850 Trans swap or S1 replacement?

captivated · Post by **captivated** » 19 Apr 2016, 21:11

94 850 Turbo automatic wagon has a s1 fault. It is fine when the tranny is cold, but as soon as it warms up, the solenoid fails and I'm without first and second gear. It's pitiful. It has well over 250,000 miles on original engine, and AW 50-42 LE trans.

I have a 96 850 N/A automatic sedan that I finally gave up on after 2 rebuilds, with 115,000 miles. The AW 50-42 LE trans is perfectly fine on it.

My question is - which makes more sense in time and money?
1) Buy the solenoid and replace it in the 94.
2) Take the solenoid off the 96 and put it in the 94.
3) Just swap the transmissions and be done.

I've seen the great picture post of the s2 replacement, so I have an idea of the time/effort it will take to replace the solenoid. I haven't done a trans swap before, so not sure the parameters for it.

I'm simultaneously replacing the gate supports, the headliner, the rear wiper motor, a turn signal assembly, and door lights. I've been running her for the two months I've had her without 1st and 2nd gear (thankfully it isn't the other solenoid, or I'd be up the creek!), but it's beyond annoying, and I'm heading to urban Florida in a few weeks with the kids and I'd rather not be stuck.

So what's my best bet?

Post by **Ozark Lee** » 19 Apr 2016, 22:31

I would do the solenoid replacement way before I would change the transmission. Changing the transmission is a big, big, big job. Getting the oil pan off of the transmission to change the solenoid is no picnic but it is still about 1/10th of the work that is involved in changing the transaxle itself.

If you are talking about swapping the '96 transmission into the '94 there are going to be some problems. The final drive ratio is different between a turbo and a N/A transmission and there are some sensor differences between the '96 and the '94. The speed sensor is the big one and the '96 doesn't have one on the transmission. You can fake your way around that by tapping an ABS wheel sensor line but the transmission will still argue with the TCU and ECU since the ratios are wrong.

If it were me I would just buy a new S1 solenoid and go through the oil pan grief once. If the transmission and engine are already out of the '96 then getting the solenoid out of that transmission is easy enough so that is certainly an option. As far as I know the solenoids are all the same between the '94 and the '96 and between turbo and N/A but check the dealer parts counter first to make sure they are the same part number.

...Lee

captivated · Post by **captivated** » 20 Apr 2016, 08:21

Thanks, Lee! Glad I asked before I tried any grandiose projects. The 96 is still complete, just parked, so looks like #1 is still the best idea. I have to do it the first week of May, because Florida comes the next week.

Back to putting the headliner in now. I hate to put it back together without new gate supports, but I have to use it in a few hours and I can't leave all the trim hanging down for my boys to destroy. I get a little over zealous sometimes.

beigg · Post by **beigg** » 20 Apr 2016, 12:06

Can captivated possibly use tuning as a viable option to 'program' both the modules to like what each other are seeing to solve the "arguing" that may occur?

What product would do such tuning that the vehicle owner (captivated in this case) could mend the calibration issues?

Post by **polskamafia mjl** » 20 Apr 2016, 14:05

While the solenoids are technically the same the brackets are not. On 94's S1 and S2 are the same on 95 and up they are different solenoids. I do not think a 96 S1 solenoid will fit your car.

Pages 3 & 4 discuss which solenoids came on which cars: https://www.matthewsvolvosite.com/forums ... 9&start=20

And there is no tuning you can do to make the S2 solenoid do the work of S1.

beigg · Post by **beigg** » 20 Apr 2016, 17:05

Tuning was in ref to swapping in the other trans entirely. Not internal parts.

Post by **polskamafia mjl** » 20 Apr 2016, 18:17

Hmm. In that case I don't understand what you're talking about.

If you replace the transmission entirely then that's a change of hardware and certainly not tuning anything. The issues that Lee mentioned when using a 96 trans in OP's 94 850 are solved by hardware changes as well, there's no tuning fix for missing hardware i.e. the speed sensor.

Post by **Ozark Lee** » 20 Apr 2016, 19:49

To Beigg's question, I guess the answer is probably yes but I don't know that for sure. You would need to get the TCU to stop complaining about the ratio being incorrect which might be accomplished by using a N/A TCU but when you swap that in the ECU is going to complain about communicating with the TCU and all the shift points are going to be wrong. It is all code and I suppose code could be written and flashed to hide the problems but you are going to wind up with a car that is geared incorrectly when all is said and done. The speed sensor is fairly easy to get around by tapping an ABS wheel sensor. The ABS and the speed sensor have the same number to pulses / revolution and that is how you get around it with a manual swap using a later model M56. The one that cant really be worked around is trying to drop an early model automatic into a later model car since the post '95 version has a second input speed sensor after the torque converter that isn't there on the early model. Again, that might be solvable with code but you can't add the sensor to make it right.

...Lee

beigg · Post by **beigg** » 21 Apr 2016, 01:32

polskamafia mjl wrote:Hmm. In that case I don't understand what you're talking about.

If you replace the transmission entirely then that's a change of hardware and certainly not tuning anything. The issues that Lee mentioned when using a 96 trans in OP's 94 850 are solved by hardware changes as well, there's no tuning fix for missing hardware i.e. the speed sensor.

I was going off this below:

Ozark Lee wrote:If you are talking about swapping the '96 transmission into the '94 there are going to be some problems. The final drive ratio is different between a turbo and a N/A transmission and there are some sensor differences between the '96 and the '94. The speed sensor is the big one and the '96 doesn't have one on the transmission. You can fake your way around that by tapping an ABS wheel sensor line but the transmission will still argue with the TCU and ECU since the ratios are wrong.
...Lee

The mismatched gear ratio might make it a funner volvo!

captivated · Post by **captivated** » 04 Dec 2016, 11:36

So, I still haven't replaced the solenoid, 40k miles later, and now it's December and cold. That means I have 1st and 2nd gear back for about 10 minutes after cranking it up. Why does it shift correctly when cold and not when warm? My fluid is certainly burnt and needs replacement desperately. Should I do a flush and fill with thicker fluid?