I have a 3/4 ton with 6.2. It is Automatic trans. It won't shift
from 2 to third while running high rpms. I told him to drive slower.
I drove it and it shifted good while going easy. But when pushing it
to the floor from a stop it wouldn't shift (from 2 to 3) unless I let off the throttle. Other gears seem OK.
The engine starts cutting out when the rpms get high. I am assuming
it is suppsoe to do that to protect from over reving.

It doesn't seem to have a modulater hooked to any vaccum lines.
It doesn't slip. Just doesn't shift.

ANy suggestions ?

I am just a backyard mechanic. Not a very good one at that.

Just ask my son.

what year and what trans? Is it a th-400 3 spd(only used until 1990),a 700r4 (4spd overdrive not normally seen in most 3/4 tons and not used after 1990 with diesels or a 4l80e(some 1990's and all 1991 and newer 6.5's,never seen one behind a 6.2 though),Smitty

New at this..forgot some important info.
It is a 1992. I don't know what kind of
transmission. I know the pics the mechanic
keeps giving me doesn't match. The one I
have has a magnetic pickup sensor of some kind at the
rear of it. This probably doesn't help you any.
If you will tell me how to tell the difference I'll
check it out and get back.

I can fix the engines don't know squat about
the trans.

Sounds like a 4L80. Put a SnapOn scanner or some other on it and give me a code.
mike