Today is my second missed work day, from this problem. I own a '98 2dr, w/159k on each- 4.3L eng & the AT., it has the dash 3 button TC selector. Last yr. i added 1qrt of TransX, AT additive, when the AT would slip at between 40-45MPH (couldn't decide which gear it wanted in, i guess). The TransX worked great (i thought). Yesterday 02-16-10, i warmed the Blazer as usual for 10 min. in garage before heading to work at 630am. Most mornings that usually allows for a smooth shifting 1/2 hr drive.... with the exception of the 1st and 2nd gear shift from 2nd to 3rd of the drive, after the secondary upshift from 2nd - 3rd gear, all subsequent shifts were "right-on" even on steep upward inclines. i found i could remedy the first 2 episodes, by easing off the gas a tad during the transition from 2nd to 3rd. We've been buried in snow recently, the roads being drifted over, made the first shift from 2nd to 3rd much later on my ride(having to drive slow). But once i got out of the drifted area and onto packed snow w/no drifts, i was accelerating like usual, this time it would not engage into 3rd or OD, from 2nd gear. With the gear selector, selected to 3rd, once i reached aprx 30mph, it went from a strong drive to "like" i was accelerating in neutral. NOW it will only go (with the selector in 3rd or OD, up untill it reaches transition speed going up from 2nd gear, then acts like it's in neutral). This scenerio caused me enough concern to return home and inspect the dip-stick....it appeared at first to be at full mark (was and is hard to determine fluid level of tranny fluid when the fluid is nearly invisible compared to the oil level on the oil-dipstick, even while wearing reading glasses and using the headlights for ilumination. After taking multiple spotlit views it was realized the actual lube level was hardly at the tip "if even that high". So i had on hand 3 qrts of tranny lube, which i slowly added taking readings at each 1/4 of a qrt intervals. So last yr when i added the TransX additive the AT worked like a charm (it probably just needed a qrt of tranny fluid). Also it does emit the trouble light, which code was read by a Autozone employee last year...(he acted stupified and said "it's reading a slipping something or other"). That was after i thought i remedied the problem w/ the qrt of TransX. Oh and i checked for leaks, there's only dripping water from melting snow from the under carriage. Oil dipstick is at normal level & not old.(level checked and verified). Air filter is clean as well and no engine problems at all (it's healthy/strong and smooth at idle and accelerating).
So anyway, Short of a $800 plus tranny rebuild; is there a shift modulator replacement, or something that i can try as a remedy?
Mike

 

Any of these sound like your problem:
4L60E Information & Common Problems - Compilation

Your 3-4 clutch pack is likely shot. The TransX was probably just a temporary bandaid. Sure it made things feel better, but it didn't fix the real problem. A rebuild is likely in your future.

And this was probably the code you received:
P1870 - Transmission Component Slipping

The search below will turn up quite a few discussions on this code as well:
https://blazerforum.com/forum/search...ss&query=P1870

 

KYLE, thnx for your response (a quick 1 at that)