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level4designs 04-24-2009 07:45 PM

Jeep TH400/quadratrac to TH400/dana20
I know this has been answered probably somewhere, but I have a 76 jeep with an amc360/th400/quadratrac and my local junkyard has a 74 wagoneer with a th400/dana20 in it.

can I bolt up that dana 20 if it has the adapterplate good on it? or are they different?

I think I heard the adapter plate is weak, novak makes just a plate strengthener? I know if it doesn't bolt up, they make a kit to do it, but htey are so damn expensive...

I was thinking these might be similar or rare enough that since it's off a wagoneer...

WILL 04-25-2009 10:40 AM

Yes, you can just pull the 400/QT and bolt in the 400/20. You should have enough rear driveshaft length to not worry about swapping the rear axle either. As for the stock adapter, my brother has been using that drivetrain behind a buick 350 in his wagoneer for almost 10 years. I'd say just check it to make sure there are no cracks when you put it in and use it till or if you ever have a problem with it.

Also, if you are asking about using your same 400 and just changing the transfer case, that won't work. You have to change the transmission output shaft which has to come out the front of the transmission and requires it to be completely disassembled. Just plan on getting the 400 with the dana 20 rebuilt.

level4designs 04-25-2009 11:04 AM

Thanks for the info.....

but my real question is can I just use the dana 20 on my TH400? or are they different TH400's? even though from jeep?

I was reading that they were different somewhere?

WILL 04-25-2009 11:24 AM

Reread my second paragraph. Yes you can use the dana 20 on your TH400 but you have to swap out the output shaft. You can either take both transmissions apart to swap the output shaft or just get the one with the dana 20 rebuilt and only take one apart.

level4designs 04-25-2009 11:43 AM

sorry about that, didn't see that paragraph... perfect, I appreciate the response, that is exactly what I needed to know.

Caver Dave 04-25-2009 02:08 PM


Originally Posted by level4designs (Post 1544284)
I think I heard the adapter plate is weak, novak makes just a plate strengthener? I know if it doesn't bolt up, they make a kit to do it, but htey are so damn expensive...

No sure which "adapter" you're referring to, but...

The *REQUIRED* bellhousing (BOC pattern case)-to-(AMC) block adapter is cast iron... never seen one broken or cracked. You'll also need to grab the flexplate for this setup, as the QT flexplate offsets the wrong direction. *IF* the '74 has a 360, you should be good to use it without re-balancing. If not, haul it to a shop with your QT flexplate and have it balanced to match.

However I'm guessing you're asking about the "pot metal" (actually [poorly] cast AL) TH-400-to-D20 adapter is a POS. Since it acts as the aft mounting point for the TH-400/D20, most of them suffer from the mounting feet/ears being broken off or worn funky. My next project is to devise a "slip-on/bolt-on girdle" for the adapters mounting section... to either rehab a broken mount or reinforce a non-broken mount. That being said, I've heard of the adapters cracking thru the body, etc., but believe this was likely an issue caused by the mount breaking/sloppy connection allowing it to bind. The feet on mine were completely gone, so a chunk of heavy angle was notched and bolted directly to the D20 for mounting. Has held up the past 7+ years of abuse. However, if money *wasn't* an object, it'd definitely be sporting one of the aftermarket (AA, Novak, BullTear) billet adapters...

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