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Old 10-28-2010, 09:35 AM   #24 (permalink)
MechEngVT
Mechanical Engineer
 
Join Date: Jun 2008
Location: Richmond, VA
Posts: 190

The Truck - '02 Dodge Ram 1500 SLT Sport
90 day: 13.32 mpg (US)

The Van 2 - '06 Honda Odyssey EX
90 day: 20.56 mpg (US)

GoKart - '14 Hyundai Elantra GT base 6MT
90 day: 32.18 mpg (US)

Godzilla - '21 Ford F350 XL
90 day: 8.69 mpg (US)
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Quote:
Originally Posted by t vago View Post
where would I find a decent diff gear that will fit my truck without me having to do a lot of machining work to make fit, and without having to spend a total of much more than $1000? I've got the tallest available 3.55 gear already.
Try the following:
Chrysler / Dodge / Plymouth Dakota Rear Differentials Chrysler 9.25 Ring & Pinion Sets Auto Parts: YUKON GEAR,YUKON AXLE,YUKON,RING PINION,RING,PINION,GEAR,DIFFERENTIAL,CROWN WHEEL,CROWN PINION,CROWN,CHRYSLER 9.25,CHRYSLER 9 1/4,CHRYSLER,RICHMOND GEA

They list a 3.21 gearset for the 9 1/4 axle for less than $300, and I seriously doubt a shop would charge more than $300 to do an install. I have that ratio in my 1988 Ramcharger with 235/75r15 (and 275/50r15) tires, but it's in an 8 1/4 axle. The 9 1/4 in my Ram has the 3.55 like yours, but with 265/65r17 tires.

I honestly think you're barking up the wrong tree if you want cost-effective efficiency improvements that will be reliable. As you state the valve arrangement of the 4.7L isn't suited to tried-and-true methods of variable displacement. Any home-brewed solution for the existing valve arrangement is likely to be insanely expensive or unreliable enough to cause major engine damage, or likely both. You may be-LIE-ve you can do it, but I wish you luck while recommending you divert attention elsewhere. Maybe modifying the heads to accept the double-rocker style actuators would have potential for reliable success, but again it would be quite expensive.
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