Unidentified Whine - Rear Differential?

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cardkid2331

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Ram Year
1997
Engine
5.2 318
Just bought a 97' ram 1500 club cab 5.2L - no service records besides oil changes. Has 133K on it and is in pretty good shape (my father in law is a mechanic for CAT and helped me pick it out.)

After putting about 250 miles on it, I started hearing a whine on a 70 mile drive to my parents'. I took it to my parents' mechanic to make sure it was okay to drive it back home, and he only had time to drive it. He didn't check anything. He said it was the rear differential and said it was okay to drive.

So my father in law and I checked the fluid. He was horrified the mechanic didn't even check the fluid before letting me drive it off the lot. Luckily, the fluid was the right color/level and had no metal filings in it - only very small air bubbles.

At this point, we're a bit confused. What exactly could this be? If it is the rear differential, what part of it? Here are some detailed symptoms:

-Whine kicks in EXACTLY at 35 mph. No less. It increases in intensity until about 55mph, and then it levels off and keeps the same volume.

-Mostly whines when you have your foot on the pedal. You can just barely press the pedal and it will start. Take it off, and it usually stops. Occasionally, it will whine when you let off the gas as it decelerates, but not every time and usually only around speeds of 65+

-Does not seem to be related to power/force. If I floor it going up a hill, it still will not whine until 35 mph...the force I would apply in that situation is much greater than keeping it level at 35 with just a bit of gas.

-Whine sounds like a supercharger or the sound of an 18 wheeler's tires going down the highway

-It is best heard with windows up, radio off, and ac off. If you try to listen out the window, you can't hear it. However, the whine is loud enough to be heard over the radio and AC.

We're not totally convinced it's the rear differential - although the symptoms point to it. What else could cause this noise? The related to speed and not power is stumping us. If it is the rear differential, what part?

Thanks!
 

HolyRamBatman

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5.9
Welcome to RF.

Bump this back up for you.

Since you say there are no metal flakes in the fluid, did you take the cover off to drain it or pump it out?

To be sure what it is you may have to jack up the back end and support it VERY WELL. By this I mean at the very least you should have 2 jack stands on the axle and 1 jack stand on each frame rail. Point your truck in a direction so that if it falls off the stands it won't hit anything. Start it up and slowly get the speed up and see what you find. SAFETY is important here, if you don't have the ability to keep it safe TAKE IT TO A SERVICE SHOP.

Any other ideas guys?
 
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cardkid2331

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1997
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5.2 318
Welcome to RF.

Bump this back up for you.

Since you say there are no metal flakes in the fluid, did you take the cover off to drain it or pump it out?

To be sure what it is you may have to jack up the back end and support it VERY WELL. By this I mean at the very least you should have 2 jack stands on the axle and 1 jack stand on each frame rail. Point your truck in a direction so that if it falls off the stands it won't hit anything. Start it up and slowly get the speed up and see what you find. SAFETY is important here, if you don't have the ability to keep it safe TAKE IT TO A SERVICE SHOP.

Any other ideas guys?

Yeah - we might do that. However, I have an update. We found a busted U-Joint on the left front - makes a clanking sound every time the tire goes around when you're under 20 mph. Hoping once we replace it, the whine will go away but I feel like they are not related.

I put bigger tires on it today and the whine moved from 35MPH and up to 45MPH and up - again backing up the tire RPM correlation and not force.
 

BAILEY1

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Dat Cummins!
Check the rear pinion bearing while you are at it. Make sure there in absolutely no play in it. The pinion bearing will whine before it goes out also.
 

dogcar3

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I would have to say it is the pinion bearing as well.
 

Casper

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Springfield, VA
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Just bought a 97' ram 1500 club cab 5.2L - no service records besides oil changes. Has 133K on it and is in pretty good shape (my father in law is a mechanic for CAT and helped me pick it out.)

After putting about 250 miles on it, I started hearing a whine on a 70 mile drive to my parents'. I took it to my parents' mechanic to make sure it was okay to drive it back home, and he only had time to drive it. He didn't check anything. He said it was the rear differential and said it was okay to drive.

So my father in law and I checked the fluid. He was horrified the mechanic didn't even check the fluid before letting me drive it off the lot. Luckily, the fluid was the right color/level and had no metal filings in it - only very small air bubbles.

At this point, we're a bit confused. What exactly could this be? If it is the rear differential, what part of it? Here are some detailed symptoms:

-Whine kicks in EXACTLY at 35 mph. No less. It increases in intensity until about 55mph, and then it levels off and keeps the same volume.

-Mostly whines when you have your foot on the pedal. You can just barely press the pedal and it will start. Take it off, and it usually stops. Occasionally, it will whine when you let off the gas as it decelerates, but not every time and usually only around speeds of 65+

-Does not seem to be related to power/force. If I floor it going up a hill, it still will not whine until 35 mph...the force I would apply in that situation is much greater than keeping it level at 35 with just a bit of gas.

-Whine sounds like a supercharger or the sound of an 18 wheeler's tires going down the highway

-It is best heard with windows up, radio off, and ac off. If you try to listen out the window, you can't hear it. However, the whine is loud enough to be heard over the radio and AC.

We're not totally convinced it's the rear differential - although the symptoms point to it. What else could cause this noise? The related to speed and not power is stumping us. If it is the rear differential, what part?

Thanks!
Probably one of those little hybrid clown cars trapped up agiainst the differential. :gr_grin:
 
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