barnesam

I'm stuck, and could really use some help pointing me in the right direction. Thanks in advance for the help. I've got a 97 suburban k1500 that recently developed a resonance-type sound that starts at around 60 mph, and gets worst at 70 mph. there is a very slight, and very high rpm vibration associated with it (feels too fast for tires), but the vibration is barely noticeable, it's mostly the loud sound that's nearly unbearable. It sounds like somebody's diving next to me with booming sub woofers all the time. It's not associated with exhaust or trans, as it is constant (does not follow engine RPMs, and stays identical when I put tranny into neutral at 70mph).

Here's the background: Truck runs great, with no issues, and has 138k; has towed a lot of trailers in those miles. recently it developed near back-to back problems as follows: the resonance noise started, a very noticeable wheel wobble suddenly got rapidly worse, and the passenger's side rear axle end started leaking. The wheel wobble turned out to be a separated tire, so I bought two new ones to have 2 matching pares. Wobble gone. I pulled that axle and found a near catastrophic failure of the wheel bearing, which had put loads of metal shavings in the gear oil in the rear end. I replaced the wheel bearings and crush sleeve, cleaned out the diff, and filled with synthetic gear oil. Now everything is fixed but the pesky resonance. I tried replacing the ujoints, which were actually in perfect shape when I pulled them, but I replaced for the doubt anyway. No change. I rotated tires, the noise doesn't move, and is worst in the back seats (thus my suspicion of rear diff).

Is this a symptom of a shot rear-end? could all that metal from the failed wheel bearing have fouled the gears and put something out of round? Is it possible I put something back together in the diff wrong when re-installing the axle? The diff also has a very mild whine that can be heard around 40 mph, but you have to listen very hard to hear it, and it disappears at higher speeds.

I'm not sure what else to try, and I'm reluctant in that case to take it in to a mechanic who may start guessing and throwing his time and my money in the wrong direction.

Any tips/thoughts? Please help, thanks.

73shark

I'm thinking rear end due to mileage, tow history, and recent diet of metal. Any change in the sound when changing from load to coast?

barnesam

no change at all under any kind of load. When I put it in neutral at 70 mph on a flat piece of highway (that's all we have in Florida) the sound is the same until it coasts below 60, at which point it's gone. When I step hard on the gas, no real change. towing a trailer, no change. The only change I've been able to create is that when I step fairly hard on the brakes while at a highway speed I can feel that slight vibration worsen a bit, but only while under the braking load. Other than that, it's totally constant to the vehicle speed.

in2pro

Rear drums dragging on the shoes?

barnesam

When I jack the rear end up and put it in neutral the wheels spin nice and free. I could check again, because I haven't really looked at that since doing the wheel bearing (about 2k miles ago). However, the noise seems too consistent and constant for a braking/rubbing problem. it's so loud my kids don't want to go anywhere if we're taking the suburban anymore. If that were the brakes causing that much noise I would think we'd smell them too. right?

Thanks for the suggestion, though. I will check on it just to be sure.

in2pro

something else to explore is the the u-joints but it sounds (no pun intended) lke it might most likely be the rear end

barnesam

U-joints were all changed, to no avail. I finally decided to take it to a mechanic to diagnose. Like you all, I keep suspecting the rear-end, but have never heard of a noise like this coming from a rear end gone-bad before, which is why I thought I'd post the question and see if anybody else had come across such a thing.

I will post what the mechanic thinks, and hopefully what the solution is when I find it. Maybe this thread could be useful later on to somebody who runs into a similar issue.

barnesam

I took it to a trusted mechanic. He road-tested, then also ran it up to 70mph up on the lift. He was nearly certain it is NOT a differential problem, and was "strongly suspecting" my transmission. His opinion was that a planetary in there is warn and therefore not spinning completely true. He said that although it presents itself as a loud resonance inside the cabin, it's actually a high-speed vibration that he thinks is coming from the transmission. He referred me to his transmission guy for further testing.

My fear of this diagnosis is what I've read on other threads. Others have had vibration problem that mechanics told them was in their transmission. $1500, and a new transmission later the problem is not fixed. When I asked my mechanic why, if its in the tranny, does the noise not change or vary in the least when you change gears, or put it into neutral and coast. His answer was that the planetary is still spinning at the speed of the wheels, so will remain unchanged even though there's no load. He's a good mechanic, but not a tranny guy. Does what he told me jive?

Anyone have and helpful thoughts or advice?

in2pro

So I wonder, could you disconnect the drive shaft, put it in gear and get the same sound?

shamrock246

something in the transfer case? any metal in the oil of either the trans or t-case?



Sean

97 4x4 burb