Hello again.

My last issue with my A/C was resolved and I’m back with another one that just popped up last week.

For info:
2005 Suburban LT w/ just over 226k miles

As I was driving home from work, I set my cruise at 75, as usual. A few minutes later, my rpm’s started jumping up and down between 2000-3000 like I was goosing the pedal. I turned off the cruise control and used my foot to keep my speed. Again, the rpm’s were all over the place and then finally stayed around 2700 at 70 mph.

I shifted down to 3, then back to Drive and there was no change in rpm’s. Stopped and checked trans fluid. Was slightly low so I added some to it. Got back on the interstate and it did the same thing.

At lower speeds it seemed to shift all the way through to 4th gear without an issue, but at highway speeds, it only gets to 3rd.

Could this be the sign that the transmission needs replaced, just a possible bad solenoid or a dirty filter?

Again, any advice and/or ideas on this would be helpful.

 

Step one is a full code scan of all the systems in the truck. Codes help point the direction to look in as the transmission has its own computer as well as the engine.
Every competent shop does a full spectrum code scan before even opening the hood.