changing diffrential fluid

[s.ga.rider]

Is it necessary to change the diff fluid in a 98 ford f150? The manual says its a lifetime fluid but my repair manual says to change it every 30k miles. Ford recommends changing it only if it is submerged in water. The oil is $10 per bottle at the parts store is it will cost me a good bit to change it. Its got 93k miles on it and I have never changed it on any vehicle. I checked the level and its a bit low. Should be at the hole but I had to stick my finger down the hole as far as I could and could barely reach the fluid. So do I change it or top it off?

 

[cousincletus]

I would go ahead and change it. It probably calls for synthetic. I have Amsoil Series 2000 75W-90 in my Dodge Ram 1500. After close to 100K miles you probably have a decent amount of metal shavings floating around in there. BTW I have noticed almost all mfgs don't recommend the servicing intervals they used to. I'm still sticking to the 30K intervals with dino, 50K with synthetic for transmissions and rears.

 

[Kestas]

I agree. When you drain the old fluid, it's look like metallic paint. All the metal dust floating around can't be good for the old lube.

 

[s.ga.rider]

When I checked it I saw all the metal flakes in it. I couldnt believe they recommend it it to stay in there although I have put over 100k miles on vehicles and never changed it and never had a problem with the rear end.

 

[porcupine73]

Manuf's like to say 'lifetime' on lot's of things because it reduces vehicle total cost of ownership. However, gear oil gets all those shavings in there, oxidizes, shears, etc., and if you do any towing at all it'll only be worse. I too use the amsoil severe gear in the 75w140 weight in some passenger cars with good results.

 

[Stooge]

And if you have a vacuum pump, you don't even have to remove the cover!!

 

[Kestas]

That's how they do it at the dealer. For the anal-retentive it's best to remove the cover, clean the magnet, and spray down the inside with brake cleaner to remove the smut clinging to the inside surfaces. But then there's the added cost of replacing the gasket.

 

[TallPaul]

Seems to me the diffy fluid should be changed after breaking, or maybe about 10,000 miles (a wild guess). Then fill it with Redline gear lube and forget about it.

 

[caprice_2nv]

When was the last time the ring and pinion were replaced? LOL j/k, I don't believe in not changing it either. The 2 years I spent at the Ford dealership saw lots of noisy rearends in 97 and up Ford trucks requiring expensive ring and pinion replacement. Our dealership recommended changing it at 100,000km's (~60k miles) or if submerged in water. The excuse Ford people had was that people were getting water in the diff and not changing the fluid but I have a hard time imagining every one of those customers I had out doing off roading through deep mud and water. Who knows though.

 

[s.ga.rider]

The only problem is getting the fluid. Its almost $15 per quart at advanced and $10 per quart for the walmart brand. I think I read somewhere that it holds just under 4 pints. Does that sound right?
Its making alot of rear end noise in the mornings when everything is cold but goes away when it gets warmed up.

 

[TallPaul]

Owner's manual should tell the diffy capacity, but seems should be more that 4 pints. My motorhome (E350) took nearly 4 quarts. Can't remember how much on the F150.

For the price of diffy lube, might as well buy Redline.

 

[ConfederateTyrant]

Yes, for that insane price, go with Amsoil Severe Gear or Redline gear oil. You can't get much better than those.

 

[alreadygone]

4 pints/pounds is about right. That's 2 of those $10-15 quart bottles. Know folks here will have a fit, but I've never had a problem with silicon gasket in a tube products for rear dif. cover. Also keep in mind full level is 1/2 to 1 inch BELOW fill hole cold to allow for fluid expansion. Full to hole cold and you are almost guaranteed a seal leak in the near future.

Bob

 

[s.ga.rider]

I didnt know that. Its about 1/2 below the hole now. I thought it was low but I guess not.
After looking around on the ford website it says it gold 5.5 pints which would be just under 3 quarts and I have read on there not to worry about a gasket. Just use the sealer and let it sit for about 15 minutes before putting it back together.

 

[cousincletus]

I use Permatex Orange silicone sealer on my diff pan w/good results. That's what the factory uses at Chrysler too. If you have an open diff and no heavy towing I would say it's OK to use dino 75W-90 oil. You can get NAPA or Carquest brand for about 3 bucks per quart. Correct me if I'm wrong, but from my understanding the major advantage of synthetic oil is longer life. If you change every 30K, no need for synthetic. If you have a posi, then add 4 oz. Trans-X diff additive with the conventional. This will lower you costs a good bit.

 

[porcupine73]

The 'if submerged in water' thing I always figured was probably for those using the vehicle for boat launches, although fording streams with the Ford might also result in submersion.

What does the service manual say about how full to fill the diff? If they wanted it filled to some point below the fill hole wouldn't they just make the fill hole lower?

 

[LargeCarManX2]

The front end oil on a 4X4 Ford will need to be sucked out because there is not cover...the center section is like a Ford or Mopar banjo style rear end. I would use Amsoil or Redline with a friction modifer for both front and rear ends.

 

[johnd]

I changed the rear fluid on the Camaro at about 36K. I had a new gasket and the old one looked so good I just reused it. That was about 40K ago, the new one is still in the drawer and the differential hasn't leaked a drop-no sealant used either.

 

[s.ga.rider]

The redline I was looking at(80w-140) says it already has the friction modifier in it so I dont know if I need to add some extra or not.

 

[ConfederateTyrant]

s.ga.rider
Don't use the friction modifier unless you hear differential chatter.