Better Mileage

[siris]

I have an 89 Poweram stock size tires, and get about 12 mpg highway. If I swap to a weber would i get a noticable increse in mileage? Also it is an autotragic and it woulnt shift into OD until i hit 65. Has anyone Sucessfully changed shift points in the allison trans? If it were a torqueflite i would have no problems but i don't know anything about this Trans. I read an artical on allpar about swaping to mpfi and thought it would be a good project but i cant find any donors around here, anyone had good luck swaping to mpfi?

[siris]

More or less i'm not looking to upgrade the carb, just trying to get rid of the stocker. It has a flat spot about 3/4 throttle, it just falls on it's face.

[siris]

thanks for the clarification i was under the impression they made a direct replacement. wich weber would run richer? sounds like a good time for a ported&polish job/upgrade exhuast right?

[siris]

2.6l i believe i found my answers about the carb on another thread. i apreiciate your help. has anyone dabled with the 4speed auto? any modifications?

[pennyman1]

force 10 has a shift kit for it- thats all I ever found for it other than a tranny cooler

[siris]

what model is the trans in the 4x4? from what i can find in my research its made by allison. is that correct?

[pennyman1]

No, its a japanese tranny made by the same people who make the automatics for the nissan 300z car. Allisons are in fullsize ram diesel trucks

[Vantastic1]

Isnt it made by Aisin?

I vaugely remember reading that its the same company that makes trannies for Mazda.

[siris]

how does it shift, by that i mean is it line pressure against springs to open valves like a torqueflite? the reason i ask is i would like od to kick in earlier like at 45-50 insted of 65.

[pennyman1]

That's rather late to go to od. Sounds like your kickdown cable is out of adjustment bigtime, or you drive with your foot to the floor all the time. After warmup, it will go to overdrive above 40. Also check to see if the sensor for the tranny ( its the one on the intake closest to the carb/throttle body) is working; if its bad it will delay od shift.