We have on 06 Lucerne and I keep feeling a "chuggle" or miss only at about 45-50. There is no CEL, no cylinder misses and I've commanded the TCC Solenoid on and off with my diagnostic scanner....... what else could be the issue?

Put the transmission in 3 instead of 4/OD and try the same and see if it does the same.

If it does, stop put the transmission in 2 instead of 3 or 4/OD and try the same and see if it does the same.

Report back.

Also, tell us:

What engine does it have?

How many miles on it?

How many miles on the spark plugs?

How many miles have you owned it?

I have done all that and when I put it in another gear it does not do that..... it has the 3800 engine and it has about 75k miles on it and we have had it since it had 29k. I really can't remember when we replaced the spark plugs and wires, but it has been some time ago.

Okay, with 75,000 miles on it, it'd still be okay on the original plugs unless it spent a lot of time idling etc. like a police car.

This issue sounds like transmission to me. Does it do this while shifting gears, probably from 3rd to 4th ?

What is the level of the transmission fluid?

Has it ever had a transmission service?