* The engine size: Different transmissions are compatible with different engines.
* The model of the pickup: C1500, K1500, Silverado, etc.
* The current transmission: What transmission is currently in your truck?
Once I have this information, I can tell you which transmissions are compatible with your 1990 Chevy pickup.
In the meantime, here are some general things to keep in mind:
* Automatic transmissions: The most common automatic transmissions for 1990 Chevy pickups were the TH350, TH400, 700R4, and 4L60E.
* Manual transmissions: The most common manual transmissions were the SM465, Borg Warner T-5, and New Process 435.
It is always recommended to consult a mechanic or transmission specialist for the best and most accurate information.