Fluid Change Questions

Chuck FB · June 8

3 hours ago, Core-Lokt said:

I think the Banks cover is higher capacity, given I don’t see oil in the sight glass. They say to observe factory capacity over sight glass. I used approximately 6 1/4 pints bc I assume not being able to fully drain bags, and a tiny bit of spillage when I squeezed. Got Amsoil ATF as-indicated on their website.

I have gas engine and six speed. Transmission service will happen after the transfer case and front differential (I’ll likely get another cover with drain, also). Besides the dipstick mod, idk what’s all underneath the pan.

That is an odd comment Banks would have about the volume given that the sight glass is there for the specific reason to allow for not only bringing the level to that range but to visually be able to check at any time that the diff has a sufficient level. I know its been commented that what GM claims is the volume required for the rear diff ends up falling short of what it actually takes if filling it to the bottom of the factory level plug, and the fact that GM ( actually the axle manufacturer ) is underfilling the diff at their factory below their own specs as mine was as well which has been a whole other issue and is leaving the oil down almost a quart low from full. As I read about the Banks cover instructions right on their webpage, they do say to go by the sight glass ( half way up the sight glass on level ground ) unless the vehicle has had the pinion angle changed due to a lift etc that throws off the factory pinion angle. I'll put it this way, if I installed a Banks cover on my own stock truck I would fill it half way up the window and then recheck after the truck has been driven and sat for hours while sitting on level ground to confirm the level.

Core-Lokt · June 8

I’m going off the instructions.

Chuck FB · June 8

1 hour ago, Core-Lokt said:

I’m going off the instructions.

Yes I read that as well on their website and its all in how its interpreted for one thing and I believe the GM spec itself does not call for enough volume to bring the oil level up to the bottom of the factory covers fill/level port which also is puzzling. Banks are also bouncing between two different truck makes in the instructions since both the Ram and the GM use AAM axles with those instructions.

The problem with not seeing the oil in the window is that one has no idea where the actual level is. Certainly anyone else on here reading this and having worked with the banks covers should chime in as they may have more information to provide. I am just simply concerned because I don't want to see someone underfill the diff as its not just the diff that is critical to lubrication, its the wheel end bearings. The dealership I bought my truck from had two HD pickups a while back have their rear wheel bearings fail because of being too severely underfilled at the factory and no one had checked and topped them off at the dealer but luckily warranty paid for a whole new complete axle housing as it mangled the axle housing spindles when the bearings failed and sent metal throughout the whole diff.

Core-Lokt · June 9

I agree it's ambiguous, and somewhat complicated with a shared application. For S&Gs, I just looked on Amsoil's website for a 2023 Ram 2500 with 6.4 gas. https://www.amsoil.com/lookup/auto-and-light-truck/2023/ram/2500-pickup/6-4l-8-cyl-engine-code-j-esb-j/

There's a lot of listings for Ram rear differentials, and too early in the morning to dig into the variants. But there's a big difference in fluid volume called for between them and GM applications, assuming it's the same axle assembly.

So, if GM differentials tend to be underfilled, what does everyone think about a 7 pint fill, as opposed to the 6.3 pints listed on Amsoil's website? It would somewhat conservatively split the difference between Ram and GM specs.

Chuck FB · June 9

I did a search outside of this forum and came across a thread from this forum from two years ago which was amusing but one I recall now from a trusted member who had himself had to add a quart on his brand new truck to bring it up to near the level plug level. Then after accumulating 5000 or so miles on the truck he pulled the cover to drain it out and wiped out the bottom of the diff housing and put the factory cover back on and in his case it took exactly 4 quarts to bring it up to within that 4/10 of an inch below the fill/level check plug, far more than the GM spec. That is a big difference between that GM spec ( which is why the GM diffs are below the level they themselves say they should be when coming out of the factory ) vs what amounts to around 8 pints of oil.

My own truck when I first got it home from new, I had not measured how much volume mine took since I used a hand pump on a 6 gallon pail of gear oil to top it off but I had measured it by using a bent wire on the flat shop floor after the truck sat overnight and a ruler and it was exactly 1" below the bottom of the fill hole on the rear diff. That fell right into line with what others have measured from a factory filled rear diff on these HD trucks, however the GM instructions are to fill from within between 4/10" of an inch or up to the bottom of the fill/level check hole as the full range. So that is why it alarmed me when you mentioned not seeing any oil in that window although I wasn't sure if that diff cover held the exact same amount as the factory cover so can only speculate its probably very close to retain the same oil flow characteristics over the top that the ring gear provides with the factory curved cover vs some of these odd flat back diff covers ( the whole video Gale does on that about some of the goofy after market covers out there ).

Core-Lokt · June 9

Good find and points, sir.

Core-Lokt · Saturday at 01:07 PM

Thinking on things over the week, I decided to use the remaining oil in the pouch. Basically, there's a gallon in the differential, minus a tiny bit of spillage and whatever remained in the bags.

I think Banks designed this cover biased towards the standard Ram fill (some of those applications are greater than others, but by Amsoil's website, capacity is minimum about a pint greater than GM applications. In the picture, the differential appears fairly tilted, but it is really slightly tilted; the camera angle is skewed.

With ~8 pints, the level is midway on the sight glass; you can see the center hole of the baffle to more closely judge the level. Regardless the 6.3 pint fill spec, I'm going to leave it as-is. I don't blame Banks for erring on the conservative side, and I don't know why there's such a difference in specs between GM and Ram. And I'd also speculate the cover volume is pretty much the same as the stamped steel, as @Chuck FB noted relative volume with his recollection of another member's fill experience.