Wehrli Fab Trans Cooler Thermostat Bypass Duramax L5P Full Install!! 

Just an FYI. Not sure if you have checked this but the 2017-2019 model years have a rub on the transmission cooler lines at the bumper mount front / passenger. side. You can see pretty easily once the cowl and the grill are removed. I checked mine and sure enough the trans cooler line is worn half way through. I was able to temporarily get a hard rubber piece wrapped around it. Im leaving on a 1 month trip pulling my 5th wheel so I went to the chevy dealer and they are 3 weeks out so I will buy the part and take with me just incase. There is GM bulletin on it and they will they fix it for free but I am certainly not going to leave my truck for 3 weeks just sitting there waiting on them. They won't order the part until a tech confirms the issue which means removing the cowl / grill / bumper etc.and then wait. If that line holds on for the 1 month trip, I will install it when I get back. It would be great video for you to do on your truck LOL. There is only 1 video on youtube that I found on how to replace that line but it was a very crude and lacking info in that video. The new designed trans cooler lines is GM part # 84444069

I just installed mine on my L5P 2018 GMC and I see a huge difference I was always at 180 but now I’m always at 125 highly recommended

Hey Scott, i finally installed the bypass plug a couple of weeks ago. What a difference! I'm seeing a 20º to 30º drop during everyday, normal driving. Great video and thanks.

I just took the spring and valve piece out and it did the same as buying that

Another great video Scott! It’s been hotter than hell here in Southern California....I’m going to go broke watching your videos and following your lead.

Also I live in Chicago and with summer heat and city traffic I am frequently seeing trans fluid temps 200-210. My truck is 2018 with 25k miles on it and it definitely seems like mine is stuck open or closed. Which ever way keeps the fluid from ever hitting the trans cooler. I frequently feel the trans cooler when I stop even after longer trips and it is always cool to the touch. I ordered my bypass last week, can’t wait for it to get here.

I did a similar mod that PPE makes for the 3.0 duramax. Did the PPE 4 quart pan & their bigger cooler and I run -30 to 40 degrees cooler towing my RV.

Thanks for this mod tip, have place my order! We tow a travel trailer here in Texas and this will certainly help keep that trans temp lower.

Well, gonna be ordering this soon for my L5P. Love the channel, thanks for the L5P vids! Great stuff!

One of them if you got warranty best put the thermostat back in before taking in to a dealer

Amazing step by step install brother, great video!

Mods I didnt even know existed . Trans cooler cover soon 👍🏼

Good stuff...wish I knew someone with L5P in TX

I would think that as long as trans temperatures are below coolant temperatures then the bypass is working. As a side note on our earlier gas trucks trans temperatures ran cooler than my new to me 2019 Duramax.

Hey Scott instead of buying to bypass plug and you just take the bottom spring off the stock Thermostat to make it closed all the time thinking ab trying it in my truck just haven’t had it out to look at it to see if it will work ?

Great info!!!

What do they have for the 10 speek l5p

I was looking at this but realized its not something I need. I towed my jeep today it was 102 outside here in California. I was watching my temp and never climbed higher than 190, thats towing up hill with an extreme climb up to 8000 feet above Shaver lake Cal.

Channel locks. Not vice grips*

Upper coolant hose

So some of you in the comments have done the swap what's been the difference? How many of you tow regularly over 10k?

Does anybody know if that kit works on a 2016 2500hd with a gas motor and I think a L680 transmission

Will these work on LMLs??