Drivetrain Suggestions?
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Joined: Feb 2005
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Drivetrain Suggestions?
I Have A 1975 F100 With A 360 And A 3-speed.the Rear End Is A 9" With 3.25 Gears.i Have 235/60/r15 Tires.the Truck Cruises At 60mph At About 2500 Rpm.i Was Considering A 2.75 Rear End But Not Sure How Much Difference That Is Really Going To Make.would A Transmission Change Help?acceleration Isnt Really An Issue Either.any Suggestions As To How I Can Get Those Rpms Down Would Be Appreciated.
Post Fiend
Joined: Mar 2005
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From: Louisiana
The 2.75 gear ratio would bring down RPMs, but you will be useing more gas on take off, b/c of such a low gear ratio(numatically) it will take more gas to get into your power band for accleration. Your tires are pretty small so you might see some benift to doing this change, as long as you don't gun it off the start it should be ok.
Also welcome to the site, and if your truck is 4wd, doesn't sound like it, but if it is you'd have to change both front and rear gears at the same time.
Just remember this is pretty much somthing for a profesional to do, and it isn't cheap.
Also welcome to the site, and if your truck is 4wd, doesn't sound like it, but if it is you'd have to change both front and rear gears at the same time.
Just remember this is pretty much somthing for a profesional to do, and it isn't cheap.
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Thanks For The Reply.when I Got My Tires I Wanted My Truck To Have A Little More Stance Than The "grandpa" Factory Look With Dogbowl Hubcaps.however I Didnt Realize That The Tire Size Would Affect It.any Suggestions On A Tire Size Using The 15" Wheel That Would Help Yet Still Have A Nice Stance To It?
Posting Guru
Joined: Apr 2004
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From: Lewistown, PA
I would rebuild the 360 into a 410 using a 428 crank.
Ditch the 3 speed for a toploader 4 spd. or a tremmec 3550 5 spd.
Keep the 3.25:1 gears with a trac-loc
Run 4 wheel disc.
I assume you want to lower rpms to increase gas mileage. Keep the gear ratio so it runs at or near torque peak when cruising. I also agree with MBBFord, too high of gear will actually eat more gas. Remember, these are bricks we're driving with the aerodynamics of a garage door.
Ditch the 3 speed for a toploader 4 spd. or a tremmec 3550 5 spd.
Keep the 3.25:1 gears with a trac-loc
Run 4 wheel disc.
I assume you want to lower rpms to increase gas mileage. Keep the gear ratio so it runs at or near torque peak when cruising. I also agree with MBBFord, too high of gear will actually eat more gas. Remember, these are bricks we're driving with the aerodynamics of a garage door.
