shakes when accelerating but it is ok if i let off the gas

[nitr0gen]

when i give my 1991 f-150 gas it has a horrible shake .It is a 5.0 fuel injection in it .When i let off the gas it will stop shaking.I ran over a tire the other day in the middle of the road and it knocked my muffler off but i drove it for a day with out a muffler and it just started doing this .

[landyacht]

This problem isn't due to hitting a tire that ripped off your muffler. This problem is in the transmission.

I don't know exactly what it is, but i had a friend with a van that did the same thing. You accelerate a bit to hard and it would shake and bang and jump like crazy. If he accelerated gently it was good, and there were no problems once the thing was up to speed.

Have a REPUTABLE transmission shop have a look at it is my suggestion.

[97chevyman]

just because it's shaking does not mean the tranny. could be a bad injector, dead hole, bad plugs wires, low fuel preesure, who know. First take a compression test on all the cylenders, then replace the plugs wires and cap while you are at. then pull one spark plug wire off at a time and see if there is a difference in the engine rpm, its hard to hear a dead hole in a 302 with loud exhaust beleive it or not. Check that before the tranny.

[landyacht]

Sorry this is a bit late coming back to this thread, chevyman can a bad injector etc. that you mentioned REALLY make a shake like that? I've never heard of a hard core shaking from that...

Then again, i'm not old enough to know everything yet!