differences in 355 vs 373 rear?
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differences in 355 vs 373 rear?
I got the 355 rear end ... I was wondering if anyone tows with this ratio. Because I don't plan on towing more than 7000 lbs I figured I would try to get better MPG under highway conditions (not when I'm towing of course) and was wondering if those who have 355's are happy with them. The dealership I bought from says he mostly gets 355's now (he may have gotten more 373's on earlier shipments) Can't seem to figure out why his later build inventory is mostly 355. He says he orders 355's now ... but who knows what the real rason may be.
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Joined: Feb 2004
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From: Sand Dune, CA
I don't have a 3.55 but I like to tell all of you what happened to me regarding this choice.
I wanted to order my truck with a 3.55 because I thought it would get better gas mileage and have lower RPM's while crusing on the highway.
To make a long story short, I had to take the 3.73 when I purchased my truck. Now, I'm glad I got the 3.73.
Highway crusing with 3.73: The stock truck cruised under 2,000 RPM. Great!
Gas mileage comparision between the 2 rearends: I don't know? The number might be small. Driving habits may affect gas mileage more.
Ok, on to the good news. I have taller tires now and the 3.73 is quicker off-the-line than the 3.55. I have heard of some guys wanting to re-gear their rearends to 4.10's or higher after a lift and tire change.
I think my truck is great with a 3.73 rear, 315/70/17 tires, and a Superchips programer.
Just my 2 cents.
I wanted to order my truck with a 3.55 because I thought it would get better gas mileage and have lower RPM's while crusing on the highway.
To make a long story short, I had to take the 3.73 when I purchased my truck. Now, I'm glad I got the 3.73.
Highway crusing with 3.73: The stock truck cruised under 2,000 RPM. Great!
Gas mileage comparision between the 2 rearends: I don't know? The number might be small. Driving habits may affect gas mileage more.
Ok, on to the good news. I have taller tires now and the 3.73 is quicker off-the-line than the 3.55. I have heard of some guys wanting to re-gear their rearends to 4.10's or higher after a lift and tire change.
I think my truck is great with a 3.73 rear, 315/70/17 tires, and a Superchips programer.
Just my 2 cents.
Last edited by FX4dude; Oct 5, 2004 at 09:21 PM.
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Joined: May 2004
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From: Mirror, Alberta
Gear ratio
Originally Posted by fanfare
I got the 355 rear end ... I was wondering if anyone tows with this ratio. Because I don't plan on towing more than 7000 lbs I figured I would try to get better MPG under highway conditions (not when I'm towing of course) and was wondering if those who have 355's are happy with them. The dealership I bought from says he mostly gets 355's now (he may have gotten more 373's on earlier shipments) Can't seem to figure out why his later build inventory is mostly 355. He says he orders 355's now ... but who knows what the real rason may be.
Cargo Master
Joined: Aug 2004
Posts: 2,542
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From: Murphysboro, IL
Originally Posted by FX4dude
Highway crusing with 3.73: The stock truck cruised under 2,000 RPM. Great!
On my 3.55 rear with a 4.6 engine I can run 80 at just a hair under 2000 rpm's. 55-60 is the sweet spot for gas mileage though. 70 mph is about 1800 rpms.
Senior User
Joined: Dec 2003
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From: Palm Harbor, Florida
I have 3.55 now, and will be upgrading to 4.10 once my suspension lift goes on next week. I also have 315/70/17's on there now.
Just with a leveling kit and the bigger tires, my get up and go is less than desirable. So im looking for best deal to do gears after my lift goes on.
Just with a leveling kit and the bigger tires, my get up and go is less than desirable. So im looking for best deal to do gears after my lift goes on.
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Joined: May 2004
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FANFARE, I have a Lariat SCrew with the 3.55. I towed my 4,000 lb. camping trailer with five of us in the cab and five bicycles in the bed to Yellowstone this summer (from TX). It towed fine. 
I turn OFF the overdrive unless I have a tailwind and level or downsloping terrain. I averaged about 11 MPG and used the air conditioning occasionally.
I turn OFF the overdrive unless I have a tailwind and level or downsloping terrain. I averaged about 11 MPG and used the air conditioning occasionally.
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Senior User
Joined: Feb 2004
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From: Sand Dune, CA
Originally Posted by Birdhunter1
What kind of speed are you rrunning, 70-80 mph?
On my 3.55 rear with a 4.6 engine I can run 80 at just a hair under 2000 rpm's. 55-60 is the sweet spot for gas mileage though. 70 mph is about 1800 rpms.
On my 3.55 rear with a 4.6 engine I can run 80 at just a hair under 2000 rpm's. 55-60 is the sweet spot for gas mileage though. 70 mph is about 1800 rpms.
I believe it was 75 MPH.
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