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Old 03-18-2003, 08:54 PM   #15
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ipso facto,
I think all the comments are worth taking. I pulled my 1977 Excella 500 31' from AZ. to TN. after buying her on ebay. I did it with my then '92 Chevy Z71 4X4 with 5.7 litre (350), 5 speed manual and 3.42 rear end ratio truck. It had been outfitted with a Jacobs Ultrateam high energy ignition that gave me a little more low end torque from stock. She was a great truck but was not the truck for the job with LT265-75-16 tires and that 3.42 rear end. On a straightaway she was just fine cruising at 65 in 5th gear. The slightest hill and I had to downshift to 4th sometimes 3rd. When I hit some of the steep hills in N.M. I had to drop all the way down into 2nd gear to make it to the top and I might have been going 35 mph. Not good. Every semi truck that passed me made me swerve all over and I am using the same Reese equalizer today that I was using then, except for a change in the hitch bar which dropped the ball down several more inches. My '01 Chevy 2500hd 4X4 extended cab doesn't break a sweat with the 8.1 litre, Allison 5 speed auto trans and 3.73 rear end. The truck is wearing a set of Firestone, yikes, Steeltex LT245-75-16 tires which are shorter than the 265's that were on my Z71. I chose this truck over an identical truck with 4.10 and now I wish I had purchased the 4.10 rear and gone with taller tires to fill up the wheel well. I think the 265's would have brought the rear end ratio down to 3.90 and I would have had even more pulling power for hills.

My suggestions on rear end are based on a half-ton truck that was not suited to the job because of rear end ratio and the happiness I have found with the 2500hd with big block engine. I guess I could have bought a 2500hd with 6 litre engine, 4.10 rear end which this engine loves and picked a 25' or shorter Airstream but that is another story. The 460 Ford engine is a good engine that shouldn't be hampered with 3.55 gears. What happened to the 3.90 rear end they offered at one time. That would be ideal.
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Old 03-18-2003, 09:21 PM   #16
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davidz71

Thanks for the educational story. You went from a base 1/2 Chevy to a full 1 ton (which is what 2500 HD is I believe). One difference is, I am dealing with an 80's A/S which is heavier than a 70's A/S.
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Old 03-18-2003, 10:05 PM   #17
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First, I have a 6.5 turbo diesel, and while I agree that they are nowhere near as bad as often painted, and I also agree that they can often be had at a substantial discount, I don't agree that it would be that great a choice for a 32' Airstream that is going to push gross weight. They just don't have the horsepower, or at least not what I would want. Granted, mine has a 3.73, but I tow a lightly loaded 25' Soverein, and it is enough of a load for me. But there are plenty of people doing it, so I could be wrong.

Second, as others have noted, it would be hard to find a better truck for towing than what you have. Any diesel truck you would want to have would take many, many years to achieve a payback in gas milage. Financially, does it make more sense to write just a $150 check every month to Chevron, or is it better to write a $100 check to Chevron AND a $500 check to GMAC finance?

If you want to throw money at the problem, I'd suggest a Gear Vendors unit. It will give you a true overdrive, and also let you split gears for easier towing. About $3,000, installed. It should get you MAYBE another mpg towing, but ought to let you get about 15 mpg highway when not towing.

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Old 03-19-2003, 10:48 AM   #18
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If you want to throw money at the problem, I'd suggest a Gear Vendors unit. It will give you a true overdrive, and also let you split gears for easier towing. About $3,000, installed. It should get you MAYBE another mpg towing, but ought to let you get about 15 mpg highway when not towing.

I've come to realize that this is indeed the way to go and everything else is either inadequate in some way or a patch. 15 MPG empty on the highway would be really outstanding for the big 460 and it would still be adequate for pulling with
the 4.10 gear.
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Old 03-19-2003, 07:34 PM   #19
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ipso,

My 95 F-250 Powerstroke has 3:55 gears in it. Maybe a bit tall but my former Argosy and my current Overlander aren't as heavy as the 80's models like yours, they got pretty bloated during those years. Gets around 18 mpg on the highway and close to 13 towing. I have some relatively tall Michelins on it presently and even though it pulls great I would like to go a little shorter to get my revs up when cruising. I like to keep the rpm's up above 2000 and to do that now I have to be running around 75 mph. I almost always drive around town with the OD button off.

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Old 03-19-2003, 10:00 PM   #20
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ipso,
I had to go back and read your original post again. Somehow I missed that you already owned an F250 with 460 but there it was was plain as day. You said you don't want a diesel. OK, strike diesel. You can forget the small block 351 because it will not be up to the task on mountainous areas you claim you will travel. I guess that leaves Gear Vendor whether you like it or not because that 460 will be sucking wind with a 3.55 rear. I gave you my experiences because I thought my half-ton was pretty stout. Oh, there is one more solution- get a small block and a smaller Airstream! Let us know how the Gear Vendor works out.
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'01 2500hd ext. cab, 8.1 litre gas, 5 sp. Allison auto
3.73 rear end
Mag-Hytec rear diff cover
Amsoil Dual by-pass oil filtration system
Amsoil synthetics all around
265 watt AM Solar, Inc. system
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Old 03-20-2003, 11:33 PM   #21
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Chas

Right. I heard that Ford F250 PSD only comes with 3.73 (or higher), 4.10 is not an option. The power of diesel, it doesn't need 4.10.

DavidZ71

I thought about sizes for a long time and decided on 30' to 32'. The latter turned out to be the ideal size (for me) and the more I think about it, the more pleased I am with this Airstream find. 34' would be too long, while 29' too short.

I deciced not to compromise with the towing vehicle. Even if I did get a lighter truck, it still wouldn't be a good daily driver. No truck is - it is also the handling, not just MPG. Decided to get something pretty light as a daily driver instead of the truck, as light as possible.
It is clear, in light of everything that has been said, that a big block gasser or diesel is necessary to safely move that kind of weight and that kind of size. I didn't know that originally. With 460 moving 8300 lbs while it is rated for 10,000 so it is beginning to approach its towing limits. It's safer to be somewhat under the towing capacity than over.
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Old 03-21-2003, 07:05 PM   #22
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ipso,
I think you have made a wise decision. A friend of mine who hunts with me is fortunate enough to have the love of his life who is raising horses. She has a Chevy 3500 dually with 454 engine she tows horse trailers around with. He pull his 5th wheel and a 24' to the campsite the first of the hunting season and then drives an old S-10 Blazer on the backroads. At the end of the season he drives the dually back and picks up the 24' which may stay at the site for up to 3 months. Of course this is a different scenario than what you posed but works quite well for him. I think your current truck is just the ticket for your situation. Have you made any mods to the engine looking to squeeze that last bit of mileage from her?
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AIR #0078
'01 2500hd ext. cab, 8.1 litre gas, 5 sp. Allison auto
3.73 rear end
Mag-Hytec rear diff cover
Amsoil Dual by-pass oil filtration system
Amsoil synthetics all around
265 watt AM Solar, Inc. system
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Old 03-21-2003, 09:48 PM   #23
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davidz71

I think you have made a wise decision. A friend of mine who hunts with me is fortunate enough to have the love of his life who is raising horses. She has a Chevy 3500 dually with 454 engine she tows horse trailers around with.

I knew someone else who pulls horse trailers with big block 454. Must be real popular for that application. Re: this thread, he said 10-11 empty and somewhat less than that pulling.

Have you made any mods to the engine looking to squeeze that last bit of mileage from her?

I don't think that it is the engine exclusively that's responsible for the low MPG. You can vary RPMs with a different tranny, an OD. I can get 12 MPG in it but I have to keep it around 2200 RPMs, which translates to 45-50 MPH. But you are stuck with dispacement forever. (But I find about improvement which can improve MPG, I will implement them)

Secondly, it is the weight. The truck weights 2 tons. No matter what drive train it has, the weight will always prevent you from getting good mileage.

Then aerodynamics.

In car like a 70's Lincoln, this same 460 can get more like 17 mpg due to the vehicle being lighter, more aerodynamic and of course a much higher gear of about 3.

I have a small block V8 (350) which is great and it gets 23 MPG on the highway going 70, full of stuff, offering more power than I need (don't think I ever floored it). With its towing package it would be a great towing vehicle for a small A/S, say 19', something under 5,000 lbs.

So in conclusion, I have decided to eventually install a better tranny with OD, or Gear Vendors or something. I haven't yet found anyone who installed GV overdrive in a similar package but it would be most interesting to see the MPG improvement. Assuming an improvement from 11 to 15MPG, it would take about 100,000 miles for the tranny to pay for itself. Which makes sense only if one plans to keep the truck for 100,000 miles, which I do. The engine has low miles on it, so it is worthwhile.
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Old 03-22-2003, 10:57 AM   #24
 
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Quote:
"the weight will always prevent you from getting good mileage."
I don't think the weight of the vehicle is the culprit here. There must be something else causing this low gas mileage: our van has a curb weight of 5433Lbs, but we still get the same mileage as the pick-ups. And, we haven't noticed much difference in MPG with a full paylod or empty.

On a subject mentioned here earlier:

I have been very bothered by the statement made by "rtaylor537", pulling a 8300Lbs GVWR Excella 30ft, with F150, 5.4L with a 3.55 rear axle.

My gut feeling told me this was not right. So, I did a lot of research on other forums, and the general opinion is 6000Lbs is the absolute SAFE weight, 26' length with such a vehicle. I have gathered a lot of numbers about that, I won't waste more space posting them.
If anybody is considering using the same rig, maybe they should check first one of the many discussions What is the biggest TT I can tow? (somebody jokingly suggests :"according to some sales people....a 65' Airstream")
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Old 03-22-2003, 11:42 AM   #25
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I don't think the weight of the vehicle is the culprit here. There must be something else causing this low gas mileage: our van has a curb weight of 5433Lbs, but we still get the same mileage as the pick-ups. And, we haven't noticed much difference in MPG with a full paylod or empty.


Possibly. But I am not aware of anyone in 1 ton truck get more than 12-13 MPG. 12 MPG is in fact most excellent for the 454 or 460. I can get that keeping the RPMs at 2200. But you are only going 50 mph then.

As has been pointed out, the same 3/4 HD truck with the smaller V8 would still get about the same MPG. And a base 3/4 truck would get a slight improvement, probably only 2 MPG. There is just something about trucks that doesn't let them get good MPG.

So in the end, I don't know what else to do with it other than getting some kind of overdrive. If I get 14-15 in it I will be most happy. But I would really like to see a testimony by someone who has done exactly that to exactly same platform (Ford F250 Heavy Duty with 460 and 3 speed tranny). I emailed Gear Vendors but haven't heard from them yet.

Quote:
Tow ratings are your ABSOLUTE MAX and only take into account one 150-lb drive and no options on the truck.
You'll generally max out at about 1000 lbs UNDER your tow rating.
This is certainly eye-opening information.
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Old 03-22-2003, 07:25 PM   #26
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ipso,
Have you investigated the Jacobs Mileage Master or Ultra Team ignition systems yet? I installed the Ultra Team on my '92 Z71 4X4 and noticed an improvement in starting and low end torque. I was already getting 19.5 to 20 mpg on the highway and I did not notice any mpg improvement. This is not the case with others though. You might see what the MH guys have experienced with this system. After my son rolled this truck it was put on a '92 Camaro with 305 and when that was sold, transferred to my son's next ride- a '90 Chevy 4X4 Sport short bed truck. It has been on there for over a year now and has helped this engine which is in dire need of a rebuild. I guess I have had that unit now for 7 yrs. and it has been back once for warranty work on the electronics. I'm considering putting one on my other son's C1500 4.3 litre tuck engine as soon as the Jasper engine people replace it under warranty (bad head with water in the oil).

I'm not saying that it will definately give you at least 1 mpg but some people are experiencing this and more. It is a simple bolt on/plug in unit with new plug wires.
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'01 2500hd ext. cab, 8.1 litre gas, 5 sp. Allison auto
3.73 rear end
Mag-Hytec rear diff cover
Amsoil Dual by-pass oil filtration system
Amsoil synthetics all around
265 watt AM Solar, Inc. system
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Old 03-22-2003, 07:46 PM   #27
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Didn't I hear that there are several electronic fuel injection systems to replace the carb on these motors? I am assuming that it would be like throtle body injection (although somebody somewhere may well have a complete mulitport fuel injection system, complete with new heads). It would undoubtedly help in city driving, but more importantly give a lot better drivablility - easier starting, better acceleration, etc.

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Old 03-22-2003, 08:06 PM   #28
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Ford started putting EFI on this engine in '88. Chevy started using EFI in '89, I think. In any case, I think if it had a carburator, I wouldn't be getting even 10 MPG, like some of these 70's big blocks.

My truck had a new engine put in it in mid-90's and I think it meant new EFI, also. (but not sure).

The nice thing about carburated systems (early 70's), they are arguably easier to fix, being 100% mechanical, no computers.

My first car, a used 70's mopar was religiously getting 13 mpg with a small block V8 and 3-speed tranny. After a new carb. it went all the way to 15. I know it is apples and oranges but I am actually somewhat impressed by this big 460 getting almost 12, with way more displacement and torque, not to mention way more weight and aerodynamic as a brick, and generally lower gears.
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