TH400 to Atlas II Transfer Case

[arhame]

Good Morning,

I've made the decision to pull out my drivetrain and do some revamping (sad part is this thing hasn't even hit the road yet).

I've ordered some Currie Ford 9inch front and rear diffs for this 77 CJ for a bit more strength in the bottom end.

Well, I also am replacing the Quadratrac Transfer case with an Atlas II 3.8:1 unit and am mating it to the TH400 that the jeep came with from the factory.

Has anyone installed one of these Atlas Transfer cases into a CJ that came from the factory with the TH400 Transmission? I'm curious as to what I should expect to run into during the swap, i.e. am I going to need to clock it a certain way, modify my transmission/transfer case crossmember/pan, etc., etc.....

Any info or suggestions on what to expect, or hints on how to make this as smooth a transition as possible would be greatly appreciated.

Thanks

[arhame]

Ok, some information I just found out.

I was thinking that I was going to either have to make a major modification to the crossmember or completely design a new one for the changeover to this transfer case.

As for the transmission - I just rebuilt this thing before installing it into the jeep (i.e. it hasn't moved since the rebuild). Am I going to need to completely disassemble the entire transmission again in order to install the new output shaft into the transmission?

I'm beginning to question this whole idea. Would I be looking at an easier swap in converting to a Dana 300 using one of the Novak Adapters instead of using an Atlas case?

This jeep currently has the TH400-Quadratrac setup. I've already ordered new front and rear diffs (rear diff being a center pumpkin vs the offset required by the quadratrac.

If I went with the 300 instead of the Atlas, I would still have to have this transmission opened again, but wouldn't necessarily have to spend the money on an Atlas (I believe I could get a Jeep Dana 300 at a fairly decent price, and go through and rebuild the thing fairly easily. Plus, hopefully, I wouldn't have any issues with my existing cross-member.

Just some ideas. Please correct me if I'm wrong.

[dan58]

Go for the Dana 300. You'll save a ton of money on it, and the D300 is a mighty fine case. You can upgrade to 4:1 gears and HD outputs if you want. D300s can be had easily for under $200. The other glitch is that the lead time for an Atlas is typically several weeks.

[arhame]

Thanks for the reply Dan.

Would you happen to know on what type of modifications I would need to my to my existing crossmember?

[arhame]

Well,

First off I enjoy talking to myself sometimes I guess. I think the more I post, the more I talk my stuff through, into, or out of things.

Second, I called the great people at Novak Adapters, and went through the entire setup I have and my possibilities. I ended up purchasing one of their own Dana 300's that they've rebuild themselves, with the appropriate adapters and just about everything. I should be able to reuse both driveshafts that I had tom woods just make for me a few months back. I will have to go through the transmission to replace the output shaft (which they provide) and drill two wholes in my existing cross member. I'll also need to cut a hole in my floor pan for the shifter (unless someone knows of another way that I could setup some type of cable shifting?).

I opted not to go with the 4:1 gears at this time. With my current axle ratio, transmission and tires, plus engine, I think I should be ok. If I decide later on, that I need to go lower, it's not that difficult to change.

Whew, what a freaking change. I don't think I'm ever going to get this thing finished. It seems like everytime I see the finish line, it gets moved another mile down the road.

Well, hopefully I should have everthing (diffs, tcase, and heater cables) in within the next three weeks or so, and begin working on getting it all setup properly.

I'll keep everyone updated.

Thanks again for letting me vent.

[Blown7]

Well,

First off I enjoy talking to myself sometimes I guess. I think the more I post, the more I talk my stuff through, into, or out of things.

Second, I called the great people at Novak Adapters, and went through the entire setup I have and my possibilities. I ended up purchasing one of their own Dana 300's that they've rebuild themselves, with the appropriate adapters and just about everything. I should be able to reuse both driveshafts that I had tom woods just make for me a few months back. I will have to go through the transmission to replace the output shaft (which they provide) and drill two wholes in my existing cross member. I'll also need to cut a hole in my floor pan for the shifter (unless someone knows of another way that I could setup some type of cable shifting?).

I opted not to go with the 4:1 gears at this time. With my current axle ratio, transmission and tires, plus engine, I think I should be ok. If I decide later on, that I need to go lower, it's not that difficult to change.

Whew, what a freaking change. I don't think I'm ever going to get this thing finished. It seems like everytime I see the finish line, it gets moved another mile down the road.

Well, hopefully I should have everthing (diffs, tcase, and heater cables) in within the next three weeks or so, and begin working on getting it all setup properly.

I'll keep everyone updated.

Thanks again for letting me vent.


Venting OK.

My questions is why can the QT?


Jeff

[arhame]

I was replacing the QT for a couple of reasons.

1. I had read a couple of articles that stated that the QT wasn't really designed to handle over 250 HP.

2. Was going with a different differential (ford 9) with a centered pumpkin vs the passenger side offset.

I guess this has all started due to the fact that I'm afraid that I'm going to destroy this AMC 20 once I get this thing running.

I had the mosier one piece axles installed with Yukon 4.56 gears and a powertrax unit when I had this rear-end setup. All the reading that I've done has been leading me to believe that the AMC 20 housing is inherently weak, and, although it could probably handle light-moderate use as it is, if I ever decide to really hammer on this thing, it wouldn't be too difficult for me to destroy. Am I mistaken on this?

[Blown7]

You know years ago maybe I would have agreed on the QT but not anymore, I have the new NV 146 which is about the design of the QT and we run well over 700 AWHP thru them with narrower width chains no less with no distress.


J

[arhame]

How drastic of a design change is it between the NV146 and the BW1339?

[striker]

well if you really don't want that junked amc 20 with all those bad aftermarket parts installed, I'll take it off your hands. :-| I had a friend that owned a 4wd shop for over thirty years. I've seen him run a 20 behind a big block chevy. the axle did give out, but it was after two years of serious abuse..that amc 20 is not as bad as you think. but if you are gonna throw it out??... :-|

[Blown7]

How drastic of a design change is it between the NV146 and the BW1339?

Internals are electric motor operated clutches, and even a narrow width chain. It won't bolt up to a TH400 however...


Jeff

[donwag]

My CJ7 has the 401, TH400, and Dana 300.

Had to move the crossmember back a few inches, used an AA adapter for the TH400 to D300. I have a Lokar shifter now, but did have a B&M ratchet style shifter. Both work good without any cutting in the tranny cover. The D300 shifter is a different matter. Had to cut into the tub about two inches. I have a Currie twin stick. I believe it could be fabbed to reach a little farther forward. Currie would not do it for me.

[dawgates]

In my opinion, I would go with the Altas case. For the money of rebuilding, upgrading (4 to 1 kit), clocking ring, adapter to t400, it would be close to the same cost to install an Atlas case. You'll still have to modify the crossmember, driveshafts, linkage either way you go.
Before you make your final decision, call Advance Adapter and see what they have to offer and get a price.
This way you'll have a new TC instead or a rebuild.

FYI, most newer adapter are made to clock your transfer case in several different degrees, so an extra clocking ring shouldn't be necessary.
If you go with a D300, don't use the 1980 version, it has less options then the 81 - 86 D300 (different rear tail housing).

[krcilek]

Also look at www . stak4x4. com they have a wide selection of T cases and dont use syncros like Atlas does. Just my 2 cents.