Rear gears, which to get and why, pros and cons with each

[Jb7]

Can someone with a lot of off-roading or rear differential experience break down the different gearing options and why we should choose a particular setup, pros and cons?

Sponsored

 

[JT1]

Can someone with a lot of off-roading or rear differential experience break down the different gearing options and why we should choose a particular setup, pros and cons?

Pick your tire size and engine/trans combo and work backwards. If you want 35's as an end goal, you will want the 4.70s if you plan to wheel it..

 

[crowdpleazer]

Gearing has to do with tire size so that the engine runs the same RPM.

 

[Jb7]

Thanks, def want 33” and would like to work up to 35’s with lift just not initially, so want to upgrade rear to 4.70 at min then it sounds like

 

[Lab00Rat]

4.46:1, 35/37 tires, and 2.7? Or get the Sasquatch for the 4.70 gears?

5.13 or 5.38 gears w/2.7L?

Sasquatch Highway RPMs with 4.7 gearing and 35" tires?

Calculator I found has the gear ratios similar to 5th for the manual and 9th for the automatic transmission.

All speeds kept similar at 70mph.

Feel free to dive deep, and let us know what you find.
https://spicerparts.com/calculators/engine-rpm-calculator

4.46-33s and 4.7-35s is closer to normal for me in RPM and driving conditions at 70mph.

 

[Jb7]

Thanks guys I appreciate y’all’s help, Im def going with the upgrade

 

[Incognito]

Thanks guys I appreciate y’all’s help, Im def going with the upgrade

Ummm....
With respect, you haven't said what you use is.

A LSD is far in the snow and mud.
A Locker rules on rocks and sand.
The basic Open differntial with computer traction control is best on the ice.

What is your use and needs?

Note that Ford's use of manually selectable lockers and computer traction aids, gets you two out if three best choices for most conditions built in.

 

[Jb7]

Well, I’m in north Ga. and travel from South Florida to West Va and looking to do some trail rides, light rock crawling, want fo run 33’s to start, so sand, mud, ice, rocks, snow, highway....

lots of up and downs with hills etc where I mostly travel, also need comfortable highway speeds of 80mph, family of 4 and most likely a hitch carrier when traveling longer distances with family, also will be maxing out the tow cap, not getting sas package so no option for 4.7, just deciding if I need 4.46 and locking rear

if I’m good with std rearend, 2.7, auto and 33’s I’d rather not spend the money of course, but I don’t want any regrets a year from now either

 

[gryphon1231]

Can someone with a lot of off-roading or rear differential experience break down the different gearing options and why we should choose a particular setup, pros and cons?

it's more than just an off road question, if the gears and the tire sizes are out of sink you get poor performance on road as well. Generally speaking and keeping it simple, as tire sizes go up your gear sizes should go up as well. If you're going with 35's or plan on running a tire larger than that later then go with the 4.7 now.

 

[2Jeeps&PatriotX1]

4.46:1, 35/37 tires, and 2.7? Or get the Sasquatch for the 4.70 gears?

5.13 or 5.38 gears w/2.7L?

Sasquatch Highway RPMs with 4.7 gearing and 35" tires?

Calculator I found has the gear ratios similar to 5th for the manual and 9th for the automatic transmission.

All speeds kept similar at 70mph.

Feel free to dive deep, and let us know what you find.
https://spicerparts.com/calculators/engine-rpm-calculator

4.46-33s and 4.7-35s is closer to normal for me in RPM and driving conditions at 70mph.

Ughh...my 3.5 EB in my f150 w/ 3.31 gears, 10speed, 35” MT tires and 6” lift runs at 2000-2100rpm climbing 7% grade at 70mph and can pass anything in its way while getting 18.1mpg. Even towing a trailer in 8th gear stays below 2400rpm. Why would I want 3K+ rpms when the power is much lower with the turbos.

 

[Lab00Rat]

Ughh...my 3.5 EB in my f150 w/ 3.31 gears, 10speed, 35” MT tires and 6” lift runs at 2000-2100rpm climbing 7% grade at 70mph and can pass anything in its way while getting 18.1mpg. Even towing a trailer in 8th gear stays below 2400rpm. Why would I want 3K+ rpms when the power is much lower with the turbos.

Numbers seem legit.
375hp and 470 lb-ft torque.

Let me know how long your transmission lasts.

 

[JT1]

Ughh...my 3.5 EB in my f150 w/ 3.31 gears, 10speed, 35” MT tires and 6” lift runs at 2000-2100rpm climbing 7% grade at 70mph and can pass anything in its way while getting 18.1mpg. Even towing a trailer in 8th gear stays below 2400rpm. Why would I want 3K+ rpms when the power is much lower with the turbos.

Huge difference in aero between a closed F150 and a jeep or bronco with no roof or doors. Also, the ratio calculator posted is in direct drive, not OD. 7th in the auto is 1:1, just like 4th in the manual.

Here's a better calculator for you:
http://www.grimmjeeper.com/gears.html

And to save some more research, here are the auto and manual trans ratios for the bronco. Remember that advertised tire specs are not close to GPS accurate, so even the 35's on the squatch will calculate to about 34" in real life.

7MT:
C 6.588:1
1st 4.283:1
2nd 2.365:1
3rd 1.453:1
4th 1.0:1
5th .776:1
6th .646:1

10A:
1st 4.714:1
2nd 2.997:1
3rd 2.149:1
4th 1.769:1
5th 1.521:1
6th 1.275:1
7th 1.0:1
8th .853:1
9th .689:1
10th .636:1

A Squatch automatic should be about 2100 rpm in 10th at 70, and the manual will be a few rpm higher

 

[2Jeeps&PatriotX1]

Huge difference in aero between a closed F150 and a jeep or bronco with no roof or doors. Also, the ratio calculator posted is in direct drive, not OD. 7th in the auto is 1:1, just like 4th in the manual.

Here's a better calculator for you:
http://www.grimmjeeper.com/gears.html

And to save some more research, here are the auto and manual trans ratios for the bronco. Remember that advertised tire specs are not close to GPS accurate, so even the 35's on the squatch will calculate to about 34" in real life.

7MT:
C 6.588:1
1st 4.283:1
2nd 2.365:1
3rd 1.453:1
4th 1.0:1
5th .776:1
6th .646:1

10A:
1st 4.714:1
2nd 2.997:1
3rd 2.149:1
4th 1.769:1
5th 1.521:1
6th 1.275:1
7th 1.0:1
8th .853:1
9th .689:1
10th .636:1

A Squatch automatic should be about 2100 rpm in 10th at 70, and the manual will be a few rpm higher

How much difference with the 33s on a BL in 10th gear at 70mph?

 

[2Jeeps&PatriotX1]

Numbers seem legit.
375hp and 470 lb-ft torque.

Let me know how long your transmission lasts.

Sorry, not sure what I was thinking when I typed that, I have the max tow package from Ford which is 3.55 gears.

 

[JT1]

How much difference with the 33s on a BL in 10th gear at 70mph?

Not sure if you are asking about squatch or not, but here's what the calculator shows:
2200 rpm (+/- 20rpm) for the 4.70 gears and 2100 rpm (+/- 20rpm) for the 4.46's

Sponsored