Check Engine Light With Code P1870 on Chevrolet Suburban 1500

The transmission may develop a harsh 1-2 shift and/or illumination of the Check Engine Light with code P1870 stored. This can be caused by wear of the bore for the TCC isolator and regulator valves in the valve body. This condition does not commonly occur until the transmission reaches normal operating temperature. If the valve body is worn, replacement will be necessary to correct this concern.

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Average mileage: 112,327 (26,500–212,000)
Drive Trains affected: 2WD, 4WD
6 model years affected: 1996, 1997, 1998, 1999, more2000, 2005
14 people reported this problem
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problem details
1997 Chevrolet Suburban 1500 - 4WD 203,000 mi,
shifting fine from 1ST to 2Nd but does not shift into 3RD or overdrive. It has an p1870 code
Drives fine until engine warms up; about 20 minutes, then shifts hard into 1st and 2nd. Turn the car off and start again it goes away for about 5 minutes and comes back again. Check engine light remains on.
first time it through this code, had some other code issues and took care of them and then the p1870 code came on. didnt do nothing as of yet. just looking around to see what everybody else is trying. p.s my truck is a chevy 1997 4x4 1500
1997 Chevrolet Suburban 1500 - 4WD 116,000 mi,
Hard shift 1-2nd gear when transmission is hot Engine code P1870 "transmission slip"
no fix yet, but research I've done shows that gm is aware of this and the fix is to have a shift kit put in. The metal for the part that actually does the shifting at different vaccuum points; wears out and has been fixed on 2000 and newer vehicles. I have not had the money to do this yet but there is a bulletin the dealer can pull up that refrences this trouble code.
1996 Chevrolet Suburban 1500 - 2WD 74,000 mi,
Hard shifting, check engine light on, P1870 code, losing reverse as well. POS...
2005 Chevrolet Suburban 1500 - 4WD 54,794 mi,
Have this same problem and have taken it in many times to dealership who can't find a problem, turn off the warning light and then comes back on and happens again. What did you do about it and has it been fixed?