99 4X4 drivetrain noise need help Please

I have a 1999 GMC suburban 4X4 with 150,000 miles that I bought new. This is my wife’s car and it has been used to run the kids around mostly with very easy driving and no 4 wheeling. The transmission fluid and filter has been changed every 40,000 miles. The front and rear end oil has only been changed at 20,000 miles when new. Here is a run down of my problem now.

1) A few weeks ago we started to hear a noise like a nail in the tire. It started at 20 mph and as the speed increased the ticking sound increased almost like every turn of the tire. I could not tell if it was from the front, back, left or right side. I thought it might be the starting of a wheel bearing going bad.
2) Three days ago I started to hear a much louder and difference sound coming from the suburban almost like a Jake brake sound. This seems to be from the center of the suburban and I cannot tell if its fount, back or in the middle. It only happens when going level or down hill, foot off the gas and slowing down between 48 and 43 mph. The sound is the same in D or N, 2 wheel or auto 4 or manual 4-wheel drive. The ticking sound is also still there and it has not change but with the Jake brake sound you cannot hear the ticking.

I have taking it to a transmission shop they said upon a test drive that they felt it was from the drive line u-joints or transfer case or fount or rear end and they felt the transmission was ok and operated normally. They would like to remove the rear and fount end cover to inspected the gears and bearing. I then took it to another shop that has done some work for me before and they tested drove it and said the it might be the rear end loading up going down hill and they want to start their. I have checked the u-joints and they seem to be fine, no rust coming for the joints and seem real tight. I have seen bad ones before when I worked in the gas station. 35 years ago. Any help or ideas would be great. Thanks Dave

Thanks for the ideas on all sites. It turns out to be the rear end. I took it to Pro-Gear in San Diego and the replaced all the bearing and one axle that had been scared with a bad wheel bearing. With new seals and the ring and pinion set up it sound good now. The bad news is that when they had it on the rack and testing it the found a bad rod bearing that’s making noise. O well something new to have fixed. Dave

I had the same thing happen to me just yesterday... I had the same noise and everything but just paid it no attention. Anyway, I was on my way to school, running late as ussual and I press the gas but I keep slowing down and it acts like it was in neutral. It ends up stoping and the way the off ramp is its a big up hill circle and I stop on it about 3/4 the way up. I din't really know what the problem was at first and but it in park and started to roll backwards with oncoming traffic! I immediatly slammed on the emergency brake (first time I have had to use it for an actual emergency) and one of my friends saw me and picked me up. End up gettin it towed to a local transmission shop and the rear end nearly falls off when they were taking it off the wreaker. My rear diff and everything is blown just like what happen with you. They looked at the rear diff and said it had a buncha mud up in it. What all did you end up having to do to get it totally fixed? The guys there said it would prob be like $1500 to $2000? Does that sound right? How much was yours to fix? What size gears and everything are in there? Would you have any advice to offer? So as of right now I have no truck and have to find rides to school untill i can get it fixed Thanks

Mine was only in the hard to hear noise stage. I took it to Pro-Gear in San Diego. They only do gear type work. They replaced all bearing, seals and I had one axle that needs to be replaced. The cost was about $850. They saved all my gears and housing. I hope this helps. Dave