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Guys with the 8.1

buffblazer

buffblazer

1/2 ton status
Joined
Jan 5, 2005
Posts
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Location
Fort Collins Colorado
looking at buying a 2006 crew cab 2500HD, truck is everything thing i want and milage and price are where i want them.

I wanted a 6.0 but this truck has the 8.1 im kinda sceptical about it, my dads 05 2500hd with the 6.0 gets about 15-16 whats the 8.1 gonna get?

also does the 8.1 live up to its size with lots of ponies? i remember the old 454 were gutless from stock and would get ****ty milage and i know it will never pull as good a diesel but im wondering how it does for a gas motor?


also what tranny is behind those?


i guess anything else that yall might think of thats different between the 6.0 and the 8.1 let me know.
 
Tranny is the allison. I personally don't have one, but everyone I know who has one, loves it. If it's in good condition, and doesn't use any oil as some do and some don't. I say it's a good choice.
 
I don't have one but, when I moved down here to South Florida, I rented a 26' u-haul truck and moved a 2 bedroom house, all my tools, and pulled a u-haul trailer with a '77 grand prix(last of the big ones) and was impressed. I had to really watch the speedo 'cause I'd be in ticket territory without even trying.........
 
I'm not sure if it has the Allison or not behind it. I drove an Avalanche that had the 8.1 and it had the 4L80E in it. The allison has a spin on oil filter, so look for that.
I thought the 8.1 did a good job. Right about between the 6.0 and the Duramax.
We got 9 mpg pulling 8000lbs to Florida and back, doing 70mph.
The owner said it does about 11-12 everyday, remember this is in an Avalanche, not a HD.
 
I bought mine new and was sceptical at the time but got such a good deal cause no one wanted to feed that pig. It gets about 11 mpg, all the time, loaded or empty. It pulls just as good as a diesel. Tows like it's empty, plenty of torque to pull with and the Allison trans is the greatest thing ever as far as automatics and towing go. The 11.5" rear AAM axle is about as strong as you can get.

The factory has the 8.1 detuned to prevent parts breakage, but it still has no lack of power when you need it. Unloaded, it's not a tire spinning monster but I have heard if you do the exhaust, intake and power programmer upgrades, it will unleash plenty of untapped power. I don't know how to describe it but in stock form it feels sluggish compared to the 6.0, but trust me the power is there. Once it's loaded up the 6.0 doesn't hold a candle to the 8.1. My friend has the same truck as me but with the 6.0 and we went to pick up a couple derby cars. On the way back we hit a 2 lane with stop lights and did the obligatory stop light drag race. The 6.0 fell behind right off the start.

If you plan to tow or haul with any kind of frequency, the 8.1 is the way to go. You won't be disappointed, except when you hit the gas pump. I bumped the front torsion bars up 1" and fit 285/75R16 tires on the stock wheels with no rub or trimming.

Teaser pic...
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I have a 06 GMC 2500HD 8.1 w/ allison 6 spd ..Hypertech programmer , throttle bdy spacer volant cold air inteake ad a granitelli MAP .

I get 11ish mixed driving . all city drops to 9.5-10 . hwy empty is about 12-13 loaded towing 9K lbs it gets about 8. Has alot of power and is a beast towing. Empty its hard not to speed on the highway . 50-90 comes up fast .lol
 
has anyone checked out what the price to have one of those Allison transmissions serviced/rebuilt?

I used to work with a guy that had a 1-ton with the Duramax/Allison combo, he told me it was something nearly $5-$10g just to have one rebuilt, guess something similar to a semi-trucks trans or something.

I'm not stating this as a fact, just from what i was told, i don't know and have never checked on it myself, as i don't have one "YET" ;)

But other than the price of a severe service, it sounds like an awesome trans to have.
 
I have one of the 2500 Avalanche's with the 8.1.
It does great towing but is a gas hog (10 in city, 14 hwy, 8 towing.) I have the 4L85E transmissi
Engine.JPG
on, so the extra gear that the trucks have with the allison would probably help out.
I have a K & N cold air intake, and a diablosport predator tuner, and I am looking for a place to make a dual exhaust.

I would say that if you tow frequently, the 8.1 is the way to go, but if you rarely tow, then a 6.0 might be a better choice.

Avside.JPG

Engine.JPG
 
wow, i'm guessing this motor has some serious potential, looking at that last pic of the engine compartment, and the size of that intake tube/throttle body,,, well, the last time i saw a tube that sized, was under the hood of one of my 12 ltr Detroit/Cat/ Cummins motored trucks :eek1: very nice :D
 
I am looking for a 8.1 crew lwb for the farm. My dad has a reg cab lwb 3/4 and it is by far the best truck we have ever had. The mpg isn't that great but seriously the 6.0s are bearly better and if your looking for mpg in a 3/4+ truck your looking in the wrong place. I can't believe how awesome it pulls and runs.
 
I've got a '01 GMC 3500 dually with the 8.1l & 5 speed Allison and like it very much. It will eventually be the tow rig for my k5 but have just been driving it around town for now. It pretty much gets 11 mpg, city/highway and didn't seem much worse heading up in to the mountains. I think having a good amount of low ends torque helps and you don't have to put your foot into it all the time......although it is fun to:D.
The 6.0l for me was not enough better mileage and some guys actually get worse mileage than the 8.1 because they run them so hard when loaded. The Allison 5 speed can be upgraded to 6 speeds but it's like $1500 for the kit.
The Suburan never came with the Allison, they told us when I worked at Chevy it wouldn't clear the body in the trans. tunnel. They also told us a Duramax wouldn't fit there either but lots of guys are converting 'Subs to them.
I got a great deal on my truck when gas prices were high and no one would touch the gassers, especially the 8.1. $11,000 for a semi-loaded 46,000 miles 4wd one ton dually ain't too shabby ;)

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crewcab035-2.jpg
 
Yours is alot cleaner than mine .lol been raining here almost all month . and had finals. need to detail it .
 
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Suburbans and Avalanches have the 4L85E tranny. It is supposed to get a little bit better mileage (like 1-2mpg). The first couple of years of the 8.1L had some minor oil consumption issues. They were fine after that. I just had a mild tune put on the Suburban. It really woke it up and improved the throttle response. I would recommend one for a good all around rig as a towing, work, and a family hauler.
 
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