Rear differential level on 2024 3500 L8T

[64BAwagon]

I searched for the discussion from a while back where we discussed the level of gear oil in our new trucks. Personally I added a full qt to bring my diff to the level prescribed by GM in their service instructions on this model (min of .4" or 10mm from bottom of fill hole) 

I wanted to share my experience further since I just completed servicing the rear diff on my truck. It now has about 5200 miles on it with around 3000 of those miles pulling a 5th wheel and cargo weighing around 13k. 

I removed the cover and wiped out the bottom of the housing. I then cleaned the cover and wiped the sludge off of the magnet (seemed typical for a new truck) 

It then took exactly 4 qts of fluid to fill the diff to the correct level. I even went so far as to drain the remaining fluid from the jugs and then put the last 16 oz or so in with a fluid hand pump I have. Very little was wasted. 

I just wanted to share the quantity info since it had been discussed before. I tried to find the old thread but couldnt along with the service document I know I save but I couldnt find either one. 

 

Scott

[64BAwagon]

I did find the last image from the document and it shows the approximate volume of the diff and lists it at 3.18 qts. 

This seems to contradict what it actually takes to fill that diff to the level GM indicates and would explain why many of us needed to add almost a qt to bring the new trucks up to the GM specified level. 

I do know that American axle and GM were made aware of this discrepancy. Where it went from there is unknown. I doubt without any documentation from dealer service depts it likely got blown off as an American axle issue since they are filled by AA at the end of their production. 

Edited April 11, 2024 by 64BAwagon

[Capt Bob]

I also put in a quart in the rear pumpkin using my pump.

Put less than a pint in the front diff.

 

 

 

 

[64BAwagon]

Some things never change. I just checked my new 2025 3500 Dmax and found it a qt below the Chevrolet service fill level. This is especially aggravating since GM claims its not an issue due to the fact that they dont get any warranty claims for it yet its not part of the PDI. I specifically asked for mine to be checked but once again the dealer dropped the ball and didnt do it. I am a little salty about it. 

[Chuck FB]

5 minutes ago, 64BAwagon said:

Some things never change. I just checked my new 2025 3500 Dmax and found it a qt below the Chevrolet service fill level. This is especially aggravating since GM claims its not an issue due to the fact that they dont get any warranty claims for it yet its not part of the PDI. I specifically asked for mine to be checked but once again the dealer dropped the ball and didnt do it. I am a little salty about it. 

I don't blame you for being miffed over this, on whatever thread it was on here that was talked about before my truck showed up at the dealership and I had come across it. So when my truck came and they had prepped it ( or so they said they did ) I had talked to the service manager and had never met him until that point and I made mention of fluid levels and he assured me they had checked them at the dealership. Ok ... made a mental note of that and when I finally had my truck home I checked it for myself just to be totally sure it had been done and you guessed it, they had done squat at the dealership. Rear diff down exactly 1 inch ( measured ), front diff down a 1/2", transfer case down about 3/8". I was using a five gallon pail pump of gear oil but the front really didn't take that much volume but the rear took quite a bit to bring it up to the fill plug threads. I was just glad I had checked it myself right off the bat and because of this forums heads up rather than believing anything I had been told. Pretty sad when this is going on and GM isn't getting on top of it at the factory component level or catching it at the dealership ( and in my case claiming they had, that's even worse ! ). No wonder its hard to gain a lot of confidence in companies that build the products as well as the shops that are authorized to catch any discrepancies.

 

By the way have you checked and what were your front diff and transfer case levels at ?

[Pryme]

Yeah not surprising. 
 

im glad for this forum or id never have checked them. I have no regrets just dropping the factory fill around 5k miles and putting in a far superior product in amsoil severe gear. Getting that break in fluid out early can’t hurt imo. 

[Flatus]

2 hours ago, 64BAwagon said:

Some things never change. I just checked my new 2025 3500 Dmax and found it a qt below the Chevrolet service fill level. This is especially aggravating since GM claims its not an issue due to the fact that they dont get any warranty claims for it yet its not part of the PDI. I specifically asked for mine to be checked but once again the dealer dropped the ball and didnt do it. I am a little salty about it. 

I never did check my rear diff fluid level but I just got my truck out of the shop last Friday from having a full rear end rebuild. I have about 29,600 miles on it. Heaviest weight it tows is about 5200-5400 lbs. It was a bit disappointing to say the least. They had my truck for 11 days. It seems to be fixed now though.

[Chuck FB]

14 minutes ago, Flatus said:

I never did check my rear diff fluid level but I just got my truck out of the shop last Friday from having a full rear end rebuild. I have about 29,600 miles on it. Heaviest weight it tows is about 5200-5400 lbs. It was a bit disappointing to say the least. They had my truck for 11 days. It seems to be fixed now though.

The service manager claimed that they had one truck if not two have their hub bearings fail and not sure if that was a last years thing or i the last couple of years and he stated it was from a low oil fill from the factory and they figured that the hub bearings were starved for oil and failing and feeding the diff filings and so the whole thing was either rebuilt or a whole new housing installed, covered on warranty however they properly repaired the truck. So he knew there was a potential issue and that was why he tells me they check the trucks now. Well either he was stretching their check of the trucks off the car hauler or his shop is telling him they are checking it, something wasn't adding up. Of course this issue originates with GM and their supplier of the axle not putting enough oil in it. As to your diff, odds are you will never know what caused the issue, if it was lack of lubrication or some defect with assembly or a bearing or gear that can start the chain reaction of contaminating everything with filings. Ford has been having some issues with some of their new larger updated diffs piling up with relatively few miles on it also, not sure what is the cause of that.

 

As dumb as this may sound I would check your oil level just to make sure it is topped off as its always possible that the hubs don't quite get filled and yet seems full in the pumpkin, depends on the axle and if the tech is patient in waiting for the oil to find its home and settle down to its true level. Won't hurt anyway and in a few thousand miles do an initial change on it and see what is on the magnet in the diff or have that shop do it ( or I assume there is a magnet stuck into the lower part of the pumpkin ). That diff should have gone for hundreds of thousands of miles with reasonable maintenance with no issues at all. 

[64BAwagon]

I generally change out eh rear diff fluid at 5k just so I can clean out any break in material. 

 

As far as the front, I am going to check that one when I grease the front end in a few days. 

 

The issue is solely on American axle and the process they use to fill them. I know for a fact that GM was made aware of the issue but like so many other things the can got kicked down the road because it would have meant someone sticking their neck out and challenging a supplier which no doubt would have led to a urinating contest. 

 

BTW, the GM service instructions for a fill on these diffs is .4"/10 mm below the fill plug line. The generally accepted practice of filling until it runs out is what I have always gone by (we used several of the kegs of gear oil every year at work) Mine was topped off to the 10mm level so I didnt even get the plug line with a full qt but at least it is to spec. 

 

Edit,  the front diff took over 300ml to get it to near the fill plug level. I stuck 90deg bent zip tie in it when I pulled the plug and it was well over an inch below the plug. 

I also got the front end greased and all the raw metal front end parts coated with fluid film. 

Edited April 25, 2025 by 64BAwagon

[the8rotor]

Looking to drain and fill the front and rear diffs on my 2024 gasser. Can someone share torque specs for both front and rear diff covers? I have fluid type and capacities, cannot find torque specs to save my life. 

[Chuck FB]

On 4/25/2025 at 6:21 AM, 64BAwagon said:

I generally change out eh rear diff fluid at 5k just so I can clean out any break in material. 

 

As far as the front, I am going to check that one when I grease the front end in a few days. 

 

The issue is solely on American axle and the process they use to fill them. I know for a fact that GM was made aware of the issue but like so many other things the can got kicked down the road because it would have meant someone sticking their neck out and challenging a supplier which no doubt would have led to a urinating contest. 

 

BTW, the GM service instructions for a fill on these diffs is .4"/10 mm below the fill plug line. The generally accepted practice of filling until it runs out is what I have always gone by (we used several of the kegs of gear oil every year at work) Mine was topped off to the 10mm level so I didnt even get the plug line with a full qt but at least it is to spec. 

 

Edit,  the front diff took over 300ml to get it to near the fill plug level. I stuck 90deg bent zip tie in it when I pulled the plug and it was well over an inch below the plug. 

I also got the front end greased and all the raw metal front end parts coated with fluid film. 

Wow, they really outdid themselves on your front diff as well. As I had referenced the distance down that the oil was on each component, the front diff took 4 strokes of my five gallon pail pump to fill it where as the rear took at least 16 pumps. The transfer case because of using a sucker gun to draw trans oil out of a new bottle and filling the transfer case and then shooting the excess back into the bottle, that took 200 ml

 

That's a good idea to shoot the raw metal with fluid film right off the bat, I had thought about it but that is as far as I got as I had also thought it might look better painted ... I will certainly try this summer if I have the opportunity to try my best with a full on fluid film application as long as the equipment I bought will work properly and I can see that being a very long drawn out procedure to get into the critical area's rather than some lipstick type application.

[64BAwagon]

I will probably do the doors next and then the rockers, break things up a little. I think I am going to get a new applicator also since my original one is a cheapy. The rear bed arches also take some time. I pull the plugs in the interior bed and lay it on thick in there. I got 2 gallons of Blaster surface shield on clearance at Advance back during the winter. I am anxious to tap in to them and try our the Blaster flavor. 

 

[64BAwagon]

8 hours ago, the8rotor said:

Looking to drain and fill the front and rear diffs on my 2024 gasser. Can someone share torque specs for both front and rear diff covers? I have fluid type and capacities, cannot find torque specs to save my life. 

Its not a lot if I recall and I know for a fact that the cover screws can be broken off if your attaching one that has a bracket, ask me how I know ? 

My guess from memory is something like 25 inch pounds

 

[Chuck FB]

3 minutes ago, 64BAwagon said:

I will probably do the doors next and then the rockers, break things up a little. I think I am going to get a new applicator also since my original one is a cheapy. The rear bed arches also take some time. I pull the plugs in the interior bed and lay it on thick in there. I got 2 gallons of Blaster surface shield on clearance at Advance back during the winter. I am anxious to tap in to them and try our the Blaster flavor. 

 

The doors have me stumped because I was hoping there would be multiple drain holes that I could stick a straw through and instead its this tiny little crack, one on each end of each door. I don't know if its required to pull the inner panels back and lift up on that inner material substance ( not sure if that product is glued onto the door ) to gain access into the cavity or were you running a tube in from the back side of the door through a factory rubber plug you removed ?. And yes those rear arches to access where one can from the underside ( probably spraying in around the tail light area if its possible to reach up there to cover whatever can be reached in that whole area ). Also I'd think it would be of benefit to drop down a portion of the rear wheel wheel liners to hit the underside of the steel inner fender, I have not dug into how easy the clips come out and if they all break off and have to have new ones on hand.

 

I tried to see if I could get the blaster product and that was a no go, they only ship up the aerosol cans to some stores but do not ship their bulk product as I had an industrial supplier who's USA subsidiary does handle the product and he found out from Blaster themselves that they do not ship their bulk product to Canada so that was a no go. I don't know if its superior or not to fluid film but the idea that for some aspects it would be a thinner product to spray as well as pour into the sprayer vs glob it in and its been reported that it doesn't have the same after smell. Of course these days with theft it would be ideal to spray ones vehicle in skunk, no one would want to park near you either but driving the vehicle would be an experience and there goes the resale value !.

[64BAwagon]

I use a rattle can of FF for the doors and just use the straw through  the drain holes. Some are obstructed by the rubber seal so you have to look closely for them.  Best done on a hot day when you can let them drip for a while. It migrates well enough so coverage is good. No way I want to pull door panels on a new truck. 

I picked the Blaster up locally for $12 gallon, and had 2 other orders cancelled at other stores. I really wanted to score a couple 5 gal pails but never could pull it off. 

Edited April 27, 2025 by 64BAwagon