K2XX Trans Cooler Thermostat Thoughts and Opinions

Grumpy Bear · April 23, 2022

1 hour ago, teagan said:

You mentioned a '15 as pre-shudder; I have read a lot of threads on here about that. I feel lucky to have a year where this is not a problem. Do we know what the general cause of the shudder is (in a nutshell)? On a entirely different note, is a "diablew" tune worth it? I have the Diablo i3 Platinum I believe and I reprogrammed some of the shift parameters in 1st-2nd gear. When it shifts from 1st-2nd, the rpm's jump, (clutch?) any thoughts?

Not the shutters I was talking about. Louvers before the radiator is what I was talking about. Did not mean to confuse you. Sorry.

swoleymammoth · May 6, 2022

Anyone had the new bypass valve installed at the dealer outside of warranty? How much did it cost? I'm sure I can install it myself if I have to but if it's not too much $ I'd rather just save the time and have it done at the dealer. Thanks!

NE18 · May 6, 2022

1 hour ago, swoleymammoth said:

Anyone had the new bypass valve installed at the dealer outside of warranty? How much did it cost? I'm sure I can install it myself if I have to but if it's not too much $ I'd rather just save the time and have it done at the dealer. Thanks!

I think I was quoted 400-500. I ended up doing it myself

CamGTP · May 6, 2022

Jebbus, it's 1 bolt holding two hoses on and they want to charge like 3 hours of labor.

I'd laugh in their face if that was the real cost.

rav3 · May 6, 2022

10 hours ago, swoleymammoth said:

Anyone had the new bypass valve installed at the dealer outside of warranty? How much did it cost? I'm sure I can install it myself if I have to but if it's not too much $ I'd rather just save the time and have it done at the dealer. Thanks!

A better option is to buy the valve & have any transmission shop install it if you don't want to crawl under the truck. Part is about $50 (without lines) Takes all of 15mins to do.

Thermal Bypass Valve Installation – TechLink (gm-techlink.com)

21-NA-199 1..3 (nhtsa.gov)

By-Pass Valve Replaces Part Number 13511136) 86774933 | GMPartsDirect.com

Grumpy Bear · May 6, 2022

I'm OLD and WEAK. Did mine on ramps in the drive in the winter in 15 minutes, ramp on to ramp off.

taylormjones3 · May 6, 2022

2 hours ago, rav3 said:

A better option is to buy the valve & have any transmission shop install it if you don't want to crawl under the truck. Part is about $50 (without lines) Takes all of 15mins to do.

Thermal Bypass Valve Installation – TechLink (gm-techlink.com)

21-NA-199 1..3 (nhtsa.gov)

By-Pass Valve Replaces Part Number 13511136) 86774933 | GMPartsDirect.com

The new style lines with a TBV are $80 from amazon. I swapped to the new lines last weekend on my '14. But the lines I received still had the 190° thermostat... Maybe newer inventory will start including the lower temp thermostat.

You can also buy the new version TBV with the lower temp thermostat and just swap the "pill" on your old TBV without swapping lines. I ran like that for a few months without issue.

stevejones · May 8, 2022

On 1/24/2022 at 8:35 PM, stevejones said:

I pick up my 158* TBV tomorrow from the dealer. Hope to get it installed this weekend on my '19 K2.

Took longer than expected, but I finally got some time this weekend to get the swap done. Pretty simple to do, only two bolts. Didn't lose much fluid, maybe a couple tablespoons' worth. Now I've gotta actually drive the truck & see what my temps drop to, lol....

rav3 · May 9, 2022

2 hours ago, stevejones said:

Took longer than expected, but I finally got some time this weekend to get the swap done. Pretty simple to do, only two bolts. Didn't lose much fluid, maybe a couple tablespoons' worth. Now I've gotta actually drive the truck & see what my temps drop to, lol....

Yes, please keep us posted on that info.

stevejones · May 22, 2022

Finally got it out for a 2-hour round-trip; mostly freeway drive. Max temp on the freeway was low 160'ish. City streets was low 170's. Not towing, ambient air temp 55 or so. Very good start!

Capt Bob · May 30, 2022

Pulled the travel trailer (6200 lbs.) this week. 7 hour run home with outside temps 90+, highest seen was 183 degrees. Mostly running in the 170s at 67mph. I'm running the low cost pill flip with Red Line full syn D6 ATF.

Edited May 30, 2022 by Capt Bob

Grumpy Bear · May 30, 2022

Posted this in my built thread but forgot to post here. The blue and orange are pill flip and cooler water thermostats. My truck has the cold side tank trans cooler only. She holds a full fill of RED LINE D6 in a PLM 8 quart pan.

I wish I had plotted the 'factory' set up. I would have scared anyone. Ran over 225 F in the summer on longer runs.

The yellow is the new GM 70C pill's effect on the orange line. Didn't look like this right away until the bugs of 150K miles were hosed out of the fins. Ops! Something that needs doing more often.

As you can see this valve actually tries to throttle the fluid temperature between 60 and 80 F air temperatures.....and then.... it runs out of cooling above 80 F air temperature. While cool enough it does point to the fact that this set up could still benefit from a small secondary cooler if I towed or headed to the southwest. This also means it is slow to recover from city paced driving on a hot day once it gets back in free air. We don't have a huge number of 85 F plus days around here. Stare at the chart long enough and you also see the slight restriction of flow above 87 F over the orange pill flip.

But, it did as I wished and warmed things up a bit for the winter months. Interesting side note is that in the summer it takes a bit longer for the trans to warm up as in this set up the cooler is a heater until the ATF is warmer than the water. Now it just heats on the work put into the fluid.

Edited May 30, 2022 by Grumpy Bear

NE18 · May 31, 2022

Pulled 3500 camper in 87F heat going 65-70 mph and temps were in the 170s. When he we hit stop and go traffic, it topped at 190.

pokismoki · May 31, 2022

On 5/29/2022 at 7:57 PM, Capt Bob said:

Pulled the travel trailer (6200 lbs.) this week. 7 hour run home with outside temps 90+, highest seen was 183 degrees. Mostly running in the 170s at 67mph. I'm running the low cost pill flip with Red Line full syn D6 ATF.

i pulled a 7000lbs trailer over the holiday with my 2500HD, it's a pre-thermostat 2012 truck, but it has the big factory trans cooler up front in the bumper. running 60mph for about a 120 miles my temps are a steady 160F. my Gross weight is close to 12,500lbs soaking wet with toys

my 2500 6l90 feels like a different transmission compared to the K2 6l80. it feels much tighter than a factory tuned k2 trans

Edited May 31, 2022 by pokismoki

NE18 · June 1, 2022

11 hours ago, pokismoki said:

i pulled a 7000lbs trailer over the holiday with my 2500HD, it's a pre-thermostat 2012 truck, but it has the big factory trans cooler up front in the bumper. running 60mph for about a 120 miles my temps are a steady 160F. my Gross weight is close to 12,500lbs soaking wet with toys

my 2500 6l90 feels like a different transmission compared to the K2 6l80. it feels much tighter than a factory tuned k2 trans

In the stop n go traffic, with tow haul mode on, it kept slamming into gear with the down shifts as it was activating the down hill descent control (was on a flat highway at the time). After I shut off the descent control it was much better. I know I’m on borrowed time with this engine/ trans combo. For the record, dropped pan at 40k and fluid swapped at 55k.