2015 High Miler

1 was about 70,000 and the other at 55-60,000. Both started to die around 95-100,000. I had an 09 that went 140,000 and towed a lot and never had any trans or engine issues. I'm a believer the heat from the high stat and probably some converter issues killed the 2015's.

230,000 yesterday. No engine issue but on my third transmission… still wouldn’t drive a Ford.

The LED bars on each side apparently have come loose. Its very noticeable at night. I am considering painting the chrome if I do get them apart. I purchased them previously converted.

OLD thread but was hoping to find someone in DFW-Austin, Texas area or in between that has done this. I have a set that has been previously modified and I need to open them and make some corrections. I don't think I have the patience to not eff them up in an oven... LOL How hot is the light when getting out of the oven? How are you handling them? switchbacks.zip

Thanks, I have found a few threads on it after posting here. Any idea an what the NEW PN is?

Have had the same issue in my 2015 and have yet to find the cause. Mine started after the first trans replacement (122,000). Had it tested and found no leaks. Only does it when stopped. As long as I’m rolling it’s not there.

My truck has had this issue for quite some time but seems to be getting worse. It does have 230,000 miles so it may be just time to replace the vacuum pump. What happens is at a drive through speed or waiting in line at a drive through car wash , the brakes will get a very hard peddle and you really have to push VERY hard or you will not stop rolling. I have found that if I put in neutral and give it a light throttle, it will bring the peddle back for a few more stops before having to do it again. What is involved in this repair? I tried a search but I was not getting any good returns. Thanks in advance

Cam, thanks for this info but TBH, I have not become very proficient yet with HPT and looking at these tunes. I've had some trouble getting my compare files to open. Most likely user error. Ill try again with this one. I def would like to be able to switch fuels. I could at one point but now its really down on power with 87 and with 91/93 its about where it used to be with 87. I drive a lot of highway miles back and forth to work and with fuel prices where they are, being able to run 87 for the long hauls would be great. With that, I am willing to run it on 91 if it makes the type of power that I think it should. it just feels really weak off the line and at one point when first tuned, it would really get it off the line. I recently pulled a two wheel trailer to DFW and back and it was horrible on power and mileage and was always in 5th gear it seems. That was with an empty load.

This is posted earlier in the thread: Builder said it’s built to handle 700 HP. More if it had a hardened input shaft.

Here is the current tune 2015 Sierra 5.3 tune 4-12-22 33 Terra Grapplers Retune 33.25 and speedo adjustment.hpt

A lot, actually. Ill post it in a few but send you a PM with my issues.

small update. New trans is doing well. I did get an updated tune to reflect the new components and its still working well. The temps are where I would expect with the cooler and the bypass. Highest I've seen is 140 in heavy city traffic. I do need to get a better tune though, both engine and trans. I have HP Tuners but I'm not very good at it yet. If anyone is in the DFW area that has some experience, Id be happy to meet up and get a look at my tune.

Generally, its the thermostat going out, but it could also be a cracked radiator tank. That is what happened on mine. I found out about the thermostat during the search regarding the running fans and cold temps. GM truck running fans Thermostat is not too hard to do. good luck

For the tune that’s on the truck now, it was no different. Crispier but not really harder. Tune was already pretty good on the shifts. He warned me that it would be considerably firmer but it’s good in my opinion.

McCoys in Garland. $4200 out the door and replaced the rear main that was leaking as well. I never noticed it but was told by a couple of techs that it was leaking. Took 4 days. Very satisfied at this point.