. When converting to a single mass flywheel the M90 can rattle at idle so the explination does make sense

[loki_the_glt]

The Exxon Valdez has 222k on the clock, and is probably on the original clutch, but I'm experiencing occasional difficulty getting 3rd gear. It might be the synchro is wearing, in which case I'll live with it but it might be that a new clutch is required.

I've had problems in the past with the inability to select 1st from idle, and both it and 2nd being "unavailable" thereby forcing a 3rd gear start, or with it not going into neutral from 1st or 2nd; the latter felt as though the gear-lever was "trapped" mechanically. The symptoms were most noticeable after a long, motorway run.

If a new clutch is required will the DMF require replacing at the same time, the car being fitted with an M90 box?

[360beast]

DMF will only need replacing if it has failed which I have never heard of one doing on the 940's.

In VW land they fail all the time as they have been made to fail to increase profit after sales.

Volvo on the other hand used to do things properly so I doubt it will need replacing unless the two halves can be moved a large amount easily.

[Laird Scooby]

Originally Posted by loki_the_glt

The Exxon Valdez has 222k on the clock, and is probably on the original clutch, but I'm experiencing occasional difficulty getting 3rd gear. It might be the synchro is wearing, in which case I'll live with it but it might be that a new clutch is required.

I've had problems in the past with the inability to select 1st from idle, and both it and 2nd being "unavailable" thereby forcing a 3rd gear start, or with it not going into neutral from 1st or 2nd; the latter felt as though the gear-lever was "trapped" mechanically. The symptoms were most noticeable after a long, motorway run.

If a new clutch is required will the DMF require replacing at the same time, the car being fitted with an M90 box?

Have you checked and/or changed the gearbox oil at all?

Everything you've said above is pointing to one of two things (possibly both) and that is either a worn clutch and pressure plate (the sprung fingers in the relase plate go weak with age and use, resulting in the clutch not being fully released) or a generally worn box.
It could also be the oil in the box has got so thin it's not supplying enough lube to let the synchro rings do their job.

However the word "worn" covers a lot of bases, it could simply be the clutch hydraulics need bleeding or maybe you have a lazy slave cylinder.

Try selecting all the different gears with the engine off, if you have difficutly, put the clutch pedal down and see if that's easier.

Once you've got a gear (lowest possible), push the clutch all the way down, release the handbrake and try starting the car. If the clutch is dragging, you'll feel it as the starter tries to turn the engine - the car will start to move. If that's the case, first port of call would be to bleed the clutch hydraulics. If that doesn't improve matters then consider a new clutch.

Conversely if you have difficulty engaging any gears with the engine off and clutch down, suspect a worn box. If this is the case, you may well find bleeding the clutch and/or replacing the clutch might give you enough movement in the clutch to make it easy enough to live with the box if it's worn.

As far as i'm aware, the DMF still has a "normal" pressure plate as part of the clutch kit, usually they come as a release/thrust bearing, driven plate and pressure plate.
If anyone can either verify that or explain what's different, that should help your diagnosis further.

[loki_the_glt]

Originally Posted by Laird Scooby

Have you checked and/or changed the gearbox oil at all?

The box apparently uses an expensive, Volvo-exclusive fluid; if it weren't such a hassle I'd replace the flywheel, clutch and box with an M47 set-up, which I prefer, but am not sure if it would take the torque of an LPT/HPT hybrid.

Originally Posted by Laird Scooby

Everything you've said above is pointing to one of two things (possibly both) and that is either a worn clutch and pressure plate (the sprung fingers in the relase plate go weak with age and use, resulting in the clutch not being fully released) or a generally worn box.
It could also be the oil in the box has got so thin it's not supplying enough lube to let the synchro rings do their job.

However the word "worn" covers a lot of bases, it could simply be the clutch hydraulics need bleeding or maybe you have a lazy slave cylinder.

Try selecting all the different gears with the engine off, if you have difficutly, put the clutch pedal down and see if that's easier.

Once you've got a gear (lowest possible), push the clutch all the way down, release the handbrake and try starting the car. If the clutch is dragging, you'll feel it as the starter tries to turn the engine - the car will start to move. If that's the case, first port of call would be to bleed the clutch hydraulics. If that doesn't improve matters then consider a new clutch.

Conversely if you have difficulty engaging any gears with the engine off and clutch down, suspect a worn box. If this is the case, you may well find bleeding the clutch and/or replacing the clutch might give you enough movement in the clutch to make it easy enough to live with the box if it's worn.

As far as i'm aware, the DMF still has a "normal" pressure plate as part of the clutch kit, usually they come as a release/thrust bearing, driven plate and pressure plate.
If anyone can either verify that or explain what's different, that should help your diagnosis further.

I'll try the handbrake off/start up procedure tomorrow; the biggest problem is the unpredictability of the balking.

[classicswede]

The gearbox is fussy on oil and could be your issue.

The DMF gives warning and will rattle away for a lot time before total failure. For a unmolested 940 I would leave it alone unless going noisey.

I would replace the gearlever bushes

on the oil

Oil:

The M90 takes 1.85 liters of oil. The only oil that should be used is the special oil from Volvo. Trust me on this one. The oil will stay in the transmission for a long time so spending a few dollars more on the Volvo oil is not going to ruin you.

The oil to use is the one on the right, with part number 1161745.



The oil bottles pictured have the old style package. In many markets these bottles look more modern.

When changing the oil in the gearbox, remove the bottom plug at the rear of the gearbox and put it on its end with a little slant. Let it sit for a good amount of time to get all the old oil out. If you want you can flush it with a few deciliters of Volvo oil and drain that as well.

Oil specifications:

1161 645:

Quality: API GL-4 / Volvo standard 1273,08 transmission oil 97308

Viscosity: SAE 75W

Density @ 15°C/59°F: 885kg/m³

Oil base: Multigrade, synthetic base

Pourpoint: -48°C/-54°F

Flashpoint: 212°C/414°F

Kinematic viscosity @ 40°C/104°F: 67.8mm²/s

Kinematic viscosity @ 100°C/212°F: 10.5mm²/s

1161 745:

Quality: API GL-4 / Volvo transmission oil MTF 97309 / WSS-M2C200-C3

Viscosity: SAE 75W-80

Density @ 15°C / 59°F: 841kg/m³

Oil base: Fully synthetic

Pourpoint: -60°C / -76°F

Flashpoint: 230°C / 446°F

Kinematic viscosity @ 40°C/104°F: 59.8mm²/s

Kinematic viscosity @ 100°C/212°F: 10.1mm²/s

[loki_the_glt]

I have carried out the basic investigative tests as per Laird Scooby's post, with the following results:

Engine off, clutch out -all 6 gears (including reverse) engageable;
Engine off, clutch in - all 6 gears engageable; there's no appreciable difference in selectability.

Having selected first gear in this manner I started the car - it didn't leap forward. I made sure there was nothing within 20 feet of either the pointed or the blunt end of the car before doing this!

It might be the gear-lever bushes - sometimes it looks as though the gear lever is moving diagonally back and to the left when going from 1st to 2nd.

I might just monitor it, and make more gentle, slower gear-changes for the time being.

[Laird Scooby]

Originally Posted by loki_the_glt

It might be the gear-lever bushes - sometimes it looks as though the gear lever is moving diagonally back and to the left when going from 1st to 2nd.

I might just monitor it, and make more gentle, slower gear-changes for the time being.

With all of the above in mind, i would change the gear lever bushes and also check the engine and gearbox mounts, if they're worn as well they could be allowing the box to move to places the gearlever wasn't intended to reach.

Also if you haven't done it, check there's nothing under your clutch pedal preventing full pedal travel and if necessary, move your seat forward 1/2" just so you know your foot/leg is definitely able to push the clutch all the way down.