Trans issue in and out of OD?

[snowmirage]

I noticed last weekend after a long drive some odd behavior from the transmission.

I had the cruise control set about 55MPH (a bit off due to the tires) and on reasonably flat ground it was like it was kicking down then back up a gear repeatedly.

1st question do we all have the 4L60E?
2nd question is it a 4 speed with over drive?

If I get on the gas more it kicks down and its fine, it seems to be only when under relatively light throttle.

Driving at higher speeds 70 + I didn't notice the problem, but I think that may be because of the weight of the vehicle the tires it wasn't getting into OD?

It's only been a week so I'm not sure if its getting worse or staying the same.

Doing some searching and reading maybe something similar to this?

viewtopic.php?f=26&t=3022&hilit=TCC

[chevycrew]

tire size?

1st question = yes
2nd question = yes


just for info, I run in overdrive with 40s and 4.56 gears at 70+

[snowmirage]

265/70 17 (~31-32") Tires

Forgot to mention that

~107k miles

Flushed the transmission fluid once since 100k miles including a new filter. I didn't notice anything different until just last week.

[bartonmd]

Yeah, common thing... Our TCC is PWM'd to achieve 3-5% slip most of the time it's engaged, and especially at lower loads and lower speeds. The valve body was designed to PWM in and out of lockup, to soften the shift, but since '00, it's been PWMing much more than they were designed for. This causes the piston to basically wear out the aluminum bore in the valve body.

James Downing had a thread on it, a few months ago, as well as his fix. He and my dad (on his '00 Silverado) both went away from the PWM, totally, by changing out to a valve that would not modulate. If you like the softness in the driveability, there is a steel sleeve and piston kit to retrofit in your valve body.

Mike

[snowmirage]

Yes I was reading his thread think its the one I linked at the end of my first post. But while I consider myself quite the gear head automatic transmissions are something I've always stayed away from. So even reading his thread I wasn't really sure if I was having the same problem he had or if it was something else entirely.

As for the softness of the shifts, I don't much care either way I just want it to last and not break.

[Trail X]

After talking with you Sunday, I think you're on the right track. Except it's not OD that's causing the problem. OD is just another word for a 4th gear that emphasizes economy gearing instead of top speed gearing. The TCC is what you're probably feeling, but I don't think its classified as OD. Maybe it's just semantics.

As I said, two options that I see. Get the same shift kit (if I did it again, I would probably only install the Iso-Con valve, which is pretty simple). Or replace the entire valve-body with a reman unit. Either one is probably going to be nearly the same amount of work. Just a matter of how much you spend, and if you want the PWM mode or not.

[snowmirage]

Since I posted this it threw the p1870 code so no I'm not so sure . I think I may have felt it slip once or twice shifting to 3 or 4 since seeing the code but I'm not sure