Several Problems with my 98 Lt

My 1998 2-Door has roughly 120,000 miles on it. There are several problems which I am noticing, the worst of which is vibration coming from the rear whenever I accelerate. The vibrating only occurs when my foot is on the accelerator, not while coasting or braking, and gets more noticeable as my speed increases. Another problem, which I suspect is related, occurs when I press the accelerator when I’m already rolling. I hear a loud "clunk" from underneath the car. I get the same sound, from the same location, when I shift gears from park to drive or reverse, or between drive and reverse.

Another problem is that I hear a clicking sound from the front driver side whenever I take turns to the right. I have been driving without a sway bar link on that side (broke several thousand miles back), but figured that it would only affect my handling and not hurt the steering or suspension.

The least of my worries, but still a bother is my dash blower. It only blows on the face no matter what setting it is in. This problem has become progressively worse so I'm thinking that the problem is related to the switch. Any ideas?

Thanks for any input or advice you give me. I hope to get my Tahoe healthy for the rainy months and all that MUD.

My 97 has 127k on it and I have similar issues with the rear. I have noticed that my pinion seal is leaking, and when you brake harder than usual and stop at a light, when you release the brake it feels like something relaxes in the rearend, like some thing is too loose. Im going to be replacing my rear dif cover with a chrome one when comes in and im going to check the pinion bearing and replace the seal at that time.

As far as the front goes, with a sound like that usually means wheel bearings. And if its clicking, they wont last much longer. Have them looked at soon as you can.

The dash issue is probably a broken vacuum line that controls the openings under the dash.

I had that kind of problem with my '97 4DR 2WD. It began at 7 or 8K miles, and the dealer tried all kinds of stuff. Replacing the rear springs, balancing the driveshaft, but it turned out to be the slipyoke was binding as it slid in and out of the transmission tailpiece as the vehicle rose up and down in the rear end when stopping or starting. They called it launch klunk. Felt like someone had bumped into me with each stop or start. This was a very common problem. They then went on to try a new, improved slipyoke, then they tried putting a rubber ball into the tailpiece before putting the slipyoke back in, then special grease, and a new output shaft, all to no avail. The klunking would stop for about 1200-2000 miles, but would return after the fresh grease had been scuffed off the yoke. I worked with the dealer quite diligently and amicably, but then went to the owner's manual to research the next complaint step. I filed a formal complaint in accordance with the GM policy. They told me it was "normal", and there was no fix. I knew that half of the 2WD models had this problem, and quite a few 4WD models too. After a bunch of postering, positioning, shucking, and jiving they offered me a new vehicle for the difference in dealer invoice between the '97 and a new '99. That amounted to about $460, and my '97 had 33,000 miles on it. I accepted the deal, knowing that the new one may have the same problem. My '99 now has 110,000 and never had the famous "launch Klunk". The 4WD versions seemed to be more easily repairable with an oil additive put into the transfer case at grease change. They had no such good luck with the 2WD's

Sounds like you have a bad U-joint. Crawl under the truck and see if you can move the drive line by hand, if so watch for play. A bad u-joint will cause clunking noises and vibrations.

Thanks guys for all the suggestions. I did notice a minimal amount of play in the U-Joint, and considerable wear in the joint itself closer to the rear diff. I'm thinking that this is deffinately the culprit. What do I do to fix this? Meanwhile the clunk noise when i shift into gear has gotten louder and I can now feel it through the floor of the driver side. I think I'm gonna haveto take the car in and have someone take a look at it. As much as I hate saying/ doing that, I cant wait any longer while I try and figure this one out.

As for the vaccum line under the dash, where exactly would I locate it?

Thanks. This site rocks.

A u-joint will cause a clunking noise when you shift, to fix the problem you need to replace the ujoints.

hey thanks a lot for the help Horse. Im going to replace the u-joints this weekend. I found some for $15 each at advance auto, but are those really top quality that are going to last?

Again, thanks for all the help. This site is GREAT.

hey thanks a lot for the help Horse. Im going to replace the u-joints this weekend. I found some for $15 each at advance auto, but are those really top quality that are going to last?

Again, thanks for all the help. This site is GREAT.
Do not use the Chinese AZ joints!! Get the best ones from NAPA.

first off you may have bad u-joints like you stated. the clunking from the rear end is normal. if you have the "corporate" 10 bolt, every one makes that sound it is backlash between the gears. the a/c controls not working is the actual control unit, very very common with these models, our systems are controlled electronically not by vacuum like the old days. the clicking sound is probably your cv shafts at the ft wheels either crawl under the ft or pull off the ft tires and look at the axle boots and see if they are split if they are the grease has come out. depending how long they have been doing this you could get away from a new boot and repack the grease, but for the amount of money its worth it to get a reman shaft from pep boys or any parts store you have local they are about 69.95-149.95 and they have a lifetime warranty.

Napa sales Precision u-joints witch are good, but if you can find someone that sales spicer u-joints they are a lot better.

Replaced both front and rear u-joints and the vibration/clunking while shifting is gone. THANK YOU ALL. This site is amazing.

My 1998 2-Door has roughly 120,000 miles on it. There are several problems which I am noticing, the worst of which is vibration coming from the rear whenever I accelerate. The vibrating only occurs when my foot is on the accelerator, not while coasting or braking, and gets more noticeable as my speed increases. Another problem, which I suspect is related, occurs when I press the accelerator when I’m already rolling. I hear a loud "clunk" from underneath the car. I get the same sound, from the same location, when I shift gears from park to drive or reverse, or between drive and reverse.

Another problem is that I hear a clicking sound from the front driver side whenever I take turns to the right. I have been driving without a sway bar link on that side (broke several thousand miles back), but figured that it would only affect my handling and not hurt the steering or suspension.

The least of my worries, but still a bother is my dash blower. It only blows on the face no matter what setting it is in. This problem has become progressively worse so I'm thinking that the problem is related to the switch. Any ideas?

Thanks for any input or advice you give me. I hope to get my Tahoe healthy for the rainy months and all that MUD.Sounds like either your u-joint 1 the other is have your rearend checked out