Transmission Thermostat Delete Pros vs. Cons

mikeyk101 · August 25, 2023

Part # is 15-11113 It also listed as part # 12674634 I bought it off Amazon as a warehouse deal and it was quite a bit cheaper. I checked it real close and looked fine. Here is a link to it and they have one warehouse deal on it now.

GM Genuine Parts 15-11113 Water Pump Outlet Assembly with Thermostat https://a.co/d/1R3PwXa

Grumpy Bear · August 25, 2023

2 hours ago, BlaineBug said:

Just remember that the engine computer is going to be tuned for that 207' thermostat.

It's tuned to a wide range. Just like the transmission it starts at ambient. With a thermostat of 160F you will need a tune. At 170F and up. No tune required. I run a Riesch Racing 170 F in an IPSCO housing in the top hose and have for years. Zero issues over 173K miles. Katech has a 174F OEM type stat that is as reliable as stock. Because it is a retuned stock thermostat.

BlaineBug · August 25, 2023

35 minutes ago, mikeyk101 said:

Part # is 15-11113 It also listed as part # 12674634 I bought it off Amazon as a warehouse deal and it was quite a bit cheaper. I checked it real close and looked fine. Here is a link to it and they have one warehouse deal on it now.

GM Genuine Parts 15-11113 Water Pump Outlet Assembly with Thermostat https://a.co/d/1R3PwXa

Thanks! This one on eBay was $30! https://www.ebay.com/itm/235113369347?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=EtuWMaTQSo6&sssrc=2047675&ssuid=5M210ch5RHm&widget_ver=artemis&media=COPY

Appears to come with OEM AC Delco box and packaging too.

Grumpy Bear · August 25, 2023

Data Update

8/24/2023

I intended to start about 2 pm today when air temps were above 92F, my last data point, and run a few hours up to 100F and fill in the blanks. But at 96F I ran into a new issue. I ran out of radiator.

Note: I run 40% glycol and Red Line Water Wetter in the summer with gives about 9% more cooling capacity. Didn't mention that last graph post.

Anyway, at 55 mph the 170F water thermostat throttles 173 F once warmed up and will hold this pretty close from about freezing to about 92F. About 93F it water temperature starts a slow drift upwards which results in a warmer cold tank temperature which results in a wider Delta T between the air temperature and the ATF temperature. Breaking pattern of 66F over ambient air temperature ATF temperature. I quit when the water temp leveled out at 179F with a Delta of 71F and oil temperature, running on the hot tank side rose by a like amount.

Easier to see in the Delta T chart than the ATF vs air temp chart. (Yellow bubble graph)

Not a well known fact; flow through thermostat is NOT linear. Throttling temperature will be a few degrees over cracking temperature and the range from cracking to fully open is about 20 F. With most control over the first 5 degrees. You can see this graphed in the Delta chart as a flat line between 55F and 77F air temp holding 142/143F ATF temp. Once it goes degree per degree it is no longer 'controlling' anything. Wider opening with the same flow.

I will delete the graphs from the previous post with a note but leave the writeup.

Edited August 25, 2023 by Grumpy Bear

mikeyk101 · August 25, 2023

3 hours ago, BlaineBug said:

Thanks! This one on eBay was $30! https://www.ebay.com/itm/235113369347?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=EtuWMaTQSo6&sssrc=2047675&ssuid=5M210ch5RHm&widget_ver=artemis&media=COPY

Appears to come with OEM AC Delco box and packaging too.

The Amazon one I bought also came in a OEM labeled box as well.

mikeyk101 · August 25, 2023

Just to add, if I bought that Amazon one now, SE Wisconsin, it would be delivered later today.

BlaineBug · August 25, 2023

17 hours ago, mikeyk101 said:

The Amazon one I bought also came in a OEM labeled box as well.

I'm sure it was, some of the ebay ones were "questionable" even if they list the manufacturer as GM, there's no guarantee. I noted that the prices were around $75 when searching for part number 15-11113 and about $30-$35 if searching for part number 12674634.

mikeyk101 · August 26, 2023

Mine also had part number on the side of the plastic base. Im pretty sure it was the 12674634 number but of course it's on the one side that I can't see right now. I did match up the numbers with the numbers on the box to make sure. The box listed both numbers on it. The AC Delco # is the 15-11113 number and the GM # is 12674634.

Here is a pic of the box.

Edited August 26, 2023 by mikeyk101

Grumpy Bear · August 26, 2023

Is there a 90 stamped on the bottom of the "pill"? Cracking temperature is always stamped in Celsius on them.

mikeyk101 · August 26, 2023

37 minutes ago, Grumpy Bear said:

Is there a 90 stamped on the bottom of the "pill"? Cracking temperature is always stamped in Celsius on them.

That's a good question but it will hopefully be many years until I can give you a definitive answer. But what I can say is that I monitored the coolant temp with my OBDII device using Torque Pro app on my phone for several weeks after installing it. I had been monitoring it anyway at the time because I had noticed the engine running a bit hot when it shouldn't have. That is when I figured that the fairly new Motorrad thermostat I installed at the beginning of the year was failing me. After installing this 194⁰ GM one, temps were normal again. Actually better. I knew the thermostat was properly opening because just before the coolant temp hit 194⁰, I could see it drop down into the 180's. It usually stayed below 200⁰. I think the only times it went above was if I was running the motor hard on purpose or when towing the toyhauler. I didn't even think to check it earlier this week when the ambient temps were pushing close to triple digits but I never saw my idiot coolant dash gauge rise past the "210⁰". So that tells me I was in good shape.

mikeyk101 · August 26, 2023

Oops, I missed on the running temps. The coolant temp with replaced lower temp GM thermostat did initially rise to 198⁰ but then dropped down to 192⁰ when it was fully opened. It only rose above 200⁰ in some heavy stop and go traffic or when I loaded the engine really got on the accelerator but still stayed at reasonable temps. I started 2 threads about coolant thermostats and this was one of the posts I made discussing the favorable results.

https://www.gm-trucks.com/forums/topic/263385-my-motor-is-running-hot-thoughts-update-i-was-right/?do=findComment&comment=2628309

Edited August 26, 2023 by mikeyk101

Grumpy Bear · August 26, 2023

@newdude gave us a list once of the cooling layouts and their changes over time from 2014 to the present T1** series. GM has tried every conceivable layout. Funny to watch actually. Ever hear it said:

"You think you know more than GM Engineering"?

:crackup:

Maybe!

:rollin:

At least we are less conflicted and fenced by outside sources in our goals. (Gov. Regs) We don't have a corporate average fuel economy target to reach and we care more about reliability, dependability and durability. Okay, some of us.

BlaineBug · August 26, 2023

11 hours ago, mikeyk101 said:

Mine also had part number on the side of the plastic base. Im pretty sure it was the 12674634 number but of course it's on the one side that I can't see right now. I did match up the numbers with the numbers on the box to make sure. The box listed both numbers on it. The AC Delco # is the 15-11113 number and the GM # is 12674634.

Here is a pic of the box.

Yes, one part number is an AD Delco part number and the other is a General Motors part number, it's the same thermostat, but if you search them individually and uniquely on eBay, you'll see that the prices vary by about double depending on which one you use as your search term!

BlaineBug · August 26, 2023

8 hours ago, Grumpy Bear said:

Is there a 90 stamped on the bottom of the "pill"? Cracking temperature is always stamped in Celsius on them.

When I swap I will take note and post in the future. When I swapped the transmission cooler bypass/thermostat assembly I disassembled the new and old and also provided the temperature stampings for both, and also for my own knowledge to rest assured that I was installing the correct part that I wanted to install.

newdude · August 26, 2023

59 minutes ago, Grumpy Bear said:

@newdude gave us a list once of the cooling layouts and their changes over time from 2014 to the present T1** series. GM has tried every conceivable layout. Funny to watch actually. Ever hear it said:

Gonna pop them in here for everyone's reference. 6 speed only just to keep things simple.

2014-2018 4.3 V6/6L80: Transmission cooler in right radiator tank, lines flow from transmission to cooler, cooler to transmission. V6 are equipped with the TBV.

2014-early 2016 5.3/6L80 and 2014-2015 6.2/6L80 (yes, these exist): 2014-early 2016 transmission cooler setup had a cooler in the left tank of the radiator, and then the aux cooler is a part of the condenser assembly aka the Combi-Cooler.

Flow would be transmission to the left lower inlet at the left radiator tank cooler, out of the top to the aux cooler (via pipe #14 below), then aux back to the transmission (via pipe #5 below). Equipped with TBV.

If the TBV is "flipped" or SureCool, these year trucks, the transmission cooling loop would operate like all the 2013 and prior 1500s where the flow was constant all the time as they had no TBV.

Late 2016-2019 5.3/6L80 "Limited/LD" (still K2XX platform): GM ditched the transmission cooler in the left tank of the radiator. The aux cooler on the condenser (the Combi-Cooler) is now the ONLY cooler brick for the transmission.

Equipped with TBV. I'm 99% sure flow is transmission to the left side of the cooler (via pipe #15 below) and then from the cooler back to the transmission (via pipe #6 below).

Side note on these trucks. When bypassed (flip or SureCool) these ones actually keep pretty cool. When I had mine, on a hot summer day making WOT pulls I struggled to see over 165F. Winter time however, it keeps TOO cool and would actually LOSE temperature. It'd get to like 105-110F and when cruising at highway speeds it would drop to 95-99F. Shifts feeel like a transmission right after a cold start. I installed the GM lower temp TBV and it drastically improved temps for the winter and improved shifts.

Edited August 26, 2023 by newdude