Originally Posted by nine4gmc
ok, i removed the 4.3l engine, 4l60e transmission, engine harness and ECM from the 94 gmc and installed a 5.7l from a running vehicle along with its harness and ECM. i found an exact replacement 4l60e in the salvage yard, they both even have goodwrench remanufactured stickers on them.
the truck is running smooth but this transmission does the exact same thing. only first and reverse, no shifting. i can put it in OD and take off, engine revs up to redline and im traveling about 15-20 mph? i let off the gas and it the rpms drop low but im still coasting fast, instead of slowing down relative to the rpms.
i can goose it while coasting and it will take off again but high rpms and no shift.
it does the same thing in 1,2,3 as it does in OD. low and reverse work seemingly fine.
any home diagnosis i can do, its apparently a common issue with these goodwrench trans...
if the shifter is in o.d. and you run it up in 1st gear and let off and theres no shift, it is going to coast as there is no engine braking unless your in manual low.
from here, you need to find out if the shift solenoids are getting command to shift, you already have power going to the trans because if you didnt, it would have 3rd gear starts, and only have manual 2nd other than that.
from what your describing, a code scan is in order. if you have a decent scan tool with a live data stream, that could help you find what the computer is doing.
i will say it is rather odd to change all this stuff out including the pcm and still have the same symptom.