1997 trans fluid ??

[car23]

whats is the best fluid to use?

[sgt dave]

Mercon V is a full synthetic and it's what ford uses now

[bleheny]

Originally Posted by car23

whats is the best fluid to use?

If you have the original torque converter and have higher mileage on the trans I would stick with Mercon III, Mercon V is thinner and can speed up failure if you have any existing problems. Ford TSB says that you can now use Mercon V, but it's more expensive and from experience, the reasons stated above.

[car23]

I was wondering about swapping to synthetic but my trans has 300000 mi on it. it seems that the mercon 3 breaks down at about 30000. last time i changed it with castol fluid and used one quart of mobil synthetic 5 30 oil and 2 tubes of that shutter guard. it seemed to work good. my friend who is a trans mech told me to use that combo. he has rebuilt a bunch of these trans. i pull alot of stuff with my truck and everytime it needs changing i get a slip code when the truck isnt pulling something. i think i will stay with mer 3.

[bleheny]

Originally Posted by car23

I was wondering about swapping to synthetic but my trans has 300000 mi on it. it seems that the mercon 3 breaks down at about 30000. last time i changed it with castol fluid and used one quart of mobil synthetic 5 30 oil and 2 tubes of that shutter guard. it seemed to work good. my friend who is a trans mech told me to use that combo. he has rebuilt a bunch of these trans. i pull alot of stuff with my truck and everytime it needs changing i get a slip code when the truck isnt pulling something. i think i will stay with mer 3.

Yep, I would stick with Merc III. I run Merc V because my trans is built, but I still change it between 12000-15000 miles. If you pull a lot, I would keep to those intervals, but that's just my .02