S70 Transmission will not engage

LucasF98 · Post by **LucasF98** » 19 Jul 2020, 05:34

Hi guys, new to the forum and new to Volvos

I picked up a 97 S70 (2.5L 20V non Turbo) the other day for next to nothing as it has the issue I'm asking about. However it has been well looked after and serviced etc, and I would like a project to work on while things are quiet.

The issue is that it's not going into any gears (occasionally has engaged, then drives for 50-100m then disengages and the engine revs like its in neutral). I hooked it up to my OBD scanner and it had a P0500 - Vehicle Speed Sensor A error on the A/T computer. This was accompanied by the flashing up arrow, check engine light and the Sport, Eco and Winter mode lights flashing.)

I cleared the code to see if that was causing anything and the warning lights have gone away and after a fair bit of testing the engine and a/t computers haven't thrown any further codes, however the issue is still persisting - just wont engage.

Occasionally there is a buzzing sound coming from the trans side of the engine, sounds like a relay or something, possibly a solenoid buzzing in and out, not 100% on the origin, but I have heard that the shift solenoids on these gearboxes can go quite regularly - however there is no code in the A/T computer about it. I have checked all resistances of the soleniod contacts in the connector and all are reading as they should.

I have noticed, that after sitting for a while when you start the engine back up there is this buzzing noise coming from in the transmission. Sounds like a pump or something to me, not too sure. Here's a clip of it.

Funny thing is - It'll drive fine as long as its making that noise, as soon as it stops like in the video you lose all drive. Noise usually lasts 15-30 secs.

Anyone heard this noise before or know what it could be?

The previous owner took it to a shop and they put new trans fluid in it, which didn't fix the issue for long enough for him to even get home, checked the fluid today and is nice and clean - not burnt and has a good level. I've also flushed about 4L through it (drain and fill) just to see if I could make it work any better, no luck as yet.

Having a look through the service history it had a second hand / recon trans put in it in 2018 unfortunately this hasn't lasted too long.

Any insight into the issue or advice on some further diagnostic / troubleshooting would be most appreciated. I'd like to try and do the work myself as well as I'm not planning to invest too much money into this more of just something to keep me occupied.

Thanks for your advice and assistance in advance.

yanga001 · Post by **yanga001** » 19 Jul 2020, 13:50

Almost sounds like a bad connection or something. Did you check the PNP switch? I had a similar issue where the car would shift fine in every gear but would be stuck in limp home mode. I replaced the TCM and the car works perfectly. Is the correct trans fluid in the vehicle? My mechanic said once that an incorrect fluid could result in strange issues or no engagement of the torque converter.

How many km's are on the car?

Post by **scot850** » 19 Jul 2020, 14:40

yanga001 has asked great questions and made good points.

These transmissions can be pretty robust if maintained and given oil changes every 80,000km. Problem is many do not do this as Volvo said originally these were sealed for life transmissions. People are also cheap and declined the cost of the oil change.

Other issue is non-Volvo repair shops using 'power flushes'. I have heard cars not even making the end of the road following this before the trans failed as all the servos were filled with old oil lacquer clogging them.

Also the correct oil as yanga pointed out has to be used. Can be either regular or synthetic. Should be a DEX3 trans oil and not the 3309 which was for later trans.

Hoping it is a simple issue as they are nice cars when running.

Good Luck.

Neil.