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Early 6.0 and 8.1 questions


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Howdy folks. I realized this morning after logging on my desktop that I had asked my question in the wrong forum last night. I didn't realize there was a 2500-specific forum. Anyways.

My wife and I are planning to purchase a 2000 - 2006 Suburban 2500 4x4. I know this is a forum for the trucks, but they share the GMT800 platform, and I'm know very little about the heavy duty gas engines on this platform.

The truck will primarily be used "around town" for short hauls and around the house projects. But, with my grandparents and great-grandfather moving nearby, we will also be using this truck to drive to visit family out of state (we're in VA, we have family in CT, NC and TX). My wife and I also plan to purchase a camper in 2 - 3 years, and this will be our mule to tow it cross country.

Some brief research found that the 6.0 engine is good to tow 10k, and the 8.1 is good for 12k (ish, its a ballpark don't nitpick me). After some checking, I figure most things we will tow will fall into the 6k - 8k range, however I have a work truck that needs towing from time to time, and that's pushing 7k before I put it on a trailer. I believe the 6.0 will do fine for most of what we want to do, and I am leaning in that direction. 

What kind of fuel economy can I expect out of a 6.0 or a 8.1? Do either engine (or their associated transmissions) have any major issues? Are either of these engines capable of running E-85 (yes, I'm aware ethanol is the devil, I just want to know if it can be run).

Thanks in advance!

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Switching to this thread now. E-85 is possible with a little modification with the 6.0 and 8.1. I am not sure how easy it is on the 8.1 though as I have never done it.

 

8.1 main issue is after market stuff if you want to go bigger/get more power out of it. Also it is a little harder to work on but nothing major. 6.0s are strong engines, best to put in a performance camshaft and swap heads to bump the compression up a bit and you will have an incredible engine. If that isn't your thing then you are completely fine going with stock. The knock sensors on these engines are known to go bad but they are easily fixed.

 

6.0 you can expect low to mid teens when not towing. 8.1 is pretty close to being the same maybe a little worse. The 4L80 is rock solid and it is very hard to get it to break lol

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The 6.0 is a work horse for sure.  The 8.1 is as well but I'm under the impression that it had oil consumption issues, but I could be wrong.  As for E85, it isn't the devil.  It is just miss represented.  Mainly by those that don't take the time to learn about it and just read all the bad things that people post.  I ran E85 in my non flex fuel 2002 Silverado 5.3 for over 40k miles at a 50/50 mix with no issues.  I just enjoyed the better performance and cleaner burning features.  Not to mention the exhaust smell. lol

 

The transmission is a solid unit as well.  As long as it was taken care of with fluid changes.  Most neglect that and then wonder why they are having issues. 

 

Make sure you look over which ever one you get really well.  If you can find a one owner with maintenance records that would be golden.

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4 hours ago, shakenfake said:

Switching to this thread now. E-85 is possible with a little modification with the 6.0 and 8.1. I am not sure how easy it is on the 8.1 though as I have never done it.

 

8.1 main issue is after market stuff if you want to go bigger/get more power out of it. Also it is a little harder to work on but nothing major. 6.0s are strong engines, best to put in a performance camshaft and swap heads to bump the compression up a bit and you will have an incredible engine. If that isn't your thing then you are completely fine going with stock. The knock sensors on these engines are known to go bad but they are easily fixed.

 

6.0 you can expect low to mid teens when not towing. 8.1 is pretty close to being the same maybe a little worse. The 4L80 is rock solid and it is very hard to get it to break lol

 

Not really looking to build a powerhouse, just a stock driver, so lack of modifications for the 8.1 isn't an issue. Lack of parts for repairs would be though. I did read about the cam position sensor going bad being quite the headache in the 8.1.

 

1 hour ago, Black02Silverado said:

The 6.0 is a work horse for sure.  The 8.1 is as well but I'm under the impression that it had oil consumption issues, but I could be wrong.  As for E85, it isn't the devil.  It is just miss represented.  Mainly by those that don't take the time to learn about it and just read all the bad things that people post.  I ran E85 in my non flex fuel 2002 Silverado 5.3 for over 40k miles at a 50/50 mix with no issues.  I just enjoyed the better performance and cleaner burning features.  Not to mention the exhaust smell. lol

 

The transmission is a solid unit as well.  As long as it was taken care of with fluid changes.  Most neglect that and then wonder why they are having issues. 

 

Make sure you look over which ever one you get really well.  If you can find a one owner with maintenance records that would be golden.

 

I did read the 8.1 has some oil consumption, but I'm looking at buying a 20-year old truck, I expect to burn some oil. I know E85 isn't really the devil, I ran it in my Tahoe all the time, and I run E15 in my Honda whenever I can find it. Like you said, its miss represented. 

 

Happy hearing good things about the transmissions right off the bat. I'm dealing with issues with my businesses F-250's transmission right now, and it's not something I'd like to revisit.

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Yeah I had only suggested those two things because the 6.0 has an incredibly weak camshaft for what it is in. And the compression bump you would gain from swapping to another stock head casting would give you some more power being that you are on an all gas engine. Just a thought :)

 

I would still go 6.0 over the 8.1 though.

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The 6.0 LQ4 is a torque engine, unlike the 6.0 LQ9 which is the same engine designed for higher rpm in Cadillacs and a couple other platforms. My '03 GMC 2500HD LQ4 CCSB was used for towing vehicles with a gooseneck hitch and car trailer before I got it, and the engine is still in great shape. Although the 4L80E was burned up, so I had it rebuilt stock in case something goes wrong on the road. 

The 8.1 has an Allison transmission behind it and is more powerful and better for towing than the 6.0/4L80E. I looked for an 8.1/Allison for quite some time, and found a few, but they cost at least 75% more that the 6.0/4L80E. So I got what I now have for $4000 and am very happy with it. 

My 7500 pound travel trailer is noticeable behind my GMC but I'm not at all concerned about it with the tow mode shift points and efi changes. After all, it's not a diesel dually meant for full-time towing. I can unhitch and have a very nice 4x4 truck to play with or just drive into town.

Good luck with your decision and new to you truck!

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