how to replace your volvo 850 transmission
MVS Forum Member kelvin6 replied:
The problem is that in the 96+ cars, the vehicle speed sensor is no longer located at the 850 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…
MVS Forum Member MadeInJapan added:
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.
MVS Forum Member cyclmck replied:
I had this same issue for my 95 850 turbo. I ordered a 850 transmission from the wrecking yard, they said they would send me a transmission from a 94 turbo(which would be the same transmission. When I got the transmission I realized the sensors were in different spots, ran the part number found out they had sent me a 97 transmission. I thought about wiring a plug too make it fit(which would not be hard). After looking at it, they are both AC pulse sensors, but they are in different location, picking up the signal off of different sized gears, producing a different signal, which I would imagine would throw codes for “incorrect gear ratios” or slipping” or something lime that. So i decided their was no way I was gonna put it in. I called the wrecking yard, they sent me the correct one(it was their fault) and let me keep the other one as they did not want to pay shipping to get it back. Whose fault was it that you got a different transmission. Maybe you can see if they will send the correct one. Also turbo and non turbo cars have a different final drive gear ratio, so make sure the transmission you use is from a turbo car.
The Project
Take a 96+ Volvo 850 Turbo trans and put it in my 95 850 Turbo
The Problem
The VSS (Vehicle Speed Sensor) wiring is different/reads from a different spot on the ‘newer’ trans. The original spot on the newer trans is filled in, and the heads on the connectors are different. Despite being both two posts/wires, my mechanic said he hooked up the wiring directly to the new trans, and it did not work. Taking his word on this, I moved onto the following.
The Solution
Take the two wires (yellow and black, green and yellow) coming from the transmission wiring harness (and would ‘normally’ plug into your ‘older’ trans), and cut the connector off.
Go over to your drivers side wheel. Remove the wheel. Properly unplug the abs sensor (while squeezing the obvious tab, wiggle it side to side to help break the ‘crud’ seal, then pull up and out). Cut the end off the ABS wheel sensor, but *leave enough room to splace more wire onto it!*… like an inch and half if you can.
Solder, and heatshrink tube, about 2 inches of wire to the ABS wheel sensor head (hence you left the extra working room). Make sure to splice and expose both ends of the new wire first, no need to solder/heatshrink and THEN try to remove the shielding on the other end. All we are doing here is giving you more room to work, or if you bugger up the end, you can try again
Solder and heatshrink tube a good foot (or two, I really only needed like 18 inches and that was almost too much) wire to the two transmission wiring harness wires.
Solder and heatshrink tube a good few inches to go onto the other end of the ABS wiring that you cut.
Well great, now you’ve got six wires hanging around, when you started off with 2. wth? =) Easy. If you are nutty like me, you want to check your work at this point. Simply plug in the ABS head again, and twist the new wires together (the black wire from abs goes back to black wire from abs wiring harness and brown(or dirty, dirty red?) wire goes back to brown (or dirty, dirty red). Turn car on, start car if crazy (I had mine secured on jack stands, both wheels in the air). No ABS codes. If your ABS and TRACS light is on, then you may have swapped wires. Oops. Swap them, and try test again. Idiot lights go out when hooked up correctly, may have to clear engine codes later.
Alright, now it’s time for the big test. Twist in your wires, bumble-bee (yellow/black from the trans harness) to the brown wire from ABS wiring, and the green/yellow from trans harness to the black. Now originally, I had my wiring at this part backwards, and it didn’t work, and I think it threw up ABS/TRAC light too (wth?). Anyway, if adding this wiring makes things worse (doesn’t work or you get idiot lights), just REVERSE the wiring, meaning put yellow/black to BLACK on the abs harness and yellow/green to BROWN on the abs harness. I’ve done it, nothing caught fire. =)
When I first had this working, I thought it was FUBAR, because at idle (make sure to put the car in DRIVE. I had it in park and thought it didn’t work! speedo won’t go no matter how high you rev in PARK!!). Anyway, in drive, at ‘idle’ with foot off the brake, it shot up to 15mph, then 25! Then back down to 15. This is NORMAL and you are ready to close shop! Remember, with the front of the car on the ground, you get a few mph. Take 3000lbs off of the car, and ‘idle’/coast = 15mph+ I had one wheel off too.
Anyway, that’s it. Once you are happy, you need to solder and heatshrink the cluster together, and then zip tie excess wiring so it doesn’t rub away the shielding and give you guff later. You want this to be water tight now, so take your time. =)
I used thick cable (10gauge, when the oem wiring is 18gauge/16gauge), because that’s what I had. Pics up when I get them off my phone. I can verify wire colors when I get under there to finish it up myself (needed more heatshrink!) But it’s great. Car actually would downshift aggressively in sport mode… the flashing up arrow… gone, the flashing econ/sport mode button, solid! =)
1 Comment
I have to change the transmission from my 850 96 with a transmission from a 850 95 what do i do with the wires