1999 chevy silverado...drives in 1st & 2nd gear, but slips when it gets to 3rd gear, then shifts back to 2nd

Great question.
PRNDL (is the cable good both ends) shifer>?
R good
L good?
Drive , selected and 1st gear car will not move ?
or 1st gear car moves good but will not up-shift.
1,2,3,4 gear. 1st slips or works??????????????
name 4T60 (transverse 4speed box) GM./
DIY?
check fuse first
scan the PCM (the PCM has TCM) the TCM tranny brain and if TCM is not happy it tells you why
so all carsChev 1992+ must be scanned, first.
the 4t60E box is electronic shifted. scan it.
what is miles on car.? 100k,300Kwhat?

causes are vast, (ever see inside any A/T box)
the next test in the book is pump pressure test
PRNDL

Remove trans pan and inspect shift solenoids. These are prone to come apart and visual inspection often finds the problem. Replacement units include a bracket to keep this from happening again.

1 Ck A/T fluid level & quality
2 Scan/ck for code(s)
3 With scan tool connected,road test vehicle/Ck parameters....
....time for a pro !!

If you need further help, reach me via phone at https://www.6ya.com/expert/ralph_2f0886b7d6af32ce

From what you are describing, it is possible either the 3-4 actuator is no longer playing with the 3rd & 4th clutch packs, only way to know for certain is to hook up the good ol' pressure gauge to trans. system, yeah, you think the Chevrolet dealer should know this right?

Sell it now if you can!
Smiles

not enough trans fluid...... if it slips after a trans flush reuse the old fluid its got the old clutch dust in it and the clutches will grab better....

If you have used the vehicle like that for as little as
a few days, you stand little chance of saving the trans
from a complete rebuild

You need a trans shop or a place you like & trust to
road test & diagnose

I think your beyond a solenoid or module fix, since
you have been using it & it slips as well ,instead of
proper shifting

I have a 92 Crown Vic first and second works fine reverse works fine when it shifts in the third gear it goes to slipping and overdraft can you help me fix this problem thank you

i got a 1996 chev. blazer s-s10 4.3 engine 4x4.problem i got is i got 1st 2nd & overdrive & reverse but no 3rd gear what should i do

I would have to say it is the tranny check the fluid make sure it is clean and at the correct level

It just holds 2nd forever. Is the 1-2 shift point high?