Similar issue with 1990 B-II
I have a 1990 B-II that the O/D stopped working in it a few weeks back, right immediately after I changed out the radiator. The symptoms are: when cold, the O/D works like it is supposed to, but when warmed up, it starts falling out of gear when you back off the throttle any, only going back into O/D when you step on it rather briskly. Eventually, it will no longer go into O/D at all. I can shift to D and it stays in gear no problem, just like it is supposed to, but if I shift back into O/D, even though it will not go into O/D, when I let off it, it falls out of gear totally, no matter what speed I am traveling.
What I've done so far: Changed the fluid and filter, checked the computer for any codes (none), and changed the throttle position sensor. It also has a 180 degree thermostat, and an open element air cleaner mounted on the fender where the old air box used to be. Also, the radiator I installed came from a 1988 model B-II with the same drive train and the donor ran fine before I stripped the radiator and a few other (cosmetic) parts from it. The donor had been wrecked and totaled by the insurance company. It was hit in the front, (obviously not bad enough to damage the radiator), and all down one side like it slid on that side, perhaps in a ditch or something. I don't think it rolled because none of the windows were broken.
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