CHECK YOUR DIFFS...

rjgvt · December 13, 2023

Went to my dealer today to get a trade in value for my current truck as my AT4 HD on order is expected to arrive by the end of December. I brought up a concern about the diffs being low on fluid. Sales guy made a note of it and claimed he hasn’t heard of it being a problem and would check with the service department. I requested they check it as part of the $75k PDI.

Also brought up the issue with the upper glove box. Sales guy knew about that one and will make sure it is functional when truck arrives.

BuckWallace · December 13, 2023

On 3/27/2023 at 10:04 AM, newdude said:

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.

Just to clarify, is the 0-10mm for both the 11.5" and 12" rear ends, or just one or the other?

the8rotor · December 13, 2023

2 hours ago, BuckWallace said:

I actually just went ahead and scheduled an appointment for them to do it. I'm at about 4,800 miles and have 2 free oil changes with the dealer (I changed it myself at 1k miles), so I just figured I'd take it in for an oil change and have them look at it tomorrow. Either way I'd rather have them document it and do it in case something happens later on (which I doubt).

Good call! My service advisor I've used for a few years was well aware of low rear and front diffs. Said it has been a problem for years.

Pryme · December 13, 2023

1 hour ago, the8rotor said:

Good call! My service advisor I've used for a few years was well aware of low rear and front diffs. Said it has been a problem for years.

I find it completely unacceptable and unbelievable that any company, especially a juggernaut like GM, can’t put their foot down and get AAM to fill them correctly. For years? lol absurd.

the8rotor · December 13, 2023

44 minutes ago, Pryme said:

I find it completely unacceptable and unbelievable that any company, especially a juggernaut like GM, can’t put their foot down and get AAM to fill them correctly. For years? lol absurd.

I know. He sounded completely defeated about the topic and said he'd go grab me some 75w90 from the parts department.

All the dealerships by me are 80%+ full of inventory with nothing selling. I hope they spend some time tackling issues like low diffs - but I will keep dreaming

newdude · December 13, 2023

15 hours ago, BuckWallace said:

Just to clarify, is the 0-10mm for both the 11.5" and 12" rear ends, or just one or the other?

Same spec for both.

diyer2 · December 13, 2023

GM isn't losing money, so it will be ignored.

Kerry Pulaski · December 13, 2023

On 12/11/2023 at 2:58 PM, Pryme said:

Yeah it’s a total joke that these are low. You’re lucky that Qtip didn’t break off in there as those have a tendency to snap once they are already bent or kinked. Probably wouldn’t hurt anything in there but my ocd would demand I get it out ha

My Front Diff. is 1" Low as well. Transfer case is OK. GMC mfg. in Flint.

The Q tips I got for the shop are a Nylon stick not wood. Think they were designed for ear wax removal, thus the odd smaller end of the tip.

BuckWallace · December 14, 2023

Took my truck to the dealer today for my oil free change and asked them to top off the diff fluid as well. They confirmed it was low, filled it up, and got it all documented. I don't suspect this will cause any long-term issues, but at least I have the paperwork.

rjgvt · December 14, 2023

22 hours ago, the8rotor said:

I know. He sounded completely defeated about the topic and said he'd go grab me some 75w90 from the parts department.

All the dealerships by me are 80%+ full of inventory with nothing selling. I hope they spend some time tackling issues like low diffs - but I will keep dreaming

My dealer has 3 GMC Pro model 2500HDs and one other model. Everything else is “in transit” including the AT4 HD I have on order. Sales guy told me most that are in transit have been ordered by someone and not for sale on the lot. There is a long row of 1500’s.

Kerry Pulaski · December 18, 2023

My '24 2500HD resolve.......Rear diff took 1.5 Qt. to get a drip out the fill hole. (measured 1.25" low with Q-tip nylon stick bent 90 deg.).

Front took .75 Qt. (measured 1.00" low with McGuiver Q-tip).

Dealer did give me 2 Qt. at N/C of 75w-90. I had no more time to waste on this. Have jack, jack stands and creeper..done.

I asked the service manager to check this before new delivery. Gave him a printed copy of the blogs as well, with the pre-delivery page checklist, before I took delivery.

Said they did, but said the tech used a spec for a 1500 ????

Yea , good help is hard to find but.....an 11.5" or 12" axle..really ?

I service , install and sell heavy industrial machinery for 43 years. Have a hard time with mistakes on my planned purchases, to babysit.

Thanks to All, for these posts, to alert us to pending disasters. Safety in numbers.

Happy Holidays !

the8rotor · December 18, 2023

7 minutes ago, Kerry Pulaski said:

My '24 2500HD resolve.......Rear diff took 1.5 Qt. to get a drip out the fill hole. (measured 1.25" low with Q-tip nylon stick bent 90 deg.).

Front took .75 Qt. (measured 1.00" low with McGuiver Q-tip).

Dealer did give me 2 Qt. at N/C of 75w-90. I had no more time to waste on this. Have jack, jack stands and creeper..done.

I asked the service manager to check this before new delivery. Gave him a printed copy of the blogs as well, with the pre-delivery page checklist, before I took delivery.

Said they did, but said the tech used a spec for a 1500 ????

Yea , good help is hard to find but.....an 11.5" or 12" axle..really ?

I service , install and sell heavy industrial machinery for 43 years. Have a hard time with mistakes on my planned purchases, to babysit.

Thanks to All, for these posts, to alert us to pending disasters. Safety in numbers.

Happy Holidays !

Did you fill the rear till fluid dripped out? Oem spec is "Fluid should be 0 – 10 mm (0 – 0.4 in) from the bottom of the fill hole."

How did you measure the front? Just concerned you overfilled.

BuckWallace · December 18, 2023

2 minutes ago, the8rotor said:

Did you fill the rear till fluid dripped out? Oem spec is "Fluid should be 0 – 10 mm (0 – 0.4 in) from the bottom of the fill hole."

How did you measure the front? Just concerned you overfilled.

Well, I guess if he filled it until it dripped out of the hole (giggity) it would be at 0mm. It can't really be above the fill hole unless he shoots it in with a bunch of pressure (really, I'm not trying to do this) and quickly plugs it.

the8rotor · December 18, 2023

23 minutes ago, BuckWallace said:

Well, I guess if he filled it until it dripped out of the hole (giggity) it would be at 0mm. It can't really be above the fill hole unless he shoots it in with a bunch of pressure (really, I'm not trying to do this) and quickly plugs it.

Very true! More so inquiring on the front diff and making sure it was okay. Judging by his lengthy experience of wrenching, I'm sure he got it right!

Kerry Pulaski · December 18, 2023

She was level on jack stands. Let it drip out to a pan till it stopped. Merely a table spoon dripped out, then capped tight.

As the spec. does say to -0- at fill hole, that is max fill level value.

I even had the Qt's of 75w-90 in hot sink water for 15 min. to make it easy to flow. If cold and stiff, then could force an overfill before capping the fill plug.

I work on industrial machines for over 43 years. These use precision planetary gearboxes. Oil viscosity and levels are critical.

I expected the same care and precision with my GMC dealer........I hate teaching a supplier of high tech product.