International Full Size Jeep Association

International Full Size Jeep Association (
-   Drivetrain (
-   -   Dana 20...TH400 adapter or not? (

Hump 07-25-2002 02:20 AM

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 07-25-2002 02:55 AM

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 :confused: . Does that help you at all?

porkchop 07-25-2002 02:57 AM

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 07-25-2002 02:59 AM

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 07-25-2002 03:53 AM

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!!!! :mad: :mad:

Crazy_Jeepman 07-25-2002 04:04 AM

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 :rolleyes:

River Beast 07-25-2002 04:18 AM

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's not that bad... honestly. Then when you have the tailshaft out, just swap it out and reassemble.

Crazy_Jeepman 07-25-2002 04:22 AM

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

Hump 07-25-2002 04:40 AM

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 07-25-2002 06:00 AM

I also have the correct tail shaft :D . 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 07-25-2002 06:43 AM

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 07-25-2002 07:03 AM

Thanks for the humor Matt. :D 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 07-25-2002 07:23 AM

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 :D :D :D !

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

Hump 07-25-2002 08:14 AM

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 07-25-2002 10:05 AM

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.

Bigums 07-25-2002 11:50 AM

I'm pretty sure the deal on the TH400/D20 behind the AMC 360 was that it was the 'nailhead' Buick-patterned TH400 and that an adapter ring was used for the AMC engines. I know that was the case for mating them to the Buick 350.

More intelligent people will reply and correct or support my claim as necessary, I'm sure. :D

J20 project 07-25-2002 03:44 PM

Ok, Here's how it went.
65-68: 327 rambler/2in adapter/nailhead Buick th400/2nd adapter/D20
69-71: 350 Buick/2in adapter/nailhead Buick th400/2nd adapter/D20
72-731/2: 360 AMC/2in adapter/nailhead Buick th400/2nd adapter/D20
73 1/2-79: 360 & 401 AMC: AMC specific th400/QT adapter/QT trans case.
80-91: 360 AMC/torqueflite 727/various new process tcases.
There was never a jeep application involving any chevy or BOP th400's.
Also, both the 327 and 360 apps w/ the nailhead case involved a 3/4in crank spacer. I just don't remember if the 350 Buick needed one or not.
Also, 65-73 1/2 used a (32?) fine splined output shaft on the th400 for the D20 set up.
73 1/2-79 Qt cased jeeps used a coarse spline tailshaft.
Chevy swaps are done easily if a chevy th400 case is used.
I'm running a 76 model th400 w/ the older tailshaft and D20 transfer case.
J20 project

porkchop 07-25-2002 05:31 PM

Hmmmmm... The 70 wag that is in front of my house has a Chevy TH400/D20 that is the original tranny. It had the buick 350 and a spacer. the tranny is a Chevy TH400. Where did you get that info from?

Bigums 07-26-2002 04:00 AM

Interesting PC. I'd be interested to get to the bottom of this.

Of course, the way AMC did things, everybody could be right... :D

Hump 07-26-2002 04:33 AM

Sounds like i've opened a whole can of worms. So I could use an older th400 that would have the correct output shaft, but I would have to use and adapter at the engine?

Ok, J20 mentioned something about a crank spacer for the 360's. I have a 401 would that need one too? Is it a slide on deal, or does that intail more major disassembly?

I'm kind of leaning towards changing the output shaft in the tranny I have so it doesn't mess up the location of the crossmember. I do have one I could practice on, but the big deal is that I don't have a large "clean" space to do it in. Just called and it looks like $400 to have it rebuilt, and they will just swap the shaft as part of the regular rebuild price.

Pete, how much do you want for that shaft?

All times are GMT -6. The time now is 03:29 PM.

Powered by vBulletin Version 3.5.4
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.