My 2004 Gmc Sierra Z71 wont change out of first gear, what could be the problem?

[Dayna]

It Reverses.
It is a automatic, i can't travel faster than 40 km/h it wont switch gears the rpms just go higher. The reverse is fine.

 

[Mazman]

Its a transmition problem which could be dangerous. I suggest you get it checked out.

 

[Savage]

It reverses when you have it in first gear?

Never heard of that before

However, if you have difficulties (or cant) switch gears it sounds like your clutch went out and needs to be replaced

 

[Tim R]

Its an electric problem in the trans itself,have any codes? i'd suspect you do,as it sounds like ecm is in limp mode,try un hooking the battery to reset the computer,if you had any codes it will reset them,try getting the codes off first then go from there,

 

[stiles]

exact same thing happened in my 95.
shift control sensor/module.....i got one for cost (knew guy at transmission shop) and was around $350. That was 7 or 8 years ago.

 

[knuckleheaf27]

unhooking the battery does not clear codes..... i would go to an autoparts store that does free diagnostics for ex. autozone. then you could see what code pops up (if any) and continue to fix the problem from there..... good luck