Borg and Warner made the t-5, not GM, Ford or Chrysler. B&W sold the trannys to GM/Ford/Chrysler and others but didn't change the mechanical design for Ford or Chrysler. So, other than the bellhousing bolt pattern, number of spines on the input and output shafts, and gear ratios, there isn't any difference in the designs of the tranny's between who put them in their cars. A NWC t-5 from ford is the same as a NWC t-5 from chevy. The syncros, bearings and guts are pretty much interchangable.
I looked at the manual published by TREMEC, the people who bought Borg-Warner's t-5 design and now manufacture only World-Class T-5's under the Tremec label and makes a tidy profit selling service parts. I paid attention to the part that said "MOST t-5s use ATF. Please refer to your owner's manual..."
I also looked on the internet and talked to several tranny people before making up my mind that I belived that the NWC tranny's need gear oil and that ATF is not viscous enough for the older bearings and brass syncros.
I guess reasonble minds can disagree- I'm going with gear oil (synthetic syncromesh), you guys go with ATF. Hopefully neither of us will suffer because of it!
I'm also open to all kinds of new information. If somebody knows of a manufacturers service bulletin, from GM or Ford, AMC or Chrysler that applies to Non-World Class t-5s that says 'use ATF', please let me know!
I think they stopped making Non-world Class tranny's almost 20 years ago (1988?) and people are just used to dealing World-Class trannys that need ATF.
