Is this transmission cooling setup normal/acceptable

[BhutJolokia]

I bought a 1996 K1500 Sierra SLE about 6 weeks ago and I'm loving it so far. The previous owner installed a secondary fan and cabin temperature gauge for the transmission. Recently I took it up a really steep grade for the first time and saw temperatures of 202 toward the top at highway speed, not off the chart but higher than I'd expect with an external cooler. I should note this was without a big load in the bed or towing.

This is the picture of the current setup with the temperature gauge on the outlet line (above my index finger in the first picture) which flows into the cooler, then a return line out the bottom of the cooler back to the transmission and through an inline filter (which I am also not used to seeing).

What made me examine this after the high temps and then question the setup is also the cap on the top of the radiator in the picture (where my thumb is in the first picture), was this originally for an inlet from the transmission? Because I am used to seeing setups where the radiator's bottom section cools the transmission fluid, then it goes out to a secondary cooler, with the return line from the secondary cooler going back to the transmission. So unless I'm missing something here, the radiator is bypassed. The previous owner did put in a new radiator within the last 10,000 miles.

Temperatures are absolutely fine around town or on the highway on flat to moderate grades. Hopefully someone on here can tell me if this setup is normal and leave it or if I should be adding some lines here, thanks in advance to anyone who can help.

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[Pinger]

What made me examine this after the high temps and then question the setup is also the cap on the top of the radiator in the picture (where my thumb is in the first picture), was this originally for an inlet from the transmission? Because I am used to seeing setups where the radiator's bottom section cools the transmission fluid, then it goes out to a secondary cooler, with the return line from the secondary cooler going back to the transmission. So unless I'm missing something here, the radiator is bypassed. The previous owner did put in a new radiator within the last 10,000 miles.

Same here - I have the same bypased saddle cooler on my C2500 - and no obvious explanation why it was done (coolant isn't leaking across it and while I haven't absolutely proven it doesn't leak externally, a rudimentary check showed no sign of it).

My concern is that I'm losing the pre-warming of the ATF (though coolant rad is cold until thermostat opens) and cooling (though how much cooling there is given quite high coolant temps is debatable). I live in a coldish climate so the pre-warming is more of a concern.

One difference I noticed is that your saddle cooler seems to have different fittings to mine. Mine are threaded (female NPT(?)).
There is another forum member who by-passed their saddle cooler as it was leaking. They aren't too worried about it!

 

[alpinecrick]

Once again, somebody in their infinite wisdom has bypassed the auxiliary cooler/heat exchanger in the radiator tank.......

It seems the auxiliary cooler does serve to cool the fluid quite a bit, so yes, I would hook up the lines and get things back to how they should be.

As Pinger mentioned the auxiliary cooler also warms up the fluid to operating temps—among other things important to keep line pressure reasonable.

There is a slight chance the auxiliary cooler is leaking inside the tank and that’s why it was bypassed.

Where is the temp sender for the gauge located?

 

[BhutJolokia]

Once again, somebody in their infinite wisdom has bypassed the auxiliary cooler/heat exchanger in the radiator tank.......

It seems the auxiliary cooler does serve to cool the fluid quite a bit, so yes, I would hook up the lines and get things back to how they should be.

As Pinger mentioned the auxiliary cooler also warms up the fluid to operating temps—among other things important to keep line pressure reasonable.

There is a slight chance the auxiliary cooler is leaking inside the tank and that’s why it was bypassed.

Where is the temp sender for the gauge located?

If you look at the first picture, my thumb is on the capped radiator inlet, the next finger up is my index pointing at the temp sensor, which is on the transmission outlet line, pre-cooling.

 

[BhutJolokia]

Once again, somebody in their infinite wisdom has bypassed the auxiliary cooler/heat exchanger in the radiator tank.......

It seems the auxiliary cooler does serve to cool the fluid quite a bit, so yes, I would hook up the lines and get things back to how they should be.

As Pinger mentioned the auxiliary cooler also warms up the fluid to operating temps—among other things important to keep line pressure reasonable.

There is a slight chance the auxiliary cooler is leaking inside the tank and that’s why it was bypassed.

Where is the temp sender for the gauge located?

Ok I will plan on tackling that. There is also a metal outlet on the drivers side of the radiator that I assume is for a return line. Does anyone have a link to a hose routing map/diagram for the cooling system on the 1996 K1500 with the 5.7L V8 Vortec L31? It’s not in the Haynes or a Chilton manual...
I’m glad I discovered this early on and not in BFE in the middle of a 9% grade rock garden in 4WD...

 

[El Tigre]

One reason some bypass the cooler built into the radiator is in the event of a leak. The transmission is quickly destroyed. Fluid thermostats can help a lot to warm fluid when cold.

 

[Pinger]

One reason some bypass the cooler built into the radiator is in the event of a leak. The transmission is quickly destroyed. Fluid thermostats can help a lot to warm fluid when cold.

That's possibly a better option for me. Do they just return oil to the box until it's hot enough to need cooling and open to the cooler? Installed externally (presumably)? Do you have a link to a suitable one?

 

[El Tigre]

These are the best I've ever seen/used. Available in 145,165,185,and 215 degree versions.http://www.improvedracing.com/oil-t...sion-differential-fluid-thermostat-p-423.htmlhttp://www.improvedracing.com/oil-t...sion-differential-fluid-thermostat-p-423.html

 

[1989GMCSIERRA]

My F250 diesel has a stand alone trans cooler. I’m adding a 6.0 31 row cooler to cool the transmission as much as possible.

my gmc I have it series from original in radiator cooler to a exterior cooler. When I redo the truck I’m using a Ford V10 cooler as a stand alone cooler and completely bypassing the in radiator cooler.

 

[96-2D-Hoe]

the cap on the top of the radiator in the picture (where my thumb is in the first picture)

That rubber cap is not used. The transmission warmer/cooler lines are fitted below. But they are missing as already mentioned.

I'd also change the rubber cap as they've have been known to fail. (@east302 )

I just put one of these on mine and I'm glad I did and my chair leg stopper was split/perished and close to failing. Bit pricey but should last forever.

https://www.ebay.com/itm/HPS-5-8-16...-bypass-heater-Vacuum-Water-Port/392669704279