trans slipping/??

[jasonroman]

well not sure if it is slipping or if problem is elsewhere.
from time to time, ill be driving at a steady speed. be it 40/45/55...either way, at a certain speed and maintaining that speed. and out of no where the truck revs up.
i know bad explination.
but when it does rev out of the norm, its quick. seconds.
for example if im doing 45 and if i had a tach, lets say it was at 3k at 45mph.
when the change comes about, i think i stay at 45 mph, but sounds as if rpms would go from 3k to 35-4k
agian, i know my explination is not too good. but thats what i notice happening.
not sure if its some sort of trans slippage or bad carb or what?

now reason id like to know problem is because i was recentley hit pulling into my driveway.
insurance only gave me 1800 to fix.
id like to take money and put into truck. but if i have a faulty trans or some major probs headed my way, i think i might look to buy another truck and put this one out back for slow but steady work.
thank for any kind of imput or suggestions