I tossed the crappy stock tranny cooler last year and added a monster. I simply have my tranny lines running straight to it. Can I just remove the return tranny line and pump out about 3 qts. at a time then adding 3 new qts. repeating this procedure until it's new and clean fluid? Also, I haven't changed my rear differential fluid since I bought the truck last summer as the previous owner had it done about 20,000 miles ago. Should I check it also? I haven't really looked at it closely, how do I exactly check that and add if needed?

 

I would remove the pan to change tranny fluid and change filter also.
The rear should be checked to see if it is full but if they changed it then the fluid should be OK but be sure it is full.

 

Here's the whole procedure:

Changing ATF Fluid in a E4OD and 4R100 transmission .: Articles

 

Where do I buy a tranny filter? Man, dropping the pan sure seems like a time consuming process. Mercon ATF is what I need?

 

Not too bad of a job. Get a big catch pan drop one side of the pan to drain then bring the whole thing down and clean it out. replace filter and gasket and put it back together. Be careful not to tighten the bolts too tight. Done, Miller time.

Get a filter at any parts store.

 

MERCON V is now the right fluid. MERCON V replaced MERCON.

 

Okay, I quickly looked under the back of the truck at the differential and didn't see where I check the fluid level. I was in a hurry and didn't lay up under like I should have, it looked as though something was running to the top of the differential.

 

There's a plug, front drivers side of the pumpkin about half way up. I believe a 3/8" ratchet fits in there. Fluid should be level with the bottom of that hole. Here's some good info. Welcome to guzzle's Ford PSD Web Page

 

where is the best place to get the tranny filter and tranny gasket besides the stealership?

 

Get my filters from NAPA. The transmission pan gasket doesn't need to be replaced on our trucks unless it has a problem. Reusable.

 

I checked the rear differential fluid and it appeared pretty clean. I stuck my little finger in there and it seem to be between 1/4 and a 1/2 inch below the fill/drain plug. Should I add until it runs out of the fill hole a little? Also, I bought the truck last summer and don't know what kind of gear oil is in there, what kind should I add?

 

bump, bump

 

Check these out. Install a nice new cover and get fresh fluid all at once.
https://www.ford-trucks.com/forums/6...r-cheap-3.html
https://www.ford-trucks.com/forums/6...-08-cover.html
If you just want to top it off I believe Royal Purple says you can mix there stuff with any existing fluid.