Ford F150 - tranny going out?

I'll be driving down the road. at about 35 and above, if i need to increase a little, my truck starts to shake violently. i thought i had a fuel problem but that hasnt done the trick. i replaced the fuel filter, fuel injectors are good, fuel pressure is good. i read in other forums that it might be a tranny problem. if it is, anyone got one i can buy off of them, new ones are too expensive. will pick up.

almost sounds like a miss to me, like plugs or wires dirty cap would do. try doing a brake torque and rev it up see if your gettin the same vibration

i've done a brake torque before, because i have a posi rear end, only one tire spins. will that make a difference. if it were a miss, why would it do only at 35 and above? wouldn't it do it all the time? I'll check them anyway.

It could be a misfire, it could be torque converter shudder.

Personally, I'd lean towards a misfire and give it a tuneup of plugs and wires.

Steve

i just replaced my plugs and wires, it still occurs. i have better pickup on acceleration now since i replaced the plugs and wires. what would cause the torque converter to shudder, not enough fluid in it. my fluid is full. my fluid is a little brown. do you think i need to flush it. would it fix my problem. there are no metal shavings in my fluid.

Brown fluid is a sign of significant friction material suspended in the fluid.

Flush the fluid, add a bottle of red LubeGuard, and cross your fingers while you save money for your inevitable transmission rebuild.

Steve