Bought replacement trans for 850 but it's DIFFERENT??HELP!!

phoenix_iii · Post by **phoenix_iii** » 04 Nov 2007, 00:14

I bought a replacement transmission for my 850T from ebay, it arrived, mechanic had it resealed, went to put it in, and says its DIFFERENT

Both are AW/50-42 (same trans in all US model 850s), but one has the (I think) engine speed sensor (or rpm?) more towards the flywheel and the other is further back on the trans. Also, they are both two post connectors, but different plugs, so would not just swap into the car.

Easy solution is to cut and adapt, but if reading from different areas/different things, could be a big problem?

What gives?? I thought all AW/50-42s were the same? This one is from a 96!! What can I do??

Post by **kelvin6** » 04 Nov 2007, 00:50

The problem is that in the 96+ cars, the vehicle speed sensor is no longer located at the transmission, but rather at the ABS Unit. For 95 and below 850's this proves to be a problem, because there is no port for a sensor on the tranny....

Now if a 96 car tried to put on a 95 and earlier tranny, they could get away with it. I'm sorry to say that only a 95 or earlier tranny would've worked for you...

Post by **sseir39** » 04 Nov 2007, 04:53

Before you give up keep searching. Seems I read on volvospeed that the conversion can be made just by changing the wiring.

phoenix_iii · Post by **phoenix_iii** » 04 Nov 2007, 06:23

sseir39 wrote:Before you give up keep searching. Seems I read on volvospeed that the conversion can be made just by changing the wiring.

I wonder if that's true cross years, or if that's just from 96 or + can use any by changing the wiring, but...

I am hopeful we can use the later year one by changing the wiring. They BOTH have the same separate two prong plug, just in different locations, with different heads...

Anyone else?

Post by **MadeInJapan** » 04 Nov 2007, 06:43

You'll apparently need to do some custom wiring to an ABS sensor to get your speedo/odometer to work properly, but how- I don't know. Like was mentioned earlier, if you search and cannot find, you may have to actually post this question over on Volvospeed. Here is just one post about this (although in reverse...a '95 trans into a later model year) over there: http://volvospeed.com/vs_forum/lofivers ... 83024.html

Oh, a guy who goes by TorqueSteer over there seems to be wanting the same answer as you (post on Sept 26) Maybe he's found out what's up and can help you. Anyway, his profile page with contact information is here: http://volvospeed.com/vs_forum/index.php?showuser=6240

EDIT: Just found this post over there (still don't know the specifics):
It's not that hard to do- just cut the ABS sensor on the driver's side. Use a voltmeter to figure out which side is ground on the speed sensor and the ABS sensor - then just tie the wires together. Tie the positive wires together as well, and plug it back into the wheel. It's been working great for about a year now! Measures about 3mph slower than the speedometer used to, but I don't see that as a dealbreaker.
Good luck, congrats on the swap - it's a whole lot of fun!

phoenix_iii · Post by **phoenix_iii** » 04 Nov 2007, 14:59

Could it just be something for OBDI/II?

Replacement

Post by **MadeInJapan** » 04 Nov 2007, 15:06

Man, I wish I knew what to tell you.

phoenix_iii · Post by **phoenix_iii** » 04 Nov 2007, 16:22

As long as it's not 'You're F~ed'. =) Anyone? What does that little plug do on regular trans? I have the docs at work, I can check there...

Post by **MadeInJapan** » 04 Nov 2007, 16:59

I just looked in VADIS and it says it's the vehicle speed sensor. Evidently the transmission speed sensor reading (similar plug on the other side of the transmission) is compared to the vehicle speed sensor's readings which are sent to the transmission control module (TCM) where adjustments are made. Without it being plugged in somewhere you'll probably set a diagnostic code and the car may even operate in limited (limp-home) mode.

phoenix_iii · Post by **phoenix_iii** » 04 Nov 2007, 17:49

Yup, just looked at the auto trans.

"VEHICLE SPEED SENSOR
Vehicle speed sensor, mounted in transaxle housing, is an
input device consisting of speed sensor rotor and speed sensor. Input
signal is delivered from speed sensor to TCM with each revolution of
axle shaft. TCM uses speed sensor input signal for controlling
transaxle operation."

Seems that both read the axle speed. GREAT. So which is which when we do the wiring? =)