Hey Guys. When I'm going down the road, when the motor is at a specific RPM range the whole front end of the truck shakes. IfI speed up, this goes away. I rotated my tires, and it didnt help.

 

first what year of vehicle, motor, 4x4? automatic transmission?
when they rotated the tires did they balance the tires? what speeds are the vibrations accuring? if you still have discover tires i would start with them!! j/k they're alright

 

Does it happen while in 4 W/D?
Also check your brake rotors for warpage, and check your pistons in the brake calipers.

 

Its a 91 Fullsize K5 Blazer with a 350 TBI with an auto trans. 4wd too.I rotated the tires myself, and i didnt balance them. The vibrations occur at around 40-50 mph. Also, i checked the rotors and they dont seem too bad. They arent warped. And as for when its in 4wd, Im not sure because i dont drive the truck on the road in 4wd at all.

 

Try going that fast when not in overdrive and see if it still does it...

 

It doesnt do it when im not in overdrive. It only does it when the motor is at a certain RPM in overdrive.

 

Probably something with the torque converter, then...

When was the last time the transmission fluid got changed?

 

NOt sure. I got the truck in October. And I didn't change it. So god knows how long its been since its been changed, the guy i bought it from didnt even put it on the road...

 

Could be something to check...

Especially if it only happens when the torque converter kicks in.

 

I had a Monte Carlo that did that (shook when the converter locked up),we replaced the converter, and the lock up solenoid and I never could get it to quit. Hope you have better luck.