modifying a 1978 J10

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Topic author
phatton
Posts: 11
Joined: Tue Dec 29, 2020 2:21 pm

modifying a 1978 J10

Post by phatton »

My, new to me, J10 has a tired engine (401) and a trashed 1399 transfer case. I'm torn between rebuilding the 401 and replacing the transfer case with a 1399 from a junked truck; or pursuing a ls1 engine, trans and transfer case swap. Leaving the truck stock is easier, but finding parts to keep it running is getting hard and the gas milage is not anything to write home about. A more modern drivetrain will give me adequate power, greater reliability, and better milage. My question is will a 80's j10 front axle bolt onto my 78 frame? It seems that the modern stuff has the front drive shaft on the drivers side. Thanks and I welcome your input.
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Stuka
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Re: modifying a 1978 J10

Post by Stuka »

Most engine parts for AMC 304-401 V8's are easily purchased. With the exception of crank shafts, which can require remanufacturing. Its all the non-engine AMC/Jeep specific parts that may be tougher to find. Most most parts availability is ok.

Your fuel economy may go up by 1-3mpg with an LS swap. If you go LS, it should be for reliability and EFI (as you also state), not fuel economy.

And you would have a BW 1339 QT.

As for the front axle, yes, the 80 axle will bolt in. You may have floor clearance issues with a driver drop t-case, depending on which you go with. In '80 the floor changed for the t-case change.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

Topic author
phatton
Posts: 11
Joined: Tue Dec 29, 2020 2:21 pm

Re: modifying a 1978 J10

Post by phatton »

Thanks for the info
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