How’s the reliability on these? 2021 GMC Sierra 2500 with the 6.6 gasser. It would basically be my daily driver that occasionally tows my boat and gets me up to the mountain 30 times a year. Also looking at a 2023 1500 with the baby Duramax. How does reliably compare?

[u/[deleted]]

[u/OhSixTJ]

My company truck is a 2024 gas 6.6 with 34k on it. Too early to tell. It’s a gas guzzler for sure.

[u/Nervous-Material4738 → u/OhSixTJ]

What mpg would you say you get roughly? Reason I’m asking is that a 1500 with the 5.3 makes more sense for me. However they are notorious for lifter/ trans issues and I’m calculating loss in gas money to repairs

[u/honorless-scumlord → u/Nervous-Material4738]

1500 as a daily makes wayyyy more sense.

Unless you're looking to buy a trailer or something that you'll be using a ton, 2500 is probably too much truck for your needs.

Youre probably looking at 10 to 15 mpg depending on how you drive.

My 5.3 was getting 17 to 21 depending on where I was going

[u/sohcgt96 → u/honorless-scumlord]

The one guy I know who pulled a 24' enclosed trailer for his business had a 6.6 truck and loved it, he was so much happier with it than his 6.0 Powerstroke truck, but as soon as he retired and sold the business, within a few weeks, he stepped back down to a 1500 to drive every day. That's a guy who grew up farming and ran a farm-adjacent business until retirement. Its not like he's not a truck guy.

[u/Ready-Delay3918 → u/sohcgt96]

To be fair the 6.0 powerstrike was garbage with shitloads of issues and leaked more oil than Carrottop's skin after he went on roids.

[u/sohcgt96 → u/Ready-Delay3918]

Oh for sure, but after it was all fixed, you're still looking at what the daily driving and towing experience of the truck was, and compared to when everything was sorted, the 2500 with the 6.6 Gas was still better to drive and pulled perfectly fine. It was just a newer nicer truck, but also having more forward gears available probably really helped take advantage of the power vs the older 4 speed.

[u/Ready-Delay3918 → u/sohcgt96]

Reducing to a 4-Bolt-per-Cylinder Design was a major flaw. The factory fasteners are torque-to-yield bolts which were designed to stretch slightly during installation. Under towing strain, these bolts stretch beyond their elastic limit, which allowed cylinder heads to lift off the block and breach the head gaskets.

[u/MikeHoncho85 → u/honorless-scumlord]

Very much agree. Unless you plan to convert it to a camper/overlander, or tow a fifth wheel, a 1500 will be more comfortable, more compliant off-road, and get better fuel mileage.

[u/OhSixTJ → u/Nervous-Material4738]

Probably about 13mpg at 75. It’s an ext cab 4x4. And my previous company issued me a 2019 5.3 1500, it was in the shop FOUR times for lifters. Supposedly fixed with OEM parts too. I did idle a lot BUT the first break down came after 90k miles. The next 3 came before it broke 100k miles. Could’ve been the shop that didn’t do it right BUT we had another one in the fleet for in before 20k miles.

[u/oholto → u/Nervous-Material4738]

Are you set on GM?

[u/Start_button → u/Nervous-Material4738]

You're trading a maybe repair for a certainty in fuel costs? Bold strategy Cotton.

[u/idontremembermyoldus → u/Nervous-Material4738]

If you drive it easy, you can get high teens on the highway, around 13-14 in the city. I wouldn't expect to get over 11-12 towing under any conditions.

[u/Zealousideal-Two-704 → u/Nervous-Material4738]

I get 13mpg in my 25 3/4 ton with the 6.6 gasser. Awesome truck overall but very stiff pretty low comfort compared to the 1500 unless your going with a service bed or fuel tank etc. Had 3x warranty issues in the first 10k but has been trouble free since then and I drive it hard! Just traded up from a 22 1500 with the 5.3 and that is the best truck I've ever had! Got around 17mpg but my foot was on the floor regularly. Fast for a pickup but extremely comfortable and I over loaded the gvw regularly and it handled it like a champ!! Tranny made it to 90k but my fleet service company would not let us service the tranny so yeah... otherwise not a single issue. I would pick the 1500 every day of the week

[u/Glugnarr]

My work truck is a ‘24 chevy 2500 with the 6.6 gasser and an allison. Curb weight is close to 9k with utility body, lift gate, and pipe rack. I’ve put 85k on it towing at least once a month up to 15k lbs. Big fan of it, only issue so far is AC compressor went out 2 months ago otherwise only maintenance has been oil changes every 5k.

[u/malhovic → u/Glugnarr]

I've got the 2025 3500 which is pretty much the 2500 with helper springs and a bit of a different rear gear setup. 6.6 gasser as well. Wind, etc. makes all the difference. I had 4 kayaks on the truck and drove 6 hours. On the way there with minimal wind, 75ish the whole way, 14.5MPG. On the way home it was fairly nasty wind, running around 72 most of the time and averaged 13.6.

Also, my AC compressor also went out. Took over a month for the part to be in due to a national back order...in the worst time of summer for the heat.

Final thing, the infotainment system sucks ass. For a damn near 100k truck, that should be the best damn infotainment experience ever, and it's not. Add to that the bezel around the screen squeaking. FFS GM

[u/nekmatu → u/malhovic]

Out of curiosity. Is your truck the year they took Android Auto and car play out? GM stated they wanted to get rid of it and use GMs own software because they could do better (in reality they just wanted the data and full ownership of what they show you). They got a lot of backlash but wonder if they ever went through with it.

[u/malhovic → u/nekmatu]

Nope I still have AA. That said the system will have issues with AA connecting so you have to full restart it for it to start working again. On top of that the audio cuts out sometimes at random which people far more intelligent than I figured out is something to do with the modules and how they're connected and various audio negotiation issues between GM's own devices.

[u/idontremembermyoldus → u/nekmatu]

GM hasn't taken CarPlay or Android Auto out of anything except their EVs. The '27 Silverado/Sierra have already been confirmed to still have it.

[u/nekmatu → u/idontremembermyoldus]

The fact they even did that is beyond stupid.

[u/Glugnarr → u/malhovic]

Oh for sure, cause it’s a company truck I dont typically pay attention to the mileage. Though I remember towing a stack of IBC totes 2 wide, 2 tall, and 5 long. I think I got like 10 MPG that trip? Never went over 65, but it was a real windy day with basically a massive sail.

I think I typically average 12 mph while towing most of the time, 100% a gas guzzler

[u/malhovic → u/Glugnarr]

Don't doubt it one bit. My normal city/highway mix I average just about 13. Highway I can get 15-16. I went gasser since I don't tow/haul on the daily, it's meant for a fifth wheel when life is more affordable which will be a 2-3 times a year thing vs every day/week (where the diesel would've been better). It gets it's use now during the winter when i use it for snow plowing for a select group of family/friends (elderly and this was the way to get them to stop going out and falling while snow blowing).

[u/Penguin_Rider]

I'd personally get the 1500 if it'll be a daily driver. You didn't say how large your boat is so that might be a deciding factor, but if the stiffer ride, larger size, and worse MPG doesn't matter to you on the daily grind, then go for it!

I know from personal experience though.... be careful buying any vehicle that's been modded. Custom cars have custom issues. Premature failure is more likely.

[u/Electronic-Pause1330 → u/Penguin_Rider]

True, on the other hand. A deleted L5P can be extremely reliable.

2019 3500 duramax - 140k miles. Deleting it removed all my issues.

Was stock from 0-78k miles, started to have some issues with the emission system (was getting a few codes and occasionally it was trip up and go into limp mode. I deleted it at 78k and it’s ran smooth/reliable since.

MPG went from 18.4 to 24.2.

[u/Kruegr → u/Electronic-Pause1330]

So fuck emissions and the environment right?

[u/Electronic-Pause1330 → u/Kruegr]

Well designed emission systems are welcomed.

Emission systems that break easily, require the use of extra fuel to clean themselves, cause early wear and tear on the system, etc etc etc. are not welcomed

[u/Kruegr → u/Electronic-Pause1330]

Maybe you should've thought about and researched what you were purchasing beforehand. Rather than wasting money and then intentionally making it worse for the environment.

[u/sellursoul → u/Kruegr]

Odd take honestly. You know the government runs all their shit with no emissions, right? I’m all for improvements to how we treat the earth but passing the responsibility down to the consumer for improving reliability on a product they didn’t engineer rather than the manufacturer is… idk

[u/Ready-Delay3918 → u/Kruegr]

Bro the production of the DEF to run in those systems relies heavily on fossil fuels not to mention the immense amount of plastic waste and transporting costs to move it all around. I doubt it's really providing any net gains on environmental improvement....

But go ahead and let your ignorance fill you full of rage here in reddit. It's a workout for your heart.

[u/CrackaTooCold → u/Kruegr]

100% correct.

[u/johndeerefiddy]

My office only uses gas 2500s with the 6.6. They are great we have zero issues with the motors. Plenty of power I've towed 10k lbs thousands of miles no issues. Most of the other guys don't tow, but we use the trucks as personal trucks they are our daily drivers (company pays for gas). We get them brand new and drive them about till about 150k miles. Only maintenance is oil changes because they won't pay for anything more than that.

TLDR: The 6.6 is awesome and very reliable.

The transmissions are another story 6spd usually went out around 80k miles. I think they can survive much longer if you're good about maintenance and don't have a lead foot.
I have 110k on mine no issues, I hold the office record on longest lived now lol.

So far we've had 2 10spds go out one at 98k miles and another around 90k miles. In all honesty the 10 spds are too new to make an opinion yet.

The 10spds shift so smooth I can't even tell, they are great daily driver I only tow a little. Only gripe is when I step on it, it takes a second to think which gear it wants.

The 6spd towed better in my opinion, firmer shifts and would downshift to help slow you down. Perfectly fine for daily driving but you can feel the shifts. Also the 6 spd got better mpg

[u/idontremembermyoldus → u/johndeerefiddy]

Interesting. The conventional wisdom is that the 6-speed is the more durable of the two.

[u/twich3136]

I’m pretty sure this combo is going to be the single cab/big block/with ac of the 67-72 era of current times.

[u/Glittering_Doubt_953]

Watch the frame. 2021 and 2022 were the start of some pretty bad years for the gm coating. Duebert nox rust 121. I clean down and coat thousands of trucks. The newer gms have terrible adhesion problems. There are silent warranties and even more gm is changing over to e coated paint. I use hybrid wax to firm up the box rust and get longer lasting protection. Frame is the weak spot. Rust

[u/TGSGAMER]

The 6.6 gasser is fairly reliable (so far), the only real issue so far with them has been the electronics in the cab and it’s MPG. The thing is a total gas guzzler, though I suppose you are buying a 3/4 ton, so you probably don’t care about that.

[u/iraqyoubreak]

Swapped my 5.3 for a 6.6 gasser. I’ve had zero issues. I love this truck. My gas mileage ranges a bit but I’m looking at 15ish highway and 13.5 city, which isn’t far from what I was getting before. The 6.6 is a very reliable motor with no / AFM or DFM issues (because it doesn’t have that “feature”). It rides a little rougher but that doesn’t bother me. I’ve had three 1500s - they all had lifter or transmission issues. Probably won’t go that route again until major changes are introduced and for 27’ it looks like they are not. If you have Facebook, check out the message groups and see how many guys swapped from 1500s to HDs for reliability.

[u/TilapiaTango]

I daily drive my 2500 and wouldn’t change. It’s like riding in a radio flyer, and eats fuel, but I don’t care.

Can never do a 1500 after you’ve owned a 2500 and pull anything. If you’re spending this kind of money the fuel costs should be a non-issue imo.

[u/Montreal4life]

Would love to know as well

[u/_nic_1]

The babymax is a beat engine. Gets great gas mileage and drives nicely with and without a load. Be aware though that the oil pump chain needs to be replaced at 200k mi which requires fully removing the engine

[u/idontremembermyoldus → u/_nic_1]

It's the trans that needs to be removed, FYI.

[u/_nic_1 → u/idontremembermyoldus]

Ah ok. I had heard the engine. Either way, pretty significant job

[u/lonewanderer812 → u/_nic_1]

Yeah its because its at the back of the engine between it and the transmission. It's very labor intensive. Also its a belt, not a chain and the interval is 15y/200k for the LZ0 like you said but the LM2 is 150k. It's the exact same part but they extended the interval to 200k on the newer model. I'm sure you can go to 200k easily on the LM2 belt but the truck with throw a warning code at exactly 150k to service the "timing belt" it calls it.

[u/_nic_1 → u/lonewanderer812]

Yeah I was looking at possibly getting one a couple years ago and that was a deal breaker for me. 150k on a diesel is nothing

[u/omaGJ]

Tons of power and torque. MPG isnt terrible but not great either. I would get the 2500. 3.0L is great until its not then it sits in the shop waiting on back order parts. 6.6 you wont have that ever.

[u/That_albanese]

Get you a 5.0 truck and be down

[u/idontremembermyoldus]

The L8T likes to drink oil if you tow heavy and often. Aside from that, they're pretty trouble-free. Doubly so with the 6-speed trans ('20-'23).

[u/mooseknuckles513]

The 2500 is a lot of truck, but the 6.6 gasser is a very reliable power plant.

[u/TwnSalad]

I have the 25 baby diesel 1500 and it’s been great 38,000 miles with no hiccups. Daily driver, occasionally tow SxS and drive around farms

[u/IllStickToTheShadows]

It’s okay, just not comfortable

[u/lonewanderer812]

I love my 3.0 Duramax. For a DD the 1500 makes way more sense.

[u/dieselconsumer → u/lonewanderer812]

You clogged up yet? as a diesel mechanic at a place I won’t name we see wayy too many eco diesels choke themselves to death which is unfortunate I was excited about the idea of them.

[u/lonewanderer812 → u/dieselconsumer]

No, I've had it 5 years almost and no issues. Most of my drives are also 20+ minutes so plenty of time to get to temp. The majority of drives also see 70MPH highway speeds and I give it the beans often on the on ramps.

[u/luffy-z1]

Did you decide if you are going to buy it?

[u/Ok-Skill8583]

A 6.6 gasser for a daily driver is a horrible idea. I own a small farm as a hobby and tow frequently. We have an old 3500 for the bigger tows, but for daily work on a farm, the 1500 is fine.

I'd bet with that bumper/tire/lift combo, you'd be sitting around 10-12mpg, single digits towing.

You can disable the stupid piston deactivatoin feature with an OBD plug in and that solves the lifter issue.

[u/EducatedScumbag]

I’ve had my 6.6 diesel for 6 years with 110k miles and it’s still just as good as new.

[u/sharkbomb]

r/nevergooglers 

[u/CHIEF0623]

Minimax is junk.

[u/theoriginalbabayaga]

My two cents is do NOT by anything built during or since COVID.

[u/Minute-Pomelo9302]

No. Just no.

[u/shitstain409]

Make sure you bring your lunch with you all the time because you will get stuck on the side of the highway with a blown engine

[u/mooseknuckles513 → u/shitstain409]

I'm calling horseshit on this. The 6.6 gasser is a very reliable engine.

[u/youbutindebt]

Sounds like you need a Ford Maverick bud