1991 YJ 6.0 Conversion/build thread - Jeep Wrangler Forum
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Old 10-14-2018, 10:48 AM
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1991 YJ 6.0 Conversion/build thread

Hey all, so a brief history of this beast before I dive into the LQ4 conversion that's underway...

My mom back in 1991, purchased this YJ. It's been a part of my childhood, and I have a lot of memories with this. I used to joke around that someday I'd buy it from her, but she would always say that she'd never sell it. Heck, even when I turned 15 and got my license, she wouldn't even let me drive it.

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One day, while I was staying with my dad in Canada, he got a phone call that she had been T-boned while driving it by some guy who ran a red light, and was thrown out of the Jeep and broke her back (I know - she wasn't wearing her seat belt. Yikes, but I'm just glad she's okay.) She's fine now, but her relationship with the Jeep was never the same. The Jeep, short of a few dents in the side, was miraculously fine. She rarely drove it after that, and it sat for several years.

When I turned 18, I offered her $2000 to buy it - on the condition that I would restore the Jeep to his former glory and she accepted - her condition was that if I ever decided to sell it, she had first dibs. I was blown away - I didn't think she'd accept the offer.

I've had this Jeep for close to a decade now, and have done various improvements along the way. I replaced the radiator, rebuilt the ignition system, installed a Rough Country 4.5" lift, and put on 33" wheels and tires. Recently, I even sourced a hardtop and full doors that I'm in the process of restoring.

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None of these solved the biggest problem about this Jeep. Novak Conversions definitely hit the nail on the head. That 2.5l is under powered, and the ax5 is looking for any excuse to get out of doing it's job. It's a fun vehicle to drive, but it's struggling with the 33's to even merge onto the highway.

Enter LQ4. I purchased a 6.0l LQ4 out of a 2005 GMC Yukon with all the goodies. I sourced a TJ NV3550 transmission, and this week I'll be placing a purchase with Novak Adapters for all the miscellaneous bits to mate these together, along with the transfer case and get them secured into the chassis of the YJ. After that, I'll work on getting to this engine what it needs to run. I'm new to working on V8s. I've always been an import guy, specifically Miatas (who would have guessed?) but my dream has always been to put a SBC of any generation into a vehicle. I can't wait to be able to successfully merge onto the highway. Who knows, maybe I'll be able to use the left lane for once!

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Old 10-14-2018, 05:19 PM
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Old 10-14-2018, 06:25 PM
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Old 10-15-2018, 05:51 PM
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Today I ordered all the bracketry and driveline parts necessary to rebuild the transfer case with a SYE and mate the NV3550 and LQ4 together as well as install it into the YJ from Novak Conversions. Craig was extremely helpful in getting this order together. Parts should be in by the end of the week.

We got the LQ4 torn down to bare block. I won't be touching the rotating assembly, as the engine looked fairly healthy, but we will be redoing all the gaskets (Head Gasket Set and Oil Pan.)

I'm still figuring out how to post pictures reliably, so apologies for that. Hopefully I'll get that ironed out here soon. It seems hit or miss using Facebook as the host.
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Old 10-15-2018, 06:03 PM
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A quick search of the forum allowed me to figure out how to upload photos from the computer directly...

So plans for this conversion are ultimately of course the 6.0l Chevy LQ4 to NV3550, using Novak's clutch, flywheel, bellhousing, and adapter pieces. The 6.0l is pretty much going to remain stock - I think it'll be more than fun just with the stock output in the Jeep, coming from the 2.5l.

The transfer case is getting a rebuild, with a SYE kit, but I'm keeping the NP231. Since my Jeep is a 4 cylinder native, I believe my TC has the 21 spline input gear, so I've already purchased a 23 spline to allow it to mate to the NV3550.

I know the D35 is a weak point in the drivetrain. I'd like to keep it for now, and replace with a Ford 8.8 locker when the time comes to replace it. However, we'll find out later in the conversion which route I'll take. If I can reuse the driveshaft, I'll probably leave it for now. If keeping the D35 means I'll have to purchase another driveshaft down the road later, I'll likely go ahead and swap in favor of the 8.8.

I'm not sure which route I want to take with wiring yet. It's tempting to spend the money with someone who has experience with LS harnesses that I can simply mail my harness to and they'll modify it, but also from what I read, the YJ is a simple Jeep when compared to the TJ especially, and I can probably save a bit of money by doing the wiring myself. Any thoughts or input would be appreciated.
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Old 10-16-2018, 11:21 AM   #6
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There is so much information out there on wiring that you should be ok doing it yourself as long as you have some patience and a few brain cells. I have never been a wiring guy and have managed a MPFI 5.2 swap and an even easier TBI 5.7 swap. The LS swaps are pretty simple like my TBI one from what I understand.

I would really look into that 8.8 swap as soon as you can. I would have zero confidence in that D35 with 33's and all that torque.
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Old 10-16-2018, 12:25 PM
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I appreciate it! Yeah I am leaning heavily towards swapping it as a part of this build vs swapping it later. Seems almost silly to do all of this work just to skimp on a fairly easy axle swap for reliability and performance.
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Old 10-16-2018, 12:33 PM   #8
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I added the pics to the original thread.

Looks like you got the hang of it now, but here's a thread that explains how to post pictures

https://www.wranglerforum.com/f2/how...e-1939746.html
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Old 10-16-2018, 06:19 PM   #9
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I did my own wiring but it really depends on how much information you have available for both the Jeep and the engine. In my case I was installing a carburetor SBC so all I needed was voltage to the distributor, and a tach signal converter. I under the oil pressure sender and coolant temperature sender from the Jeep installed into the correct locations on the V8 so the Jeep didn't know the difference.
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Old 10-16-2018, 06:45 PM
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Thanks for the help getting those pictures in! As far as the wiring goes, I'm still not 100% sure on the direction I'd like to go in yet, but I'm confident enough to know that it's something I could tackle, and that would free up a couple hundred bucks in this build, which is quickly adding up. I'm also working on a spreadsheet to document as part of this build, so I can post that up afterwards for those interested in performing this swap in the future.

Got an email from Novak and Advance Auto Parts today telling me that both orders shipped. Novak of course for the various adapter pieces, and Advance for the gasket set for the engine. I think I mentioned earlier that I wasn't going to tear into the rotating assembly if it looked decent inside the engine, which it does. However, it did have some oil leaks, so I'll be addressing those.

We got the engine torn down to the block, and I even put in this nifty parts shelf to keep things a little less crazy. Novak's order will be here Friday, I am still waiting to hear when my NV3550 will be shipped out (I was told by Monday this week, but the seller on ebay keeps on pushing back the ship out date, blaming and overwhelmed shipping dept among various other things) and the Advance Auto Parts tracking number doesn't show up yet with UPS.

I work Wednesday-Saturday, as a Field Technician for Spectrum. If you guys have any cable questions, shoot them my way! Hopefully starting this Sunday I can make real progress. Thanks everyone for checking out my thread!
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Old 10-28-2018, 11:28 AM
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Alright, so making slow progress so far as I wait for parts to come in. My NV3550 transmission came in from Rhode Island, I rebuilt the LQ4, started teardown of the Jeep to gain unobstructed access to the engine, and bought a new welder!

The Novak order came in, and I realized I had bought everything except the Kit 3504, to adapt the NV3550 to the GM bellhousing. Bummer, as I was really hoping to have the Engine/trans/transfer case mounted in the jeep this week. I'll just use this time to rebuild the Transfer Case and install the SYE kit instead. Progress is progress, right?

So we went out and bought a welder. I already had a Hobart Handler 190, but it's 220v, and we're renting the place we're in right now. Rather than paying an electrician an ungodly amount of money to upgrade the electrical service and install a new 220v outlet, we opted to purchase a Klutch 120v welder. It's pretty solid. Supposedly it'll weld up to 3/16" steel with a single pass. We'll see how it works, I dialed it in on some scrap steel and it made some nice looking beads, so I have a pretty positive outlook for it's future.

When we picked up the engine, the junkyard that pulled it broke off 2 exhaust manifold bolts subflush in the head. I used the welder to build up a bead, and reversed them out with vicegrips. I found that trick on youtube - really helpful! Managed to get both bolts out without damaging the cylinder head (no drilling required either, so, win!) I heard the GM factory exhaust bolts are pretty prone to this, so I'll likely end up buying some JEGS bolts if anybody has input. They're a good bit cheaper than ARP.

More progress to come this week! Thanks guys and gals!
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Old 10-29-2018, 08:20 PM   #12
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I used the Novak adapter between my SBC bell housing and a NV3550 transmission. I also found I needed the Novak adjustable throw out bearing to allow me to address the stack-up in the clutch parts. I put the engine as far back as I could relative to the firewall and was able to use the original drive shaft with the D35 and then when I upgraded to the 8.8 rear axle I also installed 2.5" lift springs and that (with a transfer case drop) allowed me to keep that same original drive shaft.
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Old 11-20-2018, 07:38 PM
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Just a few updates since the last time...

We took a trip to Canada for about 2 weeks, so that was a lot of the hold up. This is the first weekend I've had to work on it since. Progress has been slow, but steady. Yesterday, we fought mating the Chevy Bellhousing to the Novak adapter and NV3550. To be clear, there are 2 modifications that are needed for the chevy bellhousing and the NV3550. First, you have to drill out almost a 1 1/16" hole for the shift rail boss to pass through. Then, you have to drill out the threaded holes where the bellhousing would normally bolt from the back in. You are now bolting the bellhousing from the inside to the trans.

Once that was complete, I used a dial indicator to make sure the bellhousing was concentric with the crankshaft. Here's where I ran into a few issues. First, when I replaced the oil pan gasket, I didn't realign the oil pan correctly. Initially, my TIR was at .028", and by that number needed .014" correction. I figured this out by indicating the machined side of the bellhousing that faces the trans. runout was .010", which was corrected by the oil pan. That brought my TIR on the bellhousing bore to .012" which is only .006" off - within the .010" specs, so I left it as is.

Once I got that squared away, I replaced the rear main seal on the LQ4, installed the Novak Flywheel/ARP bolts, and their clutch combo. Ran into some more issues with the Novak adjustable throwout bearing. I opted to use their "option 1" method, which was to measure using a straight edge a couple of things and use that to determine proper TOB height. However, not all my clutch fingers were the same height. some were 1/8" difference. I ended up just eyeballing it after close measurements through the fork window. Hopefully it'll be fine - it looks like it's between 1/16" and 1/8" play before contacting the PP fingers.

So now the engine and trans are together for the final time, hopefully. Did a test fit today to see how it looked. Wicked cool to see. I'm very excited for this. I can't wait to finish getting this mounted in the Jeep.
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Old 11-21-2018, 12:07 PM   #14
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Nice! Great story and cool build. Will be keeping tabs on it for sure!
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Old 11-27-2018, 08:06 PM   #15
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We're practically neighbors. I'm fixing to resume my YJ LS swap and build. I think my favorite thing about your jeep is that it's stayed in the family from day 1.
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Old 11-28-2018, 09:30 PM   #16
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Getting the drive train installed, even if only for fit check is a great feeling.
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Old 12-04-2018, 11:17 PM   #17
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Looking great! I'm curious to see how that nv3550 holds up to 6.0l torque. My suggestion is to take it easy, especially while in overdrive (5th gear).
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Old 02-07-2019, 04:22 PM
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I neglected to post for a while, sorry about that. So the build is "done" in the sense that it's running and driving. And wicked fast. This is not the Jeep I used to know at all!

So far it's driving really well. I still haven't figured out what I'm going to do for gauges. So stock cluster is still in and not connected. To monitor engine data, I'm using a bluetooth dongle and checking it on my iphone.

I got everything in, and then realized I messed up sealing the transfer case, and the clutch pivot ball Novak sent me wasn't adjustable - there was too much play before the fork would actually contact the pivot ball. So everything got torn back out, and reworked so that it was right. I'll be back to post in a more chronological order soon
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Old 02-07-2019, 07:41 PM   #19
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Great, it is always nice to hear when things are "done" and the vehicle is on the road.

When you decide to upgrade to the Ford 8.8 find a 4.10 ratio out of an Explorer (sorry I don't recall the year range) and you should be set for the long haul.
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Old 02-07-2019, 07:43 PM   #20
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I forgot to mention I used my original gauges by just using the coolant and oil pressure sensors from my 2.5 screwed into the SBC. I installed a tach signal converter to get the engine speed signal.
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