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Discussion Starter #1
I have a 98 Suburban, 4WD, 5.9 V8. approx 118K miles. I love the truck, but when accelerating between 55 and 68 mph there is a LOT of noise from the vehicle in the cabin. When I get past 70, the noise goes away and also if I let off the gas the noise continues for about 3 seconds and then stops (regardless of MPH).

Any ideas are greatly appreciated. One garage told me that my Kelly tires could be causing this as they were wearing unevenly...
 

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what rpm range? could be lifters or an imbalance in motor.....
 

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noise

I have a 98 Suburban, 4WD, 5.9 V8. approx 118K miles. I love the truck, but when accelerating between 55 and 68 mph there is a LOT of noise from the vehicle in the cabin. When I get past 70, the noise goes away and also if I let off the gas the noise continues for about 3 seconds and then stops (regardless of MPH).

Any ideas are greatly appreciated. One garage told me that my Kelly tires could be causing this as they were wearing unevenly...
Crank shaft.

I hope I'm wrong.
 

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What kind of noise is it, a whine, a rattle or what? Does it include any vibrations?
 

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Noise

There is definitely some vibration. The noise sounds like really loud road noise, and goes away when I left off the accelerator or accelerate over 70/below 58.

If it is the crankshaft as one of the other posters said, what does that involve for estimated repair costs?
 

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There is definitely some vibration. The noise sounds like really loud road noise, and goes away when I left off the accelerator or accelerate over 70/below 58.

If it is the crankshaft as one of the other posters said, what does that involve for estimated repair costs?
if its the crank your are looking at a complete rebuild... really no other way.
 

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Discussion Starter #7
Other question

Is it possible that this could be caused by bad shocks? I've changed the front ones since purchasing the truck, but don't know if the back ones have ever been touched...
 

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One of the first steps in diagnosing noises is to try and determine if it's engine or drivetrain related. You say the noise seems most prevalent between 55 and 68 mph. Assuming that's in 4th gear, the next thing to do would be to put the transmission in D (so it won't shift into 4th) and see if the noise occurs at the same vehicle speed or at the same engine speed (a slower vehicle speed). If the noise seems more related to engine speed, then start looking at engine related things (fan clutch, misfire, exhaust noise, etc.). If it seems more related to vehicle speed, then check things in the rest of the drivetrain (u-joints, suspension, tires, etc.).
 

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It's hard to say w/o hearing the noise. I've had speed-related noises be everything from out-of-balance wheels to ... yes a damaged crank in a 350.

Shorty is right, definately try to rule out the tranny. That speed range could be when you shift into 4th gear and you may have a bad 4th. Try that first.

Is the noise louder with the windows down? Do you feel vibration, espectially anything coming up through the brakes or the steering column?
 

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Discussion Starter #10
Thank you!!

I will try the items listed by Shorty and report back to the forum. I appreciate all of the responses!!!
 

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My experiences

firsts off sounds like u joints if drive train related, especially the way it goes away when you let off. Or it could be a head gasket, yes they can knock. Does the truck run rough?
 

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firsts off sounds like u joints if drive train related, especially the way it goes away when you let off. Or it could be a head gasket, yes they can knock. Does the truck run rough?
I was thinking the same thing I would get the tires balanced and the u joints checked and see how things go.

A bad u joint can make some bad harmonics through out the whole truck.
 

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Discussion Starter #13
Results of troubleshooting

We ran the truck today in 3rd gear and the exact same noise at 55mph. I'm going to get new tires on Friday since that was a suggestion from the local mechanic (and it needs them anyway). If that doesn't correct the problem, then I'll start going down the other suspension items. Any advice is greatly appreciated!!
 

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Discussion Starter #14
Answer to wildman

No, the truck runs well. Had it tuned up last year and a cam shaft issue corrected. Based on the advice here and from a friend in Illinois, here's what I'm going to have looked at tomorrow:

Tires balanced (if possible, if not I'll get new ones)
U-joints checked and replaced if needed
Rear shocks checked (front replaced less than 10K miles ago)
Transmission mounts checked and replaced if needed

Does that sound about right?
 

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Those are good things to check. You'll probably find that it's not the tires though. If the tires were making the noise, it wouldn't go away if you let off the gas. I'm thinking it's more likely drivetrain. Either unbalanced driveshaft, or could be u-joints, or rear end. Just too many variables at this point.
I never saw if you indicated where the sound comes from, (front, rear, just seems to be everywhere)
If you still have the problem after today bring a couple friends, or family members for a ride, and let them sit in different places in the vehicle, and help you identify the location of the noise.
I don't think you'll find that it's your engine either. If it was, you'd be more likely to complain of the noise as certain RPMs, rather than vehicle speed.
 

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If it is tire noise from wearing unevenly try taking it off road. Find a clear dirt road and try the same speeds. If the noise isn't present, you've found your problem.
 

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I've encountered that same exact experience in that same speed range on several vehicles (Jeep Cherokee, Ford Mustang, Dodge Caravan, and Suburban) for me each time it was the tires.

Three possibilties broken belt (inside tire), improper balancing, or tires worn beyond the suggested tread wear (sometimes the tread can still look good to the eye but still be below the minimum wear for that tire.

These three are easily checked as usually any tire sales and installation center will check this on the spot for free or a minimum fee.

Good Luck! after reading some of the other possibilties, I hope your tires just need balancing.
 

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if it has a mid shaft bearing on the drive shaft check the bearing and the middle u joint... if it soes make sure u unbolt rear ujoint from the rear end and try to turn the shaft. the ujoint freezes up. iIt will seem tight if u do the normal joint check. but if u try to spin it it will not bend. happiens alot on the pick ups
 
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