Manual Transmission and SelecTrac (Full-time 4X4)

xyzvq

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Hello fellow Liberty owners. I am a long-time member, but this is my first time reaching out for help.

I have used this forum a lot to gather information about the various upgrades that can be performed to the KJ platform. Some of the upgrades that I have performed to my Liberty are renegade light bar, fog lights, cruise control, riveted fenders, tow hooks, aftermarket head unit, heated/power leather seats, and more...

Now, I am ready to take on my most ambitious project yet. I have been threatening to upgrade my 4X2 Liberty to 4X4 almost since I got it back when I was in high school. I did a lot of research and found a few good forums, but nothing quite as thorough as Mr. Bluphant's tutorials. After much research and the acquisition of a donor Jeep from the salvage auction; I am ready to do this. Additionally, my throwout bearing went out, so my KJ is down at the moment anyway.

My dilemma comes with which transfer case to mate to my transmission? After much research, I believe that it is safe to put the SelecTrac transfer case behind the 5-speed manual transmissions that come in the KJ. I have seen a couple of threads where people claim to have done this swap and did not report any binding or other issues.

My research has lead me to believe that I can do this combination, but I will need potentially two new driveshafts that are different lengths than what is available due to this not being a factory option. And that I may need a different transfer case input shaft length/spline count to properly receive the manual transmission output shaft.

Another minor issue is that I do not see the wiring for the transfer case position switch laying on top of my 4X2 transmission. I believe I read that all Jeeps come wired for 4X4, and that the wires are just tucked on top of the transmission. I am somewhat OCD, so I definitely would like to get the cluster to show the 4X4 positions. Is this connector hidden somewhere, or do I need to steal the wire harness out of my donor Jeep? How much wire do I need to transfer?

The wheels are already in motion for this project, so any advice guidance that anyone can provide would be much appreciated!
 

LibertyTC

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Even with a donor jeep, IMHO save the many major mechanical headaches & cost, and find a 4x4 that works for you.
That being said, I completely understand your willingness to do this project.
 

tommudd

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There is a reason the factory did not combine those two ( manual transmission and select trac )
Select trac is not build to handle the manual trans , not heavy enough
of course people have done it, heck people jump off bridges all the time but it's still not a good idea
Years ago we took 2 wheel drive XJs and installed 4 wheel drive in them since it was very easy
Too many electronics, different computers etc anymore to make it worth while

Mr. Bluphant's tutorials ????? never heard of them or if he knows anything
 

jeeptorino68

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You will find the NP242 (or NV242) plenty strong. Versions of it with minor upgrades are offered behind V8 engines in a variety of mopar vehicles abd the J version in all kinds of jeeps. It will definitely hold up behind your trans.
No idea on the wiring or input shaft though. But sounds correct in driveshafts. Thats the same issue with XJs when the conversion is made.
 

tommudd

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Offered, .... but still not that strong for the abuse that some put a manual through
We had this discussion many times at my monthly M&Gs with both engineers and the guys who actually built the KJs
( Yes they'd come out to my place and hang out )
They all always agreed and said the same things, it was just not strong enough to hold up behind a manual
period
 

xyzvq

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Tommudd, since it sounds like you’ve been around some people that have discussed this topic; I’d like to run some of my assumptions by you to see if I am on the right track.

Firstly, my intent for the Full time transfer case is for primary use during heavy rain events. I know that tires play a bigger role in traction in adverse condiments, but I would like to get the benefit of all wheels receiving power when it does rain really hard. Down in Louisiana, we don’t really deal with snow or ice, except for maybe once every five years; but we get sever rain events probably at least twice a month, at least in the summer time. So my primary use is for rain, and I am sure that I will find some excuse to go 4X4ing now that I have the capabilities. But I don’t intend to go rock crawling or tackle technical off road trails. With that being said, I am not as concerned about the reduced toughness that the 242 provides, unless you have a different opinion of my situation.

My next assumption is that the input shaft on the NP242 will work fine with the 5-speed transmission since the NP231 mounts to either the auto or manual trans and there is no difference.

The next one I am not so sure about, and that has to do with the driveshaft lengths. I believe that the front driveshaft will not change since they are the same part number for either manual or automatic transmission. The rear though I am getting conflicting information. The threads where people claim to have done this swap didn’t mention anything about having to change the rear driveshaft either even though there are different rear drive shafts depending on transmission/transfer case. I plan to also transfer an ~ 2” lift from the donor Jeep; I believe I read that this helps and may eliminate my need to modify the donor driveshaft or purchase a different length one.

Are you aware of any odd issues with mating the NP242 to the NV3550, apart form the NP242 being considered a “weak” transfer case by many. I am not planning to beat on my Jeep any more than when it was only 4X2 and I really don’t see where this will be an issue.

I would love to hear your or anyone else’s feedback on my logic here. I’ve done some pretty extensive searching and haven’t really found a forum or thread where the specifics of doing this swap or discussed. If anyone know of some please, I would love to check it out. I am extremely eager to go ahead and purchase a used NP242 in preparation of my swap, but I guess I am looking for final advise/validation before dropping around $300 for something I may not be able to use.
 

WheelNut

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Are you talking about driving in heavy rain on asphalt or on a dirt/gravel road? If you are on a non-asphalt surface you can use part time 4x4 with no issues, so you can use a NV231 without issue. If you are having traction issues driving on asphalt in the rain I'm not sure 4x4 will help in any event. The vehicle will become very slightly more stable in full time 4x4, but if you are hydroplaning a lot I would look at tires before your drive wheels. Are the roads in Louisiana extremely slippery in the rain? Like slippery enough you are oversteering regularly?

Having lived in Vancouver for a few years where it rains 7 months of the year I have no issues driving in the rain on asphalt with any vehicle I have owned, but one must know to drive within the vehicle's limits just as one would in snow- slow down. If the rain is coming down that hard visibility is usually the limiting factor not traction on acceleration. 4x4 will not help you stop faster.

If you want to start driving off-road more and need the capability of 4x4 you won't really need full time 4x4 anyway as part time 4x4 is what you'll want when you are pushing the limits off road. If you aren't driving in snow I don't really see the case for using the NV242 if it makes the conversion more difficult.
 
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xyzvq

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It is not that I am necessarily having traction issues during a rain events, but that I feel having the option to engage 4X4 increases my factor of safety will driving in slippery conditions. I don’t intend to drive the vehicle like it has unlimited traction once I convert; I have had it for going on 7 years and am pretty familiar with its limitations.

Due to the roadways and weather conditions in my geographic area, part time four wheel drive modes are not that useful. I usually go camping once a month with the Boy Scout group that I am part of, so I could use part time 4X4 on some of the trails. I also live close to a spillway where a lot of my friends take their 4X4 trucks and play in the mud. I can see myself going down there every once in a while to mess around once I do the conversion. But that is the extent of my 4X4 use.

I am not totally dead set on jumping all the way to the NV242. I just see the full time option as being the most useful mode for the intended use of my Jeep. I also have yet to see a valid reason as to why this combination is not possible other than some people claiming that the NV242 is “weak” or that Jeeps did not come from the factory like this so it’s not possible.

If I’m crazy just tell me, but explain why.
 

WheelNut

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I think I was mixing up the T-case model names in my previous post.

Interestingly, according to a quote on this site: https://jeep.fandom.com/wiki/List_of_Jeep_transfer_cases#NP231
The NV company's naming convention indicates the 242 TC as being stronger than the 231. The second digit indicates the load rating of the TC.

If you don't have to have all kinds of custom parts made and the NV242 (full time 4x4) will drop in then why not just go for it? If it really is "weak" and you blow it up you can always change it out to an NV231 (part time 4x4). Sounds like you're not out there drag racing and rock crawling at full throttle, so it seems likely to me that the NV242 would hold up fine.

Anyhow, best of luck with the conversion to 4x4. I don't have any experience with swaps, so I can't offer any specific advice in regards to the rest of your queries. I would guess though that you will want to budget some time into your project to go back and forth between front prop shafts just in case you get the wrong length the first time.

I'm assuming you already have the factory service manual as well as the parts fiche documents for your model year? Those will certainly get you quite a ways along. I found that driveshaftparts.com had a fair bit of product info on their website that made ordering a front prop shaft for my KJ fairly easy.
 

tommudd

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It is not that I am necessarily having traction issues during a rain events, but that I feel having the option to engage 4X4 increases my factor of safety will driving in slippery conditions. I don’t intend to drive the vehicle like it has unlimited traction once I convert; I have had it for going on 7 years and am pretty familiar with its limitations.

Due to the roadways and weather conditions in my geographic area, part time four wheel drive modes are not that useful. I usually go camping once a month with the Boy Scout group that I am part of, so I could use part time 4X4 on some of the trails. I also live close to a spillway where a lot of my friends take their 4X4 trucks and play in the mud. I can see myself going down there every once in a while to mess around once I do the conversion. But that is the extent of my 4X4 use.

I am not totally dead set on jumping all the way to the NV242. I just see the full time option as being the most useful mode for the intended use of my Jeep. I also have yet to see a valid reason as to why this combination is not possible other than some people claiming that the NV242 is “weak” or that Jeeps did not come from the factory like this so it’s not possible.

If I’m crazy just tell me, but explain why.
Claiming LOL
OK , amazes me that people do not believe when told what has been said many times even by engineers
Go for your " city " transfer case
I hate them, no need for them
 

xyzvq

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Project Update: 05/22/2021

Parts Jeep came in on 5/20 and was in great shape with plenty of parts that I can salvage and move over to my Jeep. The driveline appears to be in great shape except for the front driveshaft. I will need a new one of those most likely. It has a lift kit on it that appears to be in good shape. I am still researching to see what system it is, so that I can upgrade to full height springs in the rear. The lift kit that the parts Jeep currently has uses spacers in the rear.

I have abandoned the idea of going for the NP242 due to reasons... Instead, I have decided to go with an actual capability upgrade in 4.10 gears and LSDs for front and rear. The parts jeep came with 31s, so I am told by my research that I will definitely want to go with 4.10 gears to regain power loss and improve mileage. Finding 4.10s for the rear is easy; however, finding them for the 30a is turning out to be a nightmare! Any suggestions on who makes 4.10s for the 30a? Part numbers/links would be helpful. I am leaning toward G2 gear, primarily because I bought G2 diff covers for my front and rear diff.

As far as LSDs, everyone seems to say that the Detriot TrueTrac is the way to go. I believe I have found the correct parts for the front (912A585) and rear (912A553). Any suggestion on where I can get a deal on these parts? I am seeing the front for ~$700 and the rear for ~450. I also got an estimate from a local shop to install front and rear for ~$1,800 o_O I am considering doing the installation myself. While I have never done ring & pinon installs before, I am fairly mechanically inclined. Youtube has also been a great resource. Would I be in good shape following the FSM, Eaton's instructions (if there are any), and watching a bunch of YouTube videos? I will also reach out to some of my mechanic friends to see if they can help me with this.

As far as actual progress, I have the transmission, driveshaft, and rear diff cover off of my Jeep. I also did the oil pan gasket and motor mounts since I noticed they needed to be replaced, while dropping the trans. I also have disassembled the front suspension on the parts jeep; removed the axle shafts; drained the transfer case, transmission, and front axle fluid; and dropped the exhaust. I just picked up a transmission jack from Harbor Freight this evening, so I'll be ready to keep disassembling the parts Jeep tomorrow.
 

JeepJeepster

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YG D30HD-410L is the front diff gears. Maybe call yukon and see if they plan on getting anymore in stock? I bought a set from them around a year ago and it was just dana gears re-boxed in a yukon box.

https://www.yukongear.com/shop/yg-d30hd-410l

As far as installing them yourself, its a chore, thats for sure. If you really study the FSM and follow it exactly, you should be ok. It would be nice to have someone that has knowledge of gear installs to check your pattern though.

This place may have some in stock. I dont recommend their 8.25 gears though.

https://www.justdifferentials.com/D...-Ring-Pinion-4-10-Ratio-p/d30kj-410lib-oe.htm
 
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