I have a 2002 F150 FX4 with 4R70W. Only 61,120 miles (was my wife's truck until I bought her a new car).
I thought I had a slipping limited slip rear end clutch until I found out it may not be limited slip at all.
I feel some slipping when taking off from a stop sometimes. More often when making a turn, especially to the right. That's why I was thinking rear axle.
The fluid level is good, been a while since change so thought I might start with that.
Any recommendations on Mercon V trans fluid? Brand? Additives? Filter?
All comments welcome and thank you.

 

Any name brand Mercon V should be fine, don't use additives in the transmission, just fluid. If axle is L/S there should be a letter in front of the number, ex. H9 is 3:55 L/S.
If it's a L/S, add some friction modifier from Ford and see if it helps.

 

Thanks for the input. I have determined the diff is not L/S.

 

I always used Valvoline MaxLife Mercon V and Motorcraft filter. I'll admit I chose that fluid because it was the only Mercon V I could find in my area by the gallon (much cheaper) but it served me well. Drove about 24k to 30k mi per year, changed fluid and filter every Spring until I got rid of it at 225k. Pan was always very clean and never had the slightest issue with the trans, even with a moderate amount of towing cars and boats.

I will say though that sticking to the maintenance schedule religiously is much more important than brand or additives. The best trans fluid in the world is a liability the first time you overheat it. That said, if I stil had that truck today I would be buying Motorcraft fluid off Amazon.

Always assume Motorcraft is the best thing for your truck unless you hear otherwise.

 

Thank you for your comments. I have always been partial to Valvoline products.
I agree that regular maintenance is the key to longevity. I don't think the fluid has ever been changed, of course my wife thinks it has.
So, as I have always done when I get a used vehicle, change ALL the fluids just so you know when it was done and when to do it again.

 

I only know a handful of folks who own or work at transmission shops, but unanimously when rebuilding or changing fluid, they all add Lubegard to the fluid...

 

I've never heard of that, the ad looks good.
Anyone else know about this product?