Differential gear oil change

[1978 Homebuilt Fords]

Hey all, I'm new here, my dad's been a member for a while, and I thought I'd join too. I've got a question, is there a specific type of oil I need to use in the front differential? I've got a 1978 Ford f150 4x4

 

[alwaysFlOoReD]

Most likely 80w/90 gear oil.

 

[DILLARD000]

Attention OriginalPoster &\or ForumAdmin:
consider changing title of this thread to "Differential GearOil Change"

Unsure about older F series trucks; for later smaller chassis Rangers\Explorers\Mountainneers\SportTracs\...
typical OwnersManual spec is 75\80w140.FullSyn in the Rear Diff & 75\80w90.FullSyn in the Front Diff,
FrictionModifier additive is needed if either is a LimitedSlip\TractionLok version.
Though here I've been using AmsOil# SAE250.FullSyn with AmsOil# SlipLok FrictionModifier with good results the last 2years,
for both the Rear LimitedSlipDiff & Front OpenSlipDiff on my 2001 SportTrac4WD,
for both the Rear OpenSlipDiff & Front PowerTransferUnit\PTU on my 2008 EdgeAWD.
My service routine is every 33kMiles\4~5years for the Diffs, 6~8kMiles\6mths for the PTU due to SevereHeatDuty.

 

[1978 Homebuilt Fords]

Thanks! I know,I messed up on the title of the thread, I realized that after I posted it. I appreciate the info. I knew it was a slightly heavier oil, but I've been slowly putting this truck together, and I checked my differential oil level and it was dry. So I wasnt sure how much or what kind to use.

 

[sgtsandman]

Before you fill it, you might want to determine why it is low or dry. Lack of maintenance? Pinion seal leak? Axle seal leak? Differential cover leak? Fix it before you fill it back up.

As far as how much you need, probably 3 bottles and fill it until the fluid comes out the fill hole.

 

[DILLARD000]

Remove FillPlug first.
Take Diff cover off & drain. Or at least suction old oil from FillBung.
Flush\Clean with BrakeCleaner, then inspect.
Reinstall Cover, using Permatex BlackRTV rated for GearOil service, or a new Gasket.
Refill with fresh GearOil until it drips from FillBung; reinstall FillPlug with a smear of BlackRTV.

 

[1978 Homebuilt Fords]

Not sure why it's dry. I recently bought it off of a guy that used it for mudding,and whenever kept up with the maintenance on it, so it could have been dry when he owned it. I've been finding alot of things that were not kept up with..

 

[sgtsandman]

I would definitely pull the cover and look inside then. Make sure the bearings aren’t damaged. Look for metal shavings in whatever oil is left in the thing. More axles fail due to neglect than anything else.

 

[1978 Homebuilt Fords]

Remove FillPlug first.
Take Diff cover off & drain. Or at least suction old oil from FillBung.
Flush\Clean with BrakeCleaner, then inspect.
Reinstall Cover, using Permatex BlackRTV rated for GearOil service, or a new Gasket.
Refill with fresh GearOil until it drips from FillBung; reinstall FillPlug with a smear of BlackRTV.

I would definitely pull the cover and look inside then. Make sure the bearings aren’t damaged. Look for metal shavings in whatever oil is left in the thing. More axles fail due to neglect than anything else.

I took the cover off, and there's no shavings inside, it's very clean, just dry. Im hoping my seals are still good

 

[sgtsandman]

I took the cover off, and there's no shavings inside, it's very clean, just dry. Im hoping my seals are still good

Since the axles seals are inexpensive and fairly easy to access, I would change them. Just to be safe. The pinion seal is inexpensive but the change process is a little more involved. You can change that one with the axle filled. So if it turns out to be that, that one is leaking, you won’t need to drain the axle to change it.

 

[LIMA BEAN]

80/90 however you may want to go synthetic just because you have that option they didn't have in 79 and your running gear will love you in Ohio winters way down South. Also be mindfull if you need friction modifier for the rear diffy. Most diffy's will have the fill/check port on the cover or side of the diffy it's self so if you remove the plug if it don't run out stick your pinky in and dip down, if you can't touch it you're low. Best advice is to remove both covers without warping them, observe what comes out, clean out the inside and brake clean it. Make sure your surfaces are super clean and re install your covers with a good sealant but don't refill until sealant is cured unless you are using a sealant like Permatex Right Stuff that is good to go right away. Fill with gear oil until it spills out and plug it. P.S. if you get old gear oil on ya or your clothes your significant other will probably make you sleep outside till you de skunk.

 

[1978 Homebuilt Fords]

Since the axles seals are inexpensive and fairly easy to access, I would change them. Just to be safe. The pinion seal is inexpensive but the change process is a little more involved. You can change that one with the axle filled. So if it turns out to be that, that one is leaking, you won’t need to drain the axle to change it.

Good point. I'll do that and save myself the frustration of having to drain my fresh oil to put new seals in

 

[1978 Homebuilt Fords]

80/90 however you may want to go synthetic just because you have that option they didn't have in 79 and your running gear will love you in Ohio winters way down South. Also be mindfull if you need friction modifier for the rear diffy. Most diffy's will have the fill/check port on the cover or side of the diffy it's self so if you remove the plug if it don't run out stick your pinky in and dip down, if you can't touch it you're low. Best advice is to remove both covers without warping them, observe what comes out, clean out the inside and brake clean it. Make sure your surfaces are super clean and re install your covers with a good sealant but don't refill until sealant is cured unless you are using a sealant like Permatex Right Stuff that is good to go right away. Fill with gear oil until it spills out and plug it. P.S. if you get old gear oil on ya or your clothes your significant other will probably make you sleep outside till you de skunk.

Haha Im single so I have no worries there

 

[LIMA BEAN]

Best to you and welcome to The Ranger Station. Amazing bunch of girls and guys here, remember the only dumb question is the one not ask. We are here for you and for sure go hang out in the Tech Library it's a treasure trove. Cheers from Alaska.

 

[1978 Homebuilt Fords]

I appreciate it a

Best to you and welcome to The Ranger Station. Amazing bunch of girls and guys here, remember the only dumb question is the one not ask. We are here for you and for sure go hang out in the Tech Library it's a treasure trove. Cheers from Alaska.

I appreciate it very much, thank you!