M46 Overdrive problem. Help?!

[MarcF]

Hi Guys,

Please let me introduce myself.

I'm Marc, and live in the Netherlands. This weekend I bought a 1994 Volvo 960 16v Turbo Estate. A very nice car with full options, but it has an issue unfortunately.

The overdrive does not work on the M46.

Whenever I push the button in fourth, tried it at various speeds with the clutch engaged and disengaged, the light comes on, but the overdrive does not engage. Very annoying while driving on the highway. It just stays in fourth basically.

Strange thing is, that when it shows OD engaged (5 light comes on), and I release the throttle and want to engine brake, the revs drop down to idle, so engine braking is not possible. When I do this with the OD disengaged, it just engine brakes, so it seems that there is a mechanical problem.

Can someone please help me, or has had the same troubles and has some tips?

Thanks,

Marc

[Laird Scooby]

Welcome aboard Marc! Have you checked the condition and level of the gearbox oil?
Also it sounds as if the solenoid on the gearbox that provides hydraulic pressure (from the oil in the box) to the overdrive mechanism could be sticky so that it's not fully engaging the overdrive gears but also that the freewheel clutch in the overdrive is doing its job.

Could also be a dirty connection on the solenoid, bad earth on the gearbox/overdrive or similar.

The good thing is overdrives a relatively simple with not much to go wrong so there won't be much to check other than the above.

Could also be lack of use - if the previous owner used it mainly for town driving there's a high chance overdrive wasn't engaged for a long period of time.

[MarcF]

Originally Posted by Laird Scooby

Welcome aboard Marc! Have you checked the condition and level of the gearbox oil?
Also it sounds as if the solenoid on the gearbox that provides hydraulic pressure (from the oil in the box) to the overdrive mechanism could be sticky so that it's not fully engaging the overdrive gears but also that the freewheel clutch in the overdrive is doing its job.

Could also be a dirty connection on the solenoid, bad earth on the gearbox/overdrive or similar.

The good thing is overdrives a relatively simple with not much to go wrong so there won't be much to check other than the above.

Could also be lack of use - if the previous owner used it mainly for town driving there's a high chance overdrive wasn't engaged for a long period of time.

Hi, thanks!

Have not checked the oil. The previous owner who's owned the car the last year has only driven it around Amsterdam, and also only rarely. Last year only couple thousand km's. So could be that he never used OD.

What should I do then, to check this, apart from the oil?

Marc

[Laird Scooby]

Based on my experience of other machinery that has used a similar system, i'd first check the solenoid.
From what i can make out in the Haynes book of Fantasy (Haynes Workshop Manual) the solenoid is on the left hand rear end of the gearbox, a cylindrical shaped animal with electrical connections - the plunger inside it is likely to be the part that's sticking.

If you find there's no obvious way of removing the solenoid without removing the overdrive and/or gearbox, check and perhaps change the gearbox oil.

Once you know the oil at least is ok, i think the answer will almost certainly lie in using it.

What i would try is driving along a flat road at about 45-60mph (70-100kmh) in 4th gear, gentle throttle (just enough to maintain speed) and switch O/D in then out again within a couple of seconds. A few seconds later, repeat.

Keep doing that for a while (or until you're thumb gets bored flicking the O/D in and out!) and see if you're making any progress. Nothing may change for a while but with a bit of luck it should start freeing up internally with each attempt at using it.

If you're lucky it should free up fairly easily - good luck and let us know how it goes!

Hopefully there should be some others on later that know a bit more about the overdrive set-up and they may be able to suggest another way of doing things.