m45 to m46

So I have a 78 244 with a m45. They have a 87 245 with an m46 at the junkyard, 120k. I was thinking that the extra gear would be nice. I know that I would have to do some wiring for the overdrive, and I know that it will all bolt up, but my major question is about the driveshaft, will i be able to use the 245's or will i have to find another 244 with an m46 and use that one? Also is it worth it? Any comments welcome, thanks.

The driveline is for an M45 is longer than an M46 because the M45 does not have the overdrive unit which sits at the back of the M46 transmission. So you would need to take the driveline off the car with the M46 (and look at the U-joints) for it to work in your car. It's totally a good idea because the OD will give you better fuel economy at highway speeds. You may also want to replace the clutch since I'm not sure the discs are the same for M45 and M46 Mk II (e.g. 1981-1991) transmissions.

If I'm wrong with anything I've said, feel free to correct me.

Last conversion I did was a 122

The driveshaft from the donor car should be OK, the wheelbase is the same for the 244 and 245. To be safe you may need to make some measurements.
Absolutely it is worth it! OD will bring those RPM's down in 5th, increase your MPG's, extend the life of the engine and just plain make it more fun to drive.
I would replace the piston seals, orings,clean the two filters and use a good synthetic like Redline MTL. See your IPD catalog. Good luck!
Possibly someone else has actually done a 244 conversion and can be more helpful.

All models...242, 244 and 245 are exactly the same dimensions so no worries about the rear half of the driveshaft. As already mentioned, you'll need the front half from the donor car.

A couple of "gotchas" to watch for.

Flange size...your M45 car will have a tiny driveshaft and, as a result, a small flange. The donor car may have the larger driveshaft and therefore larger flanges. If that's the case, you'll need the entire thing as well as the pinion flange on the rear diff. Obviously the output flange on the donor transmission will match the driveshaft, provided they're coming from the same car.

Transmission crossmember...it gets moved. There will be additional bolt holes further back in the frame rails.

Be sure the tranny mount gets replaced while you're doing this. It'll be out anyways.

Be sure to grab the entire wiring harness. There will be wiring to the shifter knob, to the relay that sits beside the glove box and wiring to the od light on the cluster as well as a power wire running to the fuse panel.

Thanks for all of the help. Been wanting to do this for a long time and now that I see that there is no fabrication needed i believe this is next in line on my project list. Again thanks, and I will chime in if I have any problems!

Well worth it

I did this in my 79 242DL and picked up 3mpg on the highway. Well worth it and everything does bolt in.

Finally dug up a thread that is close to answering my question! Swapping a B230 and M46 into a '78 242 M45.

Are the two transmission crossmembers the same (M45/M46)? Or do I need to grab an M46 crossmember? If they are the same, then I should be able to use this mount for the M46 as well, correct?

Either way, I need to move it back to the extra mounting holes, as noted by 245gti.

I believe they'll be the same, but you could always throw the tranny mount out of the donor to be sure. It's easy, and that way you're covered..

I'd rather have the M47 if I were you. M47 is shorter, lighter, has pretty much the same ratios and no wiring needed. Kind of tough to find one that has the hole for a speedo cable though.

D.E said:

I'd rather have the M47 if I were you. M47 is shorter, lighter, has pretty much the same ratios and no wiring needed. Kind of tough to find one that has the hole for a speedo cable though.

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I use the M47, and use a GPS for a speedometer, only twice has it been cloudy enough not to get a speed reading. It seems more satisfying tossing it into 5th and hearing the BOV vent as you're passing someone than clicking the little button. On my way home from the York PA meet I I had to exercise 4th gear going up this steep hill on I83, to get past a left lane hogging Civic and serving an S2000 a little Volvo humble pie and to get away from this annoying chick in a Corolla riding my ass that thought she should be in front of me. Left them all like they were standing still

D.E said:

I'd rather have the M47 if I were you. M47 is shorter, lighter, has pretty much the same ratios and no wiring needed. Kind of tough to find one that has the hole for a speedo cable though.

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I agree, although "tough to find" is an extreme understatement..

I'd don't recall moving the crossmember on my swap from an M45 to M46 in my 79 242DL. But it's all there to bolt in what you want.

But I did go with the hd tranny mount on my turbo. I also had to use spacers on the crossmember at the body because the stiffer mount pushed the trans up into the top of the tunnel. I used the stock spacers which on are the automatic cars. I then added a small plate of flat aluminum to make it thicker. There are two choices for a hd mount. A 140 series engine mount. Or a 160 series engine mount. The one for the 164 is very hard but gives the most rigid support. That's what I used. A genuine Volvo one if still available is best.

mtd240 said:

I agree, although "tough to find" is an extreme understatement..

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Well, the M47 was standard equipment for the 240 GL in 1983 and the 240 didn't get an electric speedo until 1986 so they did exist for 3 years, but aren't very common. I do not know, however, if they were ever sold in the US.

D.E said:

Well, the M47 was standard equipment for the 240 GL in 1983 and the 240 didn't get an electric speedo until 1986 so they did exist for 3 years, but aren't very common. I do not know, however, if they were ever sold in the US.

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US never got the first generation M47.