Hard 1-2 shift
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Instructor
Joined: Mar 2011
Posts: 221
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From: Vancouver, BC, Canada
Hard 1-2 shift
have 99 automatic convert which is extremely aggressive when shifting from 1-2. Just started.. Battery was removed during winter.
Can anyone offer advice please?
Can anyone offer advice please?
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From: Hickory NC
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I'm sure you have checked trans fluid level and condition?
The battery was out during winter. How long since the battery was re-installed? Have you had shift points and/or shift firmness programmed in the past?
The battery was out during winter. How long since the battery was re-installed? Have you had shift points and/or shift firmness programmed in the past?
Race Director
Joined: Apr 2017
Posts: 10,247
Likes: 888
From: Hickory NC
2025 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
2020 C5 of the Year Finalist - Modified
St. Jude Donor '17 thru '26
Are you getting any codes? Is the Check Engine Light on? There is an old GM bulletin that may address this problem.
"TSB #01-07-30-023B - (Mar 22, 2002)
Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body)
1996-2000 Chevrolet Corvette (other cars were listed, but not important to the answer)
with 4L60-E Automatic Transmission (RPO M30)
Built Prior to January 15, 2000 (Julian Date 0015)
This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (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. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), 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."
Does the problem go away after driving and the car/trans warming up?
This was addressed in an old CF discussion on an almost identical problem in C6s: http://forums.corvetteforum.com/c6-t...post1557372647
Also, look at the CF “How To” https://www.corvetteforum.com/how-to...roughly-368707
"TSB #01-07-30-023B - (Mar 22, 2002)
Harsh 1-2 Upshift, SES, MIL, or CEL Illuminated, DTC P1870 Set (Replace Valve Body)
1996-2000 Chevrolet Corvette (other cars were listed, but not important to the answer)
with 4L60-E Automatic Transmission (RPO M30)
Built Prior to January 15, 2000 (Julian Date 0015)
This bulletin is being revised to update VIN Breakpoint Date information and revise the Parts Information table. Please discard Corporate Bulletin Number 01-07-30-023A (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. Refer to the Parts Information table below. These valves are used in all transmissions produced after January 15, 2000 (Julian Date 0015), 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."
Does the problem go away after driving and the car/trans warming up?
This was addressed in an old CF discussion on an almost identical problem in C6s: http://forums.corvetteforum.com/c6-t...post1557372647
Also, look at the CF “How To” https://www.corvetteforum.com/how-to...roughly-368707
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