I have a customer with an '05 Avalanche with a built 427 that we're having issues with the converter locking/unlocking while cruising. (To get this out of the way, the misfire test is completely disabled.) It's an upgraded trans and stall from Art Carr. I need to give some specifics on the trans first: Art Carr set the K-factor to 140k (he said stock is approx. 110k). He also blocked the PWM (pulse width modulation), so to keep it from destroying the converter.
In fact, this isn't the only truck that I have experienced this issue with. I had another customer with an '02 truck with just a converter upgrade (stock trans), and his did the *exact* same thing. I sent an email to HPT about it back then (about 2.5 years ago). Here are their responses below:
Ken's response (seems like the answer):
Keith's response was:Its a TCC test from the VCM. It's looking for what pressure the TCC slips at and we don't recommend trying to get rid of it.
It only happens during the 4th shift under very light throttle.
Regards,
Ken Cannata
HP Tuners LLC
[email protected]
-----Original Message-----
From: RWTD
Sent: Monday, August 28, 2006 12:33 AM
To: Ken
Subject: Torque Converter Question
Ken and/or Keith,
Do you have any idea what may cause an aftermarket converter to *slightly* lock/unlock when at cruising speed (I believe it's a Yank 3000)? It's on on/off on/off on/off sensation that is perceptible, tho not much. The rpms may raise/lower by just 100, if even if that. It's a continuous situation that happens between 45 and 55 mph on an '02 Silverado, but once over say about 55 mph it doesn't do it anymore. The TCC controls are factory, save for a change in tire size that resulted in the values being raised slightly for lock/unlock. I've even tried various lock/unlock settings, but have only managed to either lower or raise when this is happening.
I logged it, and so did the guy's local dealer with their Tech2, and the logs show that the pcm is commanding it to lock and unlock. I set the duty cycle to 100% (Max) and 90% (Min), and it didn't change a thing.
So, my question is, who else has experienced this, and did you find a fix for it? I don't understand why the "test", that Ken stated is the culprit, just can't be disabled?
Thanks for your help in advance. My customer is patient, but I feel bad for him that this is happening, and I want to get it rectified for him.
Sincerely,
James