Rear end noise

[Delanozach]

I’ve seen this discussed in a few other threads but wanted to get some new opinions…

I’ve got a 2021 2500 with the 6.4 8 speed trans and approximately 70,000 miles. I’ve been experiencing a faint whining noise on my drive to work which is mostly 55 mph the entire way. The noise begins after letting off the gas and coasting around 55 mph. The noise stops as soon as I start to accelerate and I really only notice it in the 50-60mph range. Noise occurs in gears 6,7,8. It’s hard to say if its coming from the rear end or not. At first I thought it sounded like a wheel bearing going out. I cannot feel the whining noise in the steering wheel or pedal, I can only hear it.

Is there any chance that this could be related to the differential fluid? The truck has towed a 23’ bay boat from Tennessee to Gulf Shores, Alabama probably 10 times but other than that there has been no towing and mostly highway commute miles. The truck has not yet had the differential fluid changed and according to the manual it was due to be done at 60,000 miles.

 

[AH64ID]

Change the fluid. It’s a 20K service interval for frequent towing, but the OE fluid isn’t the best.

That will at least get you fresh fluid and you can see if it makes the noise go away.

 

[Great White North Eh]

Might be a U joint. Back in the olden days on my 05 had a similar deal and it turned out to be the rear joint. The weird thing is that the dealer actually diagnosed it! Changed under warranty and never went out again.

 

[Delanozach]

Just checked the diff fluid in the front and rear. The front fluid was about 1/4” below the fill hole which seems normal and the magnetic plug was clean, no metal or sludge. The rear diff was about 1” - 1 1/4” below the fill hole and the magnetic plug had some gray sludge on it and a few fine metal shavings but nothing more than I would have expected. I’m not concerned with what I saw on the plug but I am concerned with the fluid level. I inspected both axles and didn’t see any signs of leakage. Everything looks brand new. I have 10 quarts of Amsoil Extreme Gear 75W90 coming in the mail but I need to drive to work tomorrow so I’m going to top it off with whatever 75W85-90 I can find at the local parts store. I’m hopeful that changing the fluid will quiet that noise.

 

[AH64ID]

Just checked the diff fluid in the front and rear. The front fluid was about 1/4” below the fill hole which seems normal and the magnetic plug was clean, no metal or sludge. The rear diff was about 1” - 1 1/4” below the fill hole and the magnetic plug had some gray sludge on it and a few fine metal shavings but nothing more than I would have expected. I’m not concerned with what I saw on the plug but I am concerned with the fluid level. I inspected both axles and didn’t see any signs of leakage. Everything looks brand new. I have 10 quarts of Amsoil Extreme Gear 75W90 coming in the mail but I need to drive to work tomorrow so I’m going to top it off with whatever 75W85-90 I can find at the local parts store. I’m hopeful that changing the fluid will quiet that noise.

That’s the proper level, this is from the owners manual.

For the 2500 (Non-Power Wagon) axles, the fluid level should be 4/5 in ± 1/4 in (20.3 mm ± 6.4 mm) below the fill hole for the rear axle and it should be 1/4 in ± 1/4 in (6.4 mm ± 6.4 mm) below the fill hole on the front axle.

 

[Delanozach]

That’s the proper level, this is from the owners manual.

For the 2500 (Non-Power Wagon) axles, the fluid level should be 4/5 in ± 1/4 in (20.3 mm ± 6.4 mm) below the fill hole for the rear axle and it should be 1/4 in ± 1/4 in (6.4 mm ± 6.4 mm) below the fill hole on the front axle.

You are correct. Just looked back in my manual and saw that. I do see a lot of guys in these forums say that they fill their 2500s to the bottom of the hole and don’t have any issues. There’s some YouTube videos of mechanics doing that with my exact truck.

 

[AH64ID]

You are correct. Just looked back in my manual and saw that. I do see a lot of guys in these forums say that they fill their 2500s to the bottom of the hole and don’t have any issues. There’s some YouTube videos of mechanics doing that with my exact truck.

The 3500 and PW axle is spec’d for that. I’m guessing it’s a pinion angle difference.

 

[Delanozach]

Changed the fluid this evening. Got about 3 quarts out of it and put 4 back in. The fluid was very dark and stunk like hell. Surprisingly no metal serious metal shavings. Hopefully I caught this before it got bad.

 

[joelp]

We’re you able to re use the gasket? Going to put an AEV cover on mine with the drain hole at the bottom and was wondering about the gasket. Thanks. JP

 

[Jarynlindsay]

Did the noise go away?

 

[dieselscout80]

Were you able to re use the gasket? Going to put an AEV cover on mine with the drain hole at the bottom and was wondering about the gasket. Thanks. JP

I reused mine with the stock cover.