M46 overdrive issues

[Joe of Loath]

Hey all

I've been having issues with the overdrive on my car since I got it. Mostly it's worked OK and been reliable, but a few times, especially recently, it's become stuck. I've pressed the button and the dashboard light has turned off, but overdrive stays on in all gears. If I go down to first and drive around slowly I can make it slip in and out, but it always comes back just as I'm about to shift to second.

The last time I drove it, the overdrive stopped working completely. No light, no shift. Thankfully I was driving to work and I didn't have to go very far or faster than 50.

This behaviour suggests a bad relay to me, with sticky contacts, so I'm going to clean the relay up and reflow all the solder, is there anything else I should check? Has driving with the overdrive stuck on damaged anything? I have an M47 box and half shaft sitting in my dad's shed ready to go in, but I was hoping to keep that until I did the clutch so that I only have to drop the transmission once. Of course, I could do the clutch now and get it all over and done with.

Thanks!

[rogerthechorister]

You have two separate issues - and two knock-ons.

First, the sticking in overdrive is (almost certainly) mechanical. My B234F (which is a slightly different overdrive, the P/J) sometimes sticks in but almost always frees up after some provocation in third.

Second, you have an electrical issue - this is what is popping it back in and refusing to go into O/D at all. This is probably the solenoid rather than the wiring because of the unwanted popping into O/D - which I have never heard of before.

Third, if you are thinking about making any power in the future - avoid the M47. It is marginally weaker than the M46. Get an M46 out of a turbo or bite the bullet and convert to an M90 - not a wholly simple job.

Fourth, you don't mean "half-shaft". Those go from the diff to the wheels. You mean the front half of the prop-shaft (and if you go to another M46 or get the O/D refurbed you don't need to change the propshaft). If you DO change it, make sure you get the propshaft balanced because it will only be right in one position on the original and probably won't be right in any position in a hybrid.

[jor]

Cannot help personally - I was unable to remove whatever has to be removed to get at the o/d filter - but if the Volvo service manual (power transmission) might be of assistance you are welcome. Only a few pages with headings; replacing o/d, checking o/d pressure, replace o/d solenoid, replace non return valve, replace relief valve, clean pressure filter....
The m46 o/d is Laycock which was used by other makes, so if you do search there will be lots of info at least.

jor

[Joe of Loath]

Thanks!

Not planning on making any more power than stock (Insurance is already very expensive) so I think I'll just stick the M47 in, it sounds like less hassle even with the prop shaft (not half shaft!) needing balancing. Would that be something my local Volvo specialist could do?

Also, is a clutch and box swap something I can do on my driveway?

[WUMPSTER]

clutch job is quite easy on the 940 possibly a 2 man job t lift it out and get it back in as quite a heavy box or if your well practiced can be done one man and a good trolley jack you will need a clutch lining tool as well not expensive item but a deff must have to do it

[whattodovolvo]

My problems with M46 were oil leak and no engagement until engine and/or transmission got hot. After I "actually repairman" did following, all problems were fixed.

1. Replacing the overdrive relay
2. Replacing type P overdrive solenoid
3. Transmission oil change
4. Replacing all gaskets on M46 (Gasket set was bought from scandix.de)

[Joe of Loath]

Unfortunately I had the opposite problem, the transmission engaged fine, but would stick, especially if I engaged it from cold.

Rather than chasing gremlins I think I'm better off dropping in my M47 box. It'll cost me less money and time overall, and I have to drop the box to change the clutch anyway.

[Laird Scooby]

I'd suggest an oil change on your gearbox first Joe - chances are it's either low on oil or the old oil is so dirty it's causing the solenoid and/or valve to stick.

This might save you the time and trouble of changing a gearbox when you only need an oil change.

[Joe of Loath]

I think it's a bigger problem than just an oil change, was under the car a couple of days ago and the box is now peeing oil all over the drive, where previously neither of my cars leaked a drop (since I cleaned the flame trap in the Volvo anyway). I think it's blown a seal somewhere.

I have a new clutch to put in, because currently pulling away just requires me to prod the pedal slightly and let the slipping clutch do the rest, so the box has to come out anyway.

[Laird Scooby]

Gearbox or engine oil?

If it's the latter it could be the rear crank oil seal - flywheel off job to do that, maybe more. It will also cause an otherwise good clutch to slip like a Teflon coated ice hockey puck over a rink.