Jeep J20 6.5 swap tranny/TC question

[jteckmann]

Hi all -

First, wanted to say this is a great forum, and I plan to be a long time lurker while I'm in the planning stages of my swap!

I have a '78 Jeep J20, TH400 Tranny (AMC bellhousing), and the full-time Quadra-Trac (BW 1339)

I'm preparing for a 6.5 swap and am still searching for the elusive "perfect donor"

My question is more Jeep specific, but hopefully someone can point me in the right direction:
Will a 4L80 work with my Qudra-Trac? I've been searching on AA and Novak, but looks like I'm outta luck.

I'd like to have an OD tranny when I finish this project. My understanding is that I can get the Qudra-Trac to work with a 700R4. But I want this truck to be a capable tow rig when I'm done .... will a well-built 700R4 hold up behind a 6.5 that's regularly towing up to 8,000lbs?

Or do I just have to choose between the keeping the Quadra-Trac or gaining Overdrive? (i.e. look for a NP 241/4L80 combo donor?)

[More Power]

If it comes down to it, I'd opt for the 4L80-E/NP241. To my way of thinking, a durable OD auto would be more important than maintaining the QT.

I swapped out the TH400 in a 1989 GMC 2500 a few years ago for a 4L80-E. Aside from needing a new trans/transfer case adapter, it was a bolt in. Input/output splines and bolt patterns all matched. Unless you discover differently, I'd not assume a 4L80-E won't also bolt together with the QT.

Jim

[JeepSJ]

MP - One reason for wanting to keep the QT tcase is that it has an offset output for the rear, and the rear diff is offset to compensate. Changing to a 241 would require a new rear end with a centered diff. 241 also has the wrong side output for the front.

jteckmann - A good reason to scrap the QT is that everything is driven through the chain all the time, which makes it not the best choice for towing. Chain stretch is a problem. Converting to a 4l80e/241 would add some definite strength, and GM 14-bolt housings are fairly inexpensive.

My advice - go sell the QT over on ifsja.org and find a 4l80e with a transfer case that has the correct front output (like a 208) and swap in a centered D60 or 14bolt rear.

[jteckmann]

Thanks or the info guys!

That's sorta what I figured - that OD trumps the QT, and keeping the QT/offset diff would cause some headaches.

So I'll be keeping my eye's peeled for a 4x4 4L80 donor that I can get the whole rear end off of as well.

[HH]

If you are set on using the offset rear, you could also use an older Jeep Dana 18 TC with the offset rear output. Adapters are available at Novak and Advanced. But IMHO you would be better off with the 241 & GM 14 bolt or Dana 60

[uglyjeep]

I know this is an older thread, but...

Another option if you want to keep the rear offset diff is a dana 20. Yes, yes, I know that they normally have a centered rear output, but the parts off of a dana 18 will bolt on. I know this because one of the POs installed one under my 75 Cherokee. But you still would need the adapter to bolt it to the trans I guess.