Diesel Gears In A Gas Big Block ZF5 Case

[t120r]

So i finally found a diesel ZF5 4x4. This one has a crack in the bellhousing. My plan is to rip out the 4.14 gears from it and swap them into my gas case. The gear ratio will be much better for me and i won't feel like I'm driving a dump truck. My 429 is built pretty good, so i don't need that ultralow first gear. If the day ever comes that i do, i have 2 more ZFs under my work bench.

 

[Broncobowsher]

I've always thought about doing it. Never seen anyone who has. Pulling the input shaft will tell a lot. If the gear is the same, I bet it will be a pretty easy swap. If not you will have to keep the diesel input shaft, and the diesel clutch, and figure out the pilot bushing.

If you have parts books, it would be wise to spend a little bit of time and check the bearing numbers where it goes into the case. If all that looks like a good match, there is still the mystery if it will work. I sure hope it does. I would think those diesel gears would be great in a lot of gas rigs.

 

[lars]

So, for those of us (me, for example) who are ignorant but curious, what's the difference?

 

[Oldtimer]

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ZF S5-42, S5-47 Transmission Specs & Ratios

ZF S5-42 and S5-47 5 speed manual transmission specs, ratios, and information. The ZF S5-42 was introduced sometime during the 1987 model year and was optional in 6.9L/7.3L IDI and 7.3L Power Stroke equipped Ford pickups. The marginally stronger S5-47 was later introduced for the 1995 model year...

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ZF S5-42 & S5-47 Ratios​

Model/Type​	1st​	2nd​	3rd​	4th​	5th​	R​
S5-42 Close Ratio​	4.14 : 1​	2.37 : 1​	1.42 : 1​	1.00 : 1​	0.77 : 1​	3.79 : 1​
S5-47 Close Ratio​	5.08 : 1​	2.60 : 1​	1.53 : 1​	1.00 : 1​	0.77 : 1​	4.66 : 1​
S5-42/S5-47 Wide Ratio​	5.72 : 1​	2.94 : 1​	1.61 : 1​	1.00 : 1​	0.76 : 1​	5.24 : 1​

Both the S5-42 and S5-47 transmissions have been offered in close and wide ratio variations. While the wide ratio versions of the S5-42 and S5-47 feature identical ratios, the close ratio S5-42 contains a much taller 1st and reverse gear ratio in addition to a slightly different spread in between. The S5-47 is a heavier duty version of the 42, but is otherwise interchangeable so long as the transmissions originate from a diesel application. However, it is not advised to replace a S5-47 with a weaker S5-42; replacing a S5-42 with a stronger S5-47 presents no such problems. The greater strength of the S5-47 is attributed in part by a refined case design (smoother transitions and therefore less stress concentration points) and revised synchronizers. Many, if not most part numbers for internal components are the same for both transmissions. It's worth noting that the wide ratio S5-42 and S5-47 were offered in gas engine applications and are not interchangeable with diesel engine versions of the transmission.

 

[lars]

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http://[URL]https://www.dieselhub.com/trans/zf-5-speed.html

[/URL]

ZF S5-42 & S5-47 Ratios​

Model/Type​	1st​	2nd​	3rd​	4th​	5th​	R​
S5-42 Close Ratio​	4.14 : 1​	2.37 : 1​	1.42 : 1​	1.00 : 1​	0.77 : 1​	3.79 : 1​
S5-47 Close Ratio​	5.08 : 1​	2.60 : 1​	1.53 : 1​	1.00 : 1​	0.77 : 1​	4.66 : 1​
S5-42/S5-47 Wide Ratio​	5.72 : 1​	2.94 : 1​	1.61 : 1​	1.00 : 1​	0.76 : 1​	5.24 : 1​

Both the S5-42 and S5-47 transmissions have been offered in close and wide ratio variations. While the wide ratio versions of the S5-42 and S5-47 feature identical ratios, the close ratio S5-42 contains a much taller 1st and reverse gear ratio in addition to a slightly different spread in between. The S5-47 is a heavier duty version of the 42, but is otherwise interchangeable so long as the transmissions originate from a diesel application. However, it is not advised to replace a S5-47 with a weaker S5-42; replacing a S5-42 with a stronger S5-47 presents no such problems. The greater strength of the S5-47 is attributed in part by a refined case design (smoother transitions and therefore less stress concentration points) and revised synchronizers. Many, if not most part numbers for internal components are the same for both transmissions. It's worth noting that the wide ratio S5-42 and S5-47 were offered in gas engine applications and are not interchangeable with diesel engine versions of the transmission.

Thanks.

I can see why the close ratio S5-42 gears would be attractive. Makes the ZF more like an NV3550 or an AX-15.

 

[t120r]

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http://[URL]https://www.dieselhub.com/trans/zf-5-speed.html

[/URL]

ZF S5-42 & S5-47 Ratios​

Model/Type​	1st​	2nd​	3rd​	4th​	5th​	R​
S5-42 Close Ratio​	4.14 : 1​	2.37 : 1​	1.42 : 1​	1.00 : 1​	0.77 : 1​	3.79 : 1​
S5-47 Close Ratio​	5.08 : 1​	2.60 : 1​	1.53 : 1​	1.00 : 1​	0.77 : 1​	4.66 : 1​
S5-42/S5-47 Wide Ratio​	5.72 : 1​	2.94 : 1​	1.61 : 1​	1.00 : 1​	0.76 : 1​	5.24 : 1​

I've seen dozens of gas and diesel ZFs in my life. I've never come across the 5.08:1 version though.

 

[t120r]

Thanks.

I can see why the close ratio S5-42 gears would be attractive. Makes the ZF more like an NV3550 or an AX-15.

Yep. I have no interest in a 5.72:1 first gear. That 4.14 would drive so nice.