Rear end ratio
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New User
Joined: Mar 2019
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Rear end ratio
I just bought a 1993 F250 with a 351w and a c6 tranny. I love it! Can’t wait to dig in. Wondering how to make my few highway runs less abusive on the tranny and motor by lowing the RPM. Really don’t want to scream down the highway at 3 or 3.5 k rpm on that c6. I thought about swapping the tranny but really don’t want that much work 
and love the no problem nature of the c6. Wondering what getting a different rear end on it would do? Right now has 4:10 gear ratio. Ideas on this welcome.
and love the no problem nature of the c6. Wondering what getting a different rear end on it would do? Right now has 4:10 gear ratio. Ideas on this welcome.
Fleet Owner
Joined: Oct 2005
Posts: 20,786
Likes: 1,751
From: Kentucky
Swap in a complete 3.55 rear axle. That ratio is very common and path of least resistance. I would not go any lower on a truck designed to haul things. Another option is buy a cheap 4 cylinder car to use for your highway runs.
Tuned
Joined: Aug 2014
Posts: 305
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How often and how large of a load do you tow? What is your RPM at 60 MPH and 70 MPH?
My truck has 3.55 gearing, at 60 MPH it turns around 2300 RPM, at 70 2700 RPM. It will haul pretty much anything, but really struggles when towing. It's basically floored and takes a long time to reach 55 MPH. I tow a double axle trailer with a cord to 2 cords of wet oak, and it's all the 5.8 can handle.
So, if you tow, I'd leave you gear ratio alone.
My truck has 3.55 gearing, at 60 MPH it turns around 2300 RPM, at 70 2700 RPM. It will haul pretty much anything, but really struggles when towing. It's basically floored and takes a long time to reach 55 MPH. I tow a double axle trailer with a cord to 2 cords of wet oak, and it's all the 5.8 can handle.
So, if you tow, I'd leave you gear ratio alone.
Laughing Gas
Joined: Jun 2013
Posts: 1,026
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I wasn't, and I don't think anyone else was implying it would hurt anything except for acceleration and towing ability. Everything has its trade offs. I have to do about seven minutes of double lane highway on my commute and I do miss the taller gears then. But all other times or certainly when towing anything. I very much prefer the 4.10's. Certainly if you are doing a lot of highway miles relatively unladen the 3.55's will get you there quicker and with better fuel economy.
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New User
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These are great replies. Thx guys. Yeah I won’t be pulling super often but for sure will have wood and other things on the back. Also plan on using this to pull my 30 foot boat. Sounds like the rear is a non factor with the c6.
Great feed back guys.
Great feed back guys.
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Hotshot
Joined: Jun 2015
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I put a lot of highway miles on that truck. The tach showed somewhere around 3,000 rpm cruising down the highway.
Do routine maintenance to include fluid changes. Heat kills transmissions.
Do routine maintenance to include fluid changes. Heat kills transmissions.
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Laughing Gas
Joined: Jun 2013
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What speed would that be around at 3k My4fordtrucks? Just curious at 3k with my 5.8 5speed(in fifth obviously) with 4.10's I'm doing about 80- 85mph but that feels like she's screaming along. I only do it if I'm running late I don't like to continuously rev that high.
Elder User
Joined: May 2013
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Laughing Gas
Joined: Jun 2013
Posts: 1,026
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Than you'd like my truck. Lol. Still running the original tape player and a briefcase full of tapes. I can see getting pulled over one day and have them ask, what's in the briefcase? I'll be like you'll never believe me. 
You don't have to go to extremes of the 3.55's too. There is 3.73's that split the difference so to speak. But even still you will notice power difference IMO. If you are running the highway lots and never really ever hauling a trailer 4.10's will be thirsty(fuel) and speed limiting.
You don't have to go to extremes of the 3.55's too. There is 3.73's that split the difference so to speak. But even still you will notice power difference IMO. If you are running the highway lots and never really ever hauling a trailer 4.10's will be thirsty(fuel) and speed limiting.
Cargo Master
Joined: Mar 2010
Posts: 3,326
Likes: 292
From: Laramie, WY
What's that 30 foot boat weigh? The 21 footer I used to drag around was just under 5k lbs on the trailer full of fuel and gear. 4.10 gears would have helped, had 3.55 and 29" tires.
Laughing Gas
Joined: Jun 2013
Posts: 1,026
Likes: 23
Wow. That seems screaming for 3.55 gears? Is there that much difference between the autos and five speeds? I'm doing roughly 140kmph (which converts to 87mph) at 3k on the tach in fifth with 265/75/16 and 4.10 gears. At that speed I can almost see my fuel gauge dropping. Lol.
Cargo Master
Joined: Mar 2010
Posts: 3,326
Likes: 292
From: Laramie, WY
Wow. That seems screaming for 3.55 gears? Is there that much difference between the autos and five speeds? I'm doing roughly 140kmph (which converts to 87mph) at 3k on the tach in fifth with 265/75/16 and 4.10 gears. At that speed I can almost see my fuel gauge dropping. Lol.