Servicing Front and Rear Differentials - 3rd Gen HD's

[Cumminalong]

Manufacturer recommended interval is 15K for front and rears.

Here is the rear diff....

[Cumminalong]

First, here are pics of the front diff. I didn't take too many, as it's nearly identical to the rear, with the exception of a few bolts are a PITA to get to without a u-joint. Yes, I have a few u-joints (I'm just stubborn). The TQ specs are the same. The only difference is, obviously, the size of the diff and the fact that it's an open carrier.

After seeing the color of the fluid and the lack of any metal on the fill plug, I'm gonna push my front diff changes out to 30K. The oil looked almost brand new and there was minimal grit on the fill plug. So I'll be going 15K on the rear and 30K on the front.

Here ya go....

[nickcoletti]

great DIY! i was just thinking about this recently and KNEW there would be something up here for me to go from as soon as the weather breaks. thanks rich!!!!!

[nickcoletti]

i just got my lube in about a week ago (thanks again tommy) and i have came up with 2 questions!

first... once you remove the cover and drain the old oil out, it says to flush it out with new oil. can i use any oil to do this or does it have to be the synthetic oil that im going to be putting in. i am no oil expert and im not sure if they can be mixed, even know the regular oil would be mostly drained except for maybe a small film.

second... i have heard that some differentials need an additive that needs to be purchased by the dealer. something to do with limited slip or something alone those lines. do i need to put that stuff in there also, or is that for different set ups?

i dont plan on getting under my rig until the weather stops freezing a cup of water... so i have some time but i was just curious in the mean time!

[Kilch123]

It would be best to flush with the oil that you're gonna fill with, but you probably just got enough to do the fill.  If that's the case, just use dino gear oil for the flush, but once flushed, let as much as possible drain.  It's compatible, but the lower the amount of dino oil, the more benefit you'll get with the synthetic.  There is a small dip in the bottom of the diff case that is designed to catch the big junk that can be in there, so before flushing, and before putting the cover back on, make sure you scoop as much out of that little reservoir (I use a rubber glove on my hand, and scoop it out with my fingers)

I'm pretty sure the Dodge LSD's don't need the additive - I'll do a little research and verify that...  Stay tuned...

K

Here's what I got...

REAR AXLE

9 1/4  Mopar Synthetic Gear Lubricant 75W-140 
10 1/2 AA  Mopar Synthetic Gear Lubricant 75W-90 
10 1/2 AA EL  Mopar Synthetic Gear Lubricant 75W-90 
11 1/2 AA  Mopar Synthetic Gear Lubricant 75W-90 
248 RBI  Mopar Gear & Axle Lubricant SAE 90

NOTE: Trac-Lok differentials require Limited Slip Additive in the lubricant. Trac-Rite/Trac-Rite EL differentials DO NOT require Limited Slip Additive.

So - if you don't know if it's trac-lok, trac-rite etc, send the last 8 of your VIN to Dave, and he'll let you know - Trac-Lok does need the additive

[nickcoletti]

i did only buy enough to do the fill (7 quarts) but i suppose i could go buy one more at a local store just to be on the safe side. when you say dino gear oil, you just mean non synthetic right?

thanks for taking the time to research that brotha!

[Kilch123]

yea - dino oil (from dinosaurs) is just regular non synthetic oil (better than nothing, but would be better to use synthetic)  You don't need much - see Rich's DIY - just squirt some up toward the pinion gear to wash out any contaminants that didn't wash out as the oil drained

No Prob!

[mayfair]

I remember you posting this DIY over on the 'other' site, and i STILL want that torque wrench.

Thanks for posting it here as well Rich !!

[nickcoletti]

well i had some time after work today to get in there and turn that wrench.

everything went good, thanks for the write up rich!

i do have to say one thing about the front though, when you said those few upper bolts are a PITA to get off... that was only putting it LIGHTLY!

i even had the u-joint adapter and the extensions, it took me FOREVER to get to a few of them  's off !

i do have one question, are my magnets suppose to be THIS dirty? both front and back were like this although the back was worse.




heres the aftermath... the back was pretty dirty but the front looked almost new.

[Cumminalong]

Is that your first time changing them?

If it is, it's pretty normal.

[nickcoletti]

yes it was my first time changing them, i am at 38k.

i kind of figured it was normal but i just wanted to make sure. thanks buddy!

[BigRiver]

Question for ya'll.

I have the ATS rear diff cover. It has a drain plug as well as a fill plug. Unlike the Mag Hytec, my ATS does not have a dip stick.



I was changing the fluid the other day, using Amsoil Severe Gear 75W110. I began fill up the case, and ran out of fluid. I ordered more from Amsoil and got the order the other day.

I started thinking about how much I had already added, which was about 8 quarts. The top level of the oil was still below the fill plug hole. My initial thoughts were to fill to the top, but now I'm wondering if I could screw up by adding too much. It's been a few years and many thousands of miles since I did this and I remember filling to the top.

As with the Mag Hytec models, there is a mark on the dip stick to fill up to. I don't have this, so do I fill to the top? I want to think so....

Just asking.

[Cumminalong]

No, no, no!!!!!

Do not fill it to the top of that plug.

You don't want the fluid level above the top of the inner axle seal or it's going to be leaking on ya.

Lemme look back at mine.....it should be 7.5 qts with the bigger cover.

Gimme a sec.

[Cumminalong]

Yup!

7.5 - 8 qts is what it needs.

[BigRiver]

ATS says that this cover hold 2.5 extra quarts.

I'm not sure which diff I have, but the info for the 11 1/2 open indicates 142 oz.

142 / 32 = 4.4375 quarts plus the extra 2.5 = roughly 7 quarts

Does this sound right? If so........I have enough.

If I put too much in, it will just seep out I hope.