Accepted Answer

The J-mod is short for the Jerry Modification, after a guy named Jerry Wroblewski, who I beilieve was a tranny engineer at Ford, and is a recognized expert on the AOD and 4R70W. The J-mod consists of a bunch of modifications, which are outlined in detail in a few articles at the Thunderbird Cougar Club of America website, start learning by clicking below to get to their tech articles on transmissions:
http://www.tccoa.com/articles/tranny/index.html


My brother has a 93 Mark VIII, and he built a new trans for it using these articles and info from the Mark VIII forums:
http://www.markviii.org/htdocs/dc/dcboard.php

http://www.lincolnsonline.com/forum/forumdisplay.php?f=241

http://www.lincolnsclub.org/vbulletin/forumdisplay.php?f=77

I was not personally involved in the build, but it did involve servicing the accumulator (I think they just take the spring out, resurface the bore and replace the piston). He also sourced a beefier case from a 97-98 F-150 5.4L with a 4R70W and used it to start his build. There are lots of aftermarket parts for beefing up clutches and valve body modifications. The other thing I remember he did was to add an external fluid line to lubricate the rear bushing better, as this is thought to be a weak point.

There are several different levels of shift firmness you can select when you build it, his is a street car so he tried to keep it civil, but it is still much firmer than stock, and will kick pretty good if you let off the gas right before the shift. Under hard accel it is definitely good.

Expert:	Brian
Pos. Feedback:	100.0 %
Accepts:
Answered:	7/28/2008

Auto Service Technician

5 years Ford Technical Hotline/Service Engineer. 2005 Ford Master Cert. Automotive Technology degree