Im trying to decide whether I should buy an older pickup I ran across online yesterday afternoon. A guy has an 86 f250 he took the 6.9 out of and dropped a 7.3 idi in. He still has the stock 6.9 4 speed in the truck but says he needs a new belhousing to complete? Why would this be? Do the zf5 speeds have different bolt patterns??

 

might have been cracked ...

 

But they do match up to eachother??

 

They should mate each other

 

they should mate but if a 7.3 is already in with no tranny i'd suggest going to the junkyard and finding a 5 speed for it.

 

The ZF 5 spd is nice ... especiallly if you plan to tow and you dont wanna go for bigger tires ... I went from stock 235/85/16's to 315/75/16's and picked up a cool 2.5 mpg on freeway .... with 3.55 gears ...and a 4 spd ...

even when i tow ... milage never drops off .... In my oppinion ... if its 4x4 .... do the leveling kit on the front and get some 315/75/16 Cooper AT/3's and you will love your truck even more with that 4 spd .......

just remember these Engines dont make much power below 2K .. so rev the junk out of it ... I run mine to 3K nearly everytime I shift for the last 5 yrs ... and by grandpa driving i actually get less eco. then when i drive the beans out of it ....

 

She I got my 1993 it had /65/75R16LT up front and 285's in the rear. Did like the mileage I seemed to get, but some reason it kept blowing the right rear tire, switched to stick 265's in back also and no more blowouts. Don't understand it. Would love to put the 285's back, just seemed to make the gearing more logical. With265's 1st is pretty pointless, unless towing a load.

 

thats why i went to 315's .... love my MPG

 

The bell housing bolt pattern is the same between the 6.9 and 7.3, if he needs a new one, chances are the old one is just cracked which isn't an unusual thing to happen to those units. The ZF5spd has an integrated bell housing, so you have to make sure the transmission you get is from an IDI or even a 1st generation PSD. A ZF from a 460 can be made to work but requires some drilling and grinding. Another thing to consider is that the 86 speedometer is gear driven from the tail shaft of the tranny. The ZF used in 87-91 trucks will have this hole. The ZF units from the 92 and up trucks will not as they are driven off a sensor in the axle. You can however swap an older ZF housing and drive gear onto a newer unit.

 

I bought the truck and it ended up having the 4 speed behind a 7.3. I love this truck only took me three cycles of glow plugs in that nasty -8 degree weather for her to fire up!! Everything works great very satisfied