Welllll...yes holding it into 4th gear with a bungee cord would work for
awhile...then (as another stated) you would have to hold it firmly by
hand..then...you'd better be close to home....or a shop....
 As far as further damage...really nothing major typically happens that
isn't already out of specs. The gear's syncro teeth are angled about 3
degrees? to keep engagement once pressure is applied after it is engaged.
When the angle is gone...the gear will "sneak"out of gear,usually on
decel, at first and then because of the increased pressure from "popping"
out under load...the problem gets worserer much quickerer....the angle of
the gear teeth is the critical factor in determining when a gear set is
good or bad or marginal as far a staying in gear. The slider assy also
has an effect cause it wears WITH the gear teeth. The old tranny's with
14 million miles on them always need both replaced just cause of the pile
"o" miles on them. There now you all know the secret :)
 At times it may damage a shaft or housing...but it usually doesn't make
much difference....
 You gotta bemember the " I GOTTA get home at all cost" mentality. On a
trip or important day where ya gotta get to work for that meeting...it
doesn't matter what the end result is. Thats human nature. So do what you
gotta do then pay the piper and smile while you do.
Daryl of AA Transaxle
Duvall, WA.(Seattle area)
(425) 788-4070
1-877-377-0773 toll free
http://www.aatransaxle.com (web site)