My 97 Chev truck had a hard shift from 1st to 2nd when hot and the light came on with the 1870 max pressure set. The fix is a $5 spring, not a new transmission like so many dealers wanted to sell me.
In my view, the problem is that the 1st/2nd regulator valve wears the bore in which it slides back and forth in. When this happens the tranny fluid starts leaking by and when the tranny gets hot the viscosity of the fluid is less and more sneaks by. The computer notices this and sets the 1870 code which sets the 1st/2nd fluid pressure to maximum (this maximum pressure results in a hard 1-2 shift).
Anyway, the fix can be made several ways:
1) Replace the entire valve body = $350parts and $350 labor and expet the same problem in a year or two.
2) Bore the the valve area and put in a - Regulator Valve Kit = $200 with reamer drill bit and labor = $100 Check out these Sonnax websites:
3) This 2 hour fix will work on all L460E transmissions up to 1997 without EC3 (they only started putting EC3 in a very few 1997s). If yours is a EC3 type then you will need to do the regulator valve kit install above. You can identify which one yours is by the regulator valve (see the 2nd Sonnax website above).
Here we go: Purchase an "inner" transmission pump spring to replace the factory spring that separates the regulator valve from the isolator valve pieces in the 1-2 shift bore. The replacement spring is the one that slides through the fatter outer pump spring and is the same diameter as the original valve spring only it's twice as long. - $5 Spring can be bought at a dealer or any tranny shop.
Do it yourself by dropping the tranny pan (bend the shift linkage out of the way 1st, then disconnect the wires from the 5 areas of the valve body and note how the shift linkage attaches, then take out the valve body (about 15 bolts - note where the smaller head ones go and be careful when lowering it not to let any of the check balls fall out). Then put the valve body on a workbench and pull the clip so you can slide the regulator valve and short spring out (check the sites above for a visual on which valve you need to work on). Then cram the longer inner pump spring and old regulator valve in and clip it. The idea is to keep the regulator valve apart from the isolator valve. Then put it back together and add tranny fluid.
Note: while you have the valve body off you may want to check the valve body metal plate where the check balls hit it - they can actually beat a hole right through that metal plate. Mine was pretty beat after 225,000 km but I figured it would last another 100,000km anyway so I left it in.
Hope this helps someone out there.
Edited by Tone, 20 November 2005 - 10:50 PM.