> I recently finished a transplant of a 94 3500 2 wd 454 and
> into a 90 2500 that had a 4.3 and 400 Trans. all the
> components were swapped harness, comp, sensors ect .
> My problem is the Trans didn't work. 2nd gear only, the Trans
> was sitting
> on my garage floor empty for about 8 mo while the motor was
> When i dropped the pan to change the filter and gasket there
> was some water in the pan not even enough to cover the whole
> pan bottom.
> i found too the original harness was leaking through the case
> connector and some of the connector ends were broken
> so in went the new gm harness now i had to swap the out side
> plug over
> sooo--- the comp set the check engine light codes 56,81,82
> and 83 i think my first guess was no power checked all the
> pin outs again
> plug it in disconnected and re-connect the battery great no
> codes , and still only 2nd gear
> OK maybe the problem is in the valve body ,maybe water ,from
> went through valve body while apart. why not install shift kit
> I installed a trans go re-programing kit new plate gaskets
> ect. by the book! and i did find what i thought were stuck
> valves when changing some springs out. filter/ screen was
> re-assemble still only second gear
> other notes snap on scanner wont communicate with comp.
> aftermarket chip z-industries chip for a 1991 454 ss 1500
> race auto
> engine runs fine, i can get trouble codes from idiot light
> i am questioning ALDL harness its the 90 Chevy and the serial
> data port
> is port (E) im showing on the 94 a port (M) for the data port
> Any Help will be appreciated
Itís probably stuck in 2nd gear...limp home mode. I got my 4L80E fixed
last month,by a guy whoís a trans tech at a gmc dealership,and on the
side at his parentís farm!
Mine was stuck in 2nd.He replaced the stock 1 - 2 and 2 - 3 solenoids
(stockerís were re-designed,replacements are better),PCM, (Powertrain
Control Module),("Computer"),Cylinder temp.sensor (Not the guage
one!),and a few bad connectors & burned wires.
He said the PCM has to have the correct "PROM"(Programmable
Read-Only Memory) chip,or have it"Burned", or "Flashed" at the
This chip tells the computer what type of trans you have, what
parameters are to be used,what engine signals are important, what size
engine you have.....etc.
So: My guess is maybe you have the wrong harness,PCM,or PROM chip
needs to be "Burned" (Programmed).
Hang in there....these are one heck of a powerhouse transmission.
About 75% of the parts are TH-400ís,with another gear (OD),and a
lock-up torque converter.
They also weigh about 100 LBS. more than a 4L60E !