Gary...Your transmission slipping out of 4th gear is probably initially
due to a bad 3/4 slider hub that has also taken out 4th gear
itself...next will be the gear carrier housing ..then...??  I can
appreciate your wanting to do it your self to save $$ but you won't save
any time or much money in the long run. I highly recomend having it
rebuilt professionally...whether by me or whoever...Not a job for the
faint at heart or the shadetree mechanic...P-Mail with any questions and
we can talk prices... or call the toll free #...good luck
Daryl of AA Transaxle
Duvall, WA.(Seattle area)
(425) 788-4070
1-877-377-0773 toll free
http://www.aatransaxle.com (web site)