Slipping 4L60E trans

I recently bought a used 1998 Astro van with the 4L60E trans. At one point while driving it home (long drive) I got a hard shift from time to time and a check engine light. I added some Lucas trans fluid and the problem seemed to get better, but near home I felt the trans freewheel a couple of times. The Check Engine light went out. I borrowed a code scanner and found the typical P1870 code (slipping trans) stored in memory. I then drained enough fluid to get more
Lucas fluid in the trans (I'd only gotten 8 oz or so in it before as it was nearly full.)

I have read about a valve fix that involves reaming out a passage and installing an oversize valve. I have also read that you can 'fix' this problem with a shift kit. My question is, should I do those things or just plan to rebuild or replace the trans and install a shift kit then? The van has 126K miles on it.
-Joel.

Disclaimer: Any opinions above are mine and not those of my employer or anyone else.

I just put a re-man transmission and transfer case in a Bravada to solve this problem. The previous owner apparently drove it a lot while shifting hard from 1-2, and the spline connection was wasted. If it is slipping, and if you want to keep it, I would put in a re-man. It will cost almost twice as much as a rebuild, but the warrantee is about three time as long.

Was a rather tough find. Here's the link if anyone's interested:
http://www.sonnax.com/bulletins/tech/T3-EL-701.pdf

-Tim

I'm familiar with the Sonnax fix, thanks. However I'm more curious if there is any point in putting the effort into this trans or if I should plan on a rebuild, upgrade the clutch packs, replace the torque converter, etc. instead? I suppose at some point fixing the valve is too little too late.

-Joel.

Disclaimer: Any opinions above are mine and not those of my employer or anyone else.

Sonnax.com has a ton of info on the "dreaded" p1870 code.

before you go through the high cost of replacement i have a cheap and dirty trick i have done .drain fluid change filter and two bottles trans-x or transmedic and can sealent stop leak.drive for a week or two you have nothing to lose either way you have to decide.cheap first before the worse it might work out i have done this and it work out twice. just a though.i have 209.456 on my 88 delta olds 4t60 simular to yours transaxle yours is long with tail houseing both have same gear box problem gone.