You definitly have a 9" rear end? I know some older 70's model ford half tons had 3/4 ton axles...although for the life of me I cant recall what they are...

 

fuel economy sucks on the idi with e4od automatics, the shift points are all wrong for good fuel economy. i get between 10 &11 in town and around 15 on the highway with 3.55's and a e4od. has banks full exhaust, stock turbo and ip turned up 3 flats. my old idi-t with 4.10's and a 5 spd. got 15 mpg in town and on highway (unless i was going faster than 62 mph on highway) i short shifted in town. stick truck was better for pulling i could floor it going up hills in 5th and not have to deal with a stupid downshift.

 

Aune, the 3/4 tons had D60's and 1tons D70s. Every once in a while a 150 would see a D61 semi floater, usually with 3.08s.

Judging by him saying hes got a stuck axle so he cant pull the carrier i would all but garuntee he has a 9"

 

The shift points are adjustable through the TPS Just increase or decrease the idol voltage, I just adjusted mine up to about 2000rpms shift points and OD @ 40mph, If it goes down I will adjust it back closer to 1700 until I can find MAX mileage.

Yep thats why I have a stuck axle.... my other 78 F-250 has Dana 60 rear and Dana 44 front but the 7.3IDI 78 2x has a 9"

 

Do you have any camber problems with the IDI in there?

 

No it shouldnt its only sitting 1/2 lower, After its in there a month or so I'll remeasure to see...If it does drop I'll put F-250 springs in all 4 corners.

 

I have gotten 21.5mpg out of my idi with the e4od, and 3.55 gears. Thats mostly highway with some city. I don't see how the shift points are wrong. It shifts at 1600-1700 with light throttle. I get 16 in the city.

 

when was the last time the TPS was replaced and or checked for voltage readings?
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how many miles on the trans? is the converter stock? you should enjoy towing with the E40D more than the zf5 (that's very hard to believe if your converter is worn though.)