2004 Chevrolet 4l80E Help
Evening , I have been working on a
customers 2004 Chevrolet 2500HD. It has
the 6.0 engine and 4l80E transmission. I've
been building automatic transmissions for
30+ years, and he brought it to me to
rebuild the 4l80E transmission in it for him,
and I just got it done, and was test driving
it, and noticed another issue with it, and I
would like to have some input on what
exactly needs fixed to cure it. The
transmission shifts beautiful after getting
it done, but the problem appears when
coming to a stop. When coming to a
complete stop, and immediately give it
throttle to take back off, it seems as if it is
still in 2nd gear momentarily ,and then
kicks back to 1st gear, and that makes it
jerk. While doing this, I noticed that the
speedometer is slow coming back down to
zero, it doesn't fall back to zero
immediately when coming to a stop. I
know these GM trucks are known for
instrument cluster problems, So I tested it
again, and that time, I completely stopped,
and waited for the speedometer to come
completely back too or just below zero,
and it DOES NOT have the problem if you
do that, it takes off in first and shifts
beautiful just like it is supposed to, but if
you come to a stop, and immediately take
back off, without waiting for the
speedometer to come completely settle
back to, or just below zero, it will take off in
2nd and kick down into 1st everytime,
causing it to jerk when taking off. I tested
my theory several times, and works as its
supposed to, as long as you stay stopped
momentarily, until let the speedometer
completely drop back too zero.
Now, can someone please help me with
what is causing this issue? I need to get it
fixed before letting the customer have his
truck back. I put a new speed sensor in the
transmission while I had it out. Could
speedometer be the problem, since it is
"slow" to come back to zero, and the truck
still thinks it's in motion, when in fact it's at
a stop? I would appreciate some advice on
this so I can get it fixed and back to the
customer. Thank You!
