Changed rear diff, wrong oil??

[SigShooter]

OK so I changed my rear diff oil today. 97 F150 with 355 LS. Went to Ford dealer and got the friction modifer and Motorcraft 80w90 premium oil. That's what it said to use in the manual. Well I'm loosening the bolts for the rear cover and the oil is draining and on one of the bolts is a tag that says to use 75w140 synthetic lube. I put the 80w90 in, will I be OK? Should I drain and fill with synthetic? I don't tow anything or rarely have anything heavy in the bed. Thanks for any feedback

 

[MolaKule]

Since you're not towing, I would leave it in until summer, then drain and put in the 75W140.

You're a VIKTOM of last minute spec changes, hence the tag.

My Burb's tranny was in a similar situation, it was a mainly 700R4 with a half-way modification toward the 4L60E or sum such electronic version. The book said 4L60E, the tranny tag said
700R4, but the wiring harness was a 4L60E harness and there was a mating connector
on the 700R4 - go figure!

 

[wulimaster]

quote:

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Originally posted by SigShooter:
OK so I changed my rear diff oil today. 97 F150 with 355 LS. Went to Ford dealer and got the friction modifer and Motorcraft 80w90 premium oil. That's what it said to use in the manual. Well I'm loosening the bolts for the rear cover and the oil is draining and on one of the bolts is a tag that says to use 75w140 synthetic lube. I put the 80w90 in, will I be OK? Should I drain and fill with synthetic? I don't tow anything or rarely have anything heavy in the bed. Thanks for any feedback

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Funny how 80w90 was ok for so many years and then all of a sudden it jumps up to 75w140 and call for synthetic. I think Ford is trying to simplify production at their truck plants by specifying the most protective oil you can get and only stocking one. One size fits all.

You will get much better fuel economy with a 75w90 synthetic than with a 75w140 synthetic. I would go with a 75w90 high quality synthetic by amsoil or redline. You will be more than protected for the life of the vehicle. If you find yourself towing maximum or beyond maximum loads then I would go with the 75w140 synthetic. Motocrafts synthetic is very expensive.

I went from the 75w140 motocraft fill to 75w90 series 2000 amsoil in my excursion diesel and picked up about 10% better fuel economy.


Let us know if you pick up any mpg. If not, then you probably had an 80w90 factory fill.

The 75w140 is grey and cloudy and leaves a lot of ?moly? clinging to parts. I don't know what the 80w90 looks like.

 

[Steve S]

thicker synthetic oil provides better shock and load protection over a lighter oil..will it make a difference I dont know, but for the cost of the oil change it. Rear end parts cost more .

 

[Malibu]

SigShooter, I agree with molecule that you should use what the drain plug says; i.e. the 75W-140. Since around 1995 full sized American trucks have had a bit of trouble with overheating and failed rear differentials. Why they are more fragile than in the past I don't know, but obviously a 75W-140 synthetic offers more protection for a hot running rear end than a 80W-90.

I read about the differential overheating problems in the past 7 years worth of Trailer Life magazine.

 

[Greaser]

Pennzoil makes a 75W-140 synthetic...much better price than the dealer...the Mopar dealer was selling it at $22 CAN then it went up to $26...Pennzoil is $18.50 a litre...mind you this is in Canadian bux...I just bought a case of the stuff for $8.50 a litre...the guy at the counter made a boo-boo and I tried to tell him it was more than that,but he didn't believe me..and this is how I looked going out the door with my case of gear lube

 

[joee12]

quote:

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Originally posted by wulimaster:

Originally posted by SigShooter:
[qb] The 75w140 is grey and cloudy and leaves a lot of ?moly? clinging to parts. I don't know what the 80w90 looks like.

---

The 80W90 is grey and cloudy, I just changed mine a few months ago. I know that Ford now specs 75W140 Syn for the traction lock differentials, and 80W90 for the limited slip. It is mentioned in the manual for my Explorer. I would stick with the 80W90. -Joe

[ February 28, 2003, 09:45 PM: Message edited by: joee12 ]

 

[Whimsey]

I have a 2002 F-150 4X4 and the owners manual specifies 75W-90 oil in the front diff. and 75W-140 synthetic oil for the rear diff. Whether you have limited slip or not. If you have limited slip then you need to add the Additive Friction Modifier. The rear axle is "lubed for life"

according to Ford, unless the axle gets submerged in water. Of course they don't say anything in the maintance guide about changing the front diff oil.

Whimsey

 

[unDummy]

I vote for the owners manual. Screw the dealer's recommendation if they don't have a TSB to back it up(especially if warranty is a concern)!

Since synth is required for your truck(IMO, if 'used' as a truck), I wouldn't even bother with a non synth.
If you don't tow, plow, torment, or abuse that truck, you could probably get away with a 75-80/w90 IF it was a synth.
Soccer practice&supermarket&mall&sunday drivers probably don't need the added protection from the 140wt. Itty bitty MPG with the thinner oils is a plus for using the truck as a car.
The synths by amsoil/mobil1/royalpurple/redline....come to mind.

Lube for life is a myth. Ford had some fluid contamination issues on new axles. Changing it, within a reasonable interval, is important.

IMO, changing it again, with a quality synth, is recommended. Choose the viscosity on how you use the vehicle!

 

[Greaser]

If you ever see where axles are manufactured you would drain and fill those thing every chance you get.My brother does the tooling for American Axle (Dana) and says the place is a pigstye...I don't know about Ford but would probably be a bit better..still there is alot of residue from manufacturing and break-in on axles...drain and fill if you can..."fill for life" means "see you soon for service" in my books...but I'm synical anyways

 

[rgl]

lubed for life is circular reasoning.

Your rear end failed due to poor lubrication.
But I thought it was lubed for life?
Yes it is lubed for the life of the unit.
But it failed because the lube failed!
See - that WAS the life of the unit.

Same with those lovely no-nipple ball joints etc.

 

[Greaser]

quote:

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Originally posted by rgl:
lubed for life is circular reasoning.

Your rear end failed due to poor lubrication.
But I thought it was lubed for life?
Yes it is lubed for the life of the unit.
But it failed because the lube failed!
See - that WAS the life of the unit.

Same with those lovely no-nipple ball joints etc.

---

**** RIGHT...It's all marketing BS to give the masses a false sense of security...trying to save a few bucks on grease zerks and dipsticks

 

[MNgopher]

If its a '97 or later F150, it requires 75w140 synthetic lube in the rear diff, regardless of axle (either the 8.8 or the 9.75 units) and Limited Slip or not. LS requires the friction modifier for the cluch packs. Front diff requires 75w90. All front ends are 8.8 units on the '97 and later F150s.

If it were me, I'd drop the 80w90, and refill with 75w140. I'd also find someone who knows these trucks better than that dealership!

 

[metroplex]

My 2003 E-250 requires SAE 90 for the Dana 60 w/ 3.73 Limited Slip.

I'll be using Redline 80W-140.

 

[SigShooter]

Hey, thanks for all the replies. I got the 75w140 at the dealership and more friction modifier and changed it saturday.Man that stuff is expensive. Three quarts and friction modifier came to 59.00. Well I should be ok for quite awhile as all the gears looked fine from what I could tell when I changed it the first time. Again thanks for the help!!