99 yukon - Drive Gear Issue

[DHAM]

1999 gmc yukon, installed refreshed engine, nothing special other than stage 2 summit racing cam. also installed new jasper trans, since installation the truck no longer starts with the key, ran a push button to get the truck to start but it will not shift. put into drive and it is automatically in 3rd gear according to scan tool data, scan tool data shows the change in gear selection when manually shifting but no change in the actual gear of the trans, also noticed the dash only lights up the gear indicator intermittently and with the key in a unique position,( partially between acc and crank) just looking for any tips, we are pulling our hair out after spending close to 5k on this rig. any help is appreciated

 

[Tahoe14]

@OR VietVet. @Fless

 

[OR VietVet]

First thing that comes to mind is always checking what you just did. Inspect all wiring for pinched and disconnected power and grounds.

Maybe @NickTransmissions can chime in with transmission diagnostics that would help pinpoint.

Have you double checked the neutral safety switch?

 

[NickTransmissions]

1999 gmc yukon, installed refreshed engine, nothing special other than stage 2 summit racing cam. also installed new jasper trans, since installation the truck no longer starts with the key, ran a push button to get the truck to start but it will not shift. put into drive and it is automatically in 3rd gear according to scan tool data, scan tool data shows the change in gear selection when manually shifting but no change in the actual gear of the trans, also noticed the dash only lights up the gear indicator intermittently and with the key in a unique position,( partially between acc and crank) just looking for any tips, we are pulling our hair out after spending close to 5k on this rig. any help is appreciated

Transmission is in limp mode where you'll only have 3rd gear and reverse when in Drive. Like @OR VietVet said and you have done but re-check all electrical connections, grounds, the PCM itself, the manual lever position sensor on the side of the trans (if this goes bad or is not connected/wiring is damaged, you will not be able to fire up the vehicle).

 

[Eman85]

I would fix the first problem of not starting with the key. Sounds like you rigged yourself into a problem.

 

[DHAM]

Transmission is in limp mode where you'll only have 3rd gear and reverse when in Drive. Like @OR VietVet said and you have done but re-check all electrical connections, grounds, the PCM itself, the manual lever position sensor on the side of the trans (if this goes bad or is not connected/wiring is damaged, you will not be able to fire up the vehicle).

we did install a neutral safety switch and lever position sensor off of a working transmission, we have considered pullin motor and trans back out and inspecting all wiring for pinched areas. i appreciate the info

 

[DHAM]

I would fix the first problem of not starting with the key. Sounds like you rigged yourself into a problem.

i assume the key doesn't work because it doesn't realize the trans is in park. we wired up a quick push button to get the truck fired up. it is most definitely not a permanent thing