TCC Shudder? Yes another thread, but a slightly different symptom!

[mn_ski]

Ok, so about two weeks ago I got onto a 65 mph 4 lane highway and I noticed for the first time that the truck did a slight shudder and my RPMs were not falling below 2000 like they normally do at cruising speed. Acceleration was smooth up to this point. It was the expected drop in rpm for cruising that didn't happen and the slight shudder. Since then it has happened periodically but not consistently. I get no noises and no issues below 65mph. The shudder seems worse if I accelerate to 70 and then start to cruise. RPMs remain around 2200 and not dropping to 1800 or whatever cruising rpm is at 70mph. 5.7L, 4L60E, totally stock, 219,*** miles. Fluid looked to be at correct level and clean.

Do I have TCC lock up issues? From what I read 45-50 mph seems to be more common. I haven't read of it being at the higher speed. Should I dump in Dr Tranny Shudder Fix?

 

[Schurkey]

The torque converter clutch engages via the ECM based on speed and throttle position (load). It's disengaged with the brake pedal or the ECM.

I'd be making sure the clutch solenoid was working properly, and getting power/ground as needed from the wire harness and ECM. Assure the brake switch is good and appropriately adjusted.

A scan tool will tell you when the TCC is being commanded "on"; so if the converter clutch doesn't engage properly, you know there's a problem to be found.

If the solenoid is being powered and grounded, and the solenoid is actually working--perhaps the torque converter iteself is faulty.

 

[mn_ski]

Thank you for that reply. What are my options for obtaining a good scan tool that will do what you describe? Any apps that can use a bluetooth dongle? Do I need HP tuners, or some other laptop based program?

 

[Schurkey]

If this is your '98 K1500, there's a million options for consumer-grade scan tools at low prices.

I have little use for consumer-grade scan tools. Never worked with one.

I paid extra for a "used" professional-grade scan tool, purchased from eBay fifteen-ish years ago (and it was old even then.) Snap-On MTG2500 with software to connect with vehicles from 1980 1/2 to 2006.

Yes, there are "apps" that can talk to the vehicle computer using your laptop. I've never worked with those, either.

 

[mn_ski]

Driving the truck this Summer the issue appears to be corrected. In March I did a full tune up on the truck. Cap, rotor, plugs, and wires. All ACDelco parts. It appears to have corrected the issue. Not sure how the two would be related but the issue is gone.