GM 6.0/4sp vs. 8.1/Allison vs. 6.0/6sp

[Brisk]

Hi all.

My Towrig in Sig is getting a little long in the tooth. We just bought a New to us Toyhauler which is quite a bit heavier than our old trailer and my truck is hating life lol!! We were planning on upgrading the truck next year anyway but found a trailer we loved so we did that first.

Old 5th wheel was 8k ready to camp. I haven't weighed the new one yet but dry weight is 8200 so an educated guess would be 9500-10500 without "toys" and 12k with.

My plan is to buy a newer used truck in the next year. I have always had GMs and have had great luck with them and I know how to fix them so my plan is to stay with GM. I DO NOT WANT A DIESEL

I am curious if anyone has first hand experience towing with an 8.1/allison truck or a 6.0/6sp truck compared to a 6.0/4sp. Right now I am pulling 6% grades at 35-40mph in 1st gear (my old trailer was 60mph in 2nd)and running in 3rd at 60 on the flats at about 6.5-7mpg (old trailer was 4th at 60-65 and 8-9mpg) I am wondering how much of an improvement I should expect with an 8.1 or a 6.0/6sp.

I know what the tow ratings and hp/torque numbers are but I am looking for some real world experience.

Thanks in Advance!

[jerem0621]

I know you said no to diesel and no to anything but GM but the 6.4 gasser in the Ram is the best gasser for towing right now. 400 ish HP and its a beast. There should be some used examples popping up as towers upgrade to diesel.

I'm a Gassers guy like you and would consider any of the big three with the deepest axle ratio possible.

IMHO...an 8.1 would upgrade your motor but the trucks are getting old that surrounds them. If you can swing it I recommend going for the 6 speed. 6.0 or the 6.4 Ram with 4:10 gears

The other option is to upgrade to 4.56 years in your truck now to improve the towing experience.

Good luck...hunting is the fun part.

Thanks!

Jeremiah

[CampingN_C_]

I'm convinced the 8.1 doesn't exist in a CCSB 4x4 that's not a work truck. They are truly a needle in a haystack.

[Dadoffourgirls]

I had the 8.1 with 4sp and 4.10.

I find the 6.0 with 6sp and 3.73 sufficient for towing, and 30% better fuel economy.

I think a 6.0 with 6sp and 4.10 would work ok. The 8.1 uses oil between changes.

[kw_00]

Well I have had good experiences with my truck in the sig. I had the 02 with the 4 speed and 6.0. I have never owned the 8.1 but all of the 8.1 came with the ally it was standard , not an option. So if u come across one of those with low miles I would snag it quickly. If comparing the 6.0 gas job with both the 4 speed and 6 speed, then 6 speed hands down in my opinion. Pulling my current load with both, the 6 speed truck does it easier. Towing in fl I keep in 5th, if steep hill then 4th and up it goes without issues. On the older 4 speed I had to tow in 3rd and any hill it would drop into 2 nd. So the 6 speed in my eyes is much better overall matched with the engine. Pull the grade in 4th around 3k with the 6 speed or in 2nd at 4500 with the old 4 speed. That has been my experience, so others I am sure will vary. The 8.1 combos are hard to find with CC and 4x4, at least around here that is. Regardless good luck with your search.
Kris

[TomG2]

Even though it is better to tow with than my 2007 6.0/4-speed, my current 6.0/6-speed is no powerhouse. The six speed does allow you to match rpm's to road speed more efficiently. For instance 4th gear at 3,000 rpm's and 60mph will climb most hills that you will encounter. You have more choices for cruising than with the 4-speed.

[APT]

Paging Dick_B... He has experience with the 8.1L and now the 6.0L/6-spd. I believe his prior TV was a Suburban which did not use the Allison trans, but experience should be similar. I looked for an 8.1L Burb for about a year before buying a new 6.0L/6-spd. That is one strong engine.

Going to 6-spd with the 6.0L will feel quite a bit better. Take a look at this chart comparing the gearing and torque multiplication for the SUV 4-spd trans to the 6-spd. The Allison does a little better with a 3.1:1 first gear ratio. As far as I know, all pickups with 8.1L used the Allison trans and the Suburban/Yukon XL/Avalanche 8.1L had the in house 4-spd as Burbman mentioned.



So the newer 6.0L still likes to rev. It would still be singing or screaming at 5000rpm up some hills. The 6-spd will help get and keep the engine in it's happy range. You would probably end up spending most of your time towing in 4th gear as I don't know that it could hold 5th on flat highway. You need the 4.10 axle as the tow ratings for 6.0L/6spd/3.73 is in the 9500-ish pond range. 4.10 is about 12k until 2011 I believe which is near 14k pounds.

Honestly, at your 12k estimated weight, I would suggest 8.1L or the diesel you said you don't want.

[BurbMan]

The Ally was standard with the DMax but I thought it was optional with the 8.1, maybe I'm not remembering that right. I know wasn't available at all in the burbs 😞

The base trans in 01-02 was the 4L80E, then in 2003 the 4L85E. Look for the RPO code sticker in the glovebox when you are shopping, MT1 is the 4L80E, MN8 is the 4L85E, M74 is the Ally.

[Brisk]

I am pretty sure the Allison was standard in the 2500hd/3500 8.1 trucks. I know the Suburban and Avalanche had the 4L85E due to fitment issues.

I need a crew cab srw 4x4. I know they are few and far between but that is why i am starting my search now and am also considering 2007.5 and up 6.0 trucks with the 6sp auto. (Assuming one will pull significantly better than my current truck)

[BurbMan]

The Allison trans was an option with the 8.1L, if you could find one it would certainly do the job for you, but '08 was the last year for those in a pickup. Most folks that tow heavy ordered the DMax, and only a few 8.1L buyers paid the $$ to upgrade to the Allison...so good luck finding one.

Just did a search and there are only 49 8.1 Chevy or GMC trucks in the whole US on Autotrader, only a few of those will have the Ally trans.

Here is an GMC extended cab dually 8.1/Ally with only 30k miles about 300 miles from you.