99 Taurus 1st gear troubles

We just got this 1999 3.0 vulcan Taurus about 2 months ago.
I had some minor repairs to do, but now the tranny seems to be slipping in first gear after leaving from a stop.

There is a leak in the tranny cooloer line (top line going into the transmission
housing) - which I plan to repair today - could this be a cause of this
condition?

This just started yesterday, but the leak started about a week ago.

There is some tranny fluid loss, but the level on the dipstick is still
in the operational range.

I certainly would not get too excited until after you fix the leak and make sure the proper level and type of fluid is in the transmission.

Keeping in mind that several people have described engine misfires/vacuum leaks as 'slipping transmission,' are you sure it's transmission and not something else? Does the tachometer climb before the vehicle picks up speed? Is it really smooth, or is there some vibration/shaking when accelerating? Do you know when a tune up was last performed on the car?

-Rod

I replaced the fitting ($12.34) and put is some Mercon 5 that I had left over from my F150 tranny fluid/filter job, now all is good.

The Taurus tranny lost about 1.5 quarts more than I thought it did, I topped off the tranny and it runs good as new.

Congrats, and thank you for posting the follow-up!

-Rod