940 auto transmission glitch

[stegreg]

but surely there should be a more noticeable change in engine rpm when changing from what you say is normal revs, to 3rd lock, id hardly call 200 rpm "overdrive". My car used to run around 36oorpm if, er doing over 90mph....now it does 4500rpm to do a mere 80.

[Laird Scooby]

What he said! ^^^^^

Also if you haven't been driving regularly enough at those sort of speeds to keep the various valves moving, it's highly probable that the valves etc to control lock-up and/or overdrive are sticking so they are only "half-working".

Many moons ago when i ran V8 SD1s, the first one i had wouldn't kick down at all, even from standstill burying my foot on the loud pedal. It would change as if i was on the lightest possible throttle so into 2nd at 12mph and 3rd/top at 19mph. Even with the mahoosive torque from the V8, this meant progress was "leisurely" instead of doing what it should have done.

I drove it around under "manual" control, selecting 1st to pull away, into 2nd at a reasonable speed then 3rd/top when ready or manually downchanging to overtake for example.

It had mainly been used round town for short runs before i got it so everything was gummed up internally so it wasn't changing properly. After a couple of weeks i forgot one morning and just put it into "D" and off it went and drove as an auto should do, including kickdown.

That may or may not be relevant to your problem.

Another thing to consider is the throttle drum - is their excess play on its spindle? The bush inside it may have disintegrated causing excess movement of the drum before it opens the throttle but will still pull the kickdown cable.
Also there is a link rod between the throttle drum and the throttle butterfly, how much does the throttle drum turn before the throttle butterfly starts to move? Should be little or nothing, in other words as soon as the throttle drum moves, so should the throttle butterfly. Check and sort this before anything else, at least it's a fairly quick job that doesn't involve grovelling around under the car and the weather isn't too grim out there either.

You may well find this is part or most of the problem and the fluid, while absolutely disgusting, is only part of the problem although i expect you've already found the box is a lot smoother!

[Laird Scooby]

Originally Posted by stegreg

but surely there should be a more noticeable change in engine rpm when changing from what you say is normal revs, to 3rd lock, id hardly call 200 rpm "overdrive". My car used to run around 36oorpm if, er doing over 90mph....now it does 4500rpm to do a mere 80.

Are you confusing overdrive and lock-up? Lock-up locks the torque converter so there is no "fluid flywheel" effect and no torque multiplication, it will only drop the engine speed a small amount. Overdrive is a separate gear and will cause about a 20% drop in engine speed give or take depending on the exact ratio of the overdrive range.

The test you did shows that it appears lock-up is working in 3rd and probably will work in overdrive as well once, you get the other cause of the malfunction sorted.
As in my post above, check the throttle drum to throttle butterfly link and how much play there is on the throttle drum spindle.

[stegreg]

Ok, will check the throttle drum out as next job. Dont worry will continue with the oil changes, till its fully clear, determined to do this now, its not gonna bet me.
i drive the car a fair bit and do a fair amount of dual carriageway stuff, so am used to how the car behaves and drives and what its doing now, is not normal behaviour for it, even passengers in the car have commented on being able to hear the engine noise more [revving higher]. so i know its not just me being paranoid.
But yes i do aslo have to appreciate its done over 206,000 miles, so cant still expect it to be as new...but fairly good as. LOl

[Laird Scooby]

When i first got my current 760 with 215k on the clock, the throttle drum was worn on its spindle, wasn't causing the problems you've got but was holding onto the lower gears longer than it should and not getting overdrive until about 55-60mph when it should go into overdrive about 40-45mph.

It never goes into lock-up for the simple reason there isn't a lock-up box on mine, nor has there ever been.

Adjusted the play out of the throttle drum to throttle butterfly (making sure to check the throttle butterfly still operated the "throttle closed" switch in the Throttle Position Switch), adjusted the kickdown cable as it should be and normal service was resumed. I've also done 3 part-changes of fluid since i've had it, two because the fluid was filthy, the third was partly because the fluid wasn't completely clean but also that it had to come out because the extension housing had to come off the box to renew the output shaft bearing/bush.

[960kg]

Originally Posted by Laird Scooby

When i first got my current 760 with 215k on the clock, the throttle drum was worn on its spindle, wasn't causing the problems you've got but was holding onto the lower gears longer than it should and not getting overdrive until about 55-60mph when it should go into overdrive about 40-45mph.

It never goes into lock-up for the simple reason there isn't a lock-up box on mine, nor has there ever been.

Adjusted the play out of the throttle drum to throttle butterfly (making sure to check the throttle butterfly still operated the "throttle closed" switch in the Throttle Position Switch), adjusted the kickdown cable as it should be and normal service was resumed. I've also done 3 part-changes of fluid since i've had it, two because the fluid was filthy, the third was partly because the fluid wasn't completely clean but also that it had to come out because the extension housing had to come off the box to renew the output shaft bearing/bush.

As you say about the throttle...butterfly...drum...switch...all these things at that higher mileage will be worn.

Also your previous post about the V8 SD1 ...i had the 5 speed manual 1980 model super car for it`s time.....anything mechanical has to be used and abused some time it is not right to dribble around town All the time. Engines love to run and not walk!.....and it keeps them clean inside and in good condition.

In other words maintenance is the key and i know one thing with any automatic the servicing has to be done to keep the engine in best condition otherwise it will not change gear when it should as the torque is in the wrong place for that to happen and so gear change quality and timing is all over the place. Just a change of spark plugs and ignition leads can make a remarkable difference to how an automatic drives.

[Laird Scooby]

Originally Posted by 960kg

As you say about the throttle...butterfly...drum...switch...all these things at that higher mileage will be worn.

Also your previous post about the V8 SD1 ...i had the 5 speed manual 1980 model super car for it`s time.....anything mechanical has to be used and abused some time it is not right to dribble around town All the time. Engines love to run and not walk!.....and it keeps them clean inside and in good condition.

Funny thing was, when i came to set the idle mixture for the MoT, i discovered some numpty had altered the base idle setting! By the time i'd sorted that out, the TPS was once again in the wrong position and needed returning to its original position - pre-adjustment the first time!

I had several SD1s back in the late 80s/early 90s culminating in a late 81 Series 1.5 (best bits of the Series 1 but with the chrome door mirrors, nicer seat trim etc but not those later style electronic instruments that never looked right in the SD1) 3500SE, all automatic and superb cars for their time and for some considerable time after. When the Met heard they were being phased out, they bought a whole load of them and mothballed them for future use.

Spot-on with the comments about using and abusing engines from time to time to keep them clean. It burns off the contaminants that are in the oil, keeps everything lubricated and moving freely. I'm not saying thrash them every day but a decent Italian Decoke once a month or so works wonder, especially on diseasels!

No good doing it if the engine and gearbox maintenance isn't right though, likely to do more harm than good!

[stegreg]

2/1/18 update... still no joy yet, but not giving up, but being as a dull wet day stops any oil changing, decided to make or break to trace the overdrive relay.
YEP, found it ! It was GREEN in colour, RECTANGULAR in shape, and twice the width of a normal relay. [basically I took relays out till the amber 3rd lock light didnt work ] process of illimination. LOL
So I have replaced with a "white" relay, which works ok, put the lock light on/off and can actually hear this one "click", whereas the green on you cant hear at all.
BUT...look at the pictures before you say "oh its duff if you cant hear it, as its fully electronic. NO moving contacts, so no mechanical noise and if you look at the circuit boards, no signs of heat disruption to anything.

Was this a "mod" fitted by Volvo due to issues with the earlier white relays burning up?
Ok, so this relay also has two extra smaller connectors on its base which do show signs of actually connecting to something, but without lifting the fuseboard up to look underneath, i cant say.

SO, "incase " this has failed, will try with the new white relay in.....Not unless I should not swap/exchange these over ??
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[Laird Scooby]

I can see several dodgy looking solder joints on the main board and a slightly burned resistor. Whether the resistor is still ok and just showing signs of having got hot through use or is in fact burned out is another matter, the dry joints will prevent it working though.

Are you any good at reflowing dry solder joints? Or know someone that is?

[stegreg]

Yes, can have a go at running a soldering iron over the connectors, no probs there.
It was just a bit of a shocker finding this lump of a relay where i was searching for a white one. Admittidly i should of known better after reading the top label " Aisin AW co Ltd"......DEr .LOl