Automatic transmission on 4x2 1989 Chevy C1500
I found a transmission line leak in April. Parked the thing through the
summer. Finally got around to repairing transmission line in October. Was
down maybe 2 quarts. Topped off. It took a while to recirculate the fluid.
Shifts fine 1,2,3. But it will not go beyond that. Just winds at 40mph. Wants
to shift, but won't. Further investigation found what appeared to be rodent
damage. It looks like a vacuum line and the wiring going to the trans. But
can not find if these are actually from the trans or not. I can NOT believe
that letting it sit for 6 months would cause the transmission to just quit.
Yes it can, varnish will build up especially if it hasn’t been serviced regularly, so fix the vacuum lines and the wiring pull out 1 quart of trans fluid and add 1 quart of TransX and drive it around for about 20 minutes then park it and let it sit about 2 days then drive it again the same amount of time, you may have to do this a number of times before you start to feel anything happening. If it is varnished up the additive will start breaking it down slowly and help with any hard seals internally, if it can be helped this stuff will do it, if nothing happens then it’s too late and it will have to be rebuilt or replaced.