Friction modifier or not?

[mobilnissan1991]

Picked up this truck last week, ‘01 F250 XL with the good ‘ol 7.3, 340k miles, for 4k. It needs a few things but couldnt pass up this deal. Itll be my personal use truck as my F150 will strictly be work only. The F250 needs a few things, nothing major, runs and shifts great and I love that it has crank windows and manual locks and vinyl floors. Long bed was an absolute must. Ill also add a gooseneck hitch in the near future.

I want to change all the fluids, I ordered some HPL 75W140 for the rear, it has a 3.73 limited slip rear end. My question is, should I add some Ford XL-3 friction modifier or should the HPL with friction modifier already in it be good enough?

Also, I cannot stand the 20” American Racing wheels on the truck or aftermarket rims in general. If anyone would like to trade for some Ford 16” factory 8 lug steel wheels, please let me know.

 

[charbaby]

Nice find!
I would think that the HPL already has enough FM in it.
Others will know better about whether you should add more FM to the HPL.

 

[Rob_Roy]

I would order a bottle of the Ford FM so you have it on hand. Twice I have serviced Ford LS differentials and had them start to chatter a few months after the fluid change.

See how it does with just the HPL gear oil. If it chatters or pops on turns add the FM.

 

[4wd]

Picked up this truck last week, ‘01 F250 XL with the good ‘ol 7.3, 340k miles, for 4k. It needs a few things but couldnt pass up this deal. Itll be my personal use truck as my F150 will strictly be work only. The F250 needs a few things, nothing major, runs and shifts great and I love that it has crank windows and manual locks and vinyl floors. Long bed was an absolute must. Ill also add a gooseneck hitch in the near future.

I want to change all the fluids, I ordered some HPL 75W140 for the rear, it has a 3.73 limited slip rear end. My question is, should I add some Ford XL-3 friction modifier or should the HPL with friction modifier already in it be good enough?

Also, I cannot stand the 20” American Racing wheels on the truck or aftermarket rims in general. If anyone would like to trade for some Ford 16” factory 8 lug steel wheels, please let me know.

View attachment 303632

Change the gear oil. Find an empty parking lot - windows down and everything quiet - do a few figure 8’s - if short of FM - you can hear/feel the rear end disfunction …

 

[Wireman1987]

I would find out if it will blend with a synthetic gear oil that already contains the modifier. What I found out when I did the rear differential fluid on my 98 f150 I went with a gear oil that already contained friction modifiers for LSD’s I had zero issues afterwards.

 

[dnewton3]

The HPL is fully formulated; leave it alone.

 

[JHZR2]

The only real way to find out is to test it. But I suspect it’s sufficient.

 

[Arc]

I use the stuff with friction modifier already mixed in and have never had a problem. If anyone ever makes a gear oil that smells good I'm going to be their customer for life.

 

[#18FAN]

I use the stuff with friction modifier already mixed in and have never had a problem. If anyone ever makes a gear oil that smells good I'm going to be their customer for life.

You should use HPL you won’t believe that it’s gear oil.

 

[PontiacHO]

Nice truck. Most synthetic gear oils already have the proper amount of friction modifier in them. More would actually reduce the effectiveness of the limited slip unit. Tape off the grill and fenders and rattle can paint that front bumper. It will look new!

 

[mobilnissan1991]

Nice truck. Most synthetic gear oils already have the proper amount of friction modifier in them. More would actually reduce the effectiveness of the limited slip unit. Tape off the grill and fenders and rattle can paint that front bumper. It will look new!

Plenty planned for this truck. Removing and painting bumper, new tailgate, getting rid of those silly rims, a few engine mods, a gooseneck hitch, itll be my workhorse.