Bad Ground? Tranny kick down

[ees]

Last weekend we finally took our truck on its first road trip. All told about 800 miles. On the trip up the weather was nice and the truck performed flawlessly. While were there it rained. On the return trip it now had a speed wobble at 70 mph (probably wheel weight or something).

What was more interesting was the new "feature" the truck had. Whenever I use the turn signal to signal a lane change the torque converter would unlock. This worked with left or right. It was actually a little nice once you got used to it since when in traffic it gave you bit more punch. What was not cool was about 1 out of every 3 times it would drop the cruise control. Which if it happens while merging on a hill can be rather startling.

So this weekend I am going to look at the turn signal grounds. What else could it be?

[Govt issue]

cool, with no codes? I would think the computer would see the rpm flare and lock out the converter. I might have to rig one of those up on my truck. But really, I would think you should replace the multifunction switch. for the computer not to have locked out the converter it has to think everything is ok. The only command that will do this is by touching the brake.The part can be high. So don't take my word for it test.

[ees]

Actually I did get a couple CEL flashes. I forgot about them because they went away immediately. I had grounds stuck in my head since it had been find on the dry day of driving and problematic on the wet day.

Got to remember to check if those codes are still in there...

[JohnC]

I think you're probably on the right track with the signal grounds. Look closely at the ground on the left frame rail in the back. If the rear lights don't ground right the PCM could be seeing brake light voltage and that would cause the converter to unlock. No codes as it is "normal ops".

[diesel65]

I don't know how to provide a link but read my response to "Damork" on his topic "4L80E TCC cycling solutions?", He first posted 4/27/05 and the last post was 5/2/05.
I mentioned about checking the 7way trailer connector, if you have it.

[ees]

William great idea on the trailer connector. I have not really studied its condition, but it is nastier than the one on the old truck. Could be the cuprit.

[DeezlStinson]

I had a similar problem several years ago when my 94 Suburban got "stuck" in second gear. It turned out to be the battery cable connections. I would look for a bad ground or other electrical connection problem.


Regards,

Rick