how fast in 4 hi

[jeepdude10000]

I cannot do that. Too many variables in driving style, speed, temperature, terrain etc. for me to tell.
I'll take your word, how many mpg does it cost me to be in FT 4x4?

i loose about 4 MPG when in FT 4X4. Not to bad when u think about it.

 

[falcon556]

i loose about 4 MPG when in FT 4X4. Not to bad when u think about it.

Is your 89 with a disconnect front axle?
Disconnecting would improve mileage.
In a non disconnect, all the parts turn all the time. The transfer case differential is made to favor the rear axle. 48-52 I think.
Nothing extra moves, the diff in the TC will move a bit to account for tire mismatch and turns, otherwise I don't see where the 4mpg go.
One of these days I will have to do a couple of tightly controlled trips to verify it.

 

[jeepdude10000]

Is your 89 with a disconnect front axle?
Disconnecting would improve mileage.
In a non disconnect, all the parts turn all the time. The transfer case differential is made to favor the rear axle. 48-52 I think.
Nothing extra moves, the diff in the TC will move a bit to account for tire mismatch and turns, otherwise I don't see where the 4mpg go.
One of these days I will have to do a couple of tightly controlled trips to verify it.

no mine is not a disco, had to change diff after i got the XJ cause it was just to warn out to screw with.

ur right on the 48-52.

Ihad the same thing on a Bronco i owed years back, i mean MPG diff.