Help! Have beloved 740 with 210k miles. Need to decide whether to fix or donate.
When the car is cold reverse works fine. When warmed up, it goes dead immediately on putting in reverse. If I put in reverse after getting up speed going backward downhill, it doesn't go dead immediately but jerks and struggles; then goes dead when stop. No problem in forward gears. I removed and cleaned throttle body already with no change.
Two possibly related events:
1) I very recently washed transmission exterior vigorously to help find a fluid leak (was dumping fluid after sitting several days)... AND added "leak-stop" which fixed this problem.
2) I accidently put it into reverse momentarily while on freeway (meant to go to neutral)
THANK YOU!!!

It seems as if there is an idle problem, accompanied by weak ignition.

The problem could be related to a vacuum leak, idle air control, idle switch, throttle body adjustment, clogged air filter, or about twenty other reasons.

Mostly reverse is where the car will stall, if it has a weak idle. Even if the idle speed is right, it's easy to spin an engine at idle speed with no load.

There is no way that the transmission could be damaged so as to stall the car only in reverse. All power passes through the torque converter in one direction before it hits the gearbox part. No matter if the gearbox was locked solid, the car should stay running because it is just as if the car is sitting still in Drive or Reverse.

However, I belive that some ZF transmissions had a lockup feature on the torque converter. If that malfunctions it could cause the engine to kill. I don't think that the AW70 had a lockup in 1987. It would help to know what transmission you have. The ZF transmission is much more complex with respect to the service and repair procedures, than is the AW70.

If you bring the idle to 1000rpm and put it in reverse, does it still stall immediately? When the car is warm, I mean. As high as 1200 for test purposes, one or two times with AW70 trans only... This will rule out a trans problem, and highlight a slow or weak idle condition. If there is a little play in the driveline, the engagement into "R" can be very harsh. Ditto for drive, but it depends on how you parked the car.

With the ZF transmission, there are numerous faults that could cause either double-engagement of the transmission, harsh engagement, no engagement, etc. The Volvo diagnostic manual has about twice as much information on diagnosing ZF faults as it does on diagnosing the Borg-Warner/Aisin Warner varieties.
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Chris Herbst, in Wisconsin.

Thanks, Chris, for your quick answer and help!
The transmission was replaced a few years ago with a used transmission. I think I originally had the ZF... it had regular "D" and "overdrive D" on the selector, whereas the the replacement has 1, 2, D. I think I recall the Volvo shop saying the original one was the more complex also.

When holding the gas pedal down to maintain 1000 to 1500 rpm, the engine still dies in reverse.

Thanks,
Gary Chastine (Louisville, KY0

Hm... that is strange. It's hard to say what the cause of that is. It COULD be that there is an electronic fault caused by the movement of the engine when you put it in reverse. I mean, the engine torques one way in reverse, and the other way in forward. Perhaps there is a wiring issue that is causing it. It might not hurt to have a good shop take a quick look and see if there is something they can do to identify the problem, because there are so many possibilities.
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Chris Herbst, in Wisconsin.

Thanks, Chris!
I'll just take it in, as you suggest.

I would say you have a short in the electrical system. I assume it's an Auto tranny, if so, then there maybe a short from the reverse light switch that is shorting out the ignition. Look and see if you have wiring problems under the shifter and follow the reverse light switch wires.

I am not a Volvo expert by any means, it just seems obvious that if the engine quits when put in reverse then it is probably an electrical fault. The reason it splutters when going down hill is because the tranny is turning a dead engine. An auto transmission will turn the engine when coasting at reasonable speeds.

Thanks for replying!
It is an automatic. Good idea on the reverse light wiring. Seems it would blow a fuse though?
Thanks again.
...Gary