ZF5 to ZF6 in a 1989 f250?

firehonomichl

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Hey fellas just wondering what it take and modifying to take my ZF5 out and put in a ZF6? It is 4x4 and a 7.3L of course lol
 

IDIoit

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the 6 is essentially the same trans as a ZF5. final OD ratio is a .01 difference.
biggest difference is a granny 1st.
if you don't tow heavy, there is no need to do it.
 

Randy Bush

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the 6 is essentially the same trans as a ZF5. final OD ratio is a .01 difference.
biggest difference is a granny 1st.
if you don't tow heavy, there is no need to do it.

And if you do tow heavy a wide ratio ZF5 will give you all the granny you need .
 

Macrobb

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If you want an extra gear, basically you need to go with 3.55s(higher top gear but harder to start off the line towing), or keep your 4.10s and install an overdrive box like a Gear Vendor box.
I have a GV Overdrive on one of my trucks, and it's perfect, but expensive! Low gears for towing, A split 3rd to help if you need, plus double OD for highway cruising.
 

Randy Bush

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If you want an extra gear, basically you need to go with 3.55s(higher top gear but harder to start off the line towing), or keep your 4.10s and install an overdrive box like a Gear Vendor box.
I have a GV Overdrive on one of my trucks, and it's perfect, but expensive! Low gears for towing, A split 3rd to help if you need, plus double OD for highway cruising.
With mine I did lose topend speed when I rebuilt it to a wide ratio, but I can still do 70 at around 2200 rpms. Towing 18k -20k I can easily let out on he clutch then throttle up.
 

Macrobb

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With mine I did lose topend speed when I rebuilt it to a wide ratio, but I can still do 70 at around 2200 rpms. Towing 18k -20k I can easily let out on he clutch then throttle up.
I don't know why? http://www.dieselhub.com/trans/zf-5-speed.html Wide ratio is .01 /taller/ ratio than short ratio. So you should see a very slight increase in MPH at the same RPM.
 

Randy Bush

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I don't know why neither, just know lost 5-10 mph on topend. But I don't care because now it will pull heavy. Before I had to be careful on a grade , slip the clutch a little to get going or kill the engine. I don't remember anymore just what the parts donor trans came out of other then a 4x4 so had to pull gears out of it to put in mine.
 

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