Replaced my transmission thermostat with a lower temp thermostat

[mrathell]

My 2015 Chevy Tahoe LT with a 165K miles runs great and the transmission works great as well. The temp of the fluid usually hits between 190 - 200 F on a typical day of driving.
In this video I was looking to replace the internals of the thermostat with the kit from Superior Solutions so that the thermostat would open at about 140F instead of about 190F.
The issue I ran into was the transmission thermostat housing wouldn't allow me to open it up to replace the internals due to the effects of Wisconsin salty road conditions in the winter.
I couldn't just purchase a new thermostat because my transmission lines are the older version. Apparently there are two versions on the 2015 models and mine has the earlier version. The earlier version transmission lines will not work with the newer style transmission thermostats.
So I had to replace the entire transmission lines. The good thing was that the new transmission lines comes with a new thermostat attached but the one they sent me didn't have the updated version of the thermostat that opens at about 140 F.
Luckily I already had the kit from Superior Solutions, so I just replaced the internals on the new thermostat with the Superior Solutions kit.

In this video I'm only showing how I replaced the thermostat and the internals of the thermostat. I have a different video where I show me replacing the entire hose/line. This isn't a profession video, it's just me in my garage figuring things out as I did it. Not always the best lighting and camera angles but hopefully enough details in case it can help someone else out

 

[Sparksalot]

I ordered a new thermostat, complete with VIN cross checking and all, from one of the online GM sources. Nope, it was the new style. I was able to swap the guts, so it was still a pretty simple process.

 

[BlaineBug]

I installed that same revised thermostat myself about a year ago.

 

[TahoeEd]

I installed that same revised thermostat myself about a year ago.

I ordered the new thermal bypass valve (part# 86774933) and plan to put it in my 2019 Tahoe, but I was wondering if I need to buy the seal and O-ring as well. Every parts site I go to, they say they do not fit my vehicle. Does anyone know if they are needed on a 2019?

 

[Doubeleive]

I ordered the new thermal bypass valve (part# 86774933) and plan to put it in my 2019 Tahoe, but I was wondering if I need to buy the seal and O-ring as well. Every parts site I go to, they say they do not fit my vehicle. Does anyone know if they are needed on a 2019?

you shouldn't need anything else
you really do not need to order anything you can get a tap and a bolt at the hardware store and just bypass it entirely, the thing still runs hot even with a lower thermostat, depending on how you drive
I tapped mine, added a deep trans pan and tru cool 40k and thing still hits 180 but atleast it's not 240 anymore, with the stock setup I would hit 220 just going to the store and back

 

[mrathell]

you shouldn't need anything else
you really do not need to order anything you can get a tap and a bolt at the hardware store and just bypass it entirely, the thing still runs hot even with a lower thermostat, depending on how you drive
I tapped mine, added a deep trans pan and tru cool 40k and thing still hits 180 but atleast it's not 240 anymore, with the stock setup I would hit 220 just going to the store and back

After replacing mine, I'm topping out at about 130 degrees on most of my driving. There was a couple of occasions I hit the 150 mark, but that was during a lot of stop-and-go traffic. Most of my driving is freeway. I'm looking forward to seeing what the temp reach in the summer.

I think it's fair to say, the tran fluid temp reading on the dash most likely increases about 15-20 degrees more after you stop driving before it begins to cool off.

 

[Doubeleive]

After replacing mine, I'm topping out at about 130 degrees on most of my driving. There was a couple of occasions I hit the 150 mark, but that was during a lot of stop-and-go traffic. Most of my driving is freeway. I'm looking forward to seeing what the temp reach in the summer.

I think it's fair to say, the tran fluid temp reading on the dash most likely increases about 15-20 degrees more after you stop driving before it begins to cool off.

I have a pretty heavy foot so my particular style of driving really heats the transmission up it was never a problem on the gmt800's but the gmt900's and k2xx do not like my driving both would hit 220+ previous to modifications. mine will now typically hang around 165 in the summer as long as I am not really pushing it hard, if so then it may still hit 180+ which is perfectly fine for me, winter time it hangs around 145-160, or slightly lower if I am driving like a sane person.

 

[18tahoepremium]

I ordered the new thermal bypass valve (part# 86774933) and plan to put it in my 2019 Tahoe, but I was wondering if I need to buy the seal and O-ring as well. Every parts site I go to, they say they do not fit my vehicle. Does anyone know if they are needed on a 2019?

I have an 18 Premier and didn't need anything other than what was supplied in the kit.

 

[Rygrego]

I have an 18 Premier and didn't need anything other than what was supplied in the kit.

I know they say it but they are the correct seal.

 

[SpineDock]

I see the transmission temp on the odometer display of NBS trucks but I’m not sure how to find it on my 2015 Tahoe LT?

 

[BlaineBug]

I see the transmission temp on the odometer display of NBS trucks but I’m not sure how to find it on my 2015 Tahoe LT?

It must be enabled through the settings menu on the gauge cluster, NOT the settings menu on the infotainment screen.

 

[Sparksalot]

It must be enabled through the settings menu on the gauge cluster, NOT the settings menu on the infotainment screen.

Yep. @SpineDock the setting is there but toggled off.

 

[OR VietVet]

I don't know if all years of the NBS Tahoe/Yukon rigs have the thermostat and wiring up to the dash cluster, like mine did, but when I did the new dash cluster from Digital Dash Solutions, I just had to plug in the existing harness to the new cluster and all of a sudden, my 05 shows the transmission temps. On my long last July trip, there was a lot of driving up and down passes at hard accel situations and it never once climbed over 170-180 degrees. Just how accurate are the dash cluster transmission temp gauges?

 

[SpineDock]

It must be enabled through the settings menu on the gauge cluster, NOT the settings menu on the infotainment screen.

Douh!!! Ok, my eyes haven’t gotten past the infotainment buttons on the steering wheel LOL and the wifey gets to drive her M-F. I’ll check it out tonight.
This would’ve been good to know how she did in the Carolina mountains last week

 

[BlaineBug]

Douh!!! Ok, my eyes haven’t gotten past the infotainment buttons on the steering wheel LOL and the wifey gets to drive her M-F. I’ll check it out tonight.
This would’ve been good to know how she did in the Carolina mountains last week

It's probably around 180-190 with the OEM thermostat. There is a new "revised" unit that will run it a little bit lower, I installed one about 13-14 months ago in my 2019.

 

[SpineDock]

It's probably around 180-190 with the OEM thermostat. There is a new "revised" unit that will run it a little bit lower, I installed one about 13-14 months ago in my 2019.

How right you are sir!

Drove her today since toggling ON the transmission temp and she held around 187 degrees with ambient air temp around 75 degrees in sunny FL.

I am going to be starting a new thread with my transmission questions so as not to step on this threads toes but thanks for the info and advice!

 

[Doubeleive]

I don't know if all years of the NBS Tahoe/Yukon rigs have the thermostat and wiring up to the dash cluster, like mine did, but when I did the new dash cluster from Digital Dash Solutions, I just had to plug in the existing harness to the new cluster and all of a sudden, my 05 shows the transmission temps. On my long last July trip, there was a lot of driving up and down passes at hard accel situations and it never once climbed over 170-180 degrees. Just how accurate are the dash cluster transmission temp gauges?

00-23 have a transmission thermometer, unsure about pre-00

 

[73Vetteman]

My 2015 Chevy Tahoe LT with a 165K miles runs great and the transmission works great as well. The temp of the fluid usually hits between 190 - 200 F on a typical day of driving.
In this video I was looking to replace the internals of the thermostat with the kit from Superior Solutions so that the thermostat would open at about 140F instead of about 190F.
The issue I ran into was the transmission thermostat housing wouldn't allow me to open it up to replace the internals due to the effects of Wisconsin salty road conditions in the winter.
I couldn't just purchase a new thermostat because my transmission lines are the older version. Apparently there are two versions on the 2015 models and mine has the earlier version. The earlier version transmission lines will not work with the newer style transmission thermostats.
So I had to replace the entire transmission lines. The good thing was that the new transmission lines comes with a new thermostat attached but the one they sent me didn't have the updated version of the thermostat that opens at about 140 F.
Luckily I already had the kit from Superior Solutions, so I just replaced the internals on the new thermostat with the Superior Solutions kit.

In this video I'm only showing how I replaced the thermostat and the internals of the thermostat. I have a different video where I show me replacing the entire hose/line. This isn't a profession video, it's just me in my garage figuring things out as I did it. Not always the best lighting and camera angles but hopefully enough details in case it can help someone else out

Has anyone tried replacing the plunger rod inside the valve with a slightly different length rod to reduce the regulating temperature? (Assuming you have a valve not too corroded to work with). It appears to me that would be an easy and free solution to reducing the opening temperature.
I am thinking of replacing the rod with a slightly longer rod fabricated from a drill bit shank of the correct diameter. I might start at about 1/16" longer to see how much that would change the minimum temperature.
The consensus I have read about transmission temperature seems to indicate about 160 degrees is ideal. That correlates with the 158 degree opening temperature of the newer GM part.
For us that live in colder winter climates, we want the fluid to warm up to operating temperature quickly and not remain too cold. That is something that won't happen if we just bypass the thermostat. After all, GM wouldn't have gone to the expense of adding a thermostat unless there was an advantage to it. Simply bypassing the thermostat doesn't make sense to me.

 

[15burban]

GM wouldn't have gone to the expense of adding a thermostat unless there was an advantage to it.

Just my opinion but I believe most of the companies added them as a way to squeeze out every fraction of mpg they could get to appease the epa. Same with all of this cylinder deactivation stuff. Even an extra .10 mpg doesn't seem like a lot to one person(one vehicle), but add that up over the millions of vehicles that company produces it looks a lot better to the epa.

Transmissions went years and years without thermostats in them and at least for me I've never heard of one failing because of too cold of fluid. I have heard of a lot of them "burning up" from too hot of fluid though.

 

[73Vetteman]

Possibly shift quality. They definitely shift firmer when cold. People are much fussier than before about minor things like feeling the shift.
Maybe a greater consideration is the length of warranty GM has to provide now.