99 Jimmy ... rough rider

I just finished my first full week of driving this Jimmy on the 100 mile round trip to work every day. It really has a rough ride and I'm wondering if you guys can help me figure out why. I was driving a full sized GMC P/U with Michelins before. This little truck rolls like it is on about a 1/2 flat tire SOME of the time. It seems to get better after you drive a while. It seems to be worse climbing up the steep side of the mountain I cross. It has brand new (less than 1000 miles on them) Firestone Wheel Trac Radial A/T tires in 235x75-15. I have had them spin balanced, and rotated since I got it. Tire pressures are all good. It had a wheel bearing out when I bought it so I can't say how it ran with the last set of tires. I didn't buy these tires. The guy I bought it from got the tires, then had the bearing go out and sold the car. I made him get the bearing fixed before I bought it. I seem to remember reading some bad things online about ride quality on these tires but can't find it now. It swayed around a good bit when I got it. I have had a set of Monroe Air shocks put on the rear and new cheap Monroes on the front, they took out the bad swaying, but didn't do much for the ride. Anyone had a rear spring go bad? It seem to "squat" to the left rear a little bit under acceleration. The air shocks helped this but did not eliminate it altogether. I think I could pump them up more and make it better but I don't want to run them to the max pressure. The guy who installed them did not give me the instructions for them, anyone know the max? I also replaced both rear calipers last week after I had brakes put on and they both hung up. The rotors seem OK but I could be convinced to change them out if someone thinks that might be the cause for this problem. I'm off to do the steering box adjustment, intermediate shaft replacement deal right now. Thanks in advance for any advice you can offer, or similar experiences and resolutions you can share.

More info on this needed - 4wd I'd assume. Bilstens gas pressurized as they came would have helped or Reflex has had great reviews on these - air shocks will beat you to death. If 4wd torsion bars may be torqued up making the front too stiff. 35psi is correct pressure for mileage and 32psi for ride. As for the lack of power that opens a huge area so more specific details needed.

99 Jimmy, 4.3, 4wd auto electronic TC (has Auto4WD button), Auto trans, 80,000miles. I'm sorry if I caused some confusion, there is no lack of power the car runs fine. I meant the rough ride got worse going uphill. The Jimmy will run up the steep grade 80 mph if I want it to. Although I can not imagine that anyone who had it even knows what the torsion bars are and would not have had them adjusted, how do you know where they need to be? I am not in love with the air shocks, I thought they would help for towing my boat later this spring. I also thought they would help the squatting rear end. I would change them if I thought it would help the ride. I'll ebay the air shocks or see if someone on here wants them. I am going to be driving this car for a long time and for lots of miles. I got it from a guy who got a free pickup truck and whose wife is expecting Triplets, so they sold it for the payoff. I can put a little more into it and still be happy with the price.

What do you mean by rough ride, does it sway too much?

It swayed around something awful, top-heavy like, before the new shocks were put on. It is still that way a little and it rides like it is getting a flat tire. It has that washboard feel of a tire going down before it starts to make the car hard to steer. Some times it is better than others, I am thinking it may be the cold and these tires. I've also been thinking it may need U-joints. It is rough across railroad tracks. It had terrible steering response before I did the steering box adjustment today. That made a real improvement in the steering response. I ran the adjuster bolt down til it got snug, then backed it out about 2 flats and locked it down. It may be a hair too sensitive now. I'll drive it this week and decide whether to leave it alone or back it off a bit more. My mom has an '02 Chevy Tracker at 50k miles, with Tiger Paws on it that rides and drives better than this car with only 30k more miles on it. I've had S-10 pickups, and full sized GM and Ford pickups, and driven the Tracker and jeeps that don't wobble around and vibrate like this. I don't mind fixing it I just need to know what to fix. Thanks, LM.

Check you sway bar bushing and end links.

I replaced all of mine and the truck handled like it never has before.

Well, I had all of the suspension stuff checked at two different places and both guys said the ride was coming from the tires. I bought a set of Uniroyal Laredo's in the 235x70-15 that it came with and the problem is all but gone. My only remaining issue is a chatter/rumble/vibration under HARD acceleration thru first and into second gear. It will do it but not real bad if you ease into the gas. If you mash it down from a slow roll it will grumble and vibrate the whole way thru first and well into second before settling down. I had the boat on the back Friday and it rumbled and vibrated something awful pulling out of the boat launch parking lot. It seems to settle down as it goes thru the gears. It pulled the boat up the mountain steady and smooth at 50mph with no problem. I can think of simple things that would cause this, like U-joints or motor mounts, and have it in to the second mech right now to see if he can find something. I can also think of real scary things to cause this, like failed tranny's. What do you guys think???

It is the drivers side motor mount. Pretty easy fix. The guy's gonna do it on Thursday. I got a tranny cooler on the way (thanks Shawn) and am getting this little Jimmy to run the way I thought it could when I bought it. Thanks for your advice on this one and the Bravada guys. This site is the best.

If you haven't changed the oil cooler lines nows the time for that rear one under the engine when you do the motor mount on the drivers side cause its in the way. About $55 for the line but you will be verrry happy you did it. As for the tires - same with mine I went back to the Laredos and they are better - only the Mich cross Terrains were better but not at $600 plus! With the Autotrac don't forget to change the transfer case fluid with the GM Autotrak II syn fluid at $7.50 a qt and you need 2 cause GM has a bulletin on this causing chatter/vibration and its in the posts.

The rumbling could be a dry u-joint.

It is the drivers side motor mount. Pretty easy fix. The guy's gonna do it on Thursday. I got a tranny cooler on the way (thanks Shawn) and am getting this little Jimmy to run the way I thought it could when I bought it. Thanks for your advice on this one and the Bravada guys. This site is the best.
No problem buddy, you make poor college boys like myself happy. Mainly the mechanic haha. Its shipping tomm morning and you live 2 hours away.

The motor mount helped, but did not eliminate the rumble. I am not so picky I can't drive this car like it is, but I have to tow the boat and it is a BAD rumble under torque with the boat on. Classic U-joint symptom. Two mechs have told me there is nothing wrong with any U-joint, although I don't know how they would know one was dry without taking it down and uncapping it. The alternator failed on the way home last evening. I tossed another $300 at this gem today and really did not get any improvement in the way it rides. I bought this car to save a little on gas from my full sized GMC 1500. It gets better gas mileage, but since I bought it I have dumped a ton of money into it to straighten out PITA little stuff.
Motor mount
Alternator
Brakes all the way around.
2 new rear calipers
all 4 oil lines
right front wheel bearing
4 shocks
$300 in paint touchups
4 new tires
Steering box adjustment
TC fluid change- 2 times like in the bulletins, posts
Change out aftermarket radio for OEM
Tranny service, w/filter
Coolant flush and replacement
water pump 2 days later (Do we really want to flush out pristene clean 80,000 mile coolant?)
I like this machine and want to keep it for a long time. I hope it is straightened out soon. I REALLY need to save a lot on gas to get caught up on this thing. I am going to see what diff the motor mount makes towing this weekend, if it doesn't help I am getting the rear U-joints pulled off and checked or changed out. If I didn't HAVE to go Striper fishing on Sunday I'd do it myself.