Split-Case re-gearing, rebuilding and machine work (1 Viewer)

orangefj45

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We get lots of questions about split cases and gearing options, so we thought it’d be a good idea to compile a bunch of info and pics in one thread.
Sumo Gear company is our preferred vendor for rebuild kits, shafts, flanges and definitely gear sets. We have been working with them for many years, including the prototype 4:1 split case gear set for these cases.
We have built a few hundred split case combos for installation here at the shop, as well as supplying combos for customers nationwide.
We’ve discussed the different transmissions and shifters ( twin-sticks for the split cases ) on other threads, so this thread will focus on gearing options and machine work.
Sumo offers Two different low range gear sets for these transfer cases.
The first set keeps high range at a 1:1 ( direct drive ) ratio and lowers the low range to a 3.1:1, from the factory 2.28:1.
The other set they offer changes the high range to a 10% under-drive and offers a 4:1 low range ratio.
We keep their rebuild kits and gear sets in stock at all times.
Both gear sets require “clearancing” the rear case half. We have been working with a local machine shop, and once we reached our “4th generation” machine program, we were happy with the results. Our shop charges $195 to machine the cases for us.
The first pic shows a rear case half being machined.
Georg @ Valley Hybrids, Cruiser Brothers & Long Range America

ps: here’s a link to the split case video we put together a few years ago with the help of @Beno ; it’s his case I’m rebuilding in the video.


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orangefj45

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Important note!!!!
With the low gear sets, you have to run the factory drain plug on the transfer case. You cannot run the 10 mm Allen style plug because it will hit the gear.
You also have to run the transfer case main shaft from a manually shifted case, not the vacuum shifted case.
Attached is a picture showing bull shaft. The vacuum shaft with thr straight splines at the top, the mechanically shift shaft with the “pinched” splines at the bottom.

Georg @ Valley Hybrids, Cruiser Brothers & Long Range America

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So in theory if you ran the 4:1 Set say with stock 3.73 diff ratio how does the 10% underdrive work? would it run say like if you swapped in a set of 4.10s? Sorry math is hard
 

orangefj45

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So in theory if you ran the 4:1 Set say with stock 3.73 diff ratio how does the 10% underdrive work? would it run say like if you swapped in a set of 4.10s? Sorry math is hard
That’s correct. It’s like re-gearing your diffs from 3.70 to 4.10 ....... roughly.
 
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That’s correct. It’s like re-gearing your diffs from 3.70 to 4.10 ....... roughly.

Thats pretty dang cool. Definitely going to have to add this to the list. The 4:1 in lee majors was awesome. Im assuming this doesnt have gear lever popping out issues like the Orion does right?
 
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dbbowen Yeah, it had my head spinning too, and add to that I have a Ranger Torque Splitter in the mix also. I just went for it and ordered the 4:1...
 

orangefj45

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Thats pretty dang cool. Definitely going to have to add this to the list. The 4:1 in lee majors was awesome. Im assuming this doesnt have gear lever popping out issues like the Orion does right?
As long as you run the output shaft I pictured, your case won’t pop out of gear.
Georg @ Valley Hybrids, Cruiser Brothers & Long Range America
 

HemiAlex

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3000 rpm with a true 33” tire is 70mph in an h42f truck

3000 rpm with a true 33” tire is 84mph with an h55f and it’s .84 od gear
 
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orangefj45

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Another item worth mentioning is the “full-spline” input gear. This great upgrade replaces the factory gear, spacer and PTO gear ( where applicable; some tcases had a double-length spacer instead of a single spacer and PRO gear ). The entire length of the gear hub is splined so even if your transmission ( or adapter spud ) shaft has worn splines, the gear will transfer power via the good splines without making that nasty clunk most of us have heard; it’s typically caused by worn shaft and gear splines.
We stock these gears as well in the early 34-tooth and later 32-tooth version. No machine work is required for these gears but when it comes to low gear sets, they can only be used in conjunction with the 3:1 set. The 4:1 set utilizes a different tooth count input gear; we have discussed this with our gear vendor snd we’re hoping that the 4:1 set will feature a long spline input gear in the future.

Georg @ Valley Hybrids, Cruiser Brothers & Long Range America

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Spook50

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Great tech Georg. From the looks of it, given machining, needing the necessary output shaft, and if one would want to use the long spline input, would it be cost effective to just buy a complete case assembly from you and assemble it onto the tranny, or still worth it to order just the individual parts including housing and do the rebuild ourself? I'm talking strictly financially speaking; not taking into consideration someone's mechanical knowhow.
 

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