i just bought a '94 f150 4x4 351. 180000 miles, one owner. the transmission fluid was really low, and once i dropped the pan saw that it was pretty black too. so i drained the torque converter and replaced the atf with dextron III/mercon (i would have put in a new filter and gasket, but the parts store sold me the wrong kit, and i needed the truck to be up and running later that day).
anyway, i'm a little worried that i have a rebuild in the near future. this is my first,4x4, rear wheel drive, auto transmission vehicle, so i'll try to describe everything as best as i can. bear with me, and thanks in advance - this is after the fluid change.
shifting from park to reverse, there is a little lag (maybe 1-2 secs), and a gentle bump. same when going from drive to reverse.
when driving, the shifts are smooth, sometimes i can't even tell what gear i'm in (no tach), but i know that i can get into OD because when i turn it off, i feel a downshift.
what really worries me is when i'm on the highway and i floor it, it downshifts, the engine races, but the truck does not pick up the type of speed i would expect from a vehicle with a 5.8L engine.
from what i've gleaned in this forum, the thing is to do is "pull the codes". is that something i have to get a transmission shop to do for me, or can i buy an inexpensive code puller to do it (and what should i expect to pay for such a tool?). i understand that for a '92, that's sufficient, but for a '96 gotta go to a shop. where does my '94 fall? is it even worth it, should i start saving up for a new/used tranny? someone suggested that if i have to go that route, to go with a C6 because this truck is mainly going to be used as a tow vehicle (22ft '72 prowler)
again, many, many thanks. i sincerely appreciate this resource, as it has already helped me as a brand new owner of a f150 (this truck came with completely worn out u-joints, which i was able to diagnose thanks to y'all).

 

Ford Fuel Injection » How To Run a Self-Test Here is a link on how to get any codes without a code reader. However to make life easier you could buy an Equus 3145 code reader for under $30.00.
Black fluid is never a good sign and usually spells trouble but check for codes first.
Hopefully other opinions will follow.