Tranny shudder
 

So I had changed my cracked radiator from my 2005 Chevy blazer S10. Didn't get a new thermostat (yet). I also had to get a transmission flush. The reason being, I tried a used rad from a wrecker that somehow mixed my tranny fluid with coolant. I had a bit of a strawberry milkshake going on in the tranny. I returned the used one and bought a brand new one. But since the whole mixing of fluids ordeal I've had a shuddering at highway speeds 80kms +. Now research tells me this could be my torque converter, and to test for that I was told to not push but put my foot on the brake pedal which caused the RPM to rise whenever the shudder happened. Which worked when the shudder occurs in my vehicle.

MY question is. Can another flush help? Perhaps the coolant wasn't flushed out properly. And also my vehicle seems to run cooler then it did before, it sat smack dab in the middle of the gauge and now sits just over a quarter of the way. I also cannot seem to get heat from the defrost or fans. It all feels like cool ac air. Is this from not changing my thermostat? Perhaps it is stuck open? Sorry for the novel. Any input is appreciated

First a second flush sure won't hurt. The 4L60E transmission is known for its internal leaking which can cause converter issues. I have had two Blazer 4x4s with this transmission. I abused the first one real bad, but got good service from it.
What I have learned & done are a few things. First install a good trans cooler, my preference is a B&M SuperCooler from Jegs or Summit. A small one I think it is a 5"x11" 3/4" thick. I have had 3 of these, one on each of my Blazer 4x4 & I put one on my 98 Jeep GC 5.9 Limited. They work great.
The other thing that has worked for me on several Automatic transmissions is a product called LubeGard. It drops the tranny temps 40+ degrees under heavy usage.
The last thing both my Blazer have thrown PO1870 codes a few times. This is converter lock up. After a lot of research I find that the problem starts in the front pump then the valve body gets with the program & the next thing you have a code. A temp fix that has worked is two things one is have a trans shop install a shift kit with a replacement valve that let more oil into the converter lockup. The second which I like to do first is add a quart of Lucas Transmission Stop Leak. It thickens the oil a little & seems to help with the internal leakage. I did both on my 97 Blazer it went with the Lucas for 80,000 miles then the tranny shop visit, it is still going strong I sold it but I know the guy that bought it. On my 98 Blazer the the SuperCooler is on the LubeGard was put in months ago & last month the Lucas went in. I had the tranny serviced when I bought it & when I bought it the fluid was clean looking.
So that is my experience & success.
As for the cooling system. I never open up one of these newer cooling systems without installing a new thermostat. They are cheap to buy & every time I tried to cheat it bite me every time.
So install a new thermostat & my guess is your problem will be fixed.

You got some cool stuff going on here. I think the last thing you would want to do is put anything close to a thickining agent in there. I don't know if that's what Lucas is.
The more flushes the better. Strawberry shake could srew with your transfer case switch mukking your HVAC actuators.
Low temp is your thermostat stuck open. Who the heck knows what kind of gunk got mixed with what.

I changed the thermostat which helped with my heating issue. Although my mechanic friend feels I may have an air lock in the heater core as a result of not flushing my coolant. It doesn't get nearly as hot as it did and it can be a little finicky. Also, I took it to a transmission shop who experienced the shudder I did upon driving and felt that another flush may not help as the fluid is no longer milky and perhaps the torque converter is shot due to coolant entering the system. So looks like I may not be able to avoid an inexpensive fix. Estimated $1000 for the repairs.