"new" 1993 f150. trans problems
 

so my brother just picked up a beautiful 93 f150 4x4 flareside with the 5.0 engine and E4OD trans.

the previous owner said when he bought the truck it had a shift kit in it.

here is the problem though. when driving without a lead foot, the truck shifts beautifully. it also shifts beautifully when you put the tranny in "1" and shift it manually to "2", then "D".

however, if you mash the gas when its in "D" the truck runs up to about 5K rpm, then it shifts into 3rd (maybe 4th? because the rpms drop to about 1K) and there is a huge "THUD", then the truck must realize it shouldnt be in 3rd or 4th, whichever it is, and it shifts back into 1st and revs up to 6K.

after it did this a few times it ended up throwing a code.

Code 637: TOT circuit above maximum voltage
and
Code 624: EPC solenoid circuit fault.

any ideas what is goin on?