I have 79 suburban with a 350 motor and 350 trans it runs fine in park and neutral but in drive and reverse it runs rough any ideas why
lots of things could cause you greif here, I'd guess a miss. So first check or replace your spark plugs and wires, dist cap and rotor. Also be looking for vacuum leaks, broken vacuum lines or broken intake gaskets or carb gaskets. other possibilities are more serious.
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