Well, got a 550 a couple of months ago. It has 488 gears and pulls really well. The problem I have is the gas (diesel) milage when empty. Not very good. At 70 mph, she is taching 26 or 2700 rpm's. I know this rig is built for pulling/hauling and not for milage, but with todays fuel prices,.......
I have a couple of options:
1) Change RE ratios (both, 4x4), but I really don't want to do that, as it won't pull as good.
2) Get a over-drive from US Gear and drop the rpm's 400 or so... prolly the best option.
3) Now this is the question, I know the wheels are 19.5's, but the tires are really low profile. Can I buy a taller tire and raise the ratio?? (drop the rpm's)?? If so, what size tire would make it comparable to a 4.33 RE?? Or will I be creating a whole new set of problems???
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1) Change RE ratios (both, 4x4), but I really don't want to do that, as it won't pull as good.
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Changing the rear end (and front diff) to a lower (numerically) number will make it a better commuter car, but kill it as a toter.
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2) Get a over-drive from US Gear and drop the rpm's 400 or so... prolly the best option.
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That's probably the ticket. Both Gear Vendors and U.S.Gear make the overdrives. One is best for 4x2 and the other is best for 4x4, but I don't remember which is which.
Both offer around a 25% OD. So in effect that changes the 4.88 to a 3.66. Just about perfect for a commuter car. [img]/ubbthreads/images/graemlins/cool.gif[/img]
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3) Now this is the question, I know the wheels are 19.5's, but the tires are really low profile. Can I buy a taller tire and raise the ratio?? (drop the rpm's)??
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Good in theory, but it won't work in real life. Because nobody makes a 19.5" tire that's much taller.
Your tires are 225/70R19.5 w/648 tire revs/mile.
Some make a 245/70R19.5 with only 625 to 619 revs/mile, but they won't fit on your 6" wide wheels. You'll need new 6.75" wide wheels to drop your effective rear end ratio down to only 4.71.
Michelin does make one odd-ball tire that will give you a hair more tire diameter, but those require 7.5" wide wheels. It's the XZA(2) in size 8R19.5 with 616 tire revs/mile, or equivalent to about 4.64 rear end ratio. But finding those wheels without paying an arm and a leg and your first-born son would be a challenge. [img]/ubbthreads/images/graemlins/smile.gif[/img]
So look into the double-overdrive solution first before you commit to buying 4 new tires and wheels.
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My Sierra Blanca is a '99.5 PSD CrewCab hot-rod Towing Machine! BTS tranny; TurboRamAir intake and 4" stainless turbo-back exhaust; DP-Tuner tunes flashed into an Edge Evolution tuner; ISSPRO EV gauges and TTM; AIC; SP-Diesel exhaust brake and torque converter controller. I special-ordered it new and plan to drive it until it quits.
JMO, but I would go with the overdrive unit. That way you should get better fuel milage in everyday running without loosing the towing/hauling capability you bought the truck for.
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Bob
"I'm not saying we wouldn't get our hair mussed. But I do say no more than ten to twenty million killed, tops. Uh, depending on the breaks."
I have a GearVendor installed on my F550 and have been very pleased with it.
I use it as a gear splitter when towing although I rarely tow in double overdrive. Double overdrive provides a great road gear when not towing. It provides much lowered RPM at freeway speeds.
Some folks disfavor the GearVendor for a couple of reasons. It doesn't work in 4WD and it doesn't hold up well when used with an exhaust brake. Neither weakness bothers me.
I have GV's installed on two vehicles. One on an 87 Chev Suburban with 155K miles....125K of them towing. The other on my current tow vehicle with 85K towing miles.
I service them and take precautions against their known weakness. They have done me well.
Happy hunting,
Roger
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2001 F550, Crew Cab, Royal Sport bed, John Woods transmission, 4.88 gears, Gear Vendor, A pillar gauges, Banks Power Elbow, 4" turbo back exhaust, Cyclone fan, Zoodad, AFE Magnum Force intake system, Westin Nerf Bars, 70 gal.aux tank(installed in the bed gravity feed), 10 wheel TireSentry pressure monitoring system, pulling a Dutchmen 35SRV toyhauler with a Harley Roadking Classic or a Polaris RZR in the "garage".
I agree with crrroger2, my Gearvendor has worked very well. On the way home tonight I checked my RPMs with the GV and this is what I found.
55 mph with GV on, 1650 RPMs.
60 mph without the GV = 2300 RPMs.
60 mph with the GV on =1800 RPMs.
70 mph with the GV on =2075 RPMs.
I guess it is saving some fuel but I still think it will take about 300,000 miles to pay for it!!!LOL
I like the fact that I am crusing at lower RPMs,and less wear and tear on the equipment .
I think an overdrive is the simplest way to go and I would do it again..
Greg
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2004 F550 Lariat Fontaine Classic Traveler 4x4, auto,Oxford white, transferflow 33 gal aux tank, link air ride suspension, hadley air horns, ventvisor window covers, curt turnover gooseneck hitch, alcoa 19.5 wheels, 4" exhaust, gearvendor,Brakesmart brake controller,painless wiring kit, 3 gauge pillar pod with pyro, trans & boost, ONKI grill-brush guard. Hella 1000 driving lights. Stull Shadow grill insert,clifford remote start alarm w/turbo cool down, dual rancho stearing stabilizer, towing a 2003 Silverado 3 horse 12" LQ gooseneck.
If fuel keeps going up it might pay for itself a good bit quicker! [img]/ubbthreads/images/graemlins/phoney.gif[/img]
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2001 F-350 SuperCrewzer, Crew Cab Dualy LB XLT, 7.3L PSD, 4.10 LS, Oxford White w/ Silver lower tone, Med Grey interior, Power 40/20/40, Auto w/ Dacco Super Hauler TC and Magnafine, Towing Pkg w/ Dual Alts, Ford AIC, Prodigy, Gentex Mirror, Cobra 29WXNWST, 5ft Firestik II, X Monitor, Baldwin Coolant Filter, Sony OH Video system, Yakima Racks and basket, 45 gal auxiliary tank and 12V Pump, Towing a 26 Foot Prowler Lite.
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