I have a 91 740. the trans was apparently a manual overdrive unit and after searching pull-a-part several times during the past several months I concluded that either these are very good units or they didnt make many of them.Anyway I purchased the elect overdrive unit and now have to go back for the driveshaft,some relays,etc.I am a fairly experienced mechanic and have fallen down slippery slopes,am I going down one now? thanks chris

If I read your thread correctly you currently have an M47II gear box, you have acquired a P or J type overdrive that would normally go onto an M46 box and you would like to know if it is possible to put the overdrive unit on the back end of the M47II? If this is so then no it is not really doable.

If you are talking about a direct swap, take out the M47II and stuff in an M46 complete unit? Well then the answer is yes, that is infinitely doable. It would be best to have a donor car, that is what the local pick-a-part is for anyhow right? You will need the wire harness which will run from the shifter to the fuse box, to the cluster, and to the trans. You will need the correct drive shaft ( you can probably get away with the correct front half but if cost is all the same at the bone yard you might as well buy the whole thing), the correct shifter if it did not come with the trans. I would think that the clutch release should be the same between the two, but just double check it while you are under it. Subframe I would think would be the same and the speedo should pick up from the rear end so there should be no issues there.

Good luck, Mark

Thanks rule 308 I apreciate the quick response. I felt I was on the right track,but its nice to have some confirmation.This car came to me with the trans out and disassembled, so I was at a disavantage...I love doing things the hard way. thanks again

" felt I was on the right track,but its nice to have some confirmation."

No offense, but it would have been nice if you had identified what kind of transmission your car has. You stated that it had an overdrive unit....which is not the case with an M47II. If you said that you wanted help converting from an M47II to an M46, I think that you would have received more responses and more information.

sorry charles I don't know. The car has a shifter with 1-5 on it and no button or switch. It also had no elect overdrive unit attached to the trans.the one I got to replace it does have the aformentioned items,but aside from the driveshaft and electrical components I was hoping there were no computer clashes etc. I think I can handle the mechanical electrical end but the electronic would be another story. thanks chris

Hi,
I think we've got it straight now - you have the 5-spd M47 and you are swapping in a 4spd+OD M46. Pretty straightforward, but if I recall correctly the flywheel for the M47 is dished like the turbos, so in addition to the driveshaft & the OD wiring harness you'll also need the flywheel & clutch ass'y from the donor car. I may be wrong but that's what I remember. And if it's out of a 240 you need to find a shifter linkage from a 740 M46. Electronics? None to speak of aside from wiring up the harness for the OD relay. No worries with the ECU, it's not involved with the transmission.
-Chris
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Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf

I am confused by your post. Your car has an M46 4 speed manual transmission with overdrive? Volvo used two different types of the Laycock overdrive, a type "P" and a type "J." Check your original unit - the type should be embossed on the casing. The pick-and-pull overdrive needs to be the same type. An overdrive from a normally aspirated 240 or 740 will slip under the torque of your engine. This will cause problems even when the OD is disengaged.

I said that I was confused because both Type P's and Type J's are actuated electrically via a relay which powers a solenoid on the tranny. When the relay is on and the solenoid is "open", the OD engages. It's possible that your original OD can be brought back to life with a new solenoid, or just by cleaning and rebuilding the existing solenoid with new seals.

You say manual overdrive? Does it not have the electric button for OD on the shifter like all I have seen.
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"Be blessed in your quest'' 89 764 (110K), '94 940T (180K) , '92 745T (totaled 2-10-05 RIP)

i too scored a great find with only one m47 in the pull a part yard. I did get it with the warranty, but alot of good that does with them being very rare here in the states. The only difference is i am swapping the aw for the m47.
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85 740 b230f+t