'98 S-10 error code

'98 S-10, 4.3, auto, 4X4 131,000, error code P1870

A search produces Manufacturer case transmission transfer case switch circuit failure

There are also references to: TSB 02-07-30-001

I'm looking for suggestions and ideas as to what can be expected. ANyone ever tackled this themselves?

TIA

Steve Sharp

Hey, I had a P1870 on my 97 Blazer 4L60E tranny last year. Shifted hard as heck, 1-2 was just like a good bracket racer ought to be. Searched the groups at the time and found that the PCM was detecting blowby at the TCC valve. This is a common problem on this and other GM trannys which are close variants of this one.I used the Sonnax reamer and replacement valve kit and it has been fine since, about 15,000 miles. Bought the valve ($35) and the reamer ($120) from Transtar at

1-800-321-8830. I talked to a guy named Jerry. I am an ASE Master Tech but have not worked in a dealership since the late '80s. The repair involves removing the pan and valve body, removing the valve and reaming its hole, cleaning the whole mess up and getting everything back in the right place. I bought a trans specific manual on E-bay to make sure I got it all right. Not a job for the shade tree mechanic, but if your ability is moderate or above then it's worth a try. If you screw it up a junk yard trannny is $400 - $800. By the way, I parked mine immediately after it started shifting hard. I knew it was an issue and would break hard parts if I continued driving it. If yours has been driven a significant distance it may in fact reuire a complete rebuild.

(inline)

4 things. Book 'em is so original; I've never heard that one before.... But seriously, my post says "junk yard tranny", not guaranteed or "gauranteed" as "Scrib" spells it. Yard trannies are generally 90 day warranty but are never guaranteed to be good since this is the one item on a wrecked vehicle that is IMPOSSIBLE to fully check. They are put in drive and reverse and if they go into gear they get removed and put on the shelf for sale. If you get a bad one they replace it with another. Most yards are not in the business of selling parts they know or even suspect are no good since this is a business killer all around. And finally, if you need a good one call Central City Auto Parts in Columbus, Ohio. (614)-276-9617. They have several in the $400-$800 range, just like I said.