I have a 21 f150 with 48,000 miles does anyone know when i should change trans fluid, my dealer is telling me 100,000 miles

 

I'm of the opinion of not waiting to 100K. If it were mine, I would change it.

 

Owners manual does.....

 

IMO, It depends on use, and how long you’ll own the truck. Am confident transmissions today go 150,000 without an oil change. If plans are to keep it longer it might be better to change trans oil and filter by 60k, and every 30-60k thereafter depending on use. The 6R80 in my 2011 has towed often and shifts perfect at 207k miles with the above maintenance practice.

Talk to local hot rod guys and find out what transmission shop they use if looking for someone to change the oil/filter for you.

 

I do all of my transmission services at 30k regardless of make and model

 

This. You want your trans to liv e as long as possible? Changing it early in it's life and then regular service after will get you the longest life possible. The majority of clutch material and other fine debris comes out in the first 20-30K miles so if you get that out, the valve body stays clean and all those little passages and such don't have crap build up in them and clog etc. If you plan to keep the truck, it is a worth while maint thing to do.

100K is BS. Yeah they will go that long but you'll wear the crap out of the valve body. Manufacturers want to sell you a new car as soon as they can-

 

I'm personally in between the two camps. I'm at 87k and just scheduled to get transmission serviced (dropped pan, not flush). I figure a little over 1/2 of the Ford recommended 150k is safe enough.

 

Doesn't matter what Ford says, knowing what we know about these 10 speeds, cycle in new fluid (extraction, 4-6 quarts) every 30k minimum. These transmissions aren't perfect and are particularly sensitive to having CLEAN fluid at the proper level.

 

I agree with the 25 - 50K mile transmission change interval, owner's manual says 150K but to me a few hundred spent on the frequent change is much better and cheaper than having transmission work or replacement. If you do moderate hauling, towing and off road then this is considered Severe for the maintenance intervals. I have yet to find out if there is a hidden small dip stick or a side of the transmission sight window, plug for verifying the fluid level. I bought my new 23' STX 4 x 4 5L in April and haven't been motivated to do the under truck shoulder walk in the heat to find out.

 

there is a dip stick can be accessed under the truck, it’s close to the exhaust pipe and you suppose to check it when tranny is hot to get an accurate reading. Gotta love ford engineering