I have a 98 ram 1500 2wd with the 5.2l. I bought it because the po thought that the transmission was bad. After changing the fluid a couple of times, the truck has been great the past year. However, ever since I have owned it, it has had a roar somewhere in the drivetrain. It is completely dependent on the speed and has nothing to do with acceleration or deceleration. It sounds like wheel bearings going bad but I'm sure that isn't it. I just replaced the rear wheel bearings thinking that it was the problem but didn't help it. Other things I have noticed is with the driveshaft disconnected from the axle, it doesn't make the sound so I'm pretty sure its not in the transmission. My question is what would make this sound? The diff fluid looked good and the ring and pinion gear looked good too.

 

fan clutch shot and overworking te waterpump? i had a roar when i hit the gas, and it turned out to be the fan clutch

there is a spring in the middle that when it heats up, activating the fan clutch...there are grooves for the end to seat in, checkif its in position

 

does it sound kind of like when you put a stick shift in reverse....kind of a gear whining noise....thats whats driving me nuts but its very noticeable on deceleration for me and I believe its either in my transfer case or rear diff.....waiting to I have more time and $$ to troubleshoot further myself.

 

alright - you said it dependent on speed and not acceleration nor deceleration. does that mean that it gets louder as you go faster and less loud as you slow down ?

does it also mean that it only roars when in gear and moving, as opposed to sitting still and reving the motor up ?

put it up on 4 jack stands and put it in gear and see if you can reproduce it. if you can - then its in the parts that are turning - trans, drive shaft, u-joints, rear diff, rear wheel bearings. if you can't reproduce it, then your not turning the bad part - so its front axles, front u-joints, front bearings, or TIRES.

prove to yourself that its not the tires. a couple of years ago i put $600 worth of front end parts in my daughters car chasing some odd noises, most of which was just extremely hard and noisy tires.

your driveshaft out test is significant. if thats a true and repeatable test, and you've changed rear axle bearings, then what's left is pinion bearing, carrier bearings, and ring/pinion, and spider gears. i'd guess the most likely of those is the pinion. you might be able to spin the yoke by hand to reproduce some noise or dry sound.... these will need someone that knows what they're doing to setup the rear end.

 

It definitely gets louder as you go faster. Also, the first thing I did when I put it on jack stands was run it in gear and I could still hear it so I'm sure it's not the tires. If it was the pinion bearings, wouldn't it change when under load or not? When I rotated the pinion by hand it felt fine and I couldn't feel any slop. Also, the truck only has 94k miles on it.

 

do all your u-joints still have all th clips in them?

 

My rearend started that about 200,000 miles.Ran it like that after a gear oil change(with Lucas) for 2 years, until I found one for $200.

 

+1 on that, Lucus is excellent to be running in these. i run all but one quart of Mobil 1 full synthetic 80W90, and a quart of the lucus. i got 193K my 4.10 gears about 50K and its awesome, smooth as a babys bottom

 

I've got same truck same noise. i only hhere it when i let off the gas though. when i had my tranny rebuilt(unrelated incident) the mechanic said he heard it during test drive and believed it to be rear diff

 

Well if it is in the rear end, do you think it will lock up or something anytime soon? It's been doing it for at least 10k miles and hasn't seemed to change all that much.