sierraZ71SS

Can a pulse width modulation valve cause my truck to feel like it has a slipping converter? It seems sluggish and wont downshift past third at 65, even when I go to wide open throttle.

sierraZ71SS

Its a 2000 GMC Sierra 5.3 4x4 1/2 Ton.

stevenc

iTrader: (1)

you would likely throw a p1870 code (does not illuminate the CEL) if you were getting that much slipping in the converter. You would also experience full pressure neck breaking shifts from my experience.

sierraZ71SS

Yea I cant check those types of codes. But my pressure does spike quite alot. But only sometimes a real hard shift.

stevenc

iTrader: (1)

If you were throwing that code, it would be maxed all the time.

sierraZ71SS

Well the pulse width modulation valve contols the amount of torqure converter lockup. Not the transmission pressure.

AKlowriderZ71

iTrader: (22)

FYI, a slipping converter(or band) will not set a P1870.

Not sure if that helps you or not, but it is true.

stevenc

iTrader: (1)

right but the code i mentioned will control pressure


when my converter took a dump it set the code.

AKlowriderZ71

iTrader: (22)

Cool, but I've seen plenty of others that did not set the code, so.........

We're both right.

oldred95

When I first got my 99 I noticed the converter was cycling a lot. Every 3-15 seconds it would unlock then relock. No codes and the IIRC I did the P1870 test with the Tech 2 and it all checked good. I installed a transgo HD2 shift kit in it and among other things it shoved that stupid little valve out of the way and made the circuit either on or off and its worked flawlessly ever since. Lockup feels like it could be a 5th gear.