Sorry for the long posting but I wanted to give you as much detail as poss.

Name Gary Phillips. Location England. U.K
Vehicle, Volvo 850 GLT 5 door Estate / Wagon. 1993 model, 90,000 miles.
Engine type B5204S 1984cc, 20 Valve normally aspirated.
Transmission type AW 50-42 LE Computer controlled fully automatic 4 speed.

The problem / fault,
On Tuesday evening after a normal journey of about 5 or 6 miles I returned home, whilst reversing slowly in-to my driveway the vehicle came to a halt, when I gave it a little more acceleration the car started to move forward. The gearshift is in R but the vehicle is now moving forward after initially moving backwards.
I put it into neutral and rolled down the slight incline and parked on my driveway.
I have been on several short test drives with mixed results on each occasion, these include;

1. When in D and with gentle acceleration the vehicle moves forward but only in first gear, then at about 10 mph when it would normally shift up to second it seems to go into neutral and the vehicle coasts for a short time, as it looses speed it pops back into first gear, the cycle then repeats between first gear and neutral.

2. When in R the vehicle moves forward, I apply the foot brake when this happens and therefore I do not know how far or how fast the vehicle will travel when moving forward after selecting R. However I have noticed that there seems to be some resistance like the handbrake is slightly on and more acceleration is needed in order to move the vehicle.

3. When I select 3 or L the vehicle behaves the same as in D ie, first gear only.

4. Park and neutral seem to be behaving normally.

Observations,
The service reminder light came on about 2 weeks ago but as the vehicle was serviced last September I ignored it. The garage that recently serviced the vehicle are not a Volvo dealership therefore, I assumed that they had simply overlooked to re set the light as it was not illuminated at the time of the service.
There was no prior indication that the fault was about to occur, no bangs rattles strange noises or anything like that, the vehicle has been used daily without any problem since last Saturday when I fitted a new Battery and a set of spark plugs.

There are no warning lights or fault lights illuminated on the dashboard / instrument panel, ie blinking / flashing arrow. (the bulb is good as it lights up when in 3 or L)

Action taken;
After reading several posts on the Volvo forums and reading the transmission section of my Haynes manual, I have done the following;

I have checked the transmission fluid level when cold and again when hot and it is within normal limits on both the hot & cold side of the dipstick. However I do not know if it has ever been changed / flushed as I have only had the vehicle for 7 months

I have repeatedly shifted the gear lever from P to L at least 20 times with the engine running and foot brake applied. (A ratchet cleaning)

The LED diagnostic unit in the engine compartment gave me a fault code 1-2-4 which I believe to be “Driving mode selector circuit shorted to earth” I have removed the driving mode selector switch from the console, dismantled it, cleaned the contacts within it and refitted it. (Note, with the switch removed I also got the fault code 1-1-4 “Break in driving mode selector circuit” but I expected that would happen with the switch removed) I then deleted the fault codes from the ECU with the flylead in position 1 of module A. The reading is now 1-1-1 “no fault detected”

Following this I went on another test drive, this time in SPORT mode and again with mixed results;
1. P and N worked as normal
2. In D acceleration was good up to about 25 mph and then it seemed to level out.
3. Initially when selecting R the vehicle moved forward as before, then after about half a mile driving forward in position 3 I stopped and tried R again and reverse worked but it also reversed in L. I then selected D again but I got neutral, then all shift positions including R gave me neutral.

Totally confused and about half a mile from home I put it in P and switched the engine off. After a couple of minutes I started the engine selected ECON not SPORT shifted into D and crept home at about 10 mph.

After reading other posts on Brickboard and an article on PNP switches (a.k.a Gear Position Sensor) I am wondering if this could be my problem, but the PNP replacement instructions say that;
“The requirement to replace the PNP switch is usually prompted by the up arrow on your instrument cluster flashing” (Not on mine)
“Maybe the mode select switch flashing between modes” (No)
“Possibly the turning on of the check engine light” (Yes, but about 2 weeks ago)
“You might also notice that your car is stuck in 3rd gear” (Nope)
“The first thing to do for a 313 code recovered from the A-1 diagnostic socket is to clear the code and then do what I call a ratchet cleaning.” (No 313 fault code given)

I am now very confused, the symptoms are like those of a PNP switch fault but without any of the confirmation warning lights or error codes.
Can my fault be the PNP switch or is this a more serious problem?
Any help or advice appreciated.
Thanks for your time.

Update:
The specialist transmission workshop has not been able to find any electrical faults that would cause the vehicle to behave in the way I have previously described.

They have concluded that the clutch components within the auto transmission unit are damaged and have become locked together. This is the reason that I can no longer select reverse gear. Apparently when this happens some of the clutch components can break off and the loose pieces then cause further damage inside the transmission and also clog up the internal filter, when this happens there is a loss of fluid pressure within the transmission and then loss of all drive. Stopping the vehicle for a short time allows enough of the debris to fall from the filter and the vehicle will then drive forward until the filter clogs up again. I did experience this when on the 2-mile journey to the repair shop.

It seems that the only remedy / repair is to either replace the transmission with a reconditioned unit or to remove and repair the existing transmission, either way the bill will be in the region of £1,600 ($3,000 US) (not sure of the exchange rate)

I was told that if the transmission fluid had been changed at regular service intervals, say every 30,000 miles, then this terminal and expensive failure might have been avoided.
It is not 100 % guaranteed that the fluid being changed would have prevented this failure, but when you compare the cost of a £70 fluid change every 30,000 miles to a £1,600 replacement transmission at 90,500 miles, as in my case, then possible prevention has to be better than an expensive cure.

There are probably hundreds of 850’s out there that are still running like new with the original fluid and half a million miles on the clock, but it seems likely that they are running on borrowed time.

I am annoyed with Volvo and their inappropriate guidelines regarding transmission fluid change intervals, if they stand by their guidelines (ie, “Renewal of the automatic fluid is not a service requirement”) then they should take responsibility for the transmissions that suffer such failures where fluid is or has been a factor.

There is little I can do other than to post this message and make other Volvo 850 owners aware of the potential expensive repairs that await them if fluid changes are not carried out. I hope that you will not suffer the same fate as I have.

On the other hand I have also seen posts from owners that are having transmission problems after a flush, so you can't win.

I welcome your comments on any of the above.

hmmm...i think this is not entirely accurate...

1. the 850 auto box famously doesnt have an internal filter (its one of the things thats often held agasinst it!)

2. volvo recomend that the tranmission fluid is cahnged every 37000 miles IF the car is used as a taxi or for continual towing, othewrwise they recomend inspection of the fluid and change as required...

3. given (1) above i think i would tend to be a little wary of the statements made by the shop (they may be correct that this has happened and its blockin g things up..but not a filter....which you might reaasonably expect them to know...)

4. If it was me I would replace the transmission switch anyway, and do a fluid flush and then see what happens, realistically you can do both for a lot less than sixteen hundred quid and look at the swithc as preventative maintenance...the fluid well its a 70 quid punt...but it might telll you a lot!
I did mine 2.5 at 60k and awas amazed at the vile stuff that came out and it made one hell of a diference...

5. The shop may be absolutely right...on not...but got to be worth doing 2 jobs you can DIY and for minimal cost first...

Thanks to “the kick inside” for your input.

I put my trust in the transmission workshop mechanic because he told me that he had worked at my local Volvo dealership in the past, and it was the Volvo dealership that recommended him to me in the first place. So I wonder why he expected to find a clogged internal filter in 850’s transmission if they are famous for not having one? Could it be different spec in the U.K.? I will look into this with Volvo.
Maybe the mechanic in question was sweeping the floor in his former occupation and I was suckered into trusting him with the old “Oh, yeh I used to work for Volvo” It was probably “Oh yeh, I used to work for Ford” with his next potential victim.

The vehicle is back home now, I am seriously considering doing a flush myself and see what effect that has before spending my hard earned cash on a replacement transmission.

Hi gary,

I too am in the UK and believe that there is NO difference in the transmissions uk or us...

of course the guy could be quite right the transmission is toast...but o nthe other hand it seems to me that when you change the switch position (and the position of the gear lever) its all electrical...now I would wonder about a bad switch, a bad connection or a transmission computer issue...

of course the volvo dealer really cant be bothered..its an 850 and not exactly in their '3 years old or younger' prime market...

as to the shop saying its got a filter..given the exploded view of the trans i have just looked at, plus comments on this board spherical objects is all i can say.

I believe if you pull the transmission computer (battery disconected) you can then drive the car using the stick as a mnaul shifter...but dont take my word on that...

If i were you I would do the gear selector switch and the flush and see..your porbably going to have to do the selector at some point anyway...

If you want to asses the honest quality of your fluid get some fish tank type tubing (clear poly pipe 3/8 diameter) and pass it down the transmission dipstick then attach a syringe to it and draw fluid up into it...(or use a longer pipe and suck!) I bet the fluid is black....

when i did mine the fluid looked FINE on the dipstick - ok maybe the brown side of red but really ok...when i drained it it looked like treackle....

good luck with it, the guy may know his stuff, he may have worked for volvo but sounds to me as if its a 'if it doesnt work right swap it' moment to me...

and hes starting by swapping the MOST expensive bit! -l ike i say he may be right, but it seems to me hes blowing smokeo n the filter bit...

also has anyone connected an analysis unit to the instrument cluster, or a presure guage to the transmission itself? - both recomended test procedures from volvo i beleive

Quote from “the kick inside”

I believe if you pull the transmission computer (battery disconnected) you can then drive the car using the stick as a manual shifter...but don’t take my word on that...

Not heard of this idea before, I will try it and see what happens, not sure how it will be possible to manually shift up through all of the gears when there is only D, 3 & L to choose from. I will try starting in L and shift to 3. But I will never get into 4th.
Maybe this works better on other makes with a 3 speed box and shift positions 1, 2, & 3 to choose from?

Quote
If I were you I would do the gear selector switch and the flush and see. Your probably going to have to do the selector at some point anyway.

Yes, I think this will be my next move.

Quote
Also has anyone connected an analysis unit to the instrument cluster, or a pressure gauge to the transmission itself? - Both recommended test procedures from Volvo I believe

Not sure what the bloke connected up or tested, as I could not be there at the time. When I left the car he told me that he would be able to “test drive” the transmission using his workshop computer, thus eliminating my on board ECU. He later reported that there was no fault found with the electrical components of the system, but I don’t know exactly how he arrived at this, or if he tested each and every electrical component separately.
His conclusion was mechanical failure, when I questioned the torque converter? he said that was unlikely, the failure was most probably the clutch. He made no mention of testing the pressure.

I will keep you posted.
850 transmission problem…… to be continued…….

Gary i got my ideas from some volvo literature...


if you want i could email u a scan or something..

Yes please, a scan might be useful. If you don’t mind please send it to; Gary850glt@manorview.freeserve.co.uk


Also, I have now acquired 2 computer discs (Volvo TIS workshop manuals)
From them I have found several tests that I can run from the onboard diagnostic unit it will check the operation of each of the electrical switches and sensors on the transmission. It is also possible to run a test mode where each solenoid and other transmission related items are operated in sequence to test that they are receiving the correct signals from the ECU and operating correctly. I presume that the garage has already done these tests but on the other hand I don’t know for sure, I have nothing to loose in running the test sequence myself.

Gary

Thanks for your replies they were helpful.
I have spoken to my local Volvo service department and they referred me to an auto transmission specialist, they advised me to get the vehicle into their workshop and hook it up to the equipment for a full diagnostic check over.
Approx £50 to £70.
They claim that the workshop equipment will check all of the electrical circuits and also “test drive” the transmission to see if it is responding correctly under different simulated driving conditions.
As for the flush, they both responded with a similar answer, a good idea as a preventative measure but they didn’t think that just changing the fluid would be the magic quick fix I was seeking, and if it didn’t work I had just poured money into a transmission that might already be dead.
I think that I have taken this diy approach as far as my limited experience and knowledge allows, so on Monday the brick is off to the tranny workshop for a very intimate hook up with a trendy tranny computer.
I will keep you updated, as I am sure that mine is not the only 850 with transmission problems. Thanks once again to those who took the time to respond.

Make sure the shop is familiar with that kind of transmission, but I'm sure they are if they were referred to you by the dealer. A lot of small tranny shops over here in the states (Southern California) are quick to tell you you need a new transmission. Good luck!
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'94 854 N/A.

Let us know what happens.

Matt 93 GLT

i had a dodgy pnp stopping my reverse lights from working and i had no error light on the dash either.

take it to a dealer and get them to diagnose only about £45 , no point guessing at it. if it is the pnp it cost me about £120 to get the dealer to supply and fit add another £70 if u want them to renew the atf.

it does sound like the pnp though.

[I do not know if it has ever been changed / flushed as I have only had the vehicle for 7 months]

It's possible the car still has the origional ATF in the tranny as Volvo "didn't address" changing it so a lota folks never did. You need a sample to look at and more than the few drips on the dipstick. You can pull the drain plug and drain off a sample (messy) or the easy way is to get a piece of 1/2" ID vinyl tubing and an empty plastic milk jug or whatever. Take the upper tranny hose loose from the radiator by carefully spreading the retainer clip and pulling it out of the rad. Insert the end of the tranny hose into the vinyl tubing and stick the end in your container. Start the engine for about 5-10 seconds until about a pint of fluid is pumped out and shut off the ignition. Look at the fluid which will look like cherry cough syrup if fairly new.(good sign), brownish if well used (not great but usually OK) or black (not good). You don't have much to loose by doing a complete flush if the fluid is brown or black and I'd try that before getting into more expensive options.

It sounds like an electrical problem to me, as the gearbox is electronically controlled. Reverse in L gear, that must mean that the gearbox is getting a signal to go into R. At this point, seeing that you dismantled the shifter, you should consult Volvospeed.com or the archives for alignment of the PNP switch. I have never done it myself, but I read that you can do it simply by calibrating the switch with the shifter in R and centering it using the reverse lights as a guide (engine off, of course). The PNP switch needs to be aligned properly so that the shifter positions relate to the corresponding positions on the PNP switch, and the PNP delivers the correct output signal for the position of the shift lever. I would definitely try that first. Gearbox failures at that mileage are pretty rare. Best of luck.
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'94 854 N/A.