940 auto transmission glitch

[mylittletony]

This is the plate I bought
https://rover.ebay.com/rover/0/0/0?m...2F362007789161

There is info on how to modify the solenoid to bypass it. Or solenoids are available online for ~£150.

I would say that if the box is behaving well in all other aspects than 3rd-4th, your solenoid is clogged. There could be a problem with the relay or switch, worth investigating before shelling out.
A fluid change might dislodge the problem

[Laird Scooby]

Definitely worth investigating the switch and wiring before shelling out on a solenoid, i haven't looked at the diagram but if my guess is right, in the "Off" position, the current that would pass to the solenoid in the "On" position goes to light the warning lamp on the dash. Although that may light up as it should, it still doesn't necessarily prove the wiring to the solenoid from the switch.

I'd still try a part-change of the ATF first though.

[stegreg]

I am definately going to sort the box oil first, thats a definate, but have to wait for the pump to arrive.
I dont want to simply "blank off" the solenoid hole, as I prefer to keep it original, PLUS i do like the option of 4th lockout, especially as I do use it for towing on occaisions, dropping to manual 2nd is too much, but 3rd is great with the turbo boost.

Solenoids are available from the states as i did say AND for a mere £34, plus shipping which still brings one over to the Uk for around £60 total, way better than shipping from Europe.

I dare say the solenoid is "partially sticking" as i can actually "feel" the thing lockout when i can actually get it to drive in 4th, its just as soon as i try to ease a biy of throttle on...to maintain the road speed 4th simply slips out and it drops to 3rd gear.
BUT.

OIL FIRST.

Its the one thing thats way overdue. so lets start with this and then work around. If I do too much elswhere before hand, im not really gonna know what was the original cause.

ALL your suggestions are greatfully appreciated and all are noted, so I have plenty to go at if solution 1 does not cure.

[MiniNinjaRob]

Which transmission fluid is best? I have a 97 940 auto - I think it has the AW71 box? (really not sure)

[Laird Scooby]

Originally Posted by MiniNinjaRob

Which transmission fluid is best? I have a 97 940 auto - I think it has the AW71 box? (really not sure)

https://www.ebay.co.uk/itm/Carlube-A...QAAOSwBEpZpY7F



There you go - better than Dexron and backwards compatible with it, smoother shifting, better economy and performance, meets JWS3309 and the other Volvo spec with the long number that i can't remember. Use it in all my boxes and PAS too and even the trolley jack.
Other uses include adding 0.5 - 1.0L to the engine oil to free sticky hydraulic tappets, gently clean the engine internally and condition the seals or mix it 50/50 with acetone, give it a good shake and you have an amazing penetrating oil.

Alternatively you could use Valvoline ATF but that's more expensive.......

[stegreg]

Right, after patiently waiting for the snow and ice to melt away, so I could at least walk out to the Volvo. With electric oil drain pump in hand, I let the vehicle warm up for a while, then drained some of the transmission fluid out. Pic attached, so yep, definate a difference in colour.

i am yet to fully drive the car, that may happen friday if I get a phone call...so further updates to come Guys.20171214_140644.jpg

[Laird Scooby]

That definitely looks past its sell-by date!

How much did you get out? Should have been between 2.5 ~ 3.5L in there.

TBH i'm amazed it was still running with fluid like that, hopefully you've caught it in time!

[stegreg]

thats approx 1.25 ltrs in the bottle. Didnt want to take out too much....following your kind guidance so as not to upset the seals etc.

Will run it for a while now, "as is", then do a second....then a third as recommended.

[Laird Scooby]

Fair comment - normally i'd say you'd be perfectly safe letting the pump run until it won't suck anymore which would be 2.5-3.5L depending how full it was before you started. Given how dirty that old fluid is i think you were wise to go extra gently though!

The total capacity is about 6-7L (can't remember the exact figure just now) so each part-change of completely draining the sump with the pump takes about a third or just over. The rest of the fluid is held in the torque converter, valves/hydraulic system inside the box and obviously the pipework to and from the cooler and the cooler itself.

I'd give it a short run to see if there is any difference and to warm the fluid before the next part-change but on that one, let the pump run until it's not pulling anymore fluid, then top up to where it should be, take it for a short run and re-check the level, topping up as necessary.

One thing for sure, as long as the fresh fluid clears the problem (which i'm pretty confident it will having seen the old stuff!) you'll be surprised just how smooth it is on the new stuff!

[stegreg]

yes, managed to take it for a run over to Hinckly and back today, a run of approx 80 miles. I shall ignore the run out...lets say " letting the oils mix", now on the run back...If you reach approx 50 - 60mph, on the flat or slightly downhill....if you ease off the throttle, you can definately feel the box change up to 4th, the revs drop around 1200rpm too....BUT you just slightly touch the throttle to "keep the same speed" and the box drops back to 3rd and the revs pick back up again.

NO, still not condemming anything yet, will run for another week or so, then do another oil change first.

Im not ruling anything out yet. but just to let you know theres no adverse effects.
Up change to 3rd is slicker.... and also when slowing down and pulling away again, no harsh[ish] changes noticed, as did occur before.

So ALL GOOD so far, no negatives in my mind.

I know its not going to be a sudden click of the fingers job, its my own fault for putting off the oil change as long as i did.