CHECK YOUR DIFFS...

[gemarsh]

Read about 2 others with 3500's that the diff was low on gear lube. One was wiped out at 3000 miles, other was 1.5 qts low.

I checked the '23 2500 this afternoon. ~1.5 qts low on the rear and ~.5 qt low on front diff. Not exact, but it took 2 qts between them.

Front diff had a blue index marker mark on fill plug. Plug was finger loose. Marks were lined up. Either plug was out a full turn or was just marked loose. Has not been in water yet, so not worried about drain and refill. These are not the old school NPT plugs, but use a flat o-ring to seal. So don't bare down on it.

Diffs take full synthetic 75w90 per dealer.

If you can't do it yourself, hire it done!

My '22 3500 drw is still setting on dealers service lot, waiting on engine harness, goingon 5 months. Will have them fill diffs before I pick it up and check myself when she's home.

Will check the '21 1500 this evening when wife gets home.

Edited March 24, 2023 by gemarsh
Spelling

[77xbody]

Thanks for the info I'll have to check mine ,by the way is filled about half inch down from the plug ?

[gemarsh]

First joint of my pinky. So yeah.

[Pryme]

That is ridiculous. I will have to check mine. Should it seep out when you pull the plug or are you saying it should be down like an inch from coming out?

[Pryme]

Okay it’s a blizzard outside today so I was bored and made this quick video when I checked my diffs. 
 

The rear diff was about 1” from the top. 
 

The front was maybe 3/8ths from the top. 
 

Both bolts were nice and tight. The front has 2.4 written right on the diff with blue marker and the blue marker on the front bolt. 
 

I may do the rear diff fluid this spring regardless just because fluid is cheap and any gear mesh dust will be removed. 
 

anyone know the actual specs for the diffs? @newdude??

 

Thanks

 

 

[gemarsh]

5 hours ago, Pryme said:

Okay it’s a blizzard outside today so I was bored and made this quick video when I checked my diffs. 
 

The rear diff was about 1” from the top. 
 

The front was maybe 3/8ths from the top. 
 

Both bolts were nice and tight. The front has 2.4 written right on the diff with blue marker and the blue marker on the front bolt. 
 

I may do the rear diff fluid this spring regardless just because fluid is cheap and any gear mesh dust will be removed. 
 

anyone know the actual specs for the diffs? @newdude??

 

Thanks

 

 

 

I have learned it is 0.0 to .4" below fill hole.

[Pryme]

25 minutes ago, gemarsh said:

 

I have learned it is 0.0 to .4" below fill hole.

From where. I’ve read .6-.8 below in the rear. I haven’t researched the front yet. Mine was right about that .8 down. So it’s kinda splitting hairs. 
 

im most likely putting amsoil severe gear 75w-90 in. It appears 75w90 synthetic is what our trucks take. 3.15 qts in the rear. 

 

Edited March 26, 2023 by Pryme

[gemarsh]

GM Service Information by Ottowood copy and paste.

 

Rear Axle Lubricant Level Inspection

Note: All axle assemblies are filled by volume of fluid during production. They are not filled to reach a certain level. When checking the fluid level on any axle, variations in the readings can be caused by factory fill differences between the minimum and the maximum fluid volume. Also, if a vehicle has just been driven before checking the fluid level, it may appear lower than normal because the fluid has traveled out along the axle tubes and has not drained back to the sump area. Therefore, a reading taken five minutes after the vehicle has been driven will appear to have a lower fluid level than a vehicle that has been stationary for an hour or two. Remember that the rear axle assembly must be supported to get a true reading.

1. Raise and support the vehicle. Lifting and Jacking the Vehicle
2. Make sure the vehicle is level.
    
3. Inspect the axle lubricant level, it should be 0 – 10 mm (0 – 0.4 in) below the fill plug opening.
4. If the axle lubricant level is low, add lubricant until the level is 0 – 10 mm (0 – 0.4 in) below the fill plug opening. Use the appropriate axle lubricant. 

 

[Pryme]

43 minutes ago, gemarsh said:

GM Service Information by Ottowood copy and paste.

 

Rear Axle Lubricant Level Inspection

Note: All axle assemblies are filled by volume of fluid during production. They are not filled to reach a certain level. When checking the fluid level on any axle, variations in the readings can be caused by factory fill differences between the minimum and the maximum fluid volume. Also, if a vehicle has just been driven before checking the fluid level, it may appear lower than normal because the fluid has traveled out along the axle tubes and has not drained back to the sump area. Therefore, a reading taken five minutes after the vehicle has been driven will appear to have a lower fluid level than a vehicle that has been stationary for an hour or two. Remember that the rear axle assembly must be supported to get a true reading.

1. Raise and support the vehicle. Lifting and Jacking the Vehicle
2. Make sure the vehicle is level.
    
3. Inspect the axle lubricant level, it should be 0 – 10 mm (0 – 0.4 in) below the fill plug opening.
4. If the axle lubricant level is low, add lubricant until the level is 0 – 10 mm (0 – 0.4 in) below the fill plug opening. Use the appropriate axle lubricant. 

 

I think that might be for the outgoing model with the 6.0. The 2020+ I believe are .6-.8

 

Hopefully Newdude can chime in. I know his specs sticky is also what I’ve read for capacity. 1.9qt front and 3.15-17 rear. 

 

it’s completely absurd that any of these fluids should not be exact from the factory. 

Edited March 26, 2023 by Pryme

[Another JR]

Here is an interesting Banks video where they replace a stock differential cover with a same-shape clear cover allowing you to see how the oil flows, and then they compare it to a flat cover. They discuss why overfilling is detrimental. 
 

 

Note that their 90 minute test representing towing at 200 hp up a constant 6% grade where the fluid overheats with a stock cover equates to a nonstop climb of about 28,000 feet, and their 60 minute test equate to 19,000 feet. Such a climb in real life is not even possible, let alone realistic. The car companies have a particular climb they do to evaluate rear axle cooling, so it’s not like they’ve neglected seriously considering differential heat in their design.  
 

So they built a cover that rejects heat better and you can buy it for $500, but I don’t think it’s needed for the vast majority of our trucks.  On the other hand, Banks makes a very good flow-based case for why you should not buy their competitors’ flat covers just because they have fins.

[Pryme]

46 minutes ago, Another JR said:

Here is an interesting Banks video where they replace a stock differential cover with a same-shape clear cover allowing you to see how the oil flows, and then they compare it to a flat cover. They discuss why overfilling is detrimental. 
 

 

Note that their 90 minute test representing towing at 200 hp up a constant 6% grade where the fluid overheats with a stock cover equates to a nonstop climb of about 28,000 feet, and their 60 minute test equate to 19,000 feet. Such a climb in real life is not even possible, let alone realistic. The car companies have a particular climb they do to evaluate rear axle cooling, so it’s not like they’ve neglected seriously considering differential heat in their design.  
 

So they built a cover that rejects heat better and you can buy it for $500, but I don’t think it’s needed for the vast majority of our trucks.  On the other hand, Banks makes a very good flow-based case for why you should not buy their competitors’ flat covers just because they have fins.

Thanks for the video I’ll check it out. Yeah I’ve read diff guts say slightly underfilled would be better than slightly over. I plan on using the gm recommendation of 3.15

[gemarsh]

3 hours ago, Pryme said:

Thanks for the video I’ll check it out. Yeah I’ve read diff guts say slightly underfilled would be better than slightly over. I plan on using the gm recommendation of 3.15

Atleast you will know you have gear lube.

[Black02Silverado]

I always change mine over to AMSOIL right away.  These Easy Packs make it nice and clean to do. 

[newdude]

On 3/25/2023 at 3:22 PM, Pryme said:

Okay it’s a blizzard outside today so I was bored and made this quick video when I checked my diffs. 
 

The rear diff was about 1” from the top. 
 

The front was maybe 3/8ths from the top. 
 

Both bolts were nice and tight. The front has 2.4 written right on the diff with blue marker and the blue marker on the front bolt. 
 

I may do the rear diff fluid this spring regardless just because fluid is cheap and any gear mesh dust will be removed. 
 

anyone know the actual specs for the diffs? @newdude??

 

Thanks

 

 

 

 

 

3.17 quarts.  Fluid should be 0 – 10 mm (0 – 0.4 in) from the bottom of the fill hole.  All level checking and filling should be done with the vehicle level so axle supported by stands or vehicle on a 4 post drive on lift or parked on flat level ground when checked and filled.  Also, if driven prior, wait 5 minutes for drainback from the axle tubes.  

Edited March 27, 2023 by newdude

[Grumpy Bear]