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Old 03-13-2003, 08:51 AM   #1
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Experience with GM454 and MPG

Well I'm looking for a tow vehicle and I know roughly what I want.
I have been looking for a 88-91 Suburban. I'm more looking for a 2500 (3/4 ton) because I really don't think the 10 bolt in the 1/2 tons is a very good axle for towing. The 14 bolt is about indistructable. I honestly could get a 14 and install it in anything but finding the 6 lug 14 is hard but 8 lugs you can get for $100 all day long. Problem is converting the front to 8 lug would be a pain in the butt.
Anyway on to my question. In I think 90 GM started installing the 4L80 Heavy duty over drive transmission to replace the TH400/475 three speed tranny. My tow rig is going to have to be my daily driver so MPG is a concern with my 44 mile drive every day. Thankfully I don't deal with traffic so I cruise right along at 70mph.
While Our Airstream is relativly light at under 4k ready to go. I am concidering occasionally pulling a 8,500lb load. not sure a 350 would be up to it and I don't care for the Deisel's GM was using back then.
I know a 4x4 1500. 5.7 with OD will get 18 hwy. I can llive with that. I am running accross a lot of 454 3 speed 2500's What will I get out of one of those?
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Old 03-13-2003, 09:09 AM   #2
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Toaster,

Our '85 3/4 ton (2wd) w/ the TH400 got between 7-9 mpg pulling about 7,000lbs and about 11 without.

It had a monster 4bbl. In the 90s as you already know, they finally had fuel injection for the 454, so those numbers are most likely to only increase (if only modestly).

There was a guy on this forum that has the 2500HD w/ the 8.1L and I thought I reacall him saying that he was getting about 13, MAYBE 14mpg, but I am not sure if that was pulling or not.

One thing is for certain, the 454 will more than be up to the task. I think the 3/4 ton is the only way to go dealing with what you are talking about. If you can find one with or install one after, the 4L80 is a great trans and would make the package even better. Ours (above) pulled the weights stated and we barely (outside of watching the 40 gallon tank's gas needle slowly move south) knew the box camper was back there at all!

And you are also right, the diesels were nothing like the ones they have now. The 6.2L although strong always made me a bit nervous. Mabye it was because of all the bad things in the 80s GM did with diesel that freaked me out, who knows, but I think I'm on the same page with you on the diesel from that age/era.

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Old 03-13-2003, 09:45 AM   #3
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Yeah I hope that one of the FI's will get about 16 hwy. I can find tons of those. I just have too many cars right now and I can't afford the insurance for an econo box DD and the Suburban. It has to do double duty. I wish my wife would concider it as a DD. She's a stay at home mom so a tank of gass in her 79 Blazer lasts a month. She want's a car because of the kids We have a two year old and she is only 5ft so loading the kid UP into the car seat is difficult and something she will have to deal with for a few more years so understandable. I have even concidered a Fffff....Ffffoo......Ffffeeerr......Fffffooorrrr.. ...Fffffooorrrrd. There said it.
Friend has a 94 Power stroke crew for sale. It would be up to the task and I could pretty well sell off my utility trailer. They get 19-20 hwy.
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Old 03-13-2003, 10:05 AM   #4
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You said the "F" word! You said the "F" word!

My god, where are the moderators!

The power stroke is a nice machine, but the F word?

Tisk, tisk, tisk. Toaster.......you know better than that.........


A bad day with a Chevy still beats a great day with a FFFF (but you do have a need that needs to be balanced--still the host of the GM truck forum driving a F). Next cats and dogs will live together in harmony, mass hysteria, EEEK!



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Old 03-13-2003, 10:47 AM   #5
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I would not hesitate to get a 350 with a 4.10 rear end. I don't know that I'd like it pulling 8,000 plus pounds with a 3.73. They are such amazingly stout motors.

On the other hand, I have a '94 Chevy with the 6.5 turbo diesel, and have been very pleased with it. Sometimes pushes 20 mph empty, and seldom drops below 14 when towing. At the time I bought it (used) the difference in price between it and a Ford diesel was enough to buy a new diesel engine for the Chevy! I prefer the Ford diesel, but not that much more! But then I don't think I'd want to tow 8,000 pounds with it either. Maybe not even with a 4.10.

Mark
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Old 03-13-2003, 11:02 AM   #6
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Quote:
Originally posted by j54mark
I would not hesitate to get a 350 with a 4.10 rear end. I don't know that I'd like it pulling 8,000 plus pounds with a 3.73. They are such amazingly stout motors.

On the other hand, I have a '94 Chevy with the 6.5 turbo diesel, and have been very pleased with it. Sometimes pushes 20 mph empty, and seldom drops below 14 when towing. At the time I bought it (used) the difference in price between it and a Ford diesel was enough to buy a new diesel engine for the Chevy! I prefer the Ford diesel, but not that much more! But then I don't think I'd want to tow 8,000 pounds with it either. Maybe not even with a 4.10.

Mark
See the Diesel scares me. There is one with the Banks kit on it for sale near me also. Problem is injector pumps on those years are not super reliable and your talking $600-1000 if you have one of those give out. The Durmax I like but at this point it's out of my price range. Also your general maintance is much higher on a deisel. Take a long time to overecome that in MPG.
I don't maybe I look at this Banks equipped truck.
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Old 03-13-2003, 11:32 AM   #7
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The injection pumps can be expected to go 100,000 mi, give or take. You can find horror stories, of course. Cost and life depends on whether it is mechanical or electronic. I have 154,000 on mine, with the original pump, so I am probably overdue.

Parts is parts. I had an Astro with a $300 EGR valve! My brother just had the head gaskets replaced on his 5.7 at $300. My mother's transmission failed on her Chrysler minivan at 70,000 mi. ($$$). So if I need a $700 pump rebuild someday, so be it. That is just over a month's payment on a new Duramax.

Actual repair bills on my '94 diesel this past 12 months/35,000 mi. were $84. That was for a bad wiper controller.

As far a general maintanence, I don't know what you mean. I change 8 quarts of oil and filter every 5,000 mi, and, uh, well that's about it.

But you don't want to get into 6.2 or 6.5 diesels without information, in my opinion. They have their quirks. But they really are quite decent motors. The key is to get a substanial price break off the equivalent Ford.

Mark
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Old 03-13-2003, 11:33 AM   #8
 
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All these talks about MPG with a Chevy 454 make us feel so much better. We thought ours was a gas guzzler !!!!

We towed for about 9 years with a 1990 Chevy G-30 , 454. The van was always very loaded, the trailer was about 6850Lbs.
The best we got was about 6 or 7 MPG. Had to use mid grade when towing, and super when towing in mountain.
We never used it much without the trailer to be sure, but I think once we got 11 MPG.
We just used it to bring home our 32', 160 miles. Trailer was empty, must weigh about 6500Lbs. Very little amount of cargo in the van. We used regular gas, it pulled like a dream. Really great engine.
The main problem we had was when not towing. Had to be careful of its power. That's the reason we liked to have that big anchor to slow it down. Not fun to drive around a campground after un-hitching, always keeping the foot on the brake. Same thing around town. It's an engine made for highway driving, definitively not for suburban commute or grocery shopping.
A pick-up is of course easier to handle in town than a big van, so it may be more fun to drive around a mall !!!!
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Old 03-13-2003, 02:44 PM   #9
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My biggest gripe w/ our '85 was braking. Dry, all was good, but wet.....watch out!

Toaster, I share your concerns with the late 80s early 90s diesel. I know there are 10 success stories for every bad one, but I too like diesels very much, however I get a bit uneasy with those years as well. Go with your gut here.

I am not sure that diesels cost more in maintenence. There is a bit more oil and as you said injector pump, but Mark is essentially right, a good diesel is pretty low maint and at the very least equal to that of what the 454 or other gas engines are around.

I looked at the Chevy site. That duramax is a $5k option! YIKES!

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Old 03-13-2003, 03:36 PM   #10
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Experience with GM454 and MPG

I have been very favorably impressed with my '99 7400 VORTEC. It is in the Suburban that I special ordered in 1998 (one of the first delivered to my local dealer in April of 1998) with 4.10 differentials (it's a K2500 4 X 4) and full heavy duty trailering package. It now has in excess of 102,000 miles and the only issue regarding maintenance has been the electronic controls for the transfer case that were a constant headache for the first 72,000 miles until GM came out with a revised component that solved the failure problem.

The fuel mileage with this rig has been equal to or better than the '95 K1500 Z71 Club Cab pickup that I traded on the Suburban. My day-to-day solo fuel economy runs between 15.5 and 16 MPG with my best trip highway solo fuel economy being 17 MPG. Towing fuel economy with the '64 Overlander averages right at 12 MPG with my highest being 15 MPG on very flat Interstates at a constant 55 MPH in Overdrive. My lowest economy reading was towing in the Rocky Mountains at 10.5 MPG. The Minuet has not had any impact on fuel economy - - the Suburban has averaged about the same towing the Minuet as it does solo - - this only reflects about 2,500 miles,however. I always utilize Premium grade unleaded fuel in the Suburban, and the only time that I don't use overdrive is when the transmission begins to hunt - - then I downshift. Approximately 60% of my total miles have been towing or about 61,000 miles.

Kevin
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Old 03-13-2003, 07:06 PM   #11
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Towing Airstream, varies 9.5 to 10.5 mpg. Empty, up to 14.8 mpg, is the highest I have ever seen. Got 11 mpg towing Jeep Grand Cherokee on towbar down to Marco Island, FL. I average around 12 mpg tooling around town in summer, about 10 in winter. Truck has almost 27,000 on it now, running Amsoil 5W30 oil.

I really like the big block gas engines. I think they are a super value, and I would not go back to a small block.

I have been branded a "gasoholic" over at irv2.com for my views on gas vs diesel.
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Old 03-13-2003, 08:15 PM   #12
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I sure liked my '92 Z71 with 5.7 and 5 speed trans. It got 19.5 and sometimes 20 mpg on reg. gas on the highway without A/C. It was not up to the task of pulling my 31' Excella, especially with a 3.42 rear end. The 8.1 in my 2500 pulls like a champ and gets between 10-13 when towing, around 14.6-14.9 when not towing on the highway. 10 in town with A/C. She has the 3.73 rear end and LT245-75-16 itty bitty tires.
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Old 03-13-2003, 08:45 PM   #13
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Some of these mileage quotes are unbelievable!! Come on fellas get real! I especially like the one who claims no sacrifice in mpg when pulling the smaller of his two trailers. Every experience I have ever had as far as mpg with a big block GM has been sickening. I would of been lucky to get into the double digits when towing with any of my big block tow vehicles. A 98 K2500 Suburban I had for a couple of years was the worst. Not far behind was the 93 2wd model I had. Just bite the bullet my friends and get the diesel, any diesel!! I would take an old Ford 6.9 or a Chevy 6.5 any day over a big block Chevy!

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Old 03-13-2003, 08:52 PM   #14
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I actually test drove a used PSD Furd (I didn't say it) 250 and a V10 in the 250. I was disappointed in the performance and felt neither could get out of their own way. If I had the money I would have bought the Duramax but didn't so that left me with the big block. Sure I would like better gas mileage when not towing but I guess I'm lucky to get just under 15 with a light foot.
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