940 auto transmission glitch

[stegreg]

Hi Guys, a wierd thing has just started with my 940 Auto. It does not want to "hold" in 4th [overdrive]. 1st, 2nd, 3rd are great, no slip and pulls smoothly/changes smoothly. BUT you cant feel it drop in to 4th, not unless you ease off the throttle slightly, ...then it eases in as you see the revs drop, but the moment you touch the throttle pedal to gently maintain the speed, it slips back down to third and obviously..the revs shoot up.
Ive tried the overdrive switch when it is in 4th and yes, it does operate and lock it down to 3rd. so that seems to be working.
Its almost as if the kickdown cable is too tight, but have slackened the adjustment off and tried it with more than the specified "slack" of 2mm.
i did add in to another thread to say i was going to change the auto oil, but not got that far yet. could it be the oil strainer is clogged and the box mot picking up sufficient oil from the sump pan? afterall, its clocked 206,000 so am aware its as good as new, but the rest is still so good and the engine still has loads of energy its a shame to declare it junk yet.
any advise [as aways] appreciated.

[mylittletony]

There's a lot of info on this online, try searching "AW71 overdrive"

The 4th gear is locked out using a solenoid which can get gummed up, a fluid flush will help a lot.

I had similar symptoms and ran 8 litres of fluid through it and it now holds 4th from 60mph upwards. I need to do more though as I have to lift the throttle to get it to shift at all.

I've also bought a solenoid replacement blank but have yet to fit it. That just removes the lockout function so it operates as a 'normal' 4 speed box.

[stegreg]

thanks for the info. Ive spoken to "Volvo Parts" [aarrggh] and they want ...sorry would of wanted £166.60 for the solenoid...IF AVAILABLE, but now sadly Obsolete, not even held by their classic parts dept.. but the states have plenty at approx £34 plus shipping....if anyone else interested, volvo part number ref is 1239928 if you need to cross reference.
so before i venture under the motor, especially in this weather. will await the new solenoid, then replace and do oil flush same time, not unless its ok to do the flushing at the radiator cooling end? it it ok to remove the return pipe to the gearbox off the cooler and drain from there?

[Laird Scooby]

Don't flush it! Not with nearly 300k miles on it!

Do a "part-change" instead, drain the sump, either by removing the drain plug or using an oil extraction pump (about £15 on ebay and no crawling underneath!) and refill to the correct level using new fluid. I use Carlube ATF-U and have found it's an excellent fluid and suited to the Aisin-Warner box very well.

The first part-change will probably give you an instant improvement, do another in about a months time then another about a month later. This will in effect change all the fluid very gently and get a lot of dirt/contamination out of the box while reducing the risk of blowing seals with new, much thicker, fluid.
It also gives the seal conditioner present in the new fluid time to work which will help the seals much more than flushing it through with umpteen litres of new, thick fluid that could easily blow a weak seal to oblivion.

After the 3 part-changes, do one part-change a year to maintain the service changes at the right interval.

[stegreg]

Thanks for the advise on oil change, yes, ive already got the oil you suggested on an earlier post, found a reasonable supplier on ebay, far cheaper than local stores.
I dont have a drain plug on the box sump, only the dipstick pipe that bolts to the side of the sump pan, so will give your second suggestion a go too.

Many thanks again for the reminder, always greatful.

[Casheye]

Another option if the problem is related to the solenoid, giving you 123 and overdrive permanently.

+1 for some 'ebay special' ATF though. I bought Dexron III when I needed to do a complete change. Something like £2 a litre.

[Laird Scooby]

Originally Posted by stegreg

Thanks for the advise on oil change, yes, ive already got the oil you suggested on an earlier post, found a reasonable supplier on ebay, far cheaper than local stores.
I dont have a drain plug on the box sump, only the dipstick pipe that bolts to the side of the sump pan, so will give your second suggestion a go too.

Many thanks again for the reminder, always greatful.

Here's the oil extraction pump i was on about, i'm sure there are others cheaper on ebay in the UK but gives you an idea what to look for :

https://www.ebay.co.uk/itm/Fluid-ext...tf3mPkShojEutw

The drain plug on my AW-71 is quite well hidden in a recess in the transmission sump pan so you might have one, it's just hiding!

Another thought on the lack of overdrive - what is the temperature gauge doing? Mine doesn't want to go into overdrive at any speed/throttle opening unless the engine is above a certain temperature, not sure if there's a thermal switch somewhere to inhibit overdrive below a preset temperature.
If so it might even be a thermo-vacuum switch so it might be a broken vacuum hose as well - all worth checking!

[jpliddy]

Originally Posted by Laird Scooby

Don't flush it! Not with nearly 300k miles on it!

Do a "part-change" instead, drain the sump, either by removing the drain plug or using an oil extraction pump (about £15 on ebay and no crawling underneath!) and refill to the correct level using new fluid. I use Carlube ATF-U and have found it's an excellent fluid and suited to the Aisin-Warner box very well.

The first part-change will probably give you an instant improvement, do another in about a months time then another about a month later. This will in effect change all the fluid very gently and get a lot of dirt/contamination out of the box while reducing the risk of blowing seals with new, much thicker, fluid.
It also gives the seal conditioner present in the new fluid time to work which will help the seals much more than flushing it through with umpteen litres of new, thick fluid that could easily blow a weak seal to oblivion.

After the 3 part-changes, do one part-change a year to maintain the service changes at the right interval.

hi dave how does the car lube ATF compare to euro car parts ATF i used theres last time which has the best spec for my ZF auto box as it will be changed in the good weather .i will get 2x 5litres . millers oils do a millermatic oil never used it but only ever put there xfe semi synthetic in my diesel
regards jim

[Laird Scooby]

That's a very good question Jim - a few years ago i would have said they were the same but not now.

Annoyingly for me, the ECP ATF (equiv to ATF-U) was previously compatible with Honda Z-1 ATF but they changed the formulation and it no longer is, despite what it says on their website.

That may not sound like a big problem for Volvos but the Aisin-Warner boxes that Volvo specify JWS3309 for on later models need a composition of ATF very similar to Z-1, in fact ATF-U covers both Z-1 and JWS3309 and also the later Volvo spec with the long series of digits that i can't remember just now!

With the ZF box in yours, you could get away with Dexron II but when i changed (for the second time, i'd previously used Dex II-D) the ATF on my last 740 that had a ZF box, it was so much smoother on the ATF-U that i've used it ever since in ZF and AW boxes and been rewarded with a quieter, smoother box, better acceleration and economy and a very smooth ride.

I have heard that people who previously used ECPs ATF and subsequently the newer version of it found it didn't change as smoothly and generally felt it wasn't as good. I don't have any hard facts/evidence to back that up though so it's only hearsay.

The Carlube ATF-U covers all my cars for the gearboxes and gives better changes, performance and so on in all of them so i'll stick with it, unless they change it somehow in the future.

It also makes a great PAS fluid, i use a large (250ml) syringe to empty the PAS reservoir then top up with fresh ATF-U, bleed the steering and top up. I do this once a week for 3-4 weeks or until the fluid coming out is clean as and when the fluid starts looking a bit "off colour".

A pint or so usually finds its way into the engine oil as well, it helps keep the engine clean inside, revives the oil seals and quietens things down, especially ticky hydraulic lifters.

As for the Millermatic, i know someone who is doing a long term test on that, early results aren't encouraging though. As such either Carlube ATF-U or Valvoline ATF but the Valvoline is dearer than the ATF-U.