m47 to m90 gearbox (UK PEOPLE)

[barkster1971]

It was of course a m46 not m47 but the dimensions are the same.
It drives so much better now.
still the same flywheel with a sachs diesel clutch for later 940's (1994-1998).
I didn't have a diesel prop m90 one so used one off a petrol car with the 4 bolt flange changed to a 3 bolt petrol one off the back of my dad's petrol m90.
You need a m90 diesel box with the gearstick assembly as that's particular to the diesel box being a bit longer than the petrol one.
All bolts together nicelt and the car is a lot nicer to drive.
First gear with the m46 was too short.
Plus if I wan to increase the power the box and clutch will be fine.
The m46 overdrive was working only when warmed up so it was no good.
you need the diesel gearbox support as that is slightly different. and a good m90 prop bearing as it's a lot thicker than the m46 one .

[v8volvo]

Carl,

Wanted to see if you would be willing to add some more details on how this setup has been working for you now that you have had it in there for a while, thoughts on whether it's a worthwhile upgrade and anything you would recommend doing differently.

I have been casually looking for an M90 swap kit for my 1983 760 and have now found one, complete with shift linkage, driveline, etc. Getting tired of the M46 and the need to do something to it at least every year or two. I also found parts to swap to an M47 but those have the same extra short 1st gear ratio as the M46 and are known for being more fragile, although I doubt I would break one the way I use the car. The T5 swaps are appealing and they have better ratio spacing but everyone seems to have problems getting the shifter area to seal up well and positioning the shift lever without cutting up the floor, plus they are pretty noisy. And for the cost of the adapter and machining and driveline work, plus a decent used T5 trans, the price difference in the end is minimal. So, going with the M90 that bolts right in and has better ratio spacing is a route I am considering.

Here are the specific questions I have:

- Did everything work out OK with the rear transmission mount and its crossmember? Would you be able to post some pictures of how the late style mount bolted up to the early car you have, and what the canted front motor mounts look like now with everything installed? You didn't have to swap to the late style vertical motor mounts and brackets, right?

- Did you need to change to a hydraulic clutch pedal, or were you able to continue with a cable operated clutch somehow?

- It sounds like you kept the original dog dish type solid flywheel that had been used with the old M46 and that worked fine with the M90? Is the clutch disk different, different input shaft splines etc? Or could an M46/47 type friction disk work also with an M90? M90 specific parts might be tough to source here.

- Are you happy with the shift quality, gear ratio spacing, and noise level of the gearbox? How would you compare it to the M46 you took out?

Thanks in advance for any more you can share.

[barkster1971]

There's no cabled operated clutch on a 760. Maybe on an old 240. As the floor pan and dimensions are the same as a 940 (which had the M90) everything bolts on. Don't have to mess about with engine mounts. M46 is old tech and a lot more agricultural than the M90. The gear ratios are a lot better too, I did put new gearbox oil in it. No more noise than the old one, but I miss the UP arrow in green on the dash.

[v8volvo]

Thanks for the reply and info.

Interesting your point about the cable clutch. It took me a minute to realize that that difference there is probably due to RHD/LHD variation. The LHD diesel models here, all of them (240/260 and 740/760), did have cable operated clutches. Non turbo 700 series gas cars had cable clutches too. Only the turbo gas and 16 valve gas 700 series models got hydraulic clutches here. By contrast it sounds like RHD UK cars never had cable clutches in the 700 series at all and used hydraulic action across the board.

Makes sense since running a cable from the right hand side of the firewall all the way around to the left hand side of the bellhousing probably would have been difficult, easier to use hydraulic tubing and cylinders on an RHD car.

So in short, converting from cable to hydraulic clutch is an extra step I would need to do with my 760, whereas you fortunately didn't have to worry about it.

Glad to hear you are liking it. I'm thinking about it. I guess I would need to round up a 740 Turbo clutch master cylinder and pressure line and pedal. That would be annoying, since I threw a whole set of those exact parts away a few years ago, that I removed from a turbo gas 745 I converted to turbo diesel (now owned by member RedArrow here) and had to swap the original hydraulic system to the diesel cable setup. Guess I should have kept them.