Pilot Bob is running 5:38's and turning 33's with a 3.4 and an automatic. He is very happy with the combination.
He says it will cruise highway speeds all day and still climb like a goat with the Tera Lows. IIRC he reported the milage at about 16 mpg. 17 if the wind is low. And that's pulling a trailer to the Davis Mountains.
I even called him to confirm my info is correct.

Mileage will always get better the more vaccuum you can pull on the intake. High Manifold Vaccuum # means a happy engine.
Lug the motor and you kill your milage. Enigine is working too hard.

swap in a MUA <img src="/forums/images/graemlins/smile.gif" alt="" />.

I'd go for the 5.38's my tires are worn down to 33's and Its just about right.

w/ a SC in the future, it may not be worth the trouble. Perhaps you should wait until after that upgrade to decide whether or not to install or sell the gears. But for anyone in the sub 200hp range (most of us) running 33"+ rubber, the 5.38's are a great upgrade.

If you are going to put a locker in, it makes more sense to do the gears too (cost wise).

Thanks for that reply curtis , that helps with info a lot with the same combination I have of engine and trans.I don't do much pulling , but one day might get a small trailer for hauling my motorbike with me , so then I can 4x and ride the bike around town and stuff too.

I do have a lockright locker in the front end right now , and maybe down the road will get a 12 bolt locker as that is a lot easier to install , not as much to do to tear apart the carrier.

I was more into what I would gain with the 33" tires by going to the 5:38 , whether it would up the mileage , or improve driving performance around town or on the highway.But if it does make a noticeable difference with the 3.4 and auto tranny , then I might go ahead and do the upgrade.especially if it will make a difference when i do start towing the odd thing , maybe even a small camper trailer if I end up getting another one of those.

I loved my 5.38s, before the front diff fragged.

In my 3.4v6 a/t Trooper highway performance was much better. The transmission didn't have to down shift for every hill. And I could pull my pop up trailer with ease.

The overall highway gearing is similar to my 89 Trooper RS with 4.77s and 5 speed.