99 mountaineer 5.0 AWD front diff fluid

[halo15]

Looking for the correct front diff fluid for my 99 mountaineer AWD 5.0. Manual lists 80w90, amsoil gives you 3 choices: 75w90, 80w90 and 75w110. What is everyone else using? Plan on using the vehicle on the OBX beach sand during the summer. Not sure if that matters.

Thanks

 

[410Fortune]

Factory in 99 would be 85-140 full synthetic
You can run any of those listed above

Diff will work with 80-90w or 85-140 conventional or synthetic
Being awd and always under power in the front diff I would stick with full synthetic for sure

 

[dudemancool1904]

Took my ‘97 AWD to the Valvoline quick change place as I didn’t want to fumble with the front diff (only has one plug) and let them use their vacuum machine to evacuate the fluid. They used 75w-90 in the front and 75w-140 (both synthetic) in the rear. Considering the cost of fluid and the time I saved it was actually worth it using these guys for this type of job.

 

[halo15]

Factory in 99 would be 85-140 full synthetic
You can run any of those listed above

Diff will work with 80-90w or 85-140 conventional or synthetic
Being awd and always under power in the front diff I would stick with full synthetic for sure

Took my ‘97 AWD to the Valvoline quick change place as I didn’t want to fumble with the front diff (only has one plug) and let them use their vacuum machine to evacuate the fluid. They used 75w-90 in the front and 75w-140 (both synthetic) in the rear. Considering the cost of fluid and the time I saved it was actually worth it using these guys for this type of job.

Thanks for the help

 

[CDW6212R]

I've been using Amsoil Severe Gear in all of my diff's, the 140 in the rear, and 110 in the fronts. The best gear oils will do fine using more than one viscosity, meaning the thinnest 90 weight will be okay in the front. Al Aldive used to use that to gain fuel mileage, and 110 in the rear. The Severe Gear is much better than most brands in any severe duty. So be cheap for a for sale vehicle if you have to, but don't skimp if you care about the car. Severe Gear has gone up too, about $15 a quart last time I bought some. It used to be $11-$13 about 10 years ago.

 

[C420sailor]

Apparently Ford found that the LSDs didn’t like the 80W90 as much, so they changed it to 75W140. To make the supply chain lean, and sell more expensive fluid, they spec’d the new synthetic 75/140 for all their diffs.

80W90 will work, and I got 325,000 out of an 8.8 on a diet of 80/90 (and my front is still going on it), but 75/140 is the superior fluid and is what I run now. After seeing how hot an aging diff can get, and how thin the 80/90 can get, the extra viscosity of the 75/140 is nice protection.

 

[halo15]

Apparently Ford found that the LSDs didn’t like the 80W90 as much, so they changed it to 75W140. To make the supply chain lean, and sell more expensive fluid, they spec’d the new synthetic 75/140 for all their diffs.

80W90 will work, and I got 325,000 out of an 8.8 on a diet of 80/90 (and my front is still going on it), but 75/140 is the superior fluid and is what I run now. After seeing how hot an aging diff can get, and how thin the 80/90 can get, the extra viscosity of the 75/140 is nice protection.

I went with the Amsoil 80w90 severe gear up front. Hope that works out. Will work on the rear later. Thanks