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Discussion Starter #1
Over the past few months every once and a while my 2000 Silverado 4x4 will feel as if I'm power breaking it when I try and leave a stop light. I've researched a little and have seemed to find that it is a problem with the torque converter. I'll have an increase in rpm's but no increase in speed. It doesnt happen often, just a handful of times in the past 4 or 5 months. Fluid level is fine and it doesnt seem to be burnt. Its been about 30,000 since I flushed and changed the transmission fluid thats in it. The truck has about 120,000 on it (mostly highway), any suggestions would be greatly appreciated.
 

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I know some GM tranies had a problem with torque converters controlled by the computer in the 90’s.

Maybe someone else remembers more..
 

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DTC codes?

My guess would be a valve body issue. Flush the tranny asap.

Are you getting any DTC codes? There are several GM specific codes for transmission issues.

From: motor.com

Diagnostic trouble code P1870 (Transmission Component Slippage) is a General Motors-specific code whose set parameters are determined by transmission type and engine size. The PCM monitors and compares engine speed to vehicle speed after the converter clutch has been commanded ON in either high gear or Overdrive. Should the expected rpm ratio exceed predetermined parameters, DTC 1870 sets. And upon doing so, the PCM elevates the transmission main line pressure and stops converter clutch apply.

A shop with scanner software like that from Autotap can diagnose transmission issues.

Here are some of the parameters on GM vehicles that are scanned/monitored real time by the the Autotap product.

1-2 Shift Desired WOT RPM
1-2 Shift Time
1-2 Shift Time Error
1-2 Shift WOT RPM Adapt
Shift Delay
Shift Error 1-2
Shift Error 2-3
Shift Error 3-4
Shift Pattern
Shift Pressure
Shift RPM
Shift Time 1 2
Shift Time 1-2
Shift Time 2 3
Shift Time 2-3
Shift Time 3-4
Shift Time Error 1 2
Shift Time Error 2 3
Shift Time Error for 1-2 Shift
Shift Time Error for 2-3 Shift
Shift Time Error for 3-4 Shift
Shift Time Error for Latest Shift
Shift Time Pressure Error
 

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Discussion Starter #4
Thanks for the tips...I'll try reflushing it, if that doesnt work I'll check for DTC Codes. I'll let y'all know when I resolve the problem.
 

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yeah the P1870 will more than likely be stored in the codes, having the same issue at the moment with my 99 tahoe too. the recommendation i got was to change out the TCC regulator valve and the AFL valve but not sure how far you have to go into it to do all that. Could be a fun ride, I am by no means a trans guy so unless i get a step by step how to i am going to be lost i can tell it already.
 

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Usually when you have the infamous P1870 code you won't notice any problems like you are having. This P1870 is a slip code. If it sets you will have harsh shifts as the computer goes into a failsafe mode.experiencing.
If your transmission feels like you are power braking the engine it's probably tying up in 2 gears. In any event you need to get your truck scanned. Post the codes after you get it scanned and we'll tell you how to proceed.
 

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yeah the P1870 will more than likely be stored in the codes, having the same issue at the moment with my 99 tahoe too. the recommendation i got was to change out the TCC regulator valve and the AFL valve but not sure how far you have to go into it to do all that. Could be a fun ride, I am by no means a trans guy so unless i get a step by step how to i am going to be lost i can tell it already.
The most common cause is the TCC Regulator. To repair it requires reaming the bore and installing an oversize valve. The reaming tool is expensive and if you don't have one it's cheaper to buy a Reman Valve Body. If you need a valve body I recommend Valve Body Express. Google it and you can look at their products.
 

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This is another good topic that needs to be brought to the light of day again.
 
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