I have a 1995 gmc sierra, it has a 5.7 motor. What
is the biggest transmission i can put in my truck,
The transmission your truck has can handle any load you can pull. I would install a heavy duty fan operated fluid cooler, a deep transmission pan and maybe a remote filter. You can also have your transmission beefed up to handle a lot of torque.
This might be what you want --- http://www.txchange.com/4L80Etm.htm
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