Zman82

'14 6.2 with with 6 speed, 31k miles.

So I posted this on GM trucks but and not receiving much advice, I know you guys are more gear head oriented like myself.

I'm having an issue with high transmission temps. 220-235 under normal driving unloaded. Tranmission shifts great, fluid level is perfect.

So after some trouble shooting, I found that the transmission cooler line that goes from the passenger side of the cooler back down to the transmission is cool to the touch no matter what temperature the transmission is at. The line that goes from the transmission to the cooler on the driver side, is hot.

I'm pretty confident this indicates a blockage of some sort. At the same time it seems odd that one line is hot (clearly receiving some flow) and one line is cold.

Just looking for ideas on how to diagnose and repair.

I was thinking either the cooler has a blockage or my thermal bypass valve is not opening all the way.

I also don't really know how to add fluid to these if I lose some.

madmann26

iTrader: (7)

A trans flush should unclog it. You could disconnect both ends of both lines and blow compressed air through it. That should unclog it for sure.

Zman82

Even if it's the thermal bypass?

I'm leaning towards the bypass actually, I mean with no experience on clogged coolers, it just seems unlikely a cooler could get blocked in a system that's never been opened.

Someone on the other forum said the transmission oil travels from the passenger side to the driver side. If that's true I think I'm getting flow the other way. Which could mean the lines are reversed.

I mean both the connections come to the same point when then switch from hard line to hose. Maybe it's possible they switched the two hoses during the vehicle build? Don't know

madmann26

iTrader: (7)

I would get some transmission line and route around it and see what happens. That's why it's not recommended to use a bypass because they can fail.

Zman82

Bypass is factory installed on all '14+ trucks with v8's

07Softail

I took my bypass out and plugged the port in which it loops and my temp hasn't reached 180 yet running it hard with a Circle D converter and a Magnuson Blower.

RT

Zman82

Yeah I thought about doing that, being as I'm in new jersey and spend a lot of time in the northeast, I was a little hesitant to remove it.

My buddy came over with his '09 avalanche the other day and his transmission temp was 125 degrees after 30 minutes of driving. Seems like it's too low for this climate?

FFDP

iTrader: (2)

I see about 150-170ish in the summer and now that it's cold out if I can even see 130ish on a longer driver I'm doing okay. So 125 after 30min is about right to me anyway.

I'd maybe stuff some cardboard over the cooler in the winters.

TXsilverado

iTrader: (19)

still under warranty? take it to a dealer and let it be their problem.

Zman82

Anybody know which way the fluid flows?

From the transmission.....

-One line is attached to trans cooler on top passenger side
-One line goes into driver side bottom of radiator, then a short tube to top of driver side trans cooler