Tow Report - 2004 3/4 8.1 Suburban

[ksu_j]

Hey Folks,

Some of you may remember me going back and forth here about a year ago on whether or not to trade in my 2005 Denali XL on my now 2004 3/4 Suburban. Well I did. I wanted to post a quick one year review + towing report of the "new" suburban.

My one year thoughts will be pretty short. Pros: paid for, decent ride, great power, no maintenance issues. We have upgraded to a DVD system in the car, as well as keyless entry and blue tooth radio, so it is a bit more modern than it was when I bought it. Cons: gas mileage empty is terrible, like maybe 11 mpg bad, not nearly as nice as the Denali, no bucket seats, and the 4.10 gears kind of suck to drive on the interstate at 75.

My trip report will be longer and more detailed. I loaded up the family of 5 and took off from Kansas to the Smokey Mountains of Tennessee a few weeks ago. We were pulling our new to us 2002 2505 KS Frontier. Not sure about total weight as one reason I got the 3/4 Suburban is now I don't have to worry about it. I'd guess the camper was close to 6,000lbs.

Anyway, after almost 2000 miles of towing, I couldn't have been more impressed with the suburban. We were traveling with my dad who was pulling a 27ft travel trailer behind his 2007 1500HD with the 6.0 V8. His truck is sufficient for that job, but it works it. He could go about 180 miles between fill-ups. I would often times not even be down to a half a tank with the suburban. That's a nice difference between a 26 gallon tank and a 37 gallon one. Through the rolling hills of I40 through TN, his truck would drop down to 45mph on some hills. I could have, and did sometimes, set my cruise control at 65mph and it would just chug along in high gear (thanks 4.10 gears). To be fair, my dad's camper is a fair bit taller than mine, so the wind is a big factor for him. I did the majority of the trip leading him so he could tuck in behind me.

At fillup time, I would guess I averaged right at 9 for the trip. My worst fill up was 7.8mpg and my best was 10.4. The 10.4 was impressive since I've only seen 11mpg + twice when running this thing empty.

Pulling was a fun job. Set the cruise and sit back and relax. I told the wife that we could easily do a trip to FL for Disneyworld or something by ourselves with this set up in a rather stress free fashion. Funny enough, even though my dad's truck has the smaller 6.0, when we'd stop for gas, I'd always be within half a gallon of what his truck was taking, usually taking more gas, but sometimes less. I'm very happy trading an extra half gallon of gas for the seemingly limitless power of that big block. This set up was rock solid. No sway, absolutely no braking issues even though I had a few times I had to take some quick stops. Truck rode nice and level with the WDH dialed in (really rides level without it too, but I used it anyway). All in all a fun towing experience and I was not ready to go home.

Side note: My family LOVES our "new" KZ Frontier. It has quad bunks up front which is awesome for my three kids. It has a full length couch, dinette for 4, and a queen sized rear slide-out bed. Tons of storage underneath and everything worked AWESOME on the trip. We had a lot of fun.

Takeaway thoughts from the trip: I no longer have an urge to buy a newer 3/4 suburban to try and get better non-towing mileage with. Since this beast is paid for, and does an awesome job on long towing trips (only has right at 100,000 miles) I plan to let this thing become more or less a garage-queen and use it for only towing jobs. I'm probably going to go buy a nicer newer car for myself and the wife to use as a daily driver (I work from home). The wife's Pilot is getting up there in age. 145,000 miles. My thoughts if I can get a cheaper smaller car for her and I to drive daily, this would save some life in both the Suburban and the Pilot. The Pilot will be replaced hopefully around the 200,000 mile mark. I might end up keeping this suburban for a long, long time....

Sorry for the long post.

Let me know if you all have any questions or comments!

[minnow]

I had a 2001 8.1 Suburban and now a 2004 Silverado 8.1(needed to trade out the Suburban as we went to a fifth wheel). Gas mileage is always 7-9 towing and 10-12 when not. There is not a better gas engine for towing in my opinion although I'd be interested in seeing what the Ford 6.2 does. I'd sure like to get something newer but this is working well for now and it's paid for and again not sure a newer gasser would compare to what I have now as far as power and grunt.

[ksu_j]

ktosv wrote:
BenK, I am glad you posted those curves. When comparing them to the L96 6.0L (with the 6 speed combo) you can see why GM didn't have to offer the big block anymore.

The L96 with a 3.73 and the six speed puts more force to the ground than the 8.1L/4 speed 4.10. That is assuming the off idle performance estimated from these curves. The 8100 actually has about 15 more HP off idle...so it would really be interesting to see just how close the two are.

Yeah, I should put a disclaimer on my thoughts about the 8.1 vs 6.0. The disclaimer should be "for the money". For the money I have in this 8.1 (in that it's paid for with just over 100,000 miles) it's worth it to me to stick with this as I feel the performance upgrade would be marginal at best by going with a newer 6.0 6speed. Obviously, I'm sure the mpg would be much, much better. But I figure a comparable 3/4 Suburban with the 6/6speed would cost me between $20,000 and $25,000. $20,000 buys a whole lot of gas. Add in the cheaper insurance and taxes on this older vehicle and I don't see much reason to go newer when this one does the job really well.

Like I said before though, I probably will look into getting a little 30mpg daily driver for the wife and I so that this one can be more or less strictly a tow vehicle for the next several years.

[Elbert]

8.1 3/4 sub is a great truck and a great tow rig. I had one for a while and only got rid of it because I needed a pickup. The 6.0 engine only gets around 1-2 mpg better than the 8.1. I've had two 6.0 trucks and one 8.1. Until you tip scales somewhere north of 10k in towed weight I think the 8.1 3/4 ton sub is a great option. Never had issues with mine. Short bed pickup only has 25 gallons and the long bed has about 36 gallon tank...similar to sub.

[BenK]

Yes, amazing what these small blocks can pump out...but not fair comparing
my 19 year old big block with them...

Would love to have a big block with current technology and why am noodling
for when am ready to spend some money on my Sub. I'll keep it till the wheels
fall off and can't/won't fix it anymore. Dislike the current offerings. Too
many bells and whistles and the gouging in $$$$

Forced fed and will have to design/make my own inter cooler

Rebuild the 7.4L. Must keep the OEM heads, as all the after market I like
are labeled 'off road' only. For sure either SS or maybe sodium valves. Another
for sure is a big cam of some sort

No headers

Diff's will go to something in the 4.88's or lower

GearVendors seems to be the only choice found to date. 0.7 or 0.5 ratio
and love the thought of their electronics allowing splitting all the gears
of the 4L80E to become an EIGHT speed setup

That should allow cruising at 75 MPH at about 1,800 RPM or so with torque
north of 500 ft/lbs (hoping). For my trucks, I drive to torque more than HP
For my 2 seater, I drive to HP

and a bunch of other stuff

Back to the OP's point...

Owning a tool bigger than needed (for now) allows tremendous numbers
of options

Also know that the rear GAWR is going to allow even more options
in trailer.

Main issue is the OEM receiver. Recommend changing it to a traditional
design, if the previous owner(s) have not. Just do a search here
on 'POS receiver' and that will lead to many hours of reading...

[ktosv]

BenK, I am glad you posted those curves. When comparing them to the L96 6.0L (with the 6 speed combo) you can see why GM didn't have to offer the big block anymore.



The L96 with a 3.73 and the six speed puts more force to the ground than the 8.1L/4 speed 4.10. That is assuming the off idle performance estimated from these curves. The 8100 actually has about 15 more HP off idle...so it would really be interesting to see just how close the two are.

[Wes_Tausend]

...

Great report. Thanks.

I was once looking for a 3/4 ton Suburban, but ended up with a 6.8L Ford V10 Excursion instead. The big Burbs are harder to find.

Our V10 fuel economy is significantly better than Ford's old 7.5L (460 cu in), but your 8.1L might still beat V10 towing economy, as I'm lucky to ever break over 8 while towing and have hit as low as 6.2 mpg against a stiff headwind. Like you say, the towing fuel use is not a big deal as they are all similar, and it's nice to have reserve power and a drivetrain to go with it. Though I think the heavy rear axle drag is the worst fuel use culprit when not towing, as everything else is comparable to 1/2 ton specs.

The V10 non-towing economy might be a little better than your 8.1L, as our V10 seems to average about 13 mpg, but the Ex has taller 3:73 gears too. In this 8.1L vs 6.8L difference, I wonder if your Burb would do marginally better with 3:73's? And/or it might also be due to less V10 engine displacement (only 415 cu in)? The best our Ford Excursion has ever done is 14 mpg (70 mph, no wind) non-tow, or about your same 10.4 mpg peak while towing (55 mph, tailwind).

We towed a couple of 30 foot trailers over the years, this last one a bit taller and heavier with a slide. I don't think length has much to do with fuel economy, but frontal area does.

We kept our Excursion after we got a diesel pick-up and there are those times when either truck is slightly more economical depending on gas vs fuel price fluctuations. The diesel sucks during short-trip winter driving. It blows good cabin heat early on, but takes forever to reach normal healthy engine operating temps. The gasser warms quicker, drives quieter and smells better, especially in winter. It's really a toss-up overall and I probably shouldn't have wasted money on a diesel. It gets about 11.5 mpg towing, but that is not a lot better for the trouble.

One other fuel difference may be an advantage: I would rather leave a diesel parked for extended periods, as I think the cylinder walls remain oilier, where some gasser cylinders are so dry they actually rust during long non-use periods. Gassers really should be properly moth-balled with generously oiled cylinders when parked for long periods.

Wes
...

[MegaCab_PL]

Thanks for the report, the most important think you had fun with your family, were safe and comfortably on the road. Screw the gas mileage 🙂 It's meaningless when years from now your kids will remember camping with you because soon they'll be too big and won't go with you 🙂

Your 2500 Suburban is the same class GMT800 as your dad's 1500HD, both have very similar chassis with 8600 GVW rating, both have almost same trannies: yours is I believe 4L85E, and his is 4L80E but otherwise almost same trucks. The 8.1 makes a HUGE difference as you noticed.

[BenK]

More gears (close ratio) does help keep the ICE in it's best torque/HP
curve range, but having almost full torque just off idle is what
others are saying about the 8.1L big block...my 7.4L Vortec and also
tossed in the 7.4L TBI

The 6.0L is a fine small block and the close ratio 6 speed makes it
even better...but having that torque down that low also a wonderful
thing to have...now if only I can get more gears...well it is in my
plans to put in an inline 0.5 or 0.7 gear splitter to make my old
4L80E into an 8 speed...along with going from 4.1's to something in
the 4.5x range



GM 6.0L LQ4 torque curve

GM6.0Ltorquecurve 6.0Ltorquecurve


GM 8.1L L18 torque curve

GM8.1Ltorquecurve L18torquecurve 8.1Ltorquecurve L18



GM7.4Ltbtorquecurvce tbtorquecurve 7.4ltbtorquecurve


IIRC, my spec sheet from the day I ordered mine said 410 Ft/lb torque at 1,800 RPMs...

GM7.4LVortectorquecurve 7.4Lvortectorque 7.4LvortecL29 L297.4Ltorque

[ksu_j]

ktosv wrote:

ksu_j wrote:
We were traveling with my dad who was pulling a 27ft travel trailer behind his 2007 1500HD with the 6.0 V8.

Is this a "classic" 1500HD based on the GMT800 platform? Or is this a GMT900 with the VortecMax package?

Either way, I think your dads 6L has a 4 speed transmission behind it and that would explain why your truck does so much better. It would really be interesting to compare the 6L/6 speed combo to your rig.

Glad you like your Suburban. About the only reason my wife misses hers is because the ride was a little better than her van.

It is a classic. Old body style, 4 speed transmission. He has 3.73 gears which hurts also.

That said, I'd put the 8.1 with 4.10's up against a 6 speed 6.0. The torque I can get low in the rpm band is pretty awesome. I think the 4.10's might be the bigger difference. I can run all day in high gear. Inn third gear, this thing really moves.....

[fla-gypsy]

You know what they say about having the right tool?

[ktosv]

ksu_j wrote:
We were traveling with my dad who was pulling a 27ft travel trailer behind his 2007 1500HD with the 6.0 V8.

Is this a "classic" 1500HD based on the GMT800 platform? Or is this a GMT900 with the VortecMax package?

Either way, I think your dads 6L has a 4 speed transmission behind it and that would explain why your truck does so much better. It would really be interesting to compare the 6L/6 speed combo to your rig.

Glad you like your Suburban. About the only reason my wife misses hers is because the ride was a little better than her van.

[Lessmore]

The Chevy big block 'Rat' gas motor has always been a magnificent engine. A gas hog for sure...but a lot of punch.

[ksu_j]

IdaD wrote:
Thanks for the write-up. Interesting trailer too. I'm shopping and I hadn't come across that floorplan yet. We also have three kids so I'm looking at options where everybody has a bed and I'm struggling to find that in something that isn't way too long. I'm not worried about weight or how the thing tows down the highway with my tow vehicle, but I do like to dry camp out in the mountains and getting a very long trailer into (and out of) some of those spots can be tricky. Lately I've actually been looking at toy haulers with the idea that they are more flexible for dealing with a growing family and some of them have pretty comfortable layouts and could fit the five of us pretty well. The search continues...

Glad you like the new 'burban.

Yep, I'm really happy with our camper. I park it next to our house here in town, so length was a concern when I was shopping. Parked by the house and going down the road it's 25 ft long. Opened up and set up to camp, it's right at 30 ft. I used this camper to tailgate with one weekend last year. I had 7 full grown guys sleeping in this thing for a night. Everyone had their own bed. Although mine was quite honestly by far the most comfortable, but hey, I'm paying for the thing, so....

[TXiceman]

Nothing like enough truck for the job. The 8.1 is a strong engine, but like any gasser it takes a lot of gasoline to pull a trailer.

I am a firm believer of a diesel engine for heavy work. Out 6.7L F350 Dually will typically average 9 to 10 MPG, running 63 MPH with our 40', 18500# 5th wheel. The truck running solo (weighs about 9200# loaded) will do 15 to 16 mpg.

Last fall we traveled across Tennessee headed east and maintained 9 mpg.

The Ford tank is 37.5 gallons and we added 40 gallon auxiliary tank. It makes traveling so much nicer when you are not having to watch for fuel every few hours.

Ken