Hi Guys,

I wanted to share my experience with you folks and maybe save someone some of the grief I went through. First, some backround. I recently bought a 1992 Volvo 960 w/ 109K miles. It was rough and needed all the same 'normal' repairs as all the other ones I have owned. This one was the first I have owned, however, that has the newer AW-40 electronically controlled transmission.

When cold, the trans would shift fine, but after warming up, it would act strange. After shifting into 3rd it would shift again, into 'lock-up' mode and then quickly shift into 4th and then shift again into lock-up mode. So, thats 4 shifts within about 3 seconds. it would also hunt around a lot when cruising 45-50 mph, not sure what gear it wanted to be in.

On top of this, about 1/2 the time when coming to a stop, the whole car would shutter and shake, until it got to about 500 rpm, then it would be fine.


Most folks would throw in the towel about now and spring for a new transmission. Not me. I am equal parts broke and stubborn, so I was not going to buy a new transmission, nor was I going to let this thing beat me.

The previous owner had unplugged those pesky little warning lights, like 'check engine' 'SRS' and 'tranmission' so initially I didn't know there was a trans problem.

I began my investigation, reading lots of websites and forum postings and concluded that I had 2 seperate problems. Oh, and before I forget, some of this could have been pinned down by use of the OBD box under the hood, but I could not get mine to work. Yeah this car has been a real chore!

Anyway, the trans hunting and 'overshifting' was looking like a bad trans oil temperature sensor. I read somewhere that they commonly go bad. Somewhere I read that the sensor will send bad info to the trans control module (TCM) giving the impression that the trans is getting hot. To try and protect the trans, the TCM tries to put the trans in lock-up mode, to cool it off. It made sense, as my car shifted fine when stone cold.

The trans oil temp. sensor probably isn't too hard to replace, although they are on the side of the transmission, which means getting the car up on a lift or rolling around on your back and they are over $200. Ouch. So I did the next best thing.

The TCM is located under the dash, to the left of the steering column. It is a small aluminum box with 2 connectors plugged into it. I unplugged the larger connector and cut wire #6, which is red with a white stripe. This is the wire that carries the oil temp info from the temp sensor. I connected a 400 ohm resistor into the wire and then plugged the connector back in. 400 ohms of resistance tells the TCM that the trans is running at 104 degrees, F. Problem solved! No more hunting, overshifting and no more 4 shifts within 3 seconds!

I know this is a bandaid fix, which will only be temporary. It was also only .95 cents, instead of $200+

Now, onto the shuttering and shaking when coming to a stop. My reading lead me to conclude that the lock-up solenoid was sticking. Also a common occurance. There are 4 solenoids that electronically control shifting and locking up the torque convertor. All four sit side by side inside the trans oil pan. Cost for new ones is about $250 total.

I went to a local junkyard and found the same parts for a total of $40. It is a bit risky putting in used parts as you don't know their condition, either. I guess I lucked out.

I got my car jacked up and drained the trans fluid. (Try and take note of how much comes out and then put the same amount back in). After I removed the bolt holding the dipstick, I unbolted the trans oil pan to access the solenoids. They come out real easy after dropping the oil baffle. Unplug the wires, bolt in the new ones and button it up. Real easy.

Now my car shifts like new, never shutters or shakes when coming to a stop and life is good.

Please note: I take zero responsibility for your feeble attempt at transmission repair. I have told this story hoping it will help someone, not because I want to get sued when you botch your repair job. Good luck.

 

Man, that's great! I've heard about the fluid temp sensor issue but never gave it any further thought. Great work around! I'm not a big fan of electronically controlled automatics...but it's always good to hear a success story!

 

I have a 98 S90 that was doing the shifting thing. I was driving for about an hour and came off the high way and had to stop at a stop light and was sitting there for a while. When i could go it started out fine until i got to around 40 and when it shifter it felt like it would shift up then down then up like it was searching for what gear to be in. It took me less time to get home and it didn't seem to do it again. On this model there's a button cluster right next to the shifter that has 3 buttons for different styles of shifting. E for Economy, S for Sport, and W for weather. On the way up i had it in E but on the way back i decided to try it in S to see if maybe that was part of the problem. Once i got home i put it back in E and it wouldn't do it again. Are you familiar with these Buttons? and does it sound like it could be the temp sensor?