Dana 20...TH400 adapter or not?

[Hump]

Ok guys, here's one for you. I hear all the time about this rare adapter (eight bolts) for the turbo 400's. I wanted a dana 20 transfer case to swap in where my exisiting q-trac sits. So I bought one with this adapter. Now here I am with the q-trac pulled (4 bolts) and i'm looking at the two transfer cases, and the dana 20 looks to have the same bolt pattern without the adapter (4-bolts). It appears that the q-trac used the same adapter...and that is still bolted to the back of the tranny. I'm confused.

The adapter will obviously not fit to the back of the tranny as it sits. Do I pull the adapter off the dana 20 and bolt it up, or do I pull the back off the th400 and bolt the dana 20 w/adapter to the back of the tranny? The shaft coming out the back of the tranny is held in by a large bearing, and appears to be part of the tranny. There is a piece of plywood bolted over the adapter on the dana 20, so I have not inspected what's in there...I just figured that it was a shell...kind of like a bellhousing. Can anyone give me some guidance please?

[porkchop]

OK Let me see if I can help. The D20 and the QT have very different bolt patterns. The D20 has the "texas" star pattern with 5 bolts and the QT has four bolts with the top being wider. If you take off either adapter from the tranny the other will bolt up with 6 bolts. But before you do that you must disassemble the tranny to switch the tail shaft. The QT shaft will only work with a QT. You need a TH400 short shaft for the D20 to work. I am not sure where you are getting the 8 bolts from . Does that help you at all?

[porkchop]

Oh yea on the inside of the D20 adapter there is a large bearing that goes through. Do you have any pics of the adapters?

[River Beast]

Yeah... what PC said.... You confused me with the 8 bolts as well.

Both PC and I have done the QT to D20 swap...others have to.

The adapter plates are very much different...

[Hump]

Sorry for the wrong number of bolts, I was basically glancing around and noticing that there was more than 4. I guess I need to inspect it a little more closely.

So now you're telling me that I need a different output shaft? CRAP!!! My truck is almost ready to hit the road. Where the heck am I going to find one of those? How do I get the shaft out? You said I have to disassemble the tranny? NOT COOL! Would have been so much nicer to just unbolt...bloop, of comes the q-trac...bloop on goes the dana 20, 4 bolts and i'm ready to go.

Oh yeah, did I mention that the front of my truck was elevated when I pulled the q-trac, and I ended up with a lap FULL of tranny fluid. Man did that suck. I couldn't even get out of the way because I had the t-case sitting in my lap.

Dang it, if it's not one thing it's another!!!!

[Crazy_Jeepman]

yes you will need to dissasemble the trany and swap out the tail shaft for the D20 version as well as have the adapter for the TH400 to D20. Sad but true

[River Beast]

You can use a TH400 2WD tailshaft (short shaft) to mate the D20 case... that's what I used. you nned to get an o-ring to slide on the shaft as there is no groove (at least on mine) for stopping the tranny fluid from running thru to the T-case... also use black RTV on the tailshaft splines when assembling.. this deters the fluid transfer as well.

When the tranny come apart... YES all the way down.. you can then change the tailshaft. No major components need to be broken down...it's not that bad... honestly. Then when you have the tailshaft out, just swap it out and reassemble.

[Crazy_Jeepman]

I have the correct tail shaft, grooved for O ring.

[Hump]

Hey Pete, I just might need that. I'm trying to get ahold of the guy who I got the t-case from, as he had the th400 that was in front of it. I would just as soon swap the whole transmission if I have to take it out anyways.

Is there any way to mechanically put a q-trac into e-drive? My front driveshaft is way to short, so I was just planning on running around in 2-hi until I got it lengthened. I'm kind of scared of the whole vacuum deal. If I could do that, then I guess I could at least get my truck on the road with the q-trac. Any suggestions?

[porkchop]

I also have the correct tail shaft . I made a mechanical shift for mine when I had it. It was quick and easy. If you look in the archives you should find it. Also you can do a search. It is under the title, "I fixed it! I fexed it!".

[mechanic58]

LOL, sorry Hump, but you tickled me with the "how do I get the shaft out?" I feel your pain. Murphy's law ALWAYS gets ya with these darn jeeps don't it? Pete's a good fella, I'm sure he'll hook you up with exactly what you need. Also, make sure you have yourself a good quality set of snap-ring pliers, some nice long screwdrivers and plenty of spare time when you get ready to change out that tailshaft. In the case you're not versed in automatic trannys, it might be a good idea to take the transmission to someone that IS and let them do it for you.

[Hump]

Thanks for the humor Matt. My day is going a little better now. I think I got the shaft without lubrication if you know what I mean. I'm not going to attempt the conversion myself. If that's what it comes to i'll have a shop do it. I might play around with one that I have laying around, but not for something I am going to use.

Porkchop, thanks for the advice. I don't really need a cable, as I will only use it in e-drive, so I am going to try and "lock" it somehow mechanically in e-drive and slap it back on until I can get something figured out. I really need to get this thing useable.

[porkchop]

No problem. One thing I noticed to is that you were thinking that it would just be easier to swap out the whole tranny. That is not going to be easy either. The tranny that the D20 came from most likely has a chevy bolt pattern and it won't bolt to a 360 0r 258 without an adapter. Just wanted to throw another wrench in the gears !

[ July 25, 2002, 01:25 PM: Message edited by: porkchop ]

[Hump]

You're kidding me!?!? So AMC never put a th400/d20 combo behind an amc block? I was planning on doing a auto to manual swap, but was going to use this as an "easy" filler to get the part-time function. Man you guys are full of bad news! I guess it follows the, "nothing is ever easy with a FSJ" motto.

[tuck]

Hump, AMC did. I own one. 360 v8, th400, d20. It's a '72. I'm not sure when they started or finished. But I believe that '73 started the quadratrac craze. I'm not sure when the AMC motors started to appear. An expert will have to answer that question. Bottom line is, you might have a tough time finding one of these setups. G'luck.