92 Rodeo transmission probs

My 92 will drive fine till you hit 35mph. When this happens the car will surge and does not stop unless you shut the car off and start it again and stay below 35mph. Now I have the feelin that it's the tcm, but I have had an impossible time locating one anywhere that isn't $500. Anyone know if this is the prob and if there is another place to get one of these tcm's

does the check transmission light come on?
have you had anyone read the codes from that system? (it's different from the CheckEngineLight (CEL) system.

if you mean that the engine revs and wont slow down you may want to check the rubber boot on the throttle cable
if that is not the case please give us a more detailed description of whats going on