Re-gearing help
Senior User
Joined: Dec 2012
Posts: 209
Likes: 0
From: Coastal Washington State
In my opinion 3.55 to 3.73 is not enough difference to make the swap worth it. Here's a formula that may be useful as you decide. RPM=miles per hour X gear ratio X 336 divided by tire diameter. Keep in mind that the formula counts on a final drive ratio of 1:1 so if you have an over drive tranny you have to plug that in after the 336 to make the formula accurate ie: X .85 or whatever is appropriate to your specific combo.
Cargo Master
Joined: Apr 2003
Posts: 2,408
Likes: 6
From: Parkesburg PA
Yeah, my bad, 29 -> 33" tires to get the 'stock' like gearing you go with 4.10's. That takes into account the change in tire diameter, but not the increase in weight.
The highway is the only place the shorter gears might hurt you as your cruise RPM will be higher. Around town you'll do better with the higher numerical gears.
The highway is the only place the shorter gears might hurt you as your cruise RPM will be higher. Around town you'll do better with the higher numerical gears.
Fleet Owner
Joined: Oct 2005
Posts: 20,789
Likes: 1,753
From: Kentucky
Never fear the gear....
I swapped from 2.73 to 3.73 in our old 1997 Mustang GT. I gained 2 MPG in town , lost 1 MPG on the highway. The car was transformed into a very nice all-around vehicle. With the taller tires you installed, you need every advantage you can find. Even 4.56 is not an unreasonable consideration.
When I purchased my current '04 V-10 Excursion I purposely sought out factory 4.30 gears. I love my Ex!
I swapped from 2.73 to 3.73 in our old 1997 Mustang GT. I gained 2 MPG in town , lost 1 MPG on the highway. The car was transformed into a very nice all-around vehicle. With the taller tires you installed, you need every advantage you can find. Even 4.56 is not an unreasonable consideration.
When I purchased my current '04 V-10 Excursion I purposely sought out factory 4.30 gears. I love my Ex!
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
+100.
Our 4.10 geared Ranger pulls our new dump trailer as well as my 3.55 geared F150.
Also.. you now need to recalibrate your speedo or you'll be driving faster than you think and the ODO will be racking up fewer miles than actual and making fuel consumption look worse than it is.
Our 4.10 geared Ranger pulls our new dump trailer as well as my 3.55 geared F150.
Also.. you now need to recalibrate your speedo or you'll be driving faster than you think and the ODO will be racking up fewer miles than actual and making fuel consumption look worse than it is.
Cargo Master
Joined: Apr 2003
Posts: 2,408
Likes: 6
From: Parkesburg PA
+100.
Our 4.10 geared Ranger pulls our new dump trailer as well as my 3.55 geared F150.
Also.. you now need to recalibrate your speedo or you'll be driving faster than you think and the ODO will be racking up fewer miles than actual and making fuel consumption look worse than it is.
Our 4.10 geared Ranger pulls our new dump trailer as well as my 3.55 geared F150.
Also.. you now need to recalibrate your speedo or you'll be driving faster than you think and the ODO will be racking up fewer miles than actual and making fuel consumption look worse than it is.
IMO 4.56 gears are an option unless you do lots of highway. The 351 will pull that truck with 4.10's nicely. My 89 Bronco with the 5.0, 33's and 4.10's performed very nicely.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
That only applies to trucks that have a speedo with a cable drive from the trans or transfer case which is '91 or older, everything after that has an electronic speedo that gets it's signal from the ring gear in the rear axle and the only thing that affects it is tire size.
Cargo Master
Joined: Apr 2003
Posts: 2,408
Likes: 6
From: Parkesburg PA
Good point. Other than my F350 parts truck every ford truck I've owned has been sub 91...
Do the later 4x4 trucks still have the provision for the cable speedo? I was going to swap the whole driveline into my 86. I've got a BW1356 and a NP208 that do, so I'm not too worried.
(sorry for the thread jack)...
Do the later 4x4 trucks still have the provision for the cable speedo? I was going to swap the whole driveline into my 86. I've got a BW1356 and a NP208 that do, so I'm not too worried.
(sorry for the thread jack)...
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Elder User
Joined: Jul 2011
Posts: 793
Likes: 2
From: Vernon, BC
I appreciate all the feedback. Thank you everyone. However, I now have another question. When I changed my tires from the stock tires to the 16" tires I recalibrated my speedo so that my speedo reads exactly the same as my GPS. If I change my gearing to, say 4:10, does that mean I need to recalibrate my speedo again when I do the gear change because the ring gear will be a different size?
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Fleet Owner
Joined: Oct 2005
Posts: 20,789
Likes: 1,753
From: Kentucky
I appreciate all the feedback. Thank you everyone. However, I now have another question. When I changed my tires from the stock tires to the 16" tires I recalibrated my speedo so that my speedo reads exactly the same as my GPS. If I change my gearing to, say 4:10, does that mean I need to recalibrate my speedo again when I do the gear change because the ring gear will be a different size?
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Generally no but nothing is ever a certainty with these trucks so you're just gonna have to look at your parts to know for sure.
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Elder User
Joined: Jul 2011
Posts: 793
Likes: 2
From: Vernon, BC
Thank you for the input everyone. I have decided to upgrade my gearing to 4.10 as I think 3.73 will be too small of a change to make enough difference. I still haven't talked to the shop that I want to do the work but I am beginning to save my money. Once I talk to them and get a ball park figure I will be able to put a target date on the job. This winter is looking good.
The reason I decided to go with the 4.10 gearing is that when I came home (up the ski hill) again recently my truck was not simply just low on power but it was definitely underpowered with my larger tires. It seems to be working too hard. When I go hunting and/or camping I also sometimes carry a large load (1500 lbs or so) or tow a moderately heavy trailer (2500 or 3000 lbs) so I think the 4.10's will be a good choice.
The reason I decided to go with the 4.10 gearing is that when I came home (up the ski hill) again recently my truck was not simply just low on power but it was definitely underpowered with my larger tires. It seems to be working too hard. When I go hunting and/or camping I also sometimes carry a large load (1500 lbs or so) or tow a moderately heavy trailer (2500 or 3000 lbs) so I think the 4.10's will be a good choice.
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