th400 transfer case options

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Zorm
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th400 transfer case options

Postby Zorm » Wed Jan 09, 2019 7:49 am

Picked up a 78 Cherokee Chief with the th400 and quadratrac, would there be a Chevy transfer case that would mate to the jeep th400?

thanks
83 Cherokee 4dr WT(axles)
4" lift, 351w in the works
78 Cherokee Chief 304
2007 SeaRay 205
71 F-250 Camper Special 390

HE guides my path, forgives me when I stray and lights my life.

rocklaurence
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Re: th400 transfer case options

Postby rocklaurence » Wed Jan 09, 2019 8:51 am

Youll need the Chevy tail shaft and tail housing from the trans and have it installed in the Jeep TH400. Being that its a TH400, you should be able to get a shop to do it fairly cheaply.

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derf
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Re: th400 transfer case options

Postby derf » Wed Jan 09, 2019 8:53 am

If you find a GM truck with a TH400 and a matching transfer case like an NP 203, 205, or 208, you can swap things over. You need the tail shaft from the donor TH400 that goes with the transfer case. You also need the adapter that sits between the transmission and transfer case from the donor Chevy.

The bellhousing is different between the AMC transmission and the Chevy so you can't just grab a Chevy transmission and bolt it in. But all of the guts are the same. The tail shaft that comes out of the back of the transmission is different between the Quadratrac and the Chevy transfer cases so that's really the part that you need to swap. Of course, this basically means you have to completely disassemble the transmissions (or have a shop do it) and you may as well do a full rebuild as long as you're in there.

From what I understand, the rear bolt pattern on the two transmissions has the same layout but the AMC is rotated slightly compared to the Chevy. So the transfer case will either be rotated up or down a few degrees from where it is on the Chevy. But it shouldn't be too hard to make it work.

You may need to modify driveshafts a little since the Chevy is a center rear output and the length of the transfer case may be different between the two. Also, some of the donor transfer cases have a slip-yoke (that you can convert to a fixed yoke with aftermarket parts). But you can use the offset rear axle with a center rear transfer case without too much trouble. If you get driveshaft vibrations you can always do a double ended CV shaft from some place like Tom Woods.

Zorm
Posts: 234
Joined: Thu Mar 28, 2013 8:48 am
Location: Pensacola, Fl.

Re: th400 transfer case options

Postby Zorm » Fri Jan 11, 2019 6:47 am

Got it, also, any way to tell if it has a part time kit from just looking at it? and does anyone know how much vac there needs to be. It seams to be stuck in emergency mode. Unless this 78 is supposed to have a hard time making tight circles
83 Cherokee 4dr WT(axles)
4" lift, 351w in the works
78 Cherokee Chief 304
2007 SeaRay 205
71 F-250 Camper Special 390

HE guides my path, forgives me when I stray and lights my life.

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derf
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Re: th400 transfer case options

Postby derf » Fri Jan 11, 2019 8:56 am

You can't tell by just looking at it.

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MadMax78
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Re: th400 transfer case options

Postby MadMax78 » Sat Jan 12, 2019 9:28 am

You will have to open the case to see if it has a part time kit installed. I forget what to check for. I believe it’s the chain. It’s either shorter or longer. Someone will chime in with the correct info. Check out the link below for tons of info on the quadratracs. Good luck with your build. Post up some pics. We love pics. LOL

http://jubileejeeps.org/quadratrac/
MadMax78

78 Cherokee S, Wide Track, 360, TH400, Quadra Trac, TAD's SOA, 35" BFG KM2, Edelbrock Carb & Intake, MSD Coil & Ignition

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tgreese
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Re: th400 transfer case options

Postby tgreese » Sat Jan 12, 2019 12:20 pm

You mean an overdrive part time kit? You can test for a part time kit by manipulating the e-drive to see if the front axle free-wheels when unlocked. An unlocked full-time QT requires a significant torque between the front and rear driveshafts to rotate them separately. This torque breakaway test is given in the TSM (and in the TSM chapter shown on the Jubilee Jeeps pages).

There is a 1:1 and an overdrive part time kit. You will need to open the case to distinguish between them. The overdrive kit replaces the same-sized chain sprockets in the original case with two different-sized sprockets (and a different length chain). Once you've determined that you have a part-time kit, you can guess at whether it's overdriven by comparing your speedometer speed with speed from a GPS. If you're going say 20% or 25% faster than your speedo reports, it's likely an overdriven kit. Remember to account for big tires, if present.

The Jubille Jeeps page - http://jubileejeeps.org/quadratrac/ - I suggest you read and study everything there. It will help you a lot with the Quadratrac.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
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