1998 Chevy Blazer not shifting out of 1st gear.

Hi, my automatic ‘98 Blazer won’t shift out of 1st
gear when accelerating.

The moment it reaches around 2000 RPMs, it
doesn’t shift into 2nd gear, but instead the RPMs
climb up to 3000 and beyond if I give it more gas.
At this point, the car stops accelerating and
behaves like it is in Neutral.

Top speed is about 10 mph while going on uphills.

It stays in 1st gear no matter if I set it in Drive, 3rd,
or 2nd gear. In 1st gear, I can feel the car engage
and slow down more distinctly than the other
gears.

Reverse gear, Park, and Neutral all work fine.

A few weeks ago, the speedometer began acting
up, flickering between 0-30 mph, and then working
normally once I hit 40 mph. Not sure if this would
be linked.

I noticed last month that the car would rev up
higher than usual when shifting from 1st to 2nd
gear.

Odometer on the car reads around 166,000 miles.
Transmission fluid and filter were changed about
5,000 miles ago. Fluid was black with a small
amount of red color.

I replaced both shift solenoids, but this did not fix
the shifting problem. I also did another fluid
change after replacing the shift solenoids.

Transmission fluid does not smell burnt after
driving it.


If you need more info to answer my question,
please feel free to ask and I will do my best to
include more details.

Forgive me if I included any incorrect terminology. I
am a beginner.

Any help or tips would be appreciated. Thanks.