2015 High Miler

Not as often as I should have on the first one. I think we went 80,000 before I had it serviced, but the second one was done at @ 40k and 80K and it still died.

It would most likely be safe but i know it will get your attention! Someone else may have better knowledge.

I have a 2015 Sierra 5.3 with the 6l80 that has 249,000 miles currently. The engine has been mostly flawless. I changed the plugs out of guilt at around 200,000. I am on my 3rd transmission, though. The first died at 122,000, and the dealer helped me on the warranty and covered half of the replacement cost and I got another 100,000 mile warranty. That one died with 103,000 miles on it and I decided to get it rebuilt with better parts, a 40K cooler and other mods to make it live. (fingers crossed) On the second trans, I did get the tune changed but I did not remove the thermostat. I did not know that they had them until it was too late. The rebuild does not have the thermostat. I also upgraded the convertor and had another tune put in. So far so good but I don't drive as much as I used to so it only has about 30,000 miles on it in the last 18 months. Regarding the engine, I did regular oil changes with full synthetic oil at 7500 to 10,000 miles and have been fortunate to not have had issues with the lifters. I did turn the AFM off at about 75,000 miles and then had the whole combo retuned when the trans was replaced. I had to change the radiator due to it cracking, so while we were there we also replaced the water pump, but it did not need it. It has been solid, other than the transmission. A coworker bought a 2016 and the trans went out about 120,000 miles, too. He is not into modifications, so he sold it once he got it replaced. I tried to get him to get it updated with a tune and removing the thermostat but that is just not his gig.

It should drop down from 6th to 5th. But, after I had mine retuned, it drops from 6th to 4th. 2015 Sierra

Old thread but did you get this done? My 2015 has had the lights opened before but not by me. I need to open them again and make some adjustments.

I bought a 20 19, 2500 HD last March. In October or so of last year, I started getting the occasional exhaust smell in my air conditioner as well. This truck has 74,000 miles and has zero modifications. It really is aggravating that no one can figure this out. I can’t imagine that I’m alone and have the only two trucks that have this problem.

I had mine smoke tested and there were no leaks found. I have changed my whole exhaust system: long tube headers, ORY pipe w X pipe and dual exhaust out the back. No better and no worse.

no, it still does it at 237,000 miles.

I went back with OEM. One lasted 160,000 and the other 200,000. Do you have a lift of any type? I have a 2.5 I think. its the max recommended, what ever that is.

5.3 and 6 speed.

None. its always had the tick that you can hear in the drive through at idle but no issues. My vacuum pump is weak and needs changed. I have repaired/replaced: 2 transmissions, radiator due to tank crack, 4x4 was locked on shortly after I bought it but repaired at NC, brakes ay 144,000, and 4 sets of tires. Great truck, so they dont all suck. Too many dont have that luck, though.

2015 SLT CC 231,****** miles on 3rd trans. engine has been really good though, except for I have an exhaust smell in my cabin. dealer that did the 1st trans swap says it was cracked manifold and/or gasket. I put headers on and have had it smoke tested and still have the smell at idle. Liked the truck so much I bought a 2019 2500HD with 66,000 miles on it. Aside form the trans issue, it has been stellar. Even the interior has help up well. knock on wood....

I bought a 2019 2500 HD with some sort of minor lift, not sure how much. It has 265/60/20s (stock tire and damn they are small...). Front fender is 41" and rear is 43" at the wheel centerline. Looking at 35x12.5's. Hopefully no rubbing. Anyone have the stock height on same tire to see how much lift it has? It has RC upper control arms and RC shocks front and rear but they seem worn out already.

hope you find out. I have a 10" sub under my seat with Bose but I think the noise cancelling keeping it from achieving its potential.

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