what's the best differential oil, regular or synthetic?
- Thread starter 01exp4x4
- Start date
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I doubt many change the rear diff fluid since it is supposedly lubed for life.
I believe your owners manual calls for 75w-140 synthetic for the 9.75 limited slip but you should verify. There are 2 different weight oils spec'd for the rear depending on what you have. You also do need the friction modifier so the clutches do not bind up or chatter with the limited slip.
I believe your owners manual calls for 75w-140 synthetic for the 9.75 limited slip but you should verify. There are 2 different weight oils spec'd for the rear depending on what you have. You also do need the friction modifier so the clutches do not bind up or chatter with the limited slip.
FordandPolaris
Full Access Members
I know the fluid in my front diff is factory original. The stuff in back was changed with the rear axle seals. My opinion is, you do it once, may as well do what Ford recommends, even if it is a bit more spendy. +2 on the friction modifier though, not good to try and run without it.
Qouted from owners manual :
"Your vehicle’s rear axle is filled with a synthetic rear axle lubricant and
is considered lubricated for life. These lubricants are not to be checked
or changed unless a leak is suspected, service is required or the axle has
been submerged in water. The axle lubricant should be changed any time
the axle has been submerged in water."
That clarifies it...
So, ounce I launch the boat, change the oil...
Every time?
That's going to get expensive!
Do you submerge your rear axle when launching??
I may get my rear tires in the water occasionally on a shallow ramp but never so deep that the axle is submerged. My boat is generally completely afloat long before that point. My 2000 also has the vent line run well above the differential to keep water from getting in there. I also think ford is being extra cautious in case the axle or pinion seals leak assuming the axle is sitting under water.
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OP
OP
01exp4x4
Full Access Members
Honestly,
I have not launched with the new 2003 yet.
I had a 2001 before and I definitely made it in the water.
Although not totally submerged, but the water was half way or higher on the back wheels.
The differential and axles on the gen 1 are lower...
The gen 2 is up a few inches higher because of the independent suspension.
Maybe it won't go under water at all...
I have not launched with the new 2003 yet.
I had a 2001 before and I definitely made it in the water.
Although not totally submerged, but the water was half way or higher on the back wheels.
The differential and axles on the gen 1 are lower...
The gen 2 is up a few inches higher because of the independent suspension.
Maybe it won't go under water at all...
FordandPolaris
Full Access Members
My truck has launched boats every summer since 2001, and the rear axle is fine. I have never met anyone in the land of 10,000 lakes (Minnesota) who has lost a rear axle due to launching a boat. Like Tom said, Ford is just being extra cautious.
