97 Powerstroke gearing
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97 Powerstroke gearing
I have a 97 cclb 2wd dually I'm daily driving and I'm wanting lower rpms at 70 currently running around 2600rpms. I assume its a 4.10 and i have 29 inch tires. what should I do?
Fleet Mechanic
Joined: Aug 2005
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From: MD
A gear change to 3.55s would drop that to about 2150rpms. Not a cheap thing to do if you have to pay a Mech to do. I don't rem if you could get 3.55s in a DRW from Ford. If so, scoring a complete axle from the junkyard would be less $$.
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From: Vernon, BC
You could also go to a 31 or 33 inch tire. However swapping six tires may end up costing you as much as re gearing. Offhand I don't know what the change in rpm would be if going from the stock tire size to the larger size. Now that I think of it, my F250 comes standard with 235 85 R16 and they are 31's. I thought the duallies came with the same? What size are your tires? The stock F150 tires are 29's and I think they were 245 75 R15 but don't quote me on that.
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You could also go to a 31 or 33 inch tire. However swapping six tires may end up costing you as much as re gearing. Offhand I don't know what the change in rpm would be if going from the stock tire size to the larger size. Now that I think of it, my F250 comes standard with 235 85 R16 and they are 31's. I thought the duallies came with the same? What size are your tires? The stock F150 tires are 29's and I think they were 245 75 R15 but don't quote me on that.
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Well the doors were replaced so i do not have that info plate. Otherwise i can check my diff cover around 3 today
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Fleet Owner
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From: Gilbert, PA
Just a FYI. your current 4.10s or 3.55s will net the same milage. Just the 4.10s will have more power
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how will it net the same mileage if the rpms are lower at higher speed? Less fuel is being used
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From: Vernon, BC
What is your rpm at 60? My truck has the ZF5 and at 100 km (62 mph) in 5th my rpm is 1900. I have never taken it up to 70 so I have no idea how much the rpm would change. However, comparing your truck with your tires to my truck with stock tires may give you an idea about gear changes or tire changes?
Fleet Mechanic
Joined: Aug 2005
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From: MD
Has to do with keeping the engine at an rpm where it's making peak torque and requires minimum throttle. At a lower rpm where less torque is made, more throttle will be required to maintain the same speed. There are a lot of variables here, but that the basics of it.
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What is your rpm at 60? My truck has the ZF5 and at 100 km (62 mph) in 5th my rpm is 1900. I have never taken it up to 70 so I have no idea how much the rpm would change. However, comparing your truck with your tires to my truck with stock tires may give you an idea about gear changes or tire changes?
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Yeah im not about to have 35s on the rear and 29s on the front. My fathers 7.3 has 33s and it does way better than my truck. His is a 97 f350 cclb 4x4 srw same engine trans and rear end i believe
Fleet Owner
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From: Gilbert, PA
And 2 less tires of rotational mass and less wind drag.