'02 GMC Sierra 4.3l RPM Hang Manual Trans NV3500

[defektes]

Hello guys,

 

I am getting my butt kicked here with my 2002 GMC Sierra 4.3l, Base, Vin x, and NV3500 5 Speed Standard Transmission with 225k miles.

 

I am fighting a RPM hang issue when I shift between gears, the clutch is not slipping, the RPMS just catch for a few seconds when shifting. For example I shift out of second into third the time between shifts the RPMS will maintain at 3k, wont increase and wont decrease for a few seconds. It happens more at higher RPMS, and less often at lower RPMs.

 

I have tried the following: I replaced the IAC valve with a new one because it was carboned up and when I removed it to clean the o-ring was damaged, figured I replace it. I also replaced a failed PCV elbow and checked the PCV valve and all vaccum systems for failures. I replaced the TPS sensor because it was getting lazy according to my scan tool. I also cleaned the throttle body and checked all linkages for binding.

 

The IAC valve replacement seemed to help, but not cure the problem. I am a industrial mechanic and have fluke meters and good mechanical aptitute.

 

Any and all help is appreciated, willing to purchase any testing equipment needed to diagnose the issue. No CEL are present. I also have a scan tool with live data.

 

Thank you.

[defektes]

On 6/25/2018 at 8:32 AM, defektes said:

Hello guys,

 

I am getting my butt kicked here with my 2002 GMC Sierra 4.3l, Base, Vin x, and NV3500 5 Speed Standard Transmission with 225k miles.

 

I am fighting a RPM hang issue when I shift between gears, the clutch is not slipping, the RPMS just catch for a few seconds when shifting. For example I shift out of second into third the time between shifts the RPMS will maintain at 3k, wont increase and wont decrease for a few seconds. It happens more at higher RPMS, and less often at lower RPMs.

 

I have tried the following: I replaced the IAC valve with a new one because it was carboned up and when I removed it to clean the o-ring was damaged, figured I replace it. I also replaced a failed PCV elbow and checked the PCV valve and all vaccum systems for failures. I replaced the TPS sensor because it was getting lazy according to my scan tool. I also cleaned the throttle body and checked all linkages for binding.

 

The IAC valve replacement seemed to help, but not cure the problem. I am a industrial mechanic and have fluke meters and good mechanical aptitute.

 

Any and all help is appreciated, willing to purchase any testing equipment needed to diagnose the issue. No CEL are present. I also have a scan tool with live data.

 

Thank you.

 

Ok I wanted to update this.

 

I THINK I found the issue and will post back when I have replaced the part. I beleive the speed sensor on the trans is causing the issue. I disconnected the sensor and it re-created the problem in every RPM and every shift for about 6 miles. I will replace the sensor when I get paid and report back. Never would have thought it was the speed sensor, the way I came to this was I noticed while reving the engine in neutral at higher RPMs the speed on the speedo would increase.

[defektes]

Ok the speed sensor did not cure it. I did notice the truck runs better for a little when the battery is disconnected resetting the sensors. Do not know where to look next..