2 speed rear differential
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Freshman User
Joined: Apr 2010
Posts: 30
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2 speed rear differential
'99 F250 4x4 CC
I cant be the only person to think of this, but, I find very few references to doing it. I have a 4.10 rear differential and because of the gearing I get somewhere around 10 or 11 mpg even when driving with no extra load. I keep thinking it would be nice to have a two speed differential. One gear for 2wd and no load to optimize mileage and the second for hauling loads and when 4wd is needed.
Am I missing a key point here or is there a reason Ford does not supply this option?
I cant be the only person to think of this, but, I find very few references to doing it. I have a 4.10 rear differential and because of the gearing I get somewhere around 10 or 11 mpg even when driving with no extra load. I keep thinking it would be nice to have a two speed differential. One gear for 2wd and no load to optimize mileage and the second for hauling loads and when 4wd is needed.
Am I missing a key point here or is there a reason Ford does not supply this option?
Posting Guru
Joined: Aug 2012
Posts: 1,144
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From: ALPHA ,NJ
Quick internet search I think they were only available in dump trucks or semi type deals and only years I came up with were 50-60s for sale based on that they would probably be enormous. And the point of a super duty is capability not necessarily fuel economy. It would be something that I think a large about of people would be interested in, myself personally daily drive my truck and don't tow anything so a dual geared diff would be awesome but for me would probably be cost prohibitive
Also you might want to think about changing the fluids in your drive train and possibly do a plug change with coil on plug boots to help bring up that mpg. Also driver mod helps a bunch, my mileage can change drastically depending on how I drive, between 13 and 10
Also you might want to think about changing the fluids in your drive train and possibly do a plug change with coil on plug boots to help bring up that mpg. Also driver mod helps a bunch, my mileage can change drastically depending on how I drive, between 13 and 10
Logistics Pro
Joined: Jun 2012
Posts: 4,063
Likes: 2
From: Southeastern IL
Most all 2 speed diffs are for large equipment such as dump trucks and semis. Putting a diff like that in a truck would drop fuel mileage since the truck would have to work harder to spin that giant rear end!
If someone developed one, Id be all for it! Iv always wanted to be able to go from a low rear end such as a 3.55 to a 4.10 when towing. I had an idea of somehow doing it in the driveshaft. Flip a switch and letting half the shaft spin at a different speed thus changing the gear ratio. Call me crazy! Lol
If someone developed one, Id be all for it! Iv always wanted to be able to go from a low rear end such as a 3.55 to a 4.10 when towing. I had an idea of somehow doing it in the driveshaft. Flip a switch and letting half the shaft spin at a different speed thus changing the gear ratio. Call me crazy! Lol
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,739
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From: SE Florida
There used to be bolt on overdrive units that you could install. One was made by US Gear and one by Gear Vendors. I don't think either one is made any longer, but there are probably used ones available.
Junior User
Joined: Jun 2013
Posts: 90
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From: Wautoma WI
2-speed rear end is a neat idea but you have to remember the gen public is stupid. they would not know when or how to use it and it would only be a matter of time b4 the left the rear end in high and tried to engage to 4x4 and rip the t-case in half.
Senior User
Joined: Oct 2013
Posts: 387
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From: OR
They still make them, and it would accomplish the same thing as a 2 speed rear end. Basically a gear splitter, so you would have 8 or 10 gears and an extra overdrive. They aren't cheap though.
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Logistics Pro
Joined: Jun 2012
Posts: 4,063
Likes: 2
From: Southeastern IL
If I remember correctly they were either $2500 or $3500... Iv thought about getting one before but its not worth the cost IMO
And your right, it splits every gear. Essentially, your 4 speed becomes an 8 speed. A 5 speed becomes a 10 speed. A 6 speed becomes a 12 speed... And if you put one on a new Fiat Ram 1500, youd have 16 gears!
And your right, it splits every gear. Essentially, your 4 speed becomes an 8 speed. A 5 speed becomes a 10 speed. A 6 speed becomes a 12 speed... And if you put one on a new Fiat Ram 1500, youd have 16 gears!
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More Turbo
Joined: Jul 2011
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From: Full-time RV
I sure enjoyed split-shifting those gears.
Senior User
Joined: Nov 2003
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Last I knew both are still avaliable.Very pricey though.You'd really have to pound up the miles to get your mony back!
Lead Driver
Joined: Nov 2008
Posts: 8,450
Likes: 70
From: South Jersey
Our old 88 Ford 8000 fuel deliver truck had a two speed rear, I loved learning to drive a big truck back then. Especially with that bad a$$ Caterpillar turbo V8!
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