shudder

:banghead:
hoping for some help, feel kinda smoked as i am a mobile heavy equipment mechanic. here it is, 1988 gmc suburban 4x4, 350, auto, 4" suspension lift, 35" tires, quad shocks & dual str. stabilizer.
wicked vibration through front of truck @ certain rpm's, only under load(slight accelerating), only @ exact rpm & or speed. slow up one mph, or slightly touch gas pedal, vibrations gone!! never did this until a few months ago, always lifted w/ these tires, always rode great.
i have replaced motor mounts, tranny mount & u-joints in rear drive shaft. replaced rotors, calipers, pads, checked & regreased wheel bearings. replaced drag link & both ends. checked the entire front end, everything is tight. had tires balanced & rotated. shocks not new, but highly doubt they could cause this. from reading various posts, i am leaning toward the trans. (700r4) causing this, nothing i have done has even touched on this problem. not wasting $$, truck needed those parts, just really starting to lose sanity @ tracking this prob. down. any help to look in the right dir. greatly appreciated. john

did you ever resolve this issue? My brother and friend are having the same problem with a '92 gmc van and 91 gmc pickup, both 5.7 litre's.

Problem is only under load, even at a stop. He puts it in drive, foot on the brake, slight pressure on the gas and it starts to stutter/vibrate. Much worse at 60mph.

There are no computer codes coming out. Thoughts anyone? Thanks in advance.

Well, for the forklift guy, I think the problem is in a bent or twisted driveshaft.

For Carsick, I do not think you have a driveline problem. Your engine may be running rough, (needs a tune up) or there is internal damage in the engine or torque converter

It actually turned out to be a clogged fuel filter. He sure replaced a lot of parts before getting it right, and all because of $5 fuel filter. I told him to go buy a Toyota, which didn't go over very well. Thx for the reply.