between these 2
http://cgi.ebay.com/ebaymotors/SC-4L...Q5fAccessories

and
http://cgi.ebay.com/ebaymotors/4L60E...Q5fAccessories

ive got only 98k on my 99 wondering what the difference between the 2 and ease of installation

 

I couldn't tell you exactly the differences, but what I do know that makes me shy away from those parts are this fact. I was told that the electronics in the 4L60E transmissions were updated every 2 years. Making parts not easily transferable to other model years, so when people say this will work from 1994 or whatever to 2000 something it makes me leanient to try them.

 

If you're still wondering:

The Sonnax kit requires a reaming tool (not cheap) to enlarge the TCC valve bore to fit the Sonnax valve. The Transgo kit just has you drop an imperceptibly larger valve into the bore. Of course if the bore's extremely worn, the Transgo valve will have too much play to eliminate the 1870 code.

If you're cracking into that valve body for the first time, you might find this walk-through useful: http://www.youtube.com/watch?v=rp7lzRFpttM. There's a second part as well, also on YT.