surging

Another one of my silverado problems. When accelerating up an incline, the truck appears to surge between 45-55 mph. The RPM jump back and forth slightly, as i maintain the same amount of pressure on the gas pedal. Never used to do this before. Example, going up slight incline and am in the process of building speed...30, 35, 40, 43....surging begins and stops at about 55mph. Any idea or advise. It only does this surging thing between 43-55 mph, no other speed despite going up same incline at different speeds. What's wrong with my truck !!!!!

IM gonna say take a look at your map sensor. or see if it does this in a different gear. but probably a sensor prob. maby even tps.

What year is your truck? This sounds like torque converter lock-up shudder. From what I understand this is common on newer 4L60E's that use PWM to lock up the converter.

I know that the Transgo Reprogramming kit will fix this problem. Otherwise, I think the valvebody needs to be reworked.

Any tranny guys want to comment on PWM issues?

//2000CAYukon

My truck is a 2000 silverado w/78k miles. Can you talk about this torque converter problem in more detail. I have heard someone else suggest that torque converter may be the prob, but I don't understand much about it. What is this 4l60e you mention and PWM. Again it only does this at the mentioned speed. Thanks for any help YUKON.

4L60-E is the type of transmission in your truck. They are found on many GM products (including my 96 Impala SS and my 2000 Yukon). Starting in 97 (at least I think it is 97), they started using PWM to control the lock-up. This was done for fuel economy. PWM = Pulse Width Modulation.

The converter is only locked up in OD. The shift to OD is usually at 40 MPH. Soon after that the converter is locked up (unless you give it gas). That is why you are seeing this from 43 to 55 MPH.

Is your check engine light on? It will if the problem gets worse. Most likely, you will get a P1870. Has the fluid and filter ever been changed.

The Transgo Reprogramming Kit converts the PWM style lockup to the non-PWM style. The Reprogramming kit can be installed without removing the tranny and will work with the PWM style torque converter (from what I understand). The other benefit to the Reprogramming kit is that is will improve line pressure which means the 3/4 clutch pack will live longer. I bought this kit for Impala SS but have not installed it yet.

I tried to find some info on the Internet but could not really find anything that describes the PWM style of lockup.

Hope this helps!

//2000CAYukon

By the way, if you tap the brake pedal when the surging is happening and it goes away then you know that the problem is with the torque converter locking up.

//2000CAYukon

YUKON, sounds like you know you stuff......just this past month, the service engine light, popped on. Fluid and filter were change at 50K. I guess my next step is to spend some time and money looking into this tran repro kit you are taking about. Hey, I really appreciate your advise, Thanks again.