Hi, I'd like to change my front and rear differential fluids and want to know what oil to use.

It's a 1994 F250 with the 460 and E4OD.

The front is simply marked 50

The rear is not marked

My door sticker lists axle code. C5

Is the rear limited slip requiring the additive?

Also, what's my ratio and ring gear size?

Thanks, Jeff

 

Rear axle is a Sterling 10.25 with 4.10 gears and a limited slip.
Front axle is a Dana 50 twin traction beam, also has 4.10 gears (obviously), with open diff.

A 90 weight oil (80w-90, 75w-90) should be fine for the front. I'm not sure about the rear. It might specify a 140 weight oil (75w-140, 85w-140, etc). Maybe someone else can confirm. Make sure you add the friction modifier additive for the limited slip. A lot of gear oils already have the additive mixed in though, so you may not have to buy it separately.

 

90 is fine (and probably optimal) for the rear if youre not towing anything big or on the regular. Most synthetic diff fluid doesn't require additives (unless it shudders after the cahnge, which is rare).

 

Are you going to add drain plug to the D50?

 

I wish I could add a drain plug but I don't have tools for that. I wondered why it wasn't designed that way. I'll just pump the old fluid out and pump the new fluid in.

I do haul a 9 1/2' camper and sometimes a boat. The camper pretty much lives on the truck. What fluids would you recommend for this application? Most driving is from mid March to mid November, mostly in summer with some 8500' mountains and some hot highways.

 

I'm still not clear on which weight oil to use for front and rear. This trucks primary job is to carry my 9' slide in camper and tow a 17 foot aluminum tracker boat.
75w90 for both?

 

It's not that big of a deal really, you can use 7590 for both no problem. 90 might net you a marginal bump in fuel econ, but 140 would be better protection if you are loading it long periods at high temp.

You wont go wrong with either. Keep 90 up front though.

 

Thanks 89 F2, my mpg is already marginal though

One more question.....is 35° to 40° too cold for rtv? I don't need to drive it for days if necessary.

 

naaa...anything above freezing is good. just put it on, torque up the cover, and forget about it. dont have to do anything fancy with the rtv just to seal a cover.

 

Well, I did it! The project went well except for 1 bolt which was really tight. I just used a piece of pipe on the socket wrench and pulled it gently until it came loose. The surfaces cleaned up real nice and there wasn't much metal on the magnet.

The rear fluid was long over due. It was a little goopy and a nasty brown, gray, black color and it was pretty foamy. I " washed the gears with some extra gear oil and wiped out as much guck as I could. Painted the cover, RTV''d a nice bead and put it all back together.

I went with 80w90 synthetic per the dealers manual and recommendation and a bottle of additive. The bottle of oil did not say it already contained the additive.

The front was pretty easy, just pumped out the old fluid, which looked pretty good, and pumped in the new fluid. I used regular 75w90.

Very satisfied! Time for a cold Coors!