Rear and front diff. oil recommendations

[Wrench]

I have the controltrac 4x4 driveline and my manual lists two different oils for the diffs. Traction lock rear calls for 80w90 GL-5 spec. The front (which I believe is a Dana 35) lists 4x4 gear oil, Ford p/n F1TZ-19580-A. What is that?

 

[Abom]

Front is regular 80w90 gear oil. Rear (assuming you have the LSD) is 80w90 gear oil with friction modifier.

 

[IZwack]

Just to add in, if your vehicle has a Limited Slip Differntial (LSD as mentioned earlier) in the rear, read the gear oil bottle and see if it already comes with the Friction Modifier -- some gear oils do, some dont. If it does not, you can get the Friction Modifier additive bottle from your local dealer for about $5 USD and pour that the Friction Modifier into the differential before you pour the gear oil.

 

[Abom]

Just to add in, if your vehicle has a Limited Slip Differntial (LSD as mentioned earlier) in the rear, read the gear oil bottle and see if it already comes with the Friction Modifier -- some gear oils do, some dont. If it does not, you can get the Friction Modifier additive bottle from your local dealer for about $5 USD and pour that the Friction Modifier into the differential before you pour the gear oil.

On this note, I am doing my rear when it warms up a bit. The front has already been done, but waiting until the weather warms up for the rear. I used Castrol gear oil 80w90 for the front. It says on the bottle that it has been formulated for Limited Slip Differentials as well. However, how do I know for sure if this is good for our Ex's requirements ?

Castrol's web sites states:

Hypoy C 80W-90: exceeds API MT-1 lubricant for non-synchronized manual transmissions used in buses and heavy duty trucks as well as API Service GL 5 lubricant for extreme pressure conditions. Recommended for service fill of all limited slip differentials in passenger cars and light trucks calling for SAE 80W-90 and API Service GL-5 specifications. Recommended for applications calling for Ford ESP-M2C154-A and GM 9985290 and is Mack GO-H approved.

 

[Wrench]

IZwack - yes, I too have read the spec's on some lube containers and notice that they mention the friction modifyer is already included. I was going to buy a 4L container and use it in both front & rear diff's. I don't suppose there will be any problem putting the friction modifyer in the front diff. I take it that Ford uses the term limited slip and traction lock to describe the same thing?
One thing I noticed in a shop manual was the fluid level should be about a 1/4" below the fill plug hole. Is this for expansion from heat?

 

[IZwack]

One thing I noticed in a shop manual was the fluid level should be about a 1/4" below the fill plug hole. Is this for expansion from heat?

Fill it up to the fill plug hole and call it a day. Typically, I just fill until fluid oozes out and then plug it as quickly as possible. It's a lot better to overfill a differential than underfill it.