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Airbag deployed due to shot transmission

My 86 diesel mercedes has a history of a bad transmission. Could not drive it for 2 years before having the transmission rebuilt only to end with no 3rd gear. Very loud metal sounds(not grinding) when changing gears as well as having to build up muscle tone to change gears. Anyway, driving along around 55mph when the airbag deploys with no collision. I pulled over safely, not sure how. After cutting away the airbag my husband tried to drive the car home. The stick would only move up and down but not into any gears. The car undriveable. Any ideas?

I don’t know how the two issues can be related. I’ve NEVER heard of an airbag deploying without an accident. I am aware that Mercedes Benz recommended their airbag systems be replaced periodically in the era that your '86 was made. That was pretty early in the history of SRS. They were unsure how long they’d last, and of course didn’t want any liability if one failed to pop in an accident. I don’t know of ANYONE who actually had them replaced, and I suspect that M-B decided it was not worth the effort.

So I just read the wiki definitions of what triggers airbags. Its about deceleration. Could a transmission that siezes up cause enough deceleration to trigger the airbag?

“Could a transmission that siezes up cause enough deceleration to trigger the airbag?”

Only if the sensors or other hardware involved in airbag deployment are defective.

A seized transmission would cause no more deceleration than locking your brakes in a panic stop, and panic stops do not deploy airbags when the sensors and other hardware for the SRS are functioning properly.

The worst cars ever built were built from 1981 to 1989. A decade of automotive horror and outright junk…It’s time to thank your stars, cut your losses and move on. You could buy a NEW Benz for what it is going to cost you to repair (properly repair) your old one. And when you got done, you would STILL have a 26 year old money-pit…

I think the more likley cause was a wire that shorted out somewhere in the AirBag system. Most likley in the stearing colum it self.

Well my only two cents worth is this. Two main systems were used for airbag control at the time. A basic collision sensor that saw parts of the body(bumper) collapsing and then fired the bags. The other system was an early accelerometer. It measured the rate of deceleration of the car and fired the airbags. Newer systems use the same tech with a lot of improvements.
That said the system could respond to a sharp deceleration without a collision. The time frame of the deceleration could have tripped the sensor. These were made to be better later on. The '86 was built with '79 technology and the scan time frame was several hundred milliseconds. Best they could do at the time. Cars now are normally 1000 times faster on these sensors or better. This allows for less false firing. Hey the system was old and it could be bad luck as well.

Multiple trans rebuilds? Don’t go back there, they weren’t fixing the cause, just throwing new parts in.

Call the wrecker, donate it, time to move on; if not, get a working used trans installed by a different shop.