99 Suburban Highway Rumble

[Buick]

Hey Guys, been a LONG time lurker on this forum, but I'm finally at wits end with my '99 K1500 Suburban. At highway speeds, between roughly 65-75MPH, there is a pronounced low frequency rumble. It is pretty loud, but difficult to determine where on the vehicle its coming from. Along with the rumble is a noticeable vibration, strong enough that it triggers interior rattles. The noise / rumble is non-existent at lower speeds and very much diminished above 75mph. I inherited the truck last year from my late father, who kept the truck exceptionally maintained. Of all things, my father was a career driveline engineer for General Motors (later Delphi/Nexteer), so its very near and dear to me that I figure out what's going on with HIS parts on his beloved truck!

Now the truck does have a lot of highway mileage, 289,000 to be exact. It is bone stock with the exception of factory 17" wheels from a late GMT800 truck being installed. Besides keeping up with regular maintenance items, last year he did some fairly extensive work before he passed.

Including:
- Pulled Engine to replace all seals, gaskets accessory drive items, fuel injection Etc. Runs Excellent
- All new engine/trans mounts
- Service front & rear diffs
- New shocks
- transmission & transfer case service
- new brakes (rotors & calipers, new shoes & cylinders in rear)
-4WD actuator and selector replaced
- New Rear Driveshaft & U-Joints (single piece driveshaft)

The noise was there before and was still there after the work he did (which was to primarily addressing other issues/leaks). Since taking over the vehicle, I've been frustrated by the highway noise as it's right at cruising speed. Changes in load on the engine/ driveline seem to have no affect on the noise. Its 100% speed related, this morning I even shutoff the engine at 75mph and coasted down to 60mph (neutral) and it had no affect, the noise "went away" once I dipped below 65mph or so. Engaging 4WD at highway speeds seems to add a little gear noise, but also does not alter the "rumble" in any way. In chasing the issue, I've started throwing parts at it this week.

Recently Replaced:
-Front Driveshaft pulled, (AutoTrak so front drive shaft always spins) u-joints replaced, re-balanced
-Both front wheel hubs/bearings replaced
- Brand new tires installed (had no affect)
-Drain and fill transfer case and diffs (fluid still looked new)
-Inspected trans mount, looks new

I've contemplated replacing the CV axles, but I'm very hesitant. They don't "click" when turning, or with 4WD engaged, so although they are old, I think they are perfectly fine. My dad's area of expertise and main product line were half-shafts, and time & time again he explained how aftermarket Chinese CV axles are total garbage. I'm concerned that throwing a couple hundred bucks at garbage aftermarket CV axles with neoprene boots that will tear within 6 months is just adding fuel to the fire...

Any suggestions of what to do next is greatly appreciated. Yeah I know, I can take it to a shop and throw A LOT more money at them to maybe figure out the problem, but I want to try to solve it myself. This truck meant a lot to my Dad, who always did all the work himself, and means a lot to me. I've read though just about every related thread without any smoking guns. Looking forward to the suggestions!

 

[Erik the Awful]

On long, sweeping highway turns, does one direction sound louder than the other? With all that's already been replaced, I'm thinking a rear wheel bearing is a high probability.

 

[Buick]

On long, sweeping highway turns, does one direction sound louder than the other? With all that's already been replaced, I'm thinking a rear wheel bearing is a high probability.

No, turning (and even pavement types) seems to not affect the noise. I've seen a lot of threads say it could be tire balance, but the noise remained the same from the old tires set to the new ones. I was also thinking rear axle shaft/wheel bearings as well.

 

[Erik the Awful]

Maybe side bearings in the diff? I'd consider rebuilding the rear diff all at once. I replaced the rear wheel bearing in my Mustang, and now the pinion bearing's making noise.

 

[HotWheelsBurban]

With that mileage, and given everything else you've replaced, I'd be looking at the rear axle bearings too. The ones in the axle tubes, close to the wheel, use the axle as the inner race of the bearing. So when it goes bad, it'll ruin the axle too. Been there, done that with several of my old square body trucks.
You'll need to get inside the differential and remove the bolt, that holds the pin that provides access to the C clips that retain the axle. Check the diff gears and parts to be sure there's no slop and glitter that may indicate excessive wear. When we had bearings go bad on our trucks, Dad taped a rag on a long stick to clean out the axle tubes, after we had the axle and bad bearings out.

 

[Erik the Awful]

You'll need to get inside the differential and remove the bolt, that holds the pin that provides access to the C clips that retain the axle.

They break so often that O'Reillys has the pinion shaft lock bolt in the aisle on a card. I believe the Chevy Salisbury axles and Ford 8.8 use the same bolt. If you remove it, replace it! If your bolt snaps off, may the Lord help you. You might want this kit on hand before you start. www.amazon.com/Differential-Locknut-Bolt-Extraction-ST-1440/dp/B007ZS4I3U/ My bolt broke on my Mustang, and I didn't have the kit. I stopped, bolted the main part of the bolt back in, and drove it another two years until the bearings got real bad. Then it was a complete pain in the butt to replace.

 

[Buick]

With that mileage, and given everything else you've replaced, I'd be looking at the rear axle bearings too. The ones in the axle tubes, close to the wheel, use the axle as the inner race of the bearing. So when it goes bad, it'll ruin the axle too. Been there, done that with several of my old square body trucks.
You'll need to get inside the differential and remove the bolt, that holds the pin that provides access to the C clips that retain the axle. Check the diff gears and parts to be sure there's no slop and glitter that may indicate excessive wear. When we had bearings go bad on our trucks, Dad taped a rag on a long stick to clean out the axle tubes, after we had the axle and bad bearing

Well, I may just have to tear into the bearings this weekend then. Maybe I can confirm the noise with the rear end on jack stands? I've got to say, the goose chase of wasted time is worse part when you realize the labor was for nothing. I guess I can chalk it up to "preventive" maintenance. LOO

 

[HotWheelsBurban]

Well, I may just have to tear into the bearings this weekend then. Maybe I can confirm the noise with the rear end on jack stands? I've got to say, the goose chase of wasted time is worse part when you realize the labor was for nothing. I guess I can chalk it up to "preventive"maintanence"...

Does the truck stay in 4wd full time? If it does, getting the back up on jack stands while it's running wouldn't be a good idea. If you had access to a lift, that would be much safer! Don't want you getting run over by your own truck!

 

[Eveready]

My suspicion tends toward the wheels. could one be out of true a bit? Since it only happens at a certain speed it sounds like some kind of harmonic. Before I dug into it I would try to borrow a full set of tires/wheels and switch them out and see if anything changes. I know you said no difference between old tires and new but the wheels have always been the same if I read it right.

 

[Schurkey]

My Trailblazer had a terrible highway vibration, worst at ~73 mph. Seemingly gone below 68 mph, gone above 80.

Rear U-joint was chewed-up; coupled to a rear driveshaft that wasn't perfectly true. The driveshaft shop claimed they got "most" of the bend out of the shaft; and they installed new front and rear U-joints on that rear driveshaft. Perfectly smooth afterwards--in fact, once the vibration was MISSING, I realized that I'd had minor vibration from 25 mph on up.

Lasted about two years and then came back--same vibration, same speeds.

Looked at the rear U-joint. Perfect.

Went to the Treasure Yard, got a whole different rear driveshaft. Put a rear U-joint in that one (cause it was totaled) and installed that shaft on my Trailblazer.

AGAIN, found that I'd had minor vibration starting at 25 mph that was now GONE. That's about two years ago--so far, so good.