2004 Ford 8.8 Rear Diff Fluid?

[XJ1100]

2004 Ford F-150 w/ 4.6L and 8.8" rear diff I was at the dealer today to buy some 75w-90 Motorcraft Synthetic Axle Lube as specified in my owners manual. The parts guy told me that all they have is 75w-140 synthetic and to just run that - he said that this is what Ford now specs for my diff in the service manual. I have found various brands of 75w-90 sythetic at parts stores in my area. I just thought I would run the motorcraft stuff since their fluids are usually top notch stuff. Is the 75w-140 motorcraft what I want to run even though this doesn't match my owners manual? or should I just use another brand of 75w-90 syn (Valvoline or the like). I am looking for others w/ experience running the Ford 8.8" rear end. What weight/brand have you had good luck with. Thanks Addition: I thought I should mention that the truck isn't used for heavy pulling or hauling. Mostly car like duty with the occasional 2 place ATV/Snow trailer behind it.

 

[stang5]

I would stick with the factory recomendation 75w-90 any off the shelf synthetic will be just as good, going thick like 75w-140 might make your truck sluggish and hurt gas mileage. I use Amsoil severe gear 75w 140 with Ford Friction Modifier on my 02 Mustang. Thats the viscosity my manual calls for which I think is overkill..

 

[astraelraen]

I would assume the change from 75w90 to 75w140 is because of the spec change recently? I can't remember exactly, but I know they changed the 75w90 to two specs because of the varying types of 75w90 fluids - some were up to 110 or 140 on the high end but still qualified to be labeled as 75w90.

 

[rumple]

Ford has a TSB to switch these trucks (F150's from 1997-2005) to 75W140 from the factory installed 75W90. The thinner fluid could cause issues such as chatter and whine or hum and Ford has called for replacement in all cases. Here.

 

[bdcardinal]

 Originally Posted By: rumple

Ford has a TSB to switch these trucks (F150's from 1997-2005) to 75W140 from the factory installed 75W90. The thinner fluid could cause issues such as chatter and whine or hum and Ford has called for replacement in all cases. Here.

+1, although we keep both in stock. we usually put the 140wt in unless the customer requests otherwise.

 

[Colt45ws]

I installed Amsoil Severe Gear 75w110. Somewhere in between. Quiet as can be, but I do not have a trac-loc.

 

[XJ1100]

Sounds like I will be returning and buying some 75w-140 synthetic. They also tried to sell me some Motorcraft Silicon for sealing the cover. I am assuming I can just use some permatex brand from NAPA for way cheaper...? Does anyone make a rubber gasket for these diffs?

 

[Colt45ws]

Yeah, you can just use permatex from NAPA. Not that Im aware of on the gasket, but I never looked for one.

 

[bdcardinal]

no gasket from the factory, just black silicone. i have purchased a gasket from NAPA in the past though.

 

[JustinH]

If it is a locking diff, make sure you are using either friction modifier, or a fluid with the modifier mixed in to it. Some of the full syn fluid is premixed. I used royal purple the last time I filled up an 8.8 and it was fine.

 

[Bluestream]

I went through this with my 2000 Explorer. Manual said some have 75W90 but all Trac-lok and 4:11 gears take 75W140. My dealer said they are putting 75W140 in everything now and thats in Canada. I think you can use the thiner fluid, but if you plan on putting high miles on it the 75W140 may be best. I used Redline 75W140 in mine (conventional axel with 4:11 ratio) with high miles. I think the 75W110 is also a great option for these trucks. You may get 1-2% less mileage, but you won't notice it being sluggish. If you have any noise go with the 140. Also, check your spider (side) gears when you are in there, mine were pitted. Take off the cover when axel is hot, let it drain overnight to get all the old stuff out.

 

[exranger06]

I'm running Valvoline Synthetic 75w-90 in the 8.8 diff on my Ranger. It has a Trac-lock limited slip that needs a friction modifier, but the Valvoline fluid already has it mixed in, and adding any additional modifier is not necessary. I have no chattering or noises from my diff. It performs pretty much the same as the factory fill did, no better, no worse.

 

[tig1]

Not sure if the dif in my 96 Merc GM is the same , but I use M1 75-90 in it and it's fine at 215,000 miles. My sons Ranger has it in there as well, 330,000 miles and doing well.

 

[01rangerxl]

Many 8.8s have been switched to 75W140 to get rid of chatter. You can run it with no worries. I used Motorcraft 75W140 in my old truck's 7.5 axle which called for 80W90 and had no problems. I use Permatex Ultra Black on diff covers. It seems to be basically the same as what Ford uses from the factory on most axles.

 

[MNgopher]

Put the 75w140 in and forget about it. I've had this in both my '97 and '99 F150's with the 8.8 in the rear axle. The '99 is at 176,000 miles and has been serviced once in its life (rear axle seal failure).

 

[Jason2007]

I agree with using 75w140.

 

[tom slick]

Amazing that they can have 7 years of production before realizing they should spec a thicker fluid. FWIW I have the same vehicle configuration as the OP and am running 75w-90. I didn't know about the TSB but the rear end hasn't gone kaput or made any funny noises. The original "lifetime fill" fluid drained out black at just over 50k miles.

 

[Whimsey]

 Originally Posted By: 01rangerxl

I use Permatex Ultra Black on diff covers. It seems to be basically the same as what Ford uses from the factory on most axles.

Make sure you don't use the Permatex Ultra Blue with full synthetic diff fluid. I did and after 6 + months a leak developed and kept getting worse. Used the Ford Black sealer and have ZERO leaks after 4 1/2 years. The cover bolts were tight. I can only speculate the synthetic fluid gradually ate through the Blue sealant . Whimsey

 

[Ben99GT]

 Originally Posted By: 01rangerxl

I use Permatex Ultra Black on diff covers. It seems to be basically the same as what Ford uses from the factory on most axles.

I've had bad luck with with Permatex Ultra Black after a couple years on everything I've used it on. Very prone to seepage after few years. Motorcraft TA-29 (gray, what Ford uses from the factory) kicks butt.

 

[tig1]

I use Ultra Black with M1 ATF and it has worked great. 150,000 miles and no seapage at all. Have to let it set for a while before installing fluid. 2 hours at least.