Changing the differential fluid
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Laughing Gas
Joined: Aug 2004
Posts: 1,086
Likes: 2
From: Portsmouth, VA
Changing the differential fluid
Guys, is it hard to change the differential fluid on our trucks? I was thinking about doing it today, getting it knocked out. I am going on 90,000 miles on my truck and I don't think it's ever been changed. I saw a guide online and it looks really simple, almost like changing the oil or transmission fluid.
I just get kind of worried about messing with things like this. I've changed trans fluid on two vehicles where the tranny went. It wasn't me that caused the transmission to go, they were already just barely getting by when I changed the fluid. I don't know why I let that get to me
- Chris
I just get kind of worried about messing with things like this. I've changed trans fluid on two vehicles where the tranny went. It wasn't me that caused the transmission to go, they were already just barely getting by when I changed the fluid. I don't know why I let that get to me
- Chris
Hotshot
Joined: Jul 2005
Posts: 11,931
Likes: 180
the rear alxe has a pan cover like a transmission. you have to remove about 12 bolts and pull the sheet metal cover off. clea inside, clean the cover, and RTV it back on. there is a 1/3 inch pipe plug about half way up the side of the casting. you add 1 quart of synthetic 80 w 140 gear lube and a 7 ounce bottle of friction modifier you get at Auto Zone. then top off with more gear lube till it starts to run out the hole. hardest part is squeezing the 1 quaart bottles to get them into the open hole. sometimes a shirt hose slide over the bottle top helps.----- on 4 x 4, the front end you dont have a cover. pull the 1 inch bug plug and the small fill pug above it. drain all you can, then blow in the top with air compressor if you can, or swab out the bottom with rad on a pencil tip. replace the big plug and fill same as back. dont need addative in the front. you can use regular gear lube if you want, dont have to be synthetic.
Postmaster
Joined: Nov 2006
Posts: 4,517
Likes: 3
From: SE Wyoming
It should be synthetic 75w140 for the rear and you don't need friction modifier if you have an open rear. I forget the number they say the front takes but it is a general weight, the book should say what it is.
If you ever think you will want an aftermarket rear diff cover with a fill and drain plug this would be the time to put it on. I like MagHytec's stuff myself but it is costly.
If you ever think you will want an aftermarket rear diff cover with a fill and drain plug this would be the time to put it on. I like MagHytec's stuff myself but it is costly.
Posting Guru
Joined: May 2002
Posts: 1,673
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From: Chicago Area
There are small pumps available, which screw into the top of the gear lube bottles and have a small diameter hose which you put into the hole. Then you push in the pump button like a Windex bottle. I don't remember what they cost, but I think they're pretty cheap, and they do make it much easier.
Incidentally Ford does NOT specify that the diff be filled all the way up to the fill hole ( I think they say 1/2" below), but we always have done it that way and I don't think it hurts. Probably just a way for Ford to save a few pennies per vehicle.
Also, Ford does not specify that the diff fluid ever be changed unless it has been contaminated, but I do think it is good practice if you want to run long and well.
Incidentally Ford does NOT specify that the diff be filled all the way up to the fill hole ( I think they say 1/2" below), but we always have done it that way and I don't think it hurts. Probably just a way for Ford to save a few pennies per vehicle.
Also, Ford does not specify that the diff fluid ever be changed unless it has been contaminated, but I do think it is good practice if you want to run long and well.
Last edited by MrBSS; Dec 2, 2006 at 10:05 AM.
Senior User
Joined: Aug 2003
Posts: 457
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From: SW ND
I was going to do this also, but am confused. The manual says 75W-140 but I was looking the truck over from underneath, and I found a sticker on the axle that looks to be from factory with 75W-90 on it with some other numbers that I don't remember. It kind of repeated itself, and had color bands. Does this mean anything or should I ignore that it says use the lighter oil?
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Elder User
Joined: Dec 2004
Posts: 675
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From: Springfield, OR
On my E-350 it said to use a minimum 75W-90 weight but you can use 75W-140 also. When you drain and wipe out any gunk in the diff make sure you dont spray it with any cleaner or you'll ruin it. A few guys have made that mistake. Myself, I like to use a gasket with the cover but however you do it use a inch pound torque wrench on the cover bolts to bring em to book spec-not to hard or you'll crush the gasket or distort the cover an get a leaker.
Last edited by T18skyguy; Dec 2, 2006 at 09:26 PM.
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Thread Starter
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Laughing Gas
Joined: Aug 2004
Posts: 1,086
Likes: 2
From: Portsmouth, VA
I'm confused on just one thing, what is an open rear? I have just the basic 4x2 4.2L manual tranny.
Also, Ford doesn't recommend changing the fluid unless it has been contaminated? What would classify as contamination, like it was started to leak or what not? I was reading my Haynes manual, I don't remember the miledge but it recommended it as basic maintnance after so many miles. Heck I was worried going 88,000 miles was letting it go way to long.
One last question, what brand(s) do you guys recommend. I've read that Red Line is good but certain differentials don't like it, I've also read instances that Motorcraft has been very expensive. Is synthetic the way to go?
Thanks guys I really appreciate the help
- Chris
Also, Ford doesn't recommend changing the fluid unless it has been contaminated? What would classify as contamination, like it was started to leak or what not? I was reading my Haynes manual, I don't remember the miledge but it recommended it as basic maintnance after so many miles. Heck I was worried going 88,000 miles was letting it go way to long.
One last question, what brand(s) do you guys recommend. I've read that Red Line is good but certain differentials don't like it, I've also read instances that Motorcraft has been very expensive. Is synthetic the way to go?
Thanks guys I really appreciate the help
- Chris
Senior User
Joined: Aug 2003
Posts: 457
Likes: 0
From: SW ND
Open rear, is the same as a pegleg, one wheel peeler, etc. Open rears allow turning without any chirping at all. If you have a wheel spinning it is usally the side with least amout of weight on the tire.
Contamination would be normally be water if submerged, or a failure of some type.
As for interval change Ford says it's not necessary, and says it good for lifetime, but it never hurts.
Synthetic is the way to go. According to my owners manual says it has synthetic in it. Most of the OTR truck have been using synthetic's for a long time. Their change interval is 1,000,000 miles. As to brands it doesn't seem to make much difference anymore who or what just depends on you pocket book.
Contamination would be normally be water if submerged, or a failure of some type.
As for interval change Ford says it's not necessary, and says it good for lifetime, but it never hurts.
Synthetic is the way to go. According to my owners manual says it has synthetic in it. Most of the OTR truck have been using synthetic's for a long time. Their change interval is 1,000,000 miles. As to brands it doesn't seem to make much difference anymore who or what just depends on you pocket book.
Senior User
Joined: Nov 2006
Posts: 252
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one suggestion i have is to use an actual gasket when re sealing. originally it has gasket sealer from a tube in there, but sometimes when you reapply it, if you arent very careful, you can get a leak due to uneven application. the gasket is probly 7 or 8 bucks, and its reusable for the next time you have to change the fluid. clean off the surfaces with a scraper or whizzy wheel on your die grinder, but dont dig too deep into the material.
is there a drain plug to change the fluid on manual transmissions? its to cold out there to crawl under and check. but i needa change my fluid soon.
is there a drain plug to change the fluid on manual transmissions? its to cold out there to crawl under and check. but i needa change my fluid soon.
Cargo Master
Joined: Aug 2002
Posts: 2,013
Likes: 6
From: Cajun Country
Your differential should have a tag displaying which fluid to use.It most likely reads; 75W140 SYNTHETIC ONLY
If it's an 8.8 differential it holds 2.75 quarts.If it's L/S you also have to add 4oz. of friction modifier.I like Royal Purple fluid.You can get it any Pep Boys or NAPA for $10.00 a quart.Some fluids state they have the modifier in the fluid for a L/S; if you do have L/S add the modifier anyway.
If it's an 8.8 differential it holds 2.75 quarts.If it's L/S you also have to add 4oz. of friction modifier.I like Royal Purple fluid.You can get it any Pep Boys or NAPA for $10.00 a quart.Some fluids state they have the modifier in the fluid for a L/S; if you do have L/S add the modifier anyway.
Hotshot
Joined: Jul 2005
Posts: 11,931
Likes: 180
---i used the 75W90 synthetic instead of 75w140--- it works fine..
---the friction modifier is needed if you have limit slip rear end, when you open the cover and if you have a clutch on one side to limit the axle spin, then you need the addative.
---synthetic is very good and will last for a long time.
---dont beleive ANYTHING that says never need to drain the oil. changing the factory oil and cleaning the cavity cant hurt ANY system.
---the friction modifier is needed if you have limit slip rear end, when you open the cover and if you have a clutch on one side to limit the axle spin, then you need the addative.
---synthetic is very good and will last for a long time.
---dont beleive ANYTHING that says never need to drain the oil. changing the factory oil and cleaning the cavity cant hurt ANY system.