Is this transmission cooling setup normal/acceptable

[L31MaxExpress]

There is no Dex III,and hasn't been since 2011 when GM removed all licenses/certifications. I can tell you that both my '98 C/K,and '96 Impala responded very favorably to being changed over to Dexron VI. Shifts are quick,and smooth.

My 4L85E did not like it. Go with a quality fluid manufacturer like Amsoil, Valvoline, Castrol or Mobil and Dex III will still be Dex III.

 

[El Tigre]

No such thing as Dexron III anymore... Only a variety of unlicensed derivatives.

 

[Pinger]

Back to the subject of fitting a thermostat.
What if there was any failure of the thermostat that prevented oil circulation - how would I know?
The post below (from another thread) suggests TCC unwarranted engagement. But on the highway that would go unnoticed?

My first guess would be the torque converter is locking up. It happens when there is low fluid flow caused by one or several of the valves like the line to lube valve. The reverse boost valve is known to wear as well. If the trans has that many miles on it, probably not a bad idea to go through the whole thing, but you could start with rebuilding the pump and valve body.

Here’s a good explanation:


https://www.sonnax.com/tech_resourc...in-the-pump-pr-converter-cooler-lube-circuits

The linked article suggests consequences of restricted cooler line flow are: ''converter charge and lube oil are restricted. In effect, it's choking off the oil flow, ultimately leading to converter overheating, TCC slip or lube failure in the transmission.''

In normal driving, if the TC/cooler/lube circuit flow was lost - what would alert me to that?

 

[El Tigre]

Not seeing how a thermostat failure would affect fluid flow. There are two paths for the fluid. One,or the other possibly both. But there isn't a "neither" option available...

 

[Pinger]

Not seeing how a thermostat failure would affect fluid flow. There are two paths for the fluid. One,or the other possibly both. But there isn't a "neither" option available...

Providing it's plumbed correctly!
There was a bit of confusion over the ports when I wrote that.

Which line is the 'out' line from the gearbox - the more forward one presumably?
GM manual says I can crank the engine without starting it (disable fuel pump) to verify - safe enough?

And, as I'm researching a fluid change (I've never changed fluid on an auto before) why does all the literature (GM and Haynes manuals) insist on lowering the pan to drain the oil when my pan has a drain plug? Or am I mistaken and my pan doesn't have a drain plug but something else?
Can the oil be drawn via the dipstick tube with a suction pump?

Looking at the re-fill quantities (7.3l pan removal; 12.8l overhaul) is there a way to get the whole 12.8l out rather than leave 5.5l of old fluid in there? Given that some of it is in the TC can I leave the cooler out line off and either crank (no start) or start the engine until fresh fluid displaces it? Or back flush via the same line to push the old back into the gearbox (before re-fitting the pan)?

Does the 7.3l include cooler(s)?

 

[El Tigre]

The line going into the bottom port of the radiator comes from trans. Return line generally has a removable hose clamp,and comes from the aux.cooler. Or top port if vehicle doesn't have an aux.cooler.

 

[Pinger]

The line going into the bottom port of the radiator comes from trans. Return line generally has a removable hose clamp,and comes from the aux.cooler. Or top port if vehicle doesn't have an aux.cooler.

Mine have already been disconnected (and cut) from the radiator so no clues there!

 

[Trlrider]

What does GM recommend for these old 4L60Es? I believe mine was serviced with NAPA GM compatible synthetic not long before I bought it but I’m open to the idea something else is better next time around. I have never been able to find definitive source material saying a specific brand, just Dex III, I’ve always had great luck with Valvoline.


Thank you to everyone who has replied to my original post and continues this conversation, I’ve been a shade tree mechanic for a while but I always learn something from everyone and end up with information I didn’t know I needed or hearing questions I didn’t know I should have.

My personal vehicles use Royal Purple Max ATF which far exceeds OEM Spec.
I believe from reading that the DexVI may have finally matched Royal Purple. We have recently started to stock Dex VI for anything that use to spec DexIII including transfer cases and manual transmissions.

 

[Trlrider]

The line going into the bottom port of the radiator comes from trans. Return line generally has a removable hose clamp,and comes from the aux.cooler. Or top port if vehicle doesn't have an aux.cooler.

Varies depending on manufacturer and/or aftermarket installer. Most Dodge Cummins applications have a factory remote cooler and both inlet and outlet point downward. Their must be a reason Dodge chose not to have a internal radiator trans cooler. We have 5 of them in our shop fleet, and all came from the factory with a remote cooler mounted in front of the radiator. No Internal cooler! Food for thought!

 

[El Tigre]

Assumed we were talking about these (Chevy/GMC) trucks. I should have specified...