Transmission Repair History of a 1996 Volvo 960 Purchased in August 2013

My brother had the opportunity to buy a 96 Volvo 960 wagon for a good price but it had some serious electro/mechanical problems. Sorting them out was beyond his technical ability but I am a long time Volvo owner and have kept Volvo's running since 1965. So I thought it was worth taking a chance on buying it. It had 175K on the odometer and the engine had supposedly been changed sometime recently, the rest of the history was not known.

I conferred with a expert Volvo mechanic about the flashing shift light, the check engine light and the P0733 and P0715 code. He confirmed what I had read about the transmission being pretty durable so I felt it was possible it wasn't totally shot. He leaned toward the solenoids in the transmission as a possible problem (along with the PNP switch or computer). He loaned me a Volvo transmission manual that detailed everything, and on a later trip, he also printed the specifications for the TCU and what the outputs should be and what the solenoids should be seeing signal wise. All these components can be checked to determine if the are functioning correctly.

The 960 would not shift out of park and when in park did not lock the transmission, in addition the emergency brake was not working. The check engine light was on and the shift arrow on the dash was flashing along with the lights on the E/S/W switch. The speedometer DID work correctly. When placing the car in gear the motor would race but the transmission would not engage in any gear. I knew absolutely nothing about the 960 but after doing some research found that it was a pretty good car and well built.

My brother bought the car for $800.00 and I attempted to drive it home so I could work on it. It actually went into reverse and then drive (confirming that the problem was intermittent in nature), and off we went, after about 3 miles it started to lose power, the engine was running but the transmission acted like it was in neutral, I pulled off the road and turned off the ignition and then restarted it putting it in Drive and off I went again for about a mile and the same thing happened again, the 10 mile trip home continued this way with at least 10 stops and restarts. The last ¼ mile was uphill and it took me four tries to finally pull into my driveway. The “limp home mode” the mechanic described was not a true statement as related to this car. After a couple of tries I was able to pull it up onto ramps, jacked up the rear wheels and placed jack stands under the rear of the car.

The transmission is computer controlled and many inputs give it signals that control it's operation.
For example: The Transmission Control Unit (TCU) gets inputs from :
The Mode Selector Switch
Throttle Position Sensor
Transmission Speed RPM Sensor
Gear Selection Sensor
Transmission Oil Temp Sensor ( sends signal for shifting and torque lockup)
Brake Switch (signals TCU to control solenoid for torque converter lockup)
Kick Down Switch

The first problem was to fix the park and emergency brake before I could even get into the transmission shifting problems. The car had about 10 problems all interlinked to the signals going to the computer controlled transmission. The emergency brake problem was caused by no brake shoe materiel left on the shoes so new shoes fixed that problem. I traced the voltage from the brake switch to the shift interlock switch and found that the brake switch was good but was sticking due to the car being non-operational for an extended period of time. Once 12 volts made it to the interlock switch it started functioning correctly and you could hear the solenoid energize. Sometimes the car would start in park and sometimes only in neutral, I found the shifting linkage bushings to be totally missing and when I bought and replaced the new bushings and re-adjusted the linkage, the “park” position again functioned as it was supposed to. While I was in the console area I replaced the little light for the shifter with a real neat LED that was a direct fit and will not burn out again in my lifetime. On the 96, that little bulb is removable and costs about two dollars if you replace it with a regular bulb. The LED is better and very bright. 74-xHP3: 74 LED Bulb - 3 SMD LED Wide Angle Wedge Base 74-WWHP3: Warm White http://www.superbrightleds.com/ $3.49 plus shipping total cost $6.48. There is a second choice of lamp offered but I chose this one.

My troubleshooting consisted of determining what was working and continuing until all the working things worked in unison and then determine what was not working and why. I used a ohm meter to check all the solenoids and found them to be within the specs listed. This verified that the solenoid was not shorted or burnt open. The next step was to apply power to the solenoid through the disconnected connector. One of the descriptions stated that S1 was energized when the vehicle was in reverse. I applied 12 volts to the solenoid and could hear the solenoid click inside the transmission. While in drive, I checked the other suspect solenoid and it clicked also. This only proves that the solenoid is energizing, not if it is actually doing its function of opening and closing a circuit. Next, I found the main computer and reseated the connector terminals in case they were adding to any of my problems. All the other associated wiring seemed intact and functional after re-seating all transmission related connectors.

The next step was to drain the transmission ( I measured an actual five quarts of fluid that came out of the transmission) and drop the transmission pan. I replaced the filter which was pretty dirty, cleaned the magnets and used the gasket that came with the new filter. I replaced the five quarts of fluid (with the intention of doing it again in about two to three months. This would give about 98% new fluid after two changes. While on the jack stands it seemed to be happy in all the gears--which was not the case when the project first started. I lowered it down and put all wheels on the ground, took it for a tentative drive around the two mile circle we live on. It performed perfectly. At this writing it has been over a week and several short trips, so I am confident that it is going to be okay. I bought a code reader from Amazon and it is great, I re-set the check engine light and the codes; they have not returned.

The information on the web for the problems I had were instrumental to the repair and restoration to working condition of the 96 Volvo 960 and gave me a logical step by step sequence to follow. Perhaps this additional information can benefit others. I did a very large amount of web research and read all the literature I could obtain from Volvo. If you spend enough time you can actually start to understand the Volvo transmission manual. I copied all the pertinent information for the transmission and Transmission Control Unit (TCU) and have it in my computer.