1997 ZF-5 Gas vs. diesel

[bosefes]

Anyone know the differences between the ZF-5 speed manual in the 97 F350 gas and diesel trucks. I am looking at buying a 97 F350 with a 460 gas motor and will be converting it to a 5.9 Cummins. I am just wondering if this tranny will work?

[Believer45]

I do not know about mounting but the ratios are different.

Gas version (wide ratio)

1st 5.72:1
2nd 2.94:1
3rd 1.61:1
4th 1.00:1
5th 0.76:1

Diesel version (close ratio)

1st 4.14:1
2nd 2.37:1
3rd 1.42:1
4th 1.00:1
5th 0.76:1

Gas has a lower first and works up to an equal 4th and 5th - this helps overcome the lower torque rating of the gas engine as compared to the diesel when you are trying to get a load moving.

I was considering the change to add to 3.08 gears to raise my mileage - the lower first of the gas tranny should compensate for the higher speed ratio in the differential. I finally decided the truck is OK as is.

Dave / Believer45

[bosefes]

I knew the ratios, I guess my question is: Is there any strength issues on the gas tranny? Would it hold up to a Cummins as well as a the diesel version? Thanks for the info though Dave.

Dave

[Mr_Roboto]

The ZF-5 has issues with the synchronizers. However there is likely no strength difference between gasser and diesel versions. You may have a hard time coming up with an adaptor to go from Cummins to big block Ford.

[bosefes]

Do the gas and diesel versions have the same bolt pattern on the bell housing?

[Copper]

No - a "gas" ZF has a 385-block pattern, and a "diesel" ZF has the IH pattern, which I've been told is basically the same 6.9 on up. There was also a 3rd one that bolts up to a 300-351, but I forget what the family designation is. (is it just Windsor?) To complicate it, they're all a 1-piece bellhousing/case, but allegedly the internals are interchangeable, i.e. the "gas" gears will fit in a "diesel" case, etc.

Sadly, I've been told the lower cluster is all one piece, so you can't mix and match gears - I wanted to do that in my personal pickup with 3.55's, swap in a gasser granny first gear and keep the 2-3 gears from the diesel. It'd be a big step from 1 to 2, but it'd sure be nice for picking up a load on a hill.

[bosefes]

Well that sucks, I don't think anyone makes an adapter to go from the Gas version ZF-5 speed to a Cummins.

[Copper]

I think I was told once that the Cummins conversion shop over in the Bitterroot valley (Montana) had a custom one that they sold - but I could be wrong. Now if I could remember what their name is.......

[Mr_Roboto]

Originally Posted by Copper

There was also a 3rd one that bolts up to a 300-351, but I forget what the family designation is. (is it just Windsor?)

I just call it the smallblock pattern. 240/300, 221/260/289/302/351W, 351C/a few 400's, 3.8/4.2L V6's. I think the early modulars used the smallblock pattern too, but don't quote me on it.

[mudguppy]

Originally Posted by bosefes

Well that sucks, I don't think anyone makes an adapter to go from the Gas version ZF-5 speed to a Cummins.

did you check cumminscoversions.com?? i thought i remember seeing a cummins to big block ford adapter. if so, "big block ford" refers to the 385 family, usually.

[bosefes]

As stated in my original post I am wanting to buy a Crew Cab F350 4x4 with a ZF-5 and a 460 gas motor to convert it to a 12V 5.9 Cummins. What are some other things I am going to run into? Dash gauges? fuel tank problems? fuel line problems? Would I be money ahead to just find one with a powerstroke and then convert it? Problem is most of them are 5000-7000 dollars more than an otherwise equivalent gas powered truck.

[Renagadex]

Check destroked.com, they have adapators for zf-5 gas tranmissions. Plus you don't have to cut your bell housing to make the starter fit in.

[bosefes]

Yes I actualy found that a few days ago. I might be taking a job overseas though, so the whole cummins swap deal might be put off for a while.

[matts156]

I ran across a Cummins-ZF-5 adapter here.

4BT and 6BT Cummins Adapter, Chevy 4L80E TH400 700R4 4L60E