2004 C70 Auto Trans Challenge – What’s happening?

landl4u2 · Post by **landl4u2** » 27 Nov 2014, 09:25

What is actually taking place when there is slippage or unevenness in the shift from 2nd to 3rd. Seems to function well prior to warm-up but…? Is it a matter of some sort of clutch assembly slipping… a band that could be adjusted… maybe contaminated fluid plugging some pin-hole? I’d be interested in a Best-Guess or even a factual and definitive explanation from some super-knowledgeable transmission guru.

As per recent MVS advice, beginning today to exchange 3 qts Mobil 3309 ATF for whatever’s in there. Another 3 qts in monthly installments until four exchanges have been completed. By-the-way, 2 qts overfull when purchased and totally wet under-body.

Have never delved into to the inner workings of an auto trans… don’t know why. I think I have adequate mechanical experience - and the time now that retired. It could happen one of these days.

Post by **phils94850** » 27 Nov 2014, 10:23

Some of the Volvo transmissions had a problem "shift flares" you can google it. It usually only affected 01 models I believe though. Being overfull could have caused issues as well. I would def change the fluid and get it correct and go from there.

Post by **precopster** » 27 Nov 2014, 11:03

I'm not a guru. Just a guy that has repaired 3 of these transmissions and even solved a missing 3rd gear due to a worn band clamp.

Poor timing of the 3rd gear circuit through the valve body due to sluggish SLT, SLS & SLU solenoids is the cause of 2nd to 3rd gear flares in most cases. The pintels and bushings of the solenoids attract metallic particles that slow down the actuation of the solenoids.

These solenoids control line pressures which actuate various pistons in the valve body; one of the most important being the B4 servo (not part of the valve body and situated externally near the right side wheel) which pushes a piston that tightens a band clamp around the 3rd gear drum.

Replacement or servicing of these solenoids will usually rectify this problem however the aforementioned band clamp has friction material much like a brake shoe and has wear limits. Once these limits are exceeded expect slow take up or slipping of 3rd gear.

Clean fluid helps keep the particles from sticking to the solenoids in the first place.

landl4u2 · Post by **landl4u2** » 28 Nov 2014, 08:29

Whoa!... pintels, bushings, servos, attracting particles??? Definitely a guru from my perspective. Thanks for that definitive response... MVS forum is amazing.

It sounds as though this B4 servo can be accessed externally... removed... cleaned and/or replaced. Do you think this would be time and effort well spent? Kind-of sounds like it.

Post by **phils94850** » 28 Nov 2014, 08:34

My understanding the servo replace and fluid flush works some time. I did it on my daughters 01 s60 and it worked for about a week and then went back to the shift flare. Most people just live with the issue..

Post by **precopster** » 28 Nov 2014, 14:48

The B4 servo is machine matched to the casing and can't be replaced.

The B4 servo cover was an issue amongst 2001 and early 2002 transmissioms with a serial number starting with 01C throigh 01L.. It had a poor design and the washer on the cover would dislodge resulting in changed clearances. It's unlikely yours is within that range.

Replacement of the valve body replaces all the solenoids and usually solves shift flares if the band clamp has enough friction material left.

Post by **JRL** » 28 Nov 2014, 16:16

You need a FULL fluid change now, not in drips and drabs 3 at a time BS
When done with all CLEAN FLUID, you should bring it to your dealer, check for software updates, reset the adaptions and do a drive cycle.

It may help a bit, it may fix the problem 100%, it may do nothing.
If nothing you should replace the valvebody (that includes all the solenoids), it will only become worse and eventually blow up completely,

Posting YOUR MILEAGE would help here!

landl4u2 · Post by **landl4u2** » 29 Nov 2014, 18:34

Is there a method by which one can verify the version of software update in the car and check online or with a dealer to see if there are later versions available?

Does the Control System package include this B4 servo and ALL the others. It appears to just bolt up to the side of the box. Is it a pretty straight forward remove and replace?

Really do appreciate all this input.

Post by **precopster** » 30 Nov 2014, 03:39

The B4 servo cover can be bought at IPD for under $30 HOWEVER check your serial number as I stated. The new improved ones were already fitted by mid 2002.

The control system (valve body) comes separate and you can order them from Tasca Parts cheaply (under $1,100 for a new one) or more cheaply from Reamman or VBX. I've rebuilt a low mileage valve body and got great results however higher mileage cars should get a rebuild or new one. Ask how I know....

The MVS repair database has a P2 Volvo valve body replacement guide.

The software level can be checked with an Autel EU 702 or MD 801 or the newer up-spec models like the AL 619 or the Chinese knock off Dice-Vida setup (use this myself)

landl4u2 · Post by **landl4u2** » 30 Nov 2014, 18:52

Great stuff Precopster. It'll take me some time to get my head around all of it but I think its encouraging. Will probably look at the rebuilding myself option to start. Maybe a You-Pull-It or Pick-Ur-Part yard for one to work with.
Thanks