2002 XC70 AW55-50SN Transmission swap with 04 S60 55-51SN

boneman131 · Post by **boneman131** » 02 Feb 2015, 15:51

Hello all,

Have a 2002 XC70 with 190,000km and the trans has gone. After about 5 min (warm up) of driving the transmission slips like you are in neutral - no power going to the wheels. My research has found that this is a fairly common issue with the V70/XC70s. The trans is a AW55-50SN.

My question is two fold.

1. Is my assumption that the AW55-50SN and the AW55-51SN are the same thing? I see them referred to on this forum simply as "AS55-50/51SN", which leads me to believe they are essentially the same trans?

2. Got a used 2004 AW55-51SN transmission from an 2004 S60 for $200 (75,000km) and wondering/hoping if this can be a direct swap? I'm sorry I don't know much about the computers and such but I've heard the transmissions are "coded to the VIN". The Volvo mechanic who is set to do the swap for me suggested I post here to see if you all had any advice? His concern was about possible different shift patterns of the S60 to the XC70.

Both transmissions are AWD automatics.

Any help, suggestions, advice? Thanks

Post by **vtl** » 02 Feb 2015, 21:54

1. Yes.

2. No. Ask your mechanic to send your valve body for repair, or put a refurbished one.

Also check and replace B4 servo cap if needed. And replace ATF (and do it every 30k mile or so).

Mechanically, this transmission is pretty solid and long-lasting. Linear solenoids are responsible for the most part of problems. On a higher miles cars valve body also shows symptoms of wear, that's why it is important to do the whole valve body, not just solenoids.

Popular prevention measurements are additional ATF cooler and inline Magnefine filter, search around the forum.

boneman131 · Post by **boneman131** » 02 Feb 2015, 22:29

Thank you for that info! Very helpful and I'll discuss this with my guy tomorrow.

Question then, could we not just take and use the solenoids and valve body off the spare trans and install them into the non working trans in the XC70?

Post by **precopster** » 03 Feb 2015, 02:54

They are from the same FAMILY of transmissions and LOOK identical. Lots of detail changes that the TCM (transmission control module) can't possibly deal with. A 2002 can't even have a 2003 transmission with the same model number because of those detail changes in TCM programming to match the changes in the valve body design.

I have never heard or read of a poster on any forum successfully using a AW55-51SN where a AW55-50SN was previously fitted.

If anyone can point the OP to a thread where this has been done he would at least have a reliable reference source.

Also you can't rock up at a dealer with your 2004 transmission and ask for 2004 TCM firmware. The main engine computer's firmware will not accept the 2004 firmware as version numbers need to match and be compatible.

Send it back.

boneman131 · Post by **boneman131** » 03 Feb 2015, 08:55

As always, great info. Appreciate the assistance. I will move forward with valve body repair/replacement and the B4 servo cover fix (already looked into that from IPD). We did perform a full ATF flush with the correct fluid about 6 months before it "died". Found a great tutorial on Youtube on how to do it:

Post by **vtl** » 03 Feb 2015, 08:59

ATF flush? Before it "died", did it have any severe shifting problems?

boneman131 · Post by **boneman131** » 03 Feb 2015, 09:10

Ever since we owned it (bought used at 165,000km) it had a hard shift from 2nd to 3rd. Not a huge deal and ran fine for years. On the recommendation from our Volvo mechanic, we took it to a transmission shop for them to do the ATF flush and have a look at it and see if they could diagnose anything. They called ans said "your transmission is full of 'hole's and is leaking. Needs a total rebuild for about $4k - $6K". This was only after dropping the engine pan. Not impressed with their 'diagnosis' and took it to my father in law who is a Volvo guy and we had a look. Yeah it was weeping a little bit at one seal, but nothing close to being "full of holes" that we could see. We don't want to sink 4-6k into it, just not worth it and we are not that attached to it (we have since bought an 02 V40), so we did some reading and found that doing an ATF flush can help. So we did that hoping to squeeze more life out of it, which I guess we did in a way.

We just want to get it running so we can sell it and maybe recoup some of our expenses. If not, it will just be scrap.

Post by **vtl** » 03 Feb 2015, 09:14

Did you locate a point where transmission drips from?

boneman131 · Post by **boneman131** » 03 Feb 2015, 09:41

Yes we did find a suspect area, but I can't recall now exactly where it was, but it was at a joint/seal area (it made sense). We did clean all the underside of the trans and bolted the engine pan back in place, drove it for 2 weeks then dropped the pan again to inspect for leakage and there was next to nothing.

I've read posts about people doing trans flushes and then immediately after their trans would not shift; sometimes no reverse, then sometimes no forward gears). We didn't undo the dreaded 'bolt' thinking it was a fill hole either.

Post by **precopster** » 03 Feb 2015, 13:32

I fail to see how dropping the engine pan would have helped. It would allow you to look at and inspect the rear of the torque converter only.

The transmission has no pan as you already know and no easily replacable filter. They often leak from the seams but that is more of a weeping than a leaking.

What are the final symptoms on this transmission?