Car shifts hard

i have a 1998 chevy blazer v6 about 127024 transmission shifts hard out of first gear when i get to 4 gear and it shifts hard.when car werms up really good car shifts find out of first gear but 4th gear still shifts hard.i did change transmission fluid and new filter in it and i check fuild level and it’s full

the valve body probably needs cleaning and or the solenoid needs replacing. The usual symptom of this tranny going bad is hard shifts in all gears when warm.

how do i clean valve body ? is there anything i can put in there to clean it ?

This is what an automatic transmission valve body looks like

Pretty cool, right? It’s sort of a like mechanical computer. Actually a hydraulic computer. In order for it to work correctly, all those passageways have to allow fluid to flow freely, without restriction, and they have to be sealed off from the other ones completely so they hold their pressure consistently for the shifts to go smoothly, without jerking. Ever had a situation where you turn on a faucet and it gurgles and spits water first before sending out a smooth stream of water? And the problem is the seals or seats? Same thing.

On newer transmissions there is often an electrical component added to the control mechanism, usually electro-magnet solenoids which block or allow flow based on computer command. If those stick or their seals fail, that can cause the symptom too, as mentioned by @knfenimore above.

Since you’ve change the fluid and filter, assuming you did that correctly & w/the correct fluid, it looks like it is time for the transmission shop for a further diagnosis. You may not need a complete rebuild. Or you may. But it sounds at least like your planetary gears aren’t the problem. But you may need new clutches, as clutch wear can cause hard shifts too.

If you wanted to see if you might catch a break, you could change the fluid and filter again. It’s nearly impossible to get all of the old fluid out, so another change will clean it up even more than the first change-out. Unlikely to work, but if you are feeling lucky, worth a try.

ok guys i got my blazer look at and here what they come up with so far.transmission fluid is discolored.transmission shifts late between 3rd and 4th at 52 mph.transmission slips between 2nd and 3rd gears at 32 mph.lock up 41-43 mph in and out.i never told them this but i change the transmission fluid about a week before i took it there and when i chk the fluid it was nice and clean and not burned like he said it was.he said most likely it internal damage.for them to take a look in side to see what is wrong with cost me 400.00 and i said hell no

I take it that the fluid and filter did not fix it? I would check the Mechanics Files link and see if there is a reputable transmission shop in your area.

The transmission can have internal problems based not only on the mileage but the age. All of those rubber seals, O-rings, and so on designed to maintain pressures in clutch drums, valve body ports, govenors, and so on can harden with age and quit doing their job.

The great odds are that the transmission has neared the end and must be rebuilt or replaced.
The problem with replacing it with a used unit is that it may also be suffering, or soon will be, from aged rubber.