Transmission Problems

[Pvtbrn1]

I have a 2000 Silverado 1500 Z71 5.3L

4L60E transmission

My transmission won't shift on its own.

1, 2, and R work just fine but 3 and D only works when I manually shift gears. Whenever I push down the accelerator, when in D or 3, its like it just goes into neutral rather then downshift.

 

The fluid level is correct and the fluid doesn't smell or look bad.

Also my OBD II reader does't read any codes.

 

What could the problem be and how would I fix it?

[rodram]

from what you describe... my opinion is that your 3-4 clutches are worn badly....

 

this is often one of the early signs of a transmission that is wearing out.... the transmission will need to come out of the truck for any diagnosis and/or repair

 

you need to get it to a trusted transmission mechanic for a diagnosis, but from your description I imagine that you need a total transmission and torque convertor rebuild.... once these clutches start to wear, it lis likely that other clutches and valves are also starting to go...

 

you did not state how many miles on this thing.... but an average life for a 4L60E is somewhere around 140,000 miles .... if you get more out of it... that's a bonus..