I need advice on locking the rear

[RonD]

The 3.0l Vulcan engine is designed as a high RPM engine, makes best torque at 3,600(1991), most other engines make best torque at 2,600rpms

3.0l specs here: https://therangerstation.com/tech_library/3_0performance.shtml
2.9l specs here, used until 1992 in Rangers: https://therangerstation.com/tech_library/2_9_Page.shtml

BOTH used the same automatic trans with same shift points

In a manual you can drive it as it was designed, high rpm shifts, for best power so best MPG, yes they do go hand in hand
In an automatic the shift points are designed for a 2,600rpm engine so you are basically lugging the engine around town and even on the highway, which will show up as low MPG.
The 3.0l Vulcan is 1986 technology so won't ever match newer V6s or even V8s for MPG but in an automatic its really down.

You could go with a 4.10 ratio rear axle, limited slip of course, lol, that should raise up the RPMs a bit for computers shift points, and highway cruising.

You can get a complete used L/S Ranger axle for not too much and it is just a bolt in project, although the U-bolts can be a b*cth, so may be cut them off and use new

 

[91stranger]

The 3.0l Vulcan engine is designed as a high RPM engine, makes best torque at 3,600(1991), most other engines make best torque at 2,600rpms

3.0l specs here: https://therangerstation.com/tech_library/3_0performance.shtml
2.9l specs here, used until 1992 in Rangers: https://therangerstation.com/tech_library/2_9_Page.shtml

BOTH used the same automatic trans with same shift points

In a manual you can drive it as it was designed, high rpm shifts, for best power so best MPG, yes they do go hand in hand
In an automatic the shift points are designed for a 2,600rpm engine so you are basically lugging the engine around town and even on the highway, which will show up as low MPG.
The 3.0l Vulcan is 1986 technology so won't ever match newer V6s or even V8s for MPG but in an automatic its really down.

You could go with a 4.10 ratio rear axle, limited slip of course, lol, that should raise up the RPMs a bit for computers shift points, and highway cruising.

You can get a complete used L/S Ranger axle for not too much and it is just a bolt in project, although the U-bolts can be a b*cth, so may be cut them off and use new

You do realize that I am not talking about a 1991 ranger right? My current truck is a 1999 ranger. 91stranger has just been my login name forever so I just kept the same name. its confused people in the past but I figured my profile pic is of my 1999 truck and not the 1991. So if you were giving me info about 1991 rangers then that wont be helpful lol. Thanks though.

 

[RonD]

You do realize that I am not talking about a 1991 ranger right? My current truck is a 1999 ranger. 91stranger has just been my login name forever so I just kept the same name. its confused people in the past but I figured my profile pic is of my 1999 truck and not the 1991. So if you were giving me info about 1991 rangers then that wont be helpful lol. Thanks though.

Actually 1999 3.0l Vulcan is worse, best torque at 3,750RPM

3.0l Specs here: https://therangerstation.com/tech_library/3_0performance.shtml

You need to drive these like a rented mule, which is why most say they are under powered, and they are, but not as much as most proclaim if driving them at correct RPM range to get that power.

Most 4cyl, V6, and V8 engines have best torque at 2,400-2,900 range, 3.0l Vulcan doesn't