v8 swap into 4 cylinder YJ - JeepForum.com

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post #1 of 8 Old 07-30-2001, 03:31 AM Thread Starter
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v8 swap into 4 cylinder YJ

a friend was about to pick up a 4 cylinder 5 speed with a blowm motor for real cheep ..he wants to know if the 4banger trans is the same as the 6 cylinder trans? ..also we wanted to drop in a chevy smallblock ..will the 4 cylinder trans hold up ?

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post #2 of 8 Old 08-24-2001, 12:11 PM
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They 6 cyl has the AX-15 tranny. It will work with most applicatoins unless you plan on using 38" + tires. The 4 bangers came with a AX-5 tranny (they are complete junk, replaced with a AX-15 and adaptor from AA).

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post #3 of 8 Old 07-27-2009, 01:39 PM
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yes i believe the 4cyl will have the AX-5 transmission which is not strong enough for a v8....get a better one.
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post #4 of 8 Old 07-27-2009, 04:44 PM
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I'm gonna say this because it hasn't been said......

But if your gonna put a 350 into a YJ.....it's not just the tranny you have to worry about.

Gonna need front springs since the 350 is a couple hundred pounds heavier than the 4banger.

Gonna need to take a look at axles. I never recommend that kind of torque put on the stock jeep axles. My 350....a plain jane TBI setup taken out of a blazer would "chirp" my 42" tires.....locked. You don't want that kind of torque on a stock jeep axle for anything more than driving it down the driveway.

Take a look at novakadapt.com . They have lots of good info on 350 swaps.
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post #5 of 8 Old 07-27-2009, 06:00 PM
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Novak is a really good resource for information, but I'll throw in some additional info since I did a swap with them that is just about done. Put a 2005 5.3L into my 87.

Transmission will need to be upgraded. Novak has a good comparison between the options. I was planning on a good number of highway miles on mine so I stuck with the AX15 for the OD and interchangeability. No way an AX5 will hold up and Novak won't even make an adapter for it because of that.

Transfer case will be fine.

Rear axle will be a time bomb, I went with an 8.8 with 4.10's and swapped in a front D30 to match the gear ratio (the 4cyl should already have 4.10's so that's your easiest option.

As for front springs, I did have the 4.2 and the 5.3 I swapped in is lighter than the 4.2. That being said, I ended needing (maybe being more comfortable) a suspension lift to have adequate room for the front d/s and routing the exhaust so I would've needed to replace the springs anyways.

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post #6 of 8 Old 07-27-2009, 08:54 PM
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a sm465 can be bought for around 100-200 bucks... rebuilt i think is around 400 but i cant really remember, and wife is pissed im not in bed.

700r4 are all over the place, and vary in price. best bet is finding a parts chevy truck for a few hundred bucks, take out the motor and trans, and sell it to the junkyard to get a little money back

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post #7 of 8 Old 04-01-2010, 08:32 PM
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what about cooling, fuel, and other stuff? do you have too change that as well or can you run a 350 with stock parts from a yj?
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post #8 of 8 Old 04-01-2010, 08:43 PM
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Originally Posted by speepdaedeesi View Post
700r4 are all over the place, and vary in price. best bet is finding a parts chevy truck for a few hundred bucks, take out the motor and trans, and sell it to the junkyard to get a little money back
X2 on the advice to find a complete donor vehicle - much easier to swap the engine, tranny, harness, and all related components. I would also look at a S-10 Blazer or Pickup with 4WD. You can transplant the the 4.3L Vortec, a 700R4 or 4L60E and NP231C using just the rear half of your tcase and it's output shaft and you will need no adapters - just engine and tranny mounts. I transplanted the evap system, fuel system, and guages out of my donor vehicle and it made life much easier during the swap. Also, a good shop manual with wiring diagrams for both vehicles is a must. If you must have the V8, then look for an older S10 with the 700R4/231C combo and put that behind your SB and you still get by without the adapters. I will say that I am very happy with the 4.3 in mine though.

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