!!!!!!!!transmission help needed bad!!!!!!!!!

[ChickenRammit]

ok so i installed a '96 vortec 5.7/4l60e combo. engine fires up 1st try. transmission is acting like an asshole. before i installed it i took the transmission to a tranny shop and had it rebuilt. after its all installed, it won't shift into 1st gear. i take it back to tranny shop and they hook up their test equipment and supply power to the shift selenoids and its shifting perfect. so basically the 1-2 shift selenoid is not getting a signal. so they hook up to the computer in the truck and the computer is sending the signal. so then we are assuming that there is a bad wire going from the cpu to the tranny. at this point the tranny shop just lets the truck sit there for about 2 weeks and do nothing about it. i got impatient and towed the truck home figuring its just a bad wire, i'll fix it myself. i drop the pan and connect an ohm tester to the light green wire that goes to the 1-2 shift selenoid and i connect the ohm tester to the opposite end of the wire up at the cpu, its conducting perfectly. now i'm stumped. the engine came out of a wrecked truck, so could there be some internal damage in the cpu to where the signal it is sending to the trans is no making it to the prong where the 1-2 wire connects to the cpu. please help!!!!!!!!!!

 

[ChickenRammit]

ttt

 

[1-ton]

This is not my area of expertise, but I will give it a shot. I assume there must be some type of eclectrical (wiring) input from the shft lever column to the ECM, which tells the ECM what gear the shift lever is in. If you are getting current from the ECM to the trans solonioid, then maybe the ECM is not getting a singnal from the shifter column to the ECM, telling it what gear it is in. Check the wiring from the shift lever column to the ECM. This is just a guess. I hope this reply gets some other people, with more expertise in this area to add some more input on this.

 

[4X4HIGH]

Check for the most obvious but always over looked when it is thought to be an electrical problem, GROUNDS. GM uses grounds to activate things, not postive.

 

[sweetk30]

make sure your computer has not gone into limp home mode. if so you dont have the correct stuff bypassed. limp home mode will hold it in second gear so you can get home but not do to much damage.

and also the 96ish and up have the detent switch on the side of the tranny at the shifter shaft. do a test of the positions and stuff from a test sheet . it might be bad.

 

[ChickenRammit]

yeah, i'm a dumb ass. transmission people shold've picked up on this, but there is a wire E that supplies 12 volts to the shift selenoids that i didnt have connected. the tbi and tpi engine swap book i've been reading was sort of vague in the wiring chapter so i simply didnt know about this wire until i started looking at the transmission wiring digrams in the shop manual. truck runs great now, it has twice the power with the vortec in it. thanks for everyone help.