My poor beat up old 2000 F-150 extended cab has close to 220K on it. The transmission was replaced with a used low mile transmission about 60K miles back (the truck has been in the family)
Shifts hard going into the higher gear.

Wondering if:

1. Will Mobil 1 Trans Fluid work without harming the trans?

2. Is there any chance that it might help with the hard shifting.

I've only had the truck for the last 5K miles. I doubt that the fluid has ever been changed. Planning on doing a full flush and filter change.

This truck usually only gets used for large item runs at the big box store, but is going on a 350 mile trip this week.

changing out radiator hoses, serpentine, plugs and fixing an oil leak tomorrow.

Any and all comments appreciated.

thanks!

 

It is fine to use in your trans.
It probably will help some. It may not fix the entire problem. There is also a chance the transmission will fail after the fluid change, The chances of that happening are about the same as the chances of it failing if you don't change the fluid.

It's possible that the hard shifts are due to a failure in the trans. If something has failed, new fluid isn't going to fix this.

 

When you change the plugs, torque them to 28 ft/lb to keep them from loosening and blowing out. Motorcraft plugs recommended, without using antiseize.

 

Thanks for the tips.

Just what I expected. I did read that Mercon MUST be used, but the newer trans fluids are supposed to be compatible, so I figured they are.

I'm hoping that something is sticking a little and that new fluid might help. Figure it can't hurt too much, and I know the filter needs to be changed.

I just changed the plugs in my daughter's 06 Expedition - Long story, but none broke. Torqued to 28ft. lbs. I used Champions because they are one piece and I got a deal on them. It's running great now.

I will go with Motor Craft Plugs on mine.

 

If the transmission is out of a 2001 or earlier, it should have a drain plug on the torque converter. Makes a complete fluid replacement a LOT easier. Don't do a chemical flush, just do a fluid replacement.

 

That would be Mercon V, not Mercon.

 

Mercon V replaced Mercon. In 2000 the 4R70W did specify Mercon V, but the 4R100 specified Mercon.

As long as the Mobil 1 meets Mercon V specs, it's fine.

 

If the filter needs to be changed, the trans is junk. The only time the internal filter needs to be changed is when the transmission fails.