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Front and Rear Differential Gear Oil Change

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Machspeed

Front and Rear Differential Gear Oil Change

Administrator

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!

John

"Blackie" - 1986 F150 4x4 - Mildly warmed over 351W HO - Original owner

Gary Lewis

Re: Front and Rear Differential Gear Oil Change

Administrator

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.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

ArdWrknTrk

Re: Front and Rear Differential Gear Oil Change

Administrator

In reply to this post by Machspeed

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,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Front and Rear Differential Gear Oil Change

Administrator

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

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Front and Rear Differential Gear Oil Change

Administrator

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.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Front and Rear Differential Gear Oil Change

Administrator

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.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Front and Rear Differential Gear Oil Change

Administrator

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.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

AuroraGirl

Re: Front and Rear Differential Gear Oil Change

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

Re: Front and Rear Differential Gear Oil Change

Administrator

I live in New England.
BOM's from the '80's are hard to read even with a grinder.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

AuroraGirl

Re: Front and Rear Differential Gear Oil Change

In reply to this post by AuroraGirl

Rusty crusty rust belt granola is definitely fun

ArdWrknTrk

Re: Front and Rear Differential Gear Oil Change

Administrator

Your spare tire sling is still in one piece.

It's always fun when that lets go while driving down the road!

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

AuroraGirl

Re: Front and Rear Differential Gear Oil Change

oof lol. I bet. I Just wish I had the special under the bed hardware, brackets, or tank from the 1967 f100 camper special truck bed trailer I have, because that came with factory aux tank which would sit inside the frame rail. those would have fetched some money lol.

That has a 9 inch on it. was nice when one day the drum self-actuated in the back part of my property. One side only, but getting the drum off was difficult to say the least in the mud and far from the tools lol

Machspeed

Re: Front and Rear Differential Gear Oil Change

Administrator

Jim and Gary, thanks for the responses!

So, can I use the same gear oil with friction modifiers in both differentials or would you suggest otherwise?

Gary, why would you not pull the third member? I've thought about it and the more I think about it the more I think I need to do it. I just can't half-a things and in "my mind" that's what that is. Talk me out of it....LOL! It bugs the fire out of me that I can't fully access the front differential and that I have to suck the stuff out knowingly leaving some behind.

Thanks again fellas!

John

"Blackie" - 1986 F150 4x4 - Mildly warmed over 351W HO - Original owner

ArdWrknTrk

Re: Front and Rear Differential Gear Oil Change

Administrator

I don't think there's any harm in using a gear oil that has friction modifiers already in it but I sure wouldn't add it to regular oil in a diff that has no clutches that need the protection.

Are the inner axle seals leaking?
Disassembling the entire front end of your truck (rotors, axles, spindles, beams) seems like a crazy amount of work to change the oil.
There's no internal combustion going on here to contaminate it.

I'm definitely from the "do it right, do it once" camp, but I also believe in "if it's not broke don't 'fix' it"

There's always the possibility of creating a leak if the seals don't sit on the axles just right or the heavy housing doesn't seal up to the beam correctly. (and it would be a huge ordeal to pull it apart again if you did)

Just my 2c

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Front and Rear Differential Gear Oil Change

Administrator

I agree with Jim about pulling the pumpkins. Way too much work. On the rear you have to pull the wheels, brakes, and axles, plus the drive shaft. On the front is is much harder - in fact the case is supposed to be spread open a bit to get the pumpkin out.

Just use your suction gun and change the oil. And if you are paranoid, do it again in a couple of years. That'll be easier and cheaper than pulling the pumpkins.

Gary, AKA "Gary fellow": Profile