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Discussion Starter #1
In 94 or 95 NP redesigned the transfer case used in wranglers

They changed the gear tooth profile reportedly to make it quieter so you cannot mix early and late ring gear in case half or planet set or input with sun gear because of the tooth profile

They also made the bearing that the input rides in more narrow which makes it easier to tell the early and late inputs apart

More significantly they deleted the roller bearings between the chain drive sprocket and the rear output shaft. They increased the diameter of the smooth portion of the rear output shaft to make up for the space the roller bearings occupied. All the SYE kits use this larger diameter and instruct the installer to drive out the roller bearings and discard if your sprocket has them

Now the sprocket always rotates at the same RPM as the front output yoke and the rear output shaft rotates at the same rpm as the rear output yoke so on a TJ with fixed hubs and no CAD as long as all four tires are on the ground even in two wheel drive the RPM of the sprocket and shaft are always essentially the same so the lack of roller bearings is no big deal.

However on a YJ with CAD or a TJ with add on front locking hubs unlocked or with the front wheels on a tow dolly and both drive shafts attached the chain and sprocket is basically still and the rear output shaft it rides on is rotating at rear driveshaft RPM now the lack of rollers may really matter

Wonder if it is was related that the same time they went from a yj with CAD to a TJ they dropped the roller bearings

But the transfer case change was across the board for all the NP 231 241 Chevy Dodge Jeep so maybe not related but don't think I'll be running with front hubs unlocked as much
 

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In 94 or 95 NP redesigned the transfer case used in wranglers

They changed the gear tooth profile reportedly to make it quieter so you cannot mix early and late ring gear in case half or planet set or input with sun gear because of the tooth profile

They also made the bearing that the input rides in more narrow which makes it easier to tell the early and late inputs apart

More significantly they deleted the roller bearings between the chain drive sprocket and the rear output shaft. They increased the diameter of the smooth portion of the rear output shaft to make up for the space the roller bearings occupied. All the SYE kits use this larger diameter and instruct the installer to drive out the roller bearings and discard if your sprocket has them

Now the sprocket always rotates at the same RPM as the front output yoke and the rear output shaft rotates at the same rpm as the rear output yoke so on a TJ with fixed hubs and no CAD as long as all four tires are on the ground even in two wheel drive the RPM of the sprocket and shaft are always essentially the same so the lack of roller bearings is no big deal.

However on a YJ with CAD or a TJ with add on front locking hubs unlocked or with the front wheels on a tow dolly and both drive shafts attached the chain and sprocket is basically still and the rear output shaft it rides on is rotating at rear driveshaft RPM now the lack of rollers may really matter

Wonder if it is was related that the same time they went from a yj with CAD to a TJ they dropped the roller bearings

But the transfer case change was across the board for all the NP 231 241 Chevy Dodge Jeep so maybe not related but don't think I'll be running with front hubs unlocked as much
That brings up another thought. There are a few that run around without front drive shafts either due to a bad u-joint that hasn't been taken care of, or a regear in one axle where someone is worried about 4wd being engaged....same thing as being on a tow dolly or having hubs unlocked from the transfer cases perspective.
 

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Discussion Starter #4
Similar but tow dolly is worst of the three because here the front driveshaft and thus the chain sprocket is held at a dead stop but with unlocked hubs I know the front driveshaft still spins some from viscous drag although a gloved hand can stop it and with no front driveshaft chain and sprocket can free spin but still not ideal for that sprocket directly on output shaft with no bearings

The old style tc has two separate full sets of roller bearings at that interface

If I unlock all four hubs on my tj and put in 2H the rear drive shaft is spun by engine but the front also spins but is easily stopped by a gloved hand
 

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Discussion Starter #5
Advantage one if you brake a axle or have diffy issue with full floater rear and all four manual warn hubs like I have you can limp home on which ever end is intact and free wheeling hubs on damaged end

Other advantage is tow with only hubs spinning

Finally I can do 2low without buying the terra kit

But not worth the cost but done by prior owner so not my decision
 

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Similar but tow dolly is worst of the three because here the front driveshaft and thus the chain sprocket is held at a dead stop but with unlocked hubs I know the front driveshaft still spins some from viscous drag although a gloved hand can stop it and with no front driveshaft chain and sprocket can free spin but still not ideal for that sprocket directly on output shaft with no bearings
Good point....:thumb:
 

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Nice writeup Digger and I understand the theory of what you explained. But there are many TJ owners running unlocked front hubs, me included, without transfer case problems. In fact I know of no one who has experienced the theoretically possible damage to their tcase. I ran my previous TJ with a 231and manual hubs unlocked except when off-road for 8-9 years without problem. No problems with my present manual hubs and 241 tcase. I keep my hubs unlocked until it's time to shift into 4x4.
 

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Discussion Starter #8
Mine too without probs but at least some possible insight into the jeep owners manual admonishment against a tow dolly

As just letting the front drive shaft free wheel when driving in 2wd is different than holding it still

Never looked inside a 241OR but a 1992 Chevy plain 241 did have the two roller bearing units inside the drive sprocket as expected on early NP units

Good to know others with more miles on unlocked manual hub TJs have not had an issue

So Jerry what manual hub setups did you have on previous stolen TJ and the current one?

Mine ore full size Warn from the kits warn used to sell
 

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Both of my manual hubs are Warn. The first set being the 'small' since I was only running 27 spline shafts up front back then and my current hubs being their full size big hub kit.
 

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Discussion Starter #10
So you are running a 5.5 lug circle front and back?

Mine are 5 on 5.5 to leave room for the full size hubs

Noticed something else about the 95 update on the NP231 they also deleted the syncro on the four wheel drive select

Guess they figured once CAD was gone the front drive shaft would always be already Up to speed so why not save on a few little parts and some brass or bronze

Makes me wounded if the tooth profile change was really just a easier cheeper to produce change rather then a run more quiet upgrade
 

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Yep I am running 5x5.5" wheels front and rear. NP231 not synchronized? I guess that is all how you look at it... 4Hi is synchronized for shift-on-the-fly abilities when the hubs are locked but not when the hubs are unlocked.
 

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Yep I am running 5x5.5" wheels front and rear. NP231 not synchronized? I guess that is all how you look at it... 4Hi is synchronized for shift-on-the-fly abilities when the hubs are locked but not when the hubs are unlocked.
I'd consider the the NP231 in our TJs to be pseudo synchronized. It doesn't use a synchromesh to synchronize gear speed (doesn't need to). It only has the sleeve mode synchronizer which engages the chain drive sprocket to the main shaft. I think the only reason it's called a synchronizer is the use of dog teeth, the large spacing allows for smooth engagement.
 

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Discussion Starter #13
Not from what I have seen all the pre 95 ones I have seen have the bronze syncro cone for the 4wd sprocket but all the post 95 ones omit that bronze cone and don't even bother to machine smooth the mating surface on the sprocket taper

Also the doged gear below has no slots for the projection from the Bronze cone and is missing the three little spring loaded segments

I trifled swapping in the better piece and the bronze cone but the sprocket was to rough to let it turn independently when not engaged

Couple pics with early and late sprocket and a couple early syncro cones behind them. Early also has the roller bearings inside
 

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I've seen the 231 without the roller bearings as early as 92 used in the YJ's and i have one on the bench now from an 92 Xj that doesn't have the 3 pieces either.
Not to throw a wrench in your gears
 

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Discussion Starter #16
For what it is worth the pics were from the 91-93 YJ XJ ZJ Jeep parts catalog and the 97-99 TJ Jeep parts catalog as downloaded from jeepslimited.com

I have seen chevy engines in TJs but don't think they were made that way and after 30 years a lot of parts get swapped around but unlikely that a to be latter released design found it way into the original 92 231 as it came from the factory

A few absolutes any 231 sprocket has a bore big enough to to go on the larger diameter rear output shaft (as long as any roller bearings are removed)and will also properly fit the older smaller diameter shaft if the roller bearings are pressed in.

The thing that would not work for me is trying to use the newer sproket with the bronze syncro of the early design as the taper on the sproket was too rough to spin freely inside the bronze taper

It also seems logical that with CAD,a YJ allowing front drive shaft to not be driven by front wheels any shift on the fly from 2H to 4H needs some mechanism like the syncro to bring the front drive shaft up to the matching RPM which is not needed in the TJ as originally produced

Without CAD I see no need for the syncro but with manual hubs I would prefer the sprocket to have the rollers ,but not an option with current SYE shafts all being larger diameter where sprocket rides.

I do think swaping in a non syncro 231 into a YJ with working CAD would not work well for shifting on the fly to 4Hi
 
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