Last night I performed the ‘J-mod’ on the van’s 4r70w, this involved enlarging several holes in the valve body separator plate and removing one of the 1-2 shift accumulator springs. The idea behind the j-mod is the same as any auto transmission shift kit; quicker more positive shifts to prolong transmission life. The work was easy but messy, I hate messy.
I also replaced the 2-3 shift accumulator piston since the seals were worn causing an extremely late 2-3 upshift.
Took me about three hours to complete the work, the transmission is now shifting great aside from a sledgehammer 1-2 shift thanks to the spring I removed. I’ll have to drop the pan to re-install the spring, I don’t know why people recommend that as part of the mod since it causes an abusively hard shift.
Info on j-mod:
[url]http://www.crownvic.net/tech/4R70Wnotes.pdf[/url] [url]http://www.tccoa.com/articles/tranny/shiftybusiness.html[/url] [url]http://…]
