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Old August 15th, 2015, 13:32
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PhotoJared PhotoJared is offline
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Join Date: Aug 2012
Location: Las Vegas, NV
Posts: 691
Re: Projext "V8 XJ" Build

Originally Posted by blistovmhz View Post
I just finished my swap a few months ago. Check out my thread here:

I did the entire swap in 3 weeks, start to finish, from the time I started ordering parts to the time I was back on the road. The entire conversion cost me about $3500. Much cheaper than most guys do it, and I think I could've done it cheaper.
I used an 05 LM7 5.3 from an S1500, and the matching 4l65e transmission.

I read probably every thread on the subject and a few things about most threads bother me.
1. The wiring is NOT difficult unless you have no idea how electricity works. There is one BIG caveat to the wiring that no one mentions. If you're wiring up the OBD port, it MUST get it's power from the same wire that powers the ECU. No, just because it all comes from the same battery, does not mean you can just splice in anywhere. Splice it in within a foot or two of the ECU power. If you don't, your OBD will be wonky as all hell and you'll want to kill yourself and your whole family. Ask me how I know.
Otherwise, the wiring is very easy. The Chevy harness side is insanely simple. I'd suggest, now that I've done it, just use the stock chevy harness with the bare minimum modifications required to get it into the Jeep to start. Worry about re-working the harness once the motor and everything else have been proven. Trust me on this. It'll make your life much easier.
The Jeep firewall side of the wiring is the hardest part, only because most of your wires will be stuck together and the colors faded. Find an FSM, have it in hand. Honestly, the hardest part of this swap was dealing with Jeep wiring, and even then, it wasn't hard. I'm ****ing terrible at wiring compared to my roomies because I'm too lazy and impatient, and this still wasn't a big deal for me. Don't let everyone else scare you here. You don't need a painless harness, especially because the bulk of the wiring job is on the Jeep side.

2. Novak motor mounts suck. You already have them, and they work fine, but just FYI, they're a bitch. They mount the motor unnecessarily high for most lifts, and it is zero fun whatsoever, trying to drop the motor into those mounts because the main bolts won't line up while the engine and trans are tipped back, but they have to be tipped back because the back of the intake hits the firewall and you break off the main vacuum port (if it's not tipped). Dropping the driveline into the Novak mounts is an absolute whore and I wish I hadn't wasted my money on them. It would have been easier to build my own, and I'd have my motor sitting 2" lower.

3. Lots of guys say the stock A/C compressor won't fit between the motor and frame rail. I had no problem. It has to be installed after the motor goes in, but there's 2" clearance easily. I held off on my OBA because I listened to everyone else :p. Finally looked at it and it was cake to get it in. ALso, the chevy A/C pumps are WAY higher volume and CFM than the XJ pump. Double bonus.

4. Don't bother with the 4.8. The 5.3 will net you between 17 and 26mpg depending on your aerodynamic profile. My heep is the poster child for all that can go wrong with aerodynamics, and I get 17-18mpg on the highway. That's pushing 35x12.5 shoes, 6.5" lift, full size roof basket with 52" light bar. On a more stockish XJ, I'd expect at least 22-23mpg from the 5.3, and my god is it fast. I drag race EVERYONE now, and I no longer do it just for the sake of being ironic. I win often.
The 6.0L I feel is overboard, but I've heard that it'll give very respectable fuel economy as well, in which case I feel like it's one of those "if it's a toss up between the 5.3 and 6.0L fo the same price, go with the 6.0L" things.

5. Drive shaft lengths will need to be adjusted. Front needs to be shortened an inch and rear lengthened. Maybe you have a good driveline shop that can do it for cheap. If not, TW will build you a DS with long splines (XC = 4.5" travel vs the stock 2") for $300 delivered. Well worth it.

6. The AA t-case>trans adapter sucks at sealing. The trans side might seal, the middle section with the o-ring will not, nor will the t-case side with their paper gasket. Make liberal use of RTV everywhere including the o-ring. For the t-case side, you should probably just make a new gasket and RTV the hell out of it. The stock t-case studs are barely long enough to grab the nuts with a paper gasket, assuming you're using the AA mount as well. The whole thing sucks but it's doable. You may have to pull the case several times to re-seal until you get it right.

7. I'd go with a 241/241 hybrid. You can find the long input, wide bearing 241 input gear and planetary assembly from most chevy 241's. It'll drop right into your 231 case. Don't forget to swap in the WIDE BEARING on the input side if you have a wide input gear. VERY different clearances and the narrow bearing with the wide/long input gear, will have the planetaries eating the front of your case off. Also remember that the 231/241 planetaries and ring gear have two different cuts. Something like pre and post 96. The earlier were a courser cut while the later were finer. They will intermix but they will be very whiney. I used an np241c input, np231 main with sye, np241 chain and chain drive.

8. T-case shift linkage. Really helpful to just grab a t-case shift lever from an np231c or np241c as they point up instead of down. This way you just rip out the stock linkages entirely and bolt in a pair of 3/8 rod ends and call it a day.

9. Trans linkage. Use an XJ auto shifter. I just removed my center console because I don't give a shit, and cut out some new detents in the xj shifter. Used the XJ shifter cable as well. I have no idea how to fit this in while retaining the final gear (1) location, with the shifter bezel attached, so I gave up and went mad max on my junk. I'm probably the wrong person to ask about this unless you and your wife REALLY like mad max, or enjoy looking poor.

10. Radiator. The 3 row CSF scares me a bit as the tubes are very small and easy to clog. You mileage may vary. I went with a Griffin 22x19" and made it fit by cutting out the lower rad support. Keeps me VERY cold with a taurus fan behind it. Again, I'm not the right guy for this either as lots of guys have stock size xj rads doing just fine. My way worked though as well.

11. Throttle pedal (assuming throttle by wire) is easy. Just make sure you have the TAC module somewhere. The pedal will need to be chopped and shortened to fit, but can bolt up to the stock XJ pedal mount (upper) and drill a new hole for the lower.

12. I kept the truck intake and built a big silly scoop. It looked horrible for a while during testing. I think it looks pretty decent now if you're into the zombie apocalypse.

Feel free to toss any questions my way as well. I feel like I could do this swap the second time in a solid weekend. It's really not that bad if you aren't a tard, and/or not wildly drunk :p.
Thanks for the encouragement! I'm just waiting on some commission from work to order everything then it should be game on! I have your thread bookmarked.

1. I started tearing apart the Jeep's engine harness yesterday. I found the 1999 ECU pin-outs so I'm just going to remove everything I don't need. It looks confusing, but its actually pretty easy. I also just ordered a FULL set of the 99 Jeep Cherokee FSM ($135!) Super glad I found this.

2. Thanks for the advise with the mounts

3. I have to have AC. If I cant get it in when swapping, I'll do it after.

4. I now plan on using the 5.3 or 6.0.

5. Adams Driveshaft is local to me. I'll just take it down there and have them do some driveshafts.

6. Thanks for the tip

7. I have a buddy whos doing this hybrid TC right now. Depending on how it goes I may just end up doing the same. I still might just run a stock 231 with the AA input adapter.

8. I already have the boostwerks shift linkage so I'm all set there.

9. This actually looks pretty easy to do (At least I hope)

10. I'm using the same radiator. Living in Las Vegas I can use as much cooling as possible. I have a Saab two speed fan sitting in my garage.
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