Transmission only one gear

[Jerbou71]

i have a 1994 GMC Sierra with a 5.7 and a auto trans and I took it out today and it seems to take off in one year and never shifts. Seems like it's staying in 3rd the hole time. It won't go into overdrive. Any ideas to look at?

 

[brutpwr]

Are you sure its stuck in third and not second? If its in second it may be in a "limp home" mode. Could be a problem with the transmission or could be an external condition like low voltage from driving with a weak or bad alternator etc.

 

[Jerbou71]

Yea it's 3rd and its in limp mode I think. I think it in my steering column.

 

[Supercharged111]

Check to see the trans is getting 12V. This is a wiring issue. Could even be the internal harness. Either way, not a huge deal to have to fix.