Front and Rear Differential Gear Oil Change

[Machspeed]

Hey friends, crawling around under my truck the other day, I came to the realization that the gear oil in the front and rear differentials has never been changed. Evaluating the job situation, I realized there is no drain plug on either the front or rear diff. The rear is a 9”. As such, it looks like I need to vacuum out the stuff in the front and either vacuum out the rear or pull the third member. Recommendations on how you would to do this?

Also, would appreciate recommendations on replacement quality lube. With a tag number on the front diff of E4TA AMA and referencing our documentation, it appears that it is not limited slip. However, I’m not sure what the rear is. Pictures below.

Thanks!

[Gary Lewis]

Your rear tag doesn't seem to have the "L-S" that a limited slip axle would have, as shown way below, so you don't need the friction modifiers. However, I like Mobil 1 75W-90 Synthetic Gear Lube and that appears to have the friction modifiers in it.

And the chart below from the '86 owners manual says your 9" will take 6.5 pints and your D44 will take 3.8 pints, for a total of 10.3 pints or 5.15 quarts. But you aren't going to get them completely dry so I'd bet 5 quarts will do you.

Speaking of that, I wouldn't even consider removing the pumpkin to drain it. I'd put a suction gun on and get what I could get out. And I've found that using a small hose in the end of the suction gun's tube lets me get down to the bottom easier.

As for filling, I use something like this Slippery Pete Fluid Pump. It is messy, for sure, and if the lube has the friction modifiers in it then it is stinky as well.

Given that, you might shop for a lube that comes in bags, like Valvoline FlexFill Full Synthetic SAE 75W-90 Gear Oil 1 QT Pouch.

[ArdWrknTrk]

Your rear tag does have 3L50, so it is limited slip (I can't say how good the clutches are at this point)

I have a suction gun. It looks like a cross between a grease gun and an oversized syringe.

You can get one at Horrid Fate for $10. https://www.harborfreight.com/oil-suction-gun-95468.html

You can use it to pump fluid in too.

Gear oil has come a long way since these trucks were made, so factory fill may not be your best option.

But you should definitely use LS lube (or additive) in the rear.

If you decide on additive be sure to wear gloves and don't get it on anything you want to keep.

The factory GM/Delco, Mopar or Motorcraft stuff stinks to high heaven.

[Gary Lewis]

Your rear tag does have 3L50, so it is limited slip (I can't say how good the clutches are at this point)

I have a suction gun. It looks like a cross between a grease gun and an oversized syringe.

You can get one at Horrid Fate for $10. https://www.harborfreight.com/oil-suction-gun-95468.html

You can use it to pump fluid in too.

Gear oil has come a long way since these trucks were made, so factory fill may not be your best option.

But you should definitely use LS lube (or additive) in the rear.

If you decide on additive be sure to wear gloves and don't get it on anything you want to keep.

The factory GM/Delco, Mopar or Motorcraft stuff stinks to high heaven.

Jim - You are right! I was WRONG! I was looking at the front tag instead of the rear tag.

[ArdWrknTrk]

Jim - You are right! I was WRONG! I was looking at the front tag instead of the rear tag.

I didn't mean to correct you, but I've never seen a tag like you show with L-S at the end on one of these trucks. (Not to say I've seen most, or even many)

But in my experience it is always an L where the (.) would go in the gear ratio callout.

Ford 9", 8.8 & Sterling

Anyway, John has options and knows to use a friction modifier in the back.

[Gary Lewis]

I didn't mean to correct you, but I've never seen a tag like you show with L-S at the end on one of these trucks. (Not to say I've seen most, or even many)

But in my experience it is always an L where the (.) would go in the gear ratio callout.

Ford 9", 8.8 & Sterling

Anyway, John has options and knows to use a friction modifier in the back.

I'm glad you corrected me. I was wrong and was giving bad advice.

But I agree with you about the "L" vs "L-S". In fact, when John called on Saturday I told him to look for the "L" between the "3" and "50", so I was surprised this morning when I looked up the illustration from the MPC showing the "L-S".

And I agree with you about the clutches. They were worn so badly on Dad's truck that it got stuck in a muddy field and only one tire would spin. So I had to engage the front diff. But it won't now as the Kevlar clutches come in easily on corners if you give it much throttle.

[ArdWrknTrk]

I'm glad you corrected me. I was wrong and was giving bad advice.

But I agree with you about the "L" vs "L-S". In fact, when John called on Saturday I told him to look for the "L" between the "3" and "50", so I was surprised this morning when I looked up the illustration from the MPC showing the "L-S".

And I agree with you about the clutches. They were worn so badly on Dad's truck that it got stuck in a muddy field and only one tire would spin. So I had to engage the front diff. But it won't now as the Kevlar clutches come in easily on corners if you give it much throttle.

Well, it does say Dana axles... 🙄

I don't see D44's with LS and I don't know if I've ever seen a 50, 60 or 70 the tag hasn't rotted off.

Those heavier trucks have usually seen plowing duty and plenty of salt around here.

[AuroraGirl]

Well, it does say Dana axles... 🙄

I don't see D44's with LS and I don't know if I've ever seen a 50, 60 or 70 the tag hasn't rotted off.

Those heavier trucks have usually seen plowing duty and plenty of salt around here.

a dana axle will have the list number and the identifying information on the tube and the carrier perimeter. but if this is a front ttb, then im not sure how those work. rear would be normal straight axle stuff

[ArdWrknTrk]

a dana axle will have the list number and the identifying information on the tube and the carrier perimeter. but if this is a front ttb, then im not sure how those work. rear would be normal straight axle stuff

I live in New England.

BOM's from the '80's are hard to read even with a grinder.

[AuroraGirl]

a dana axle will have the list number and the identifying information on the tube and the carrier perimeter. but if this is a front ttb, then im not sure how those work. rear would be normal straight axle stuff

Rusty crusty rust belt granola is definitely fun