BAD (and I do mean BAD) VIBRATION

Short and sweet...this just started this past weekend on a road trip.

up to 60 mph OK
61 to 69 mph bad vibration and rumbling. Like driving on the rumble strips on the side of the interstate. With slight pressure on the gas pedal, it diminishes slightly. When 100% off throttle, and rpm's drop below 1700, vibration and noise stop...smooth as silk.
71 mph plus slight vibration that decreases with a little pedal applied.

90,000 miles, 4" SuperLift, 33X10.5 BFG AT's.

I've checked the U joints and flanges and all are tight...

Any one else had this problem? Any suggestions?

im not positive what the tech did, but my 99 burban did that, it was never 100% fixed, even when i sold it, it first started when between 67 an 73 mph the entire car would shave rattle and bang all from the rear end, the fixed it for a while with new tires, then new rear shocks and struts, then new engine clamps. nothing really fixed it, was a stock except for tv's and 10 disc, nothing affecting preformace. FWIW

Did it come on all of a sudden as mine did, or was it something that started, then got worse over time?

one day i drove it and it was fine, the next it started, :skep:

they did a ton and finally before i sold it they said it was the carb's IM ase certeified and it stumbled me. im still stumbled and know it was never 100% fixed, they said the carb was sending too much fuel in and had to be rebuild, and that the shakeing and vibrations were from it trying to balance the use of fuel and send it back to the tank , i hardly belived this because it would not cause that much shakeing, would it??

SPXTrader said:

Short and sweet...this just started this past weekend on a road trip.

up to 60 mph OK
61 to 69 mph bad vibration and rumbling. Like driving on the rumble strips on the side of the interstate. With slight pressure on the gas pedal, it diminishes slightly. When 100% off throttle, and rpm's drop below 1700, vibration and noise stop...smooth as silk.
71 mph plus slight vibration that decreases with a little pedal applied.

90,000 miles, 4" SuperLift, 33X10.5 BFG AT's.

I've checked the U joints and flanges and all are tight...

Any one else had this problem? Any suggestions?

Click to expand...

My guess would be that you threw a wheel weight and now one of your wheels is out of balance. Either that or you have a tire that is separating. Either way, take it to the tire shop and have them check the balance.

What happens if you are at the speed where the problem occurs and then shift into neutral while at that speed? If it immediately goes away, that would pretty much eliminate a wheel or tire problem.

RT, the way mine vibrates it would have to be sending bowling balls back to the tank. But thanks for the info. I've got a friend that is a traveling mechanic for Pike Electric. He works on everything from their PU's to the big boom/cable trucks. He's off this week, so a ride up I81 is in the forcast.

Mike97, I never thought about a tread separation. I don't put a lot of miles on it...I bought it in 98 I think, with 58,000. It just went thru 90,000, and the BFG's have been on it for the entire time. The sidewalls look a little weak (surface cracks starting to show), but they've still got good tread depth left. I hate throwing away more $$$ on a new set of tires...but I'll check them out. Could this be a probable cause since the vibe/noise goes away, even at speed (60 or higher), once the tach drops below about 1700? This makes me fear it could be a TqC, tranny, or something I don't even want to think about: motor.

If anyone else has any opinions, I'm damn glad to hear them!

Driveshafts are all balanced from the mfr. If the balance weight comes off it'll vibrate like crazy. Usually those are welded on but I've seen them epoxied on as well. Just another idea to look at.

Unbalanced wheels/tires would vibrate regardless of engine rpm, and you said it goes away under 1700, which would normally also rule out the driveshaft and u-joints. At a steady vehicle speed, the only thing changing when the rpms drop is engine speed; everything else stays the same (driveline, tires, rear diff, etc). I would check the motor mounts, dampener on the crankshaft, and even the flexplate and torque converter possibly.

Thanks to all for the replies...guess its time to do some checking...

SPXTrader said:

RT, the way mine vibrates it would have to be sending bowling balls back to the tank. But thanks for the info. I've got a friend that is a traveling mechanic for Pike Electric. He works on everything from their PU's to the big boom/cable trucks. He's off this week, so a ride up I81 is in the forcast.

Mike97, I never thought about a tread separation. I don't put a lot of miles on it...I bought it in 98 I think, with 58,000. It just went thru 90,000, and the BFG's have been on it for the entire time. The sidewalls look a little weak (surface cracks starting to show), but they've still got good tread depth left. I hate throwing away more $$$ on a new set of tires...but I'll check them out. Could this be a probable cause since the vibe/noise goes away, even at speed (60 or higher), once the tach drops below about 1700? This makes me fear it could be a TqC, tranny, or something I don't even want to think about: motor.

If anyone else has any opinions, I'm damn glad to hear them!

Click to expand...

After thinking about it, if you had a tire separating it probably wouldn't get better when you speed up. I imagine it would only get worse the faster you go. But unbalanced wheels can actually smooth out when you speed up. I've experienced this.

JKmotorsports said:

Unbalanced wheels/tires would vibrate regardless of engine rpm, and you said it goes away under 1700, which would normally also rule out the driveshaft and u-joints. At a steady vehicle speed, the only thing changing when the rpms drop is engine speed; everything else stays the same (driveline, tires, rear diff, etc). I would check the motor mounts, dampener on the crankshaft, and even the flexplate and torque converter possibly.

Click to expand...

If you are always in the same gear, it can appear to only happen at a certain rpm range. If you shift down while the thing is vibrating, you should be able to tell if it's engine related.

The original post does not say if he was always in the same gear or not. He did not say anything about maintaining a steady speed and dropping the rpm's, I suggested he try that.

Gear didn't seem to be an issue. While climbing the mountains in route to Kentucky, I encountered some long steep grades. It would kick out of OD as expected, and downshift to keep my speed up. So regardless of the gear, the vibe/noise was still there.

Summary: No change in vibe/noise regardless of gear. Speed and RPM dictated the problems.

I'm going to do a run up Bent Mountain tomorrow and play with the gear selector to see if it has any impact on the issue.

Thanks again for all the help...

SPX

EDIT: has anone seen a 1999 Surburban with the 4WD selector on the floor? It looks just like the one in my 89 K2500 PU...

SPXTrader said:

Gear didn't seem to be an issue. While climbing the mountains in route to Kentucky, I encountered some long steep grades. It would kick out of OD as expected, and downshift to keep my speed up. So regardless of the gear, the vibe/noise was still there.

Summary: No change in vibe/noise regardless of gear. Speed and RPM dictated the problems.

Click to expand...

You are contradicting yourself here. When you shift down, you change the engine rpm's. Are you saying that the vibration stays exactly the same when you shift out of overdrive? If that is the case, then your problem has to be after the transmission. Either in the driveline, axles, hubs, or wheels.

Mike, I guess I wasn't clear in my reply. Referencing the RPM, anything above 1700 or so and it starts...Climbing the mountains it did down shift out of OD. RPM went up, and the problem remained. Only when I got off the throttle completely did it smooth out. And that happened only below about 1700 RPM.

Sorry for the confusion...

SPXTrader said:

Gear didn't seem to be an issue. While climbing the mountains in route to Kentucky, I encountered some long steep grades. It would kick out of OD as expected, and downshift to keep my speed up. So regardless of the gear, the vibe/noise was still there.

Summary: No change in vibe/noise regardless of gear. Speed and RPM dictated the problems.

I'm going to do a run up Bent Mountain tomorrow and play with the gear selector to see if it has any impact on the issue.

Thanks again for all the help...

SPX

EDIT: has anone seen a 1999 Surburban with the 4WD selector on the floor? It looks just like the one in my 89 K2500 PU...

Click to expand...

i, but the suburban has electronic shifters, i think they stopped the mechnical shifters in the early 90's like 92, but whats funny is the 06 silverado base model has mechnical shifter encless you paid 500 to get electrionic. so NOPE i have never seen a 99 with mechnical shifters. sorry. but why do you ask??

SPXTrader said:

Mike, I guess I wasn't clear in my reply. Referencing the RPM, anything above 1700 or so and it starts...Climbing the mountains it did down shift out of OD. RPM went up, and the problem remained. Only when I got off the throttle completely did it smooth out. And that happened only below about 1700 RPM.

Sorry for the confusion...

Click to expand...

So If I understand you correctly, it isn't speed dependent. It is rpm dependent. From a stop, place the gear selector in low. Drive until your engine rpm's are at 1700. Do you still have the vibration at this speed? Your first post mentioned above 60 mph. Now you are talking about it being rpm dependent. It should be fairly easy to rule out one or the other.

RT...I looked at a 99 'burban LT today and the 4WD selector was on the floor! It was a beautiful truck, sapphire (?) white with barn doors! And only 78,000 miles...

Mike, I can't say for sure it's not speed dependent. Below 60 or so (driving around town), I can't feel it at all, even with the RPM's up...but I plan on a detection drive Thursday. I'll try the first, second and third gear to 4 grand ploy and see if it appears. If all else fails, I'll grab my mechanic buddy and take him for a jaunt up the interstate. I'll let you all know what I (hopefully) find.

Thanks again..........

SPX

SPXTrader said:

RT...I looked at a 99 'burban LT today and the 4WD selector was on the floor! It was a beautiful truck, sapphire (?) white with barn doors! And only 78,000 miles...

Mike, I can't say for sure it's not speed dependent. Below 60 or so (driving around town), I can't feel it at all, even with the RPM's up...but I plan on a detection drive Thursday. I'll try the first, second and third gear to 4 grand ploy and see if it appears. If all else fails, I'll grab my mechanic buddy and take him for a jaunt up the interstate. I'll let you all know what I (hopefully) find.

Thanks again..........

SPX

Click to expand...

ya sure it was a 99, sounds intresting that they did that so late in the game, i need to research that more.

i guess it was an option still, but push button 4wd was standard on an LT, still confusing, SOURCE, EDMONDS


1993 Chevrolet Tahoe: Electronic control for the automatic transmission was one of the few changes in Chevrolet's big wagon. The new automatic also added a second-gear start feature, for increased traction on slippery surfaces.


1994 Chevrolet Tahoe: A turbodiesel engine returned to the powertrain parade, as side door-guard beams and a center high-mounted stoplamp were installed.


1995 Chevrolet Tahoe: A driver-side airbag was added, in a redesigned interior with recontoured seats. The turbodiesel engine could now go into 1500-series models as well as the 2500 series, and the standard V8 lost 10 horsepower.


1996 Chevrolet Tahoe: More-potent Vortec engines debuted for '96. The 5.7-liter gas V8 leaped from 200 to 250 horsepower. The optional 7.4-liter V8 gained 60 horsepower (now 290). Pushbutton engagement for the 4-wheel-drive system became available, and daytime running lights were installed.


1997 Chevrolet Tahoe: A passenger-side airbag was installed on '97 models. Outboard seats in the middle row gained height-adjustable shoulder-belt anchors. The standard 5.7-liter engine added five horsepower.


1998 Chevrolet Tahoe: Suburban added an optional full-time 4WD system called Autotrac. This system can remain engaged on any road surface.


1999 Chevrolet Tahoe: GM's biggest wagon was all but unchanged for '99, pending the arrival of a redesigned 2000 model.

RT, sorry, my bad...it was a 96...

[/IMG]

[/IMG]

lol, that makes more sense. nice looking though for a 96:cool2: