97 Superduty Fuel Consumption

[BIG JOE]

Originally Posted by Dogman

Sparky,
I would look at a gear change. It's going to be the cheepest way out, are you 4 wheel drive or 2 wheel drive? I looked at gearvendor and I was looking 3500.00+ after everything was done drive it home.

I'm 2WD. As I said in the post BJS linked to, I had about 2K invested in the GearVendor in my 91. That included me doing install but paying to have the D-shaft shortened. Seems I payed 1500, or so.. but that was in 92. No clue what the unit, parts & labor is today.. but I'm sure it's Higher. I'd betcha it'd be over 4K.. before you drove away, theze dayz. today.

A complete rear-end swap.. from a wreck would be cheaper (I think) than doing a gear ratio change & set-up in yours... due to parts & labor costs.

Joe

[BJS]

According to GV the unit for your SD is 3295 + install + driveline They also on their home page indicated up to 2000hp and 25000 GCVW, you're knocking right at the higher end of the weight requirement with a 16k boat and a truck that is going to weigh in at least 8k.

Your comment about having slipping on ramps leads me to say that you have adequate power but traction is the limiting factor so a gear swap would work and a locker wouldn't hurt you even with the current gearing. Depending on where you're launching many marinas will launch it for you for a small fee if the ramps are too slick for your rig. Keep in mind that when you're pulling the boat out of the water the hydraulic forces against the rear of the trailer and even the nose of the boat actually serve to unload the tongue weight. To battle any traction issues a tongue extension would be an ideal accessory, they are commonly used for launching and recovering sailboats with fixed keels or larger boats on shallow ramps. Here's a few pictures in use. This is 2 extensions in combo



The easiest (not exactly cheap) way to change the gearing is to get a taller tire for the rear end and if you are needing tires then the cost difference is minimal.

Even with a taller gear you're likely not going to see a significant mileage increase due to the weight you're pulling as well as the air drag of the boat. your speed is helping the mileage, RPM wise you're running right where I do @ 70 with 4.10 gears which is on the higher side of the desirable (economy) RPM but great for heavy loads like you're pulling.

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[JR Sparky]

You are right on the GCVW. Cat scales had the rig at 24,607# before I filled the boat with gas. The truck only has 60,000 mile; just finished gauges, chip, 4" exhaust with 3" downtube and a DIY Fleetwood filter. Power isn't an issue, she runs like a scalded dog if you put your foot in it (sans boat and trailer). Pulls much better with the modifications, much stronger on grades.
The tires are 235/85R/16 and still have 70% tread on the duallies, guess we'll live with the 7 MPG.
Most of the trips we take are launched from public ramps and except for St. Augustine last week slipping hasn't been too much of a problem.
Thanks for your input.