M46 difficulty engaging overdrive

[monkeh]

My m46 O/d is difficult to put into overdrive.
I have to hold the gearstick to the right and hold it there while I press the overdrive button to engage it. Sometimes itll engage nicely when warm, other times it wont. I have to gently release the gearstick to keep it in overdrive. Any suggestions?

[Laird Scooby]

https://www.volvopartswebstore.com/s...rimLevel=24669

According to the key to that diagram, #42 is the reverse light switch. That means #27 is anonymous but i'd hazard a very large guess it's the overdrive interlock switch so overdrive can only be engaged in 4th gear.
Check the wiring to this switch and also the switch itself, chances are the switch is worn giving the symptoms you describe.

Also worth checking the level and condition of the oil in the box/overdrive unit and all earth straps/cables to the gearbox and/or overdrive solenoid.

If the fault hasn't been found by then, check the wiring where it goes into the gear lever for the overdrive switch and maybe even the switch itself - easiest way is by substitution, use another known good switch and some wire to simulate the overdrive switch in the gear lever, can also use the same switch to simulate the interlock switch on the side of the box but be careful to not drive round with it in the 4th gear simulated position or you could end up with overdrive available on all 4 forward gears and worse still, reverse as well!

[jor]

There is a nice description of the Laycock o/d here;
www.vclassics.com/archive/laycock.htm
The symptoms you describe would seem to fit;
'If your overdrive seems to want to work, but is slow to engage, shuddering and slipping, or dropping out of overdrive when the transmission is warm, then it's likely you have a hydraulic problem' as LS suggests above.
As a first step they recommend replacing the gearbox/overdrive oil with synthetic ATF 80-90 type F - this I did last year, but did not do the next o/d step - after taking off the o/d sump removing the access plugs for pressure valve, filter and pump.
You will want to do this in order to clean the parts (kerosene) and will need to acquire or fabricate a 'pin spanner' with two pins the right distance apart in order to remove these plugs, which look like a large coin with two small holes in. Refilling box is best done with a large syringe or equivalent and some tubing with the car on jackstands and perhaps with the passenger door side slightly higher to make sure you fill to plughole level.
Anyway good news is that it does not sound like an electrical problem!

jor

[whattodovolvo]

I had similar problem especially transmission was cold. I did followings.

1. Replaced the transmission oil.
2. Replaced the M46 solenoid. There are two types, P and J. Find out which one is correct for you. Mine is P Type.
3. There is switch at transmission. You may replace it as well. I did. As Laird Scooby suggested it was item 27.
4. Check 5th gear button. It could be faulty. Mine was.

[Laird Scooby]

Originally Posted by jor

There is a nice description of the Laycock o/d here;
www.vclassics.com/archive/laycock.htm
The symptoms you describe would seem to fit;
'If your overdrive seems to want to work, but is slow to engage, shuddering and slipping, or dropping out of overdrive when the transmission is warm, then it's likely you have a hydraulic problem' as LS suggests above.
As a first step they recommend replacing the gearbox/overdrive oil with synthetic ATF 80-90 type F - this I did last year, but did not do the next o/d step - after taking off the o/d sump removing the access plugs for pressure valve, filter and pump.
You will want to do this in order to clean the parts (kerosene) and will need to acquire or fabricate a 'pin spanner' with two pins the right distance apart in order to remove these plugs, which look like a large coin with two small holes in. Refilling box is best done with a large syringe or equivalent and some tubing with the car on jackstands and perhaps with the passenger door side slightly higher to make sure you fill to plughole level.
Anyway good news is that it does not sound like an electrical problem!

jor

An electrical problem is EXACTLY what it sounds like! Prime suspect is that switch #27 in the diagram.

Hang on though - i already suggested that :

Originally Posted by Laird Scooby

https://www.volvopartswebstore.com/s...rimLevel=24669

According to the key to that diagram, #42 is the reverse light switch. That means #27 is anonymous but i'd hazard a very large guess it's the overdrive interlock switch so overdrive can only be engaged in 4th gear.
Check the wiring to this switch and also the switch itself, chances are the switch is worn giving the symptoms you describe.

Also worth checking the level and condition of the oil in the box/overdrive unit and all earth straps/cables to the gearbox and/or overdrive solenoid.

If the fault hasn't been found by then, check the wiring where it goes into the gear lever for the overdrive switch and maybe even the switch itself - easiest way is by substitution, use another known good switch and some wire to simulate the overdrive switch in the gear lever, can also use the same switch to simulate the interlock switch on the side of the box but be careful to not drive round with it in the 4th gear simulated position or you could end up with overdrive available on all 4 forward gears and worse still, reverse as well!

I only suggested checking the oil because there's a small chance that's the problem, everything points to electrical on this one.

[nu11eaf]

Another one for changing the oil and the OD filter, this gets clogged up,

[Skylaneguy]

Classic failure of the fourth gear switch as others have suggested.

[lnparry]

Hi Monkeh,

Exactly the same symptoms with my 740.

Never got round to fixing before selling but pretty certain it was the inhibitor switch as already said. Also opinion of Volvo specialist. You could tease it in and out of o/d with slight on and off rightward pressure on the gear lever. A harsh road bump would also drop it out.

I think my old MGB switch was adjustable for wear, not sure on the Volvo but others will know.

Good luck,
LeeP