03regcab sierra

iTrader: (7)

Can someone help me diagnose this problem. I did a 4l80e swap on a friends truck and when he went to get it tuned it wouldn't take first gear.
I did have to replace the internal wire harness because the one on there was broken. Is there a difference in year models with these harnesses? Could that still be the issue?

smokeshow

iTrader: (16)

Wouldn't take first gear? You mean it wouldn't start in first, so its stuck in 2nd? What method did you use to convert to 80e?

nonnieselman

iTrader: (10)

Yea sounds like a wiring or tune issue.

check the fuses under the hood?

i think theres a 10 or 15 amp fuse that runs the trans.

03sierraslt

iTrader: (22)

As stated, what year truck, what method was used wiring wise to convert and is the tune segment swapped or was the relay method used? You said you changed a wire harness, you mean the internal trans harness? Wasn't it new? There are some differences between the internal harnesses depending on year, I know the EPC solenoid had some changes as well as a couple other things just dont recall exactly what off the top of my head.

03regcab sierra

iTrader: (7)

Ok truck is a 2000 and the trans was to be from 97 and down I believe. I replaced the internal wire harness because when I had the trans swap done went to fill it with oil it was leaking through the plugin. I have a couple pics to show on that. I used a Nelson conversion harness to to the swap and the tuner did a segment swap on it to. It just won't start off in first gear. Maybe the tuner will chime in as well on what it's doing.

AKlowriderZ71

iTrader: (22)

Is it throwing any DTC's?

smokeshow

iTrader: (16)

Is first the only gear it won't go into? Manual first?

00ss408

it takes off in 2nd and if u do 1st manuely it doesnt do anything

03sierraslt

iTrader: (22)

Are you sure the trans is actually going into 1st and it the shift cable is adjusted correctly.

00ss408

it doesnt go into 1st wat i ment was when u do it manually it doesnt get 1st either it just stays in 2nd