i own a 1998 Honda Accord LX. 270k miles. transmission around 90k. transmission started off with slipping from 1st to 2nd. then it started doing it on 3rd to 4th. now it does it on all 4 gears. and this was like 3-2 weeks ago when it started doing it. it drives normal for like the first 20 min of driving then it starts to slip out of gear. problem seems to go away after turning the car off for about 15-30 min. and it wouldnt do it again after another 30 min of driving. this is my daily so i drive this car everywhere. it does it alot when city driving. but when in the highway, it seems to cruise just fine. tranny fluid is pretty clean and new. checked solenoid gaskets and they looked pretty clean. i need help diagnosing the damn car since i need it to drive to texas this march

 

Well, if that's the original, it's certainly enjoyed a good long life, let's hope there are a few things you could try.

1 - Change fluid - You say it looks fine, when was it last changed? If you are confident in the fluid, then skip this step. Do not do a flush of the transmission fluid if you do this option, just drain and replace (possibly a few times to truly get it all changed).

2 - TCU - This would be my first guess , since you say you already looked at the solenoids. Normally, to me, a solenoid failure would be where only certain gears are not working or shifting really hard, but others work. In this case, since all the gears are misbehaving, that leads me to think a more central issue is acting up, which, to me, is the Transmission computer, the TCU. You can visually inspect it to see if there is anything obvious, but just because it looks fine doesn't mean it is. You mention 20 minutes warm up before failure, whcih also makes me think TCU vs something with the trans itself.
https://www.autoecu.com/honda-accord-tcu-location/

3 - Clean the interior filter out - So these transmission have a filter inside, unfortunately you can't get to it through normal means without taking the transmission out and apart. However, someone figured out where you can drill a hole in the transmission and spray cleaner to clean out the clutch material. Not for the faint of heart, but the pictures and how to do it are here:
https://honda-tech.com/forums/honda-.../#post50667457

 

yea ima change the fluid soon after i drill the drain plug out. the drian plug is stripped. but i should be able to get it out. I'd had a feeling that it was the fluid when it first started doing that. it looks a little darker and smells burnt. thanks for the advice man

 

Remember that changing the fluid on an automatic means you have to change it, then drive a bit, then change it again, then drive, and finally a third time to get all the old stuff out. This is because the fluid in the torque convertor doesn't come out when you drain it, so you have to do this a few times to get it all out.

 

yea your right on that. and now its doing a new thing. when i have it in D4 and i accelerate. it now does this thing where it goes out of gear and back into gear repeatedly until you let off the gas and then it finally grabs the next gear. like all the rest of the problems it does it when the transmission is warmed up. and ik those clutch packs and bands are worn cause it grabs the gears hard like as if you were dumping the clutch on a manual transmission

 

That sounds less likely the TCU is the issue and more likely the clutch material has clogged the filter.