Just thought about it some more, it will happen almost anytime i am in 4th. The car has to be warmed up though, after say 1 hour on the highway.

When it does this how much does the RPM change?, perhaps 400 RPM or so?

That sounds about right. The engine does not rev way up or down, but its just enough to see it on the tachometer. At least 300RPM, but maybe you are right with 400.

2 things come to mind. A bad crank sensor can cause surging. Another thing is the TCC solenoid switch. Take a look at this write up. https://www.gmforum.com/electrical-133/tcc-solenoid-switch-284972/

Thanks. I will try to check the TCC by the test you note in the thread today or tomorrow. If not, I am guessing i can find the crank sensor and test if it is bad. Is there a thread for testing the crank sensor (just did a quick search, but could not find it)? I appreciate the help.

On a personal note, nice to meet someone from Sheyboygan. My grandma used to live there, King Park, near the lake on the South side. My great uncle owned Miesfeld'* meat market, good brats.

First, testing the crank sensor is not easy and really needs an oscilloscope, but I do have a write up here, it'* a bit involved but might help. https://www.gmforum.com/trouble-shooting-test-procedures-141/icm-test-299761/

As a kid I live about 4 blocks from Kings park no 11th st and High Ave. Now I live about half a mile from Miesfelds. Great meat.

I could actually see Kings park from my Grandma'*, she lived on Spring Ave until a year ago.

Tried to test the TCC switch as you suggest. When i apply pressure to the brake at 50, the RPMs do not change at all. Make me think the switch is not just incorrectly adjusted, but failed. I will attempt to get it out and test it as you indicate in the write-up. I really appreciate the help. Thanks.

Merry Christmas!!

It'* a bit awkward getting to it, but it'* not to bad.

So the shift kit is working great. It has really helped, and the shifts are much firmer. It has not thrown any codes either. I have only one suggestion, which i was not clever enough to try. When i did the shift kit, I only installed the parts in the 1-2 and 2-3 accumulators. It calls for two springs in the 1-2 and three springs for the 2-3. There is a spring intended for the 3-4 (i think) installed through the side panel. I obviously did not install these parts, but i wish i would have put that extra spring in the 1-2. It is just a little slow, and i think it could have gone to good use firming it up just a little more.

Dan, thanks for the write up. It helped a lot. Just about to finally look at the TCC switch today too. Why i waited until Feb is beyond me.

The extra springs help a bit, but not really necessary, they just help move things a bit faster. Shortening up the stroke does the most.