2007 Yukon..Hard Shifting.

[mentalattica]

I accidentally posted this in the 2021+ area.

Yesterday I had something weird happen and wonder if the two correlate. I used the remote start to let my 2007 Yukon SLT warm up (45 degree weather). Got in and the vents were blowing cold after running for 10-15 minutes. Sat for another 10 minutes and still cold air w/ the temp set to 90. I threw the shifter in reverse to back out of the driveway and my truck jerked back harder than I've ever felt. Put it in drive and it lurched forward the same. Then the shift from 1-2 felt like I hit a speed bump.

I pulled back in the driveway and my coolant was all but gone. I've had a slow leak at the heater core for 2 years and haven't been keeping up with the fluid loss. Topped it off and my heat is working as expected, but oddly my trans is shifting fine now. Since I don't have a trans cooler could the low coolant cause my trans to act weird? Or just purely coincidental? Checked trans fluid and it's not low or burnt/brown.

 

[CaptainAmerica1]

Coincidence

 

[mentalattica]

Coincidence

That's what I figured. I was hoping to hear that it's a common weird thing that happens to NNBSs lol. Guess I'll have to visit a trans shop in the near future.

 

[kbuskill]

You do have a transmission cooler/warmer. It is built into the radiator. All automatic transmissions have this. You just may not have an external/auxiliary cooler.

If you were low on coolant then the transmission fluid was likely very cold/thick and it will definitely affect the way it shifts.

 

[mentalattica]

You do have a transmission cooler/warmer. It is built into the radiator. All automatic transmissions have this. You just may not have an external/auxiliary cooler.

If you were low on coolant then the transmission fluid was likely very cold/thick and it will definitely affect the way it shifts.

Thanks for responding! I had a brain fart when trying to think of the word auxiliary lol. This makes a lot of sense. Drove about 30mi today with no problems... fingers crossed. I need her to last another year or so since there’s not a lot of inventory here for used full-sized trucks.