Yet, another tranny question?

[hamwow]

I have a 96 k1500 Chevy. I recently had the trans. rebuilt. When I start up and put in gear everything works like it did brand new. After it gets warmed up though if I'm at a stop light or stop sign and take off it will shift really hard from first to second. From second to third it is not too bad ,but it is still a little more than I like it. What would cause this? Is this an easy fix? It is getting a code on the computer that is a 1870 if my memory is correct. I had it read at Autozone and it came up as a trans. slip. In the mean time my fuel pump was going out, and the only way I could get it started was to spray some starter fluid in it. It misfired when I did this which sent up another code for a misfire. At least that is what I think caused the misfire.
I took it back to the guy that did the work, and he said that the reason that it is shifting hard is because of the misfire. He told me to change my plugs and plug wires, and that would take care of my problem. Well guess what? It is still shifting hard. Has anyone ever heard of this? I honestly believe that the transmission is good, this guy has been doing them for 27 years and trucks and suv's is what he specializes in. Anyway someone tell me this is an easy fix. Any help would be monumentally appreciated.

[machinist09]

how recently? recently enough that it is under warranty? if so, take it back, and safe yourself hassle and time.

[hamwow]

Yea I have 11 months left on my warranty, but I would love to know some probable causes.

[Colby 04]

Probably a worn valve body, the transmission guy should fix it if it's warrantied. Here's the TSB about it.

General Motors Informative
GM service bulletin about code p1870 - GM service bulliten about code P1870
Posted By: NJBOB on 2/28/2006

Location: Collingswood, NJ

This GM service bulliten might apply to your vehicle:

TSB # 01-07-30-023A
Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body)
1996 Buick Roadmaster
1996 Cadillac Fleetwood
1999-2000 Cadillac Escalade
1996-2000 Chevrolet Camaro, Corvette
1996-2000 Pontiac Firebird
1996-2000 Chevrolet and GMC Light Duty Truck Models
1996-2000 Oldsmobile Bravada
with 4L60-E Automatic Transmission (RPO M30)
Built Prior to January 15, 1999 (Julian Date 9015)
This bulletin is being revised to update the Parts Information.

Please discard Corporate Bulletin Number 01-07-30-023 (Section 07 -- Transmission/Transaxle).
Condition
Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated.
Diagnosis
Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs.
The scan tool may show a DTC P1870 set as a history code.
A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93°C (200°F).
Cause
The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply.

Important
DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code.
When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result.
This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle).

When the conditions for setting the DTC are met, on the second consecutive trip, a DTC P1870 is stored as a history code.
When the P1870 code is stored, the PCM will turn on the Service Engine Soon (SES), Check Engine Light (CEL), or Malfunction Indicator Lamp (MIL).
Correction
Install a control valve body with the revised TCC regulator and isolator valves. These valves are used in all transmissions produced after January 15, 1999 (Julian Date 9015), and all of the service parts currently available through GMSPO contain revised TCC regulator and isolator valves.

Important
If all of the following conditions are true, it is not necessary to rebuild the transmission or to replace additional transmission components beyond the control valve body.

Transmission operation is normal before the transmission reaches operating temperature, or before DTC P1870 is set (no slips, flares, or missing gears).
The torque converter is not blue or overheated.
The transmission fluid is not burned or has no burned odor.
The transmission fluid pan contains no abnormal debris (clutch material, bronze, brass, or metal fragments

[hamwow]

Thank you Colby. That is exactly what it's doing.

[hamwow]

Would the valve body usually be included on a transmission rebuild? Or is that something seperate?

[Colby 04]

That's something that the details of the warranty would reveal. If you paid for a full rebuild and to have it restored to OEM specs, you didn't get that.

[hamwow]

Thanks again. I'll let you know how this turns out.