Engine Swap Options

[splitz]

I want to build out the XJ to tow a travel trailer over mountains, and the I6 just won't cut it. I'm at the end of my skills, so I am going to look into hiring someone to swap the engine. I figure, why spend $10k on a used unknown truck that I have to in$ure (New Orleans insurance is stupid expensive), when I can drop that on an engine. Plus, I've already done:

Stinky Fab Off-road Steering
WJ knuckles
4.56 w/ARB Lockers
4.5" RE Coils & Leafs
35" tires on 17" aluminum
TNT Long Arm
SYE
Unibody stiffeners
Lots of non-essential upgrades

It has a D30 (yeah, I know) and 8.25. I plan to do a disk brake conversion to help while towing.

The goals are:

1. Towing 6,000 - 7,000 lbs.
2. Reliability
3. Fuel Economy (a.k.a wishful thinking)

I've started my research, but the Internet is full of disjointed information. I found a shop that specializes in Jeeps and 4BTs, which is intriguing. Of course, there's always the LS which seems popular. For anyone who has done a swap:

1. What did you put in?
2. How well does it tow?
3. What swap related problems have you had since the swap?
4. How's the fuel economy?
5. If you used a shop, then who did the swap?

 

[cal]

Thats too much to reliably tow with an XJ. It doesn't matter how much power you have, the XJ does not have the weight or stability for that much trailer.

The Xj was rated at up to 5,000 pounds, but at 5K its already sketchy as hell, and that's before you lift it.

You need an F150.

 

[splitz]

The Xj was rated at up to 5,000 pounds, but at 5K its already sketchy as hell, and that's before you lift it.

What makes 5k sketchy? Body roll?

The trailers I'm looking at are around the 5,500 dry. With stuff in it I figure it'd be around 6,000.

 

[SlowXj]

I've done loads of towing at 5k +/- with my old xj. It's not something I do now as I have vehicles designed for that task. The length and weight of the xj makes it acceptable to "walking". That's really the only issue, but that is the worst issue when towing... Trailer design, weight displacement, and driving conditions can all contribute to "walking", but why risk it?

Sent from my SM-G950U using Tapatalk

 

[Jim Malcolm]

I pull a ~3k pontoon on a regular basis through PA mountains. My 94 XJ sits @ ~3.5" on 31s with 4.10s, rear discs, hi-temp towing pads all around (hi-temp is key having overheated regular "towing" pads), 95-96 booster, Addco rear sway bar, biggest OEM front (1-1/4" I believe), front-to-rear frame stiffeners, front hitch (makes huge difference). I built this XJ due to a specific driveway that even regular cab trucks have a hard time making the switchback with the boat in tow; I have another XJ for fun. Not a chance in hell I'd sign up an XJ to pull 5k on a regular basis simply because a built XJ doesn't weight but 5k (3,400 curb stock). Given enough miles, the trailer will eventually "push through the rear" as you make too sharp of a turn and there's basically little hope of counter-steering out of it, assuming you even have enough time. Most of the time it just jackknifes and you're along for the ride at that point. I have enough brakes and just enough power/cooling to pull 3k through PA "mountains" (really just big hills), but not nearly enough weight and length to pull much more, nor to do it on anything but a sunny day. it gets real sketchy when it rains, and again, I know the route and every turn. I towed it a bit over 100 miles through PA "mountains" to get it up there and I wouldn't do it again. Believe me when I say, not a chance in hell would I build an XJ with the intent of towing 5k+ on twisty, downhill roads. Not a chance.

 

[Tim_MN]

That's too much to SAFELY tow with an XJ. It doesn't matter how much power you have, the XJ does not have the weight or stability for that much trailer.

The Xj was rated at up to 5,000 pounds, but at 5K its already sketchy as hell, and that's before you lift it.

An XJ towing 4-5000K is sketchy, and asking for disaster. Exceeding the rated towing capacity is foolish, illegal in many states, should there be a crash, could expose you to civil liability.

 

[jmg222]

1. What did you put in?

I did a zz6 350, 405 hp/ 405 pd-ft tq. I did it mostly for legacy reasons (I had dropped in a 350 back in the 90s, and dropping in an LS would have been more work than I felt like, the zz6 was a direct drop in). If I was starting from scratch, I'd do a ls.

2. How well does it tow?

I wouldn't even try it. it's not power, it's stopping ability and the short track of the truck. Unless you're just doing a light duty trailer...

3. What swap related problems have you had since the swap?

Normal stuff, biggest issue really was an overheating issue -- I think it was the block itself -- once I swapped out the original 350 for the zz6, I haven't had a single overheating issue.

4. How's the fuel economy?

With a 4spd gm auto, I'm getting around 17ish on the highway. I also don't drive it fast, it's just not set up for that.

5. If you used a shop, then who did the swap?

Local guy in long island, did an amazing job, if relevant pm me I'll send you info.

 

[Skruffy]

I put a supercharged LS3 in mine. It is a bit absurd, but fun fun fun! With a 6L80e transmission.

I used primary Novak swap components and did it myself. Really the only hard part was integrating the waiting harness so that all of my gauges work. Spent about half of my time with that portion of the swap.

For highway driving at 60 mph I get about 18mpg, but that number goes down pretty quick if I am getting on it at all or go much faster than 60mph. The same Jeep before the swap got 13mpgs under the same conditions so it is definitely better with the 6.2L.

And now for towing...
Just like everybody else has said towing much more than 3000lbs with an XJ is not the deal. I have a 3000lb travel trailer and it is really the limit of what I would tow for any significant distance. I only tried pulling that trailer once with my 4.0 and it was hopelessly underpowered. With the new engine of course it pulls it better but it doesn’t solve any of the weight/length problems.
Pulling the same trailer with my 2018 wk2 trailhawk diesel (which has less than half the horsepower and weighs 1000lbs more than the XJ) is significantly more manageable. That vehicle has a 6500lb towing capacity.
XJs are rated to 5000lbs but that is kind of a fantasy in my opinion. Having a trailer brake controller is a must for a heavy trailer and I also have rear disc brakes and VANCO brakes on the front. With all those upgrades it is acceptable but still not as good as the wk2.

Best of luck with your endeavor! You really can’t go wrong with an LS. Tons of people have done it so you don’t need to invent much and GM made millions and millions of those engines.
You will get at least double the horsepower and at least 50% more torque and better gas mileage.

 

[splitz]

It turns out Tim Allen lied to me and it's not just about "More Power!" I thought the disks all around and "frame" stiffeners would have made a difference, but it sounds like it really is not enough. Thanks for all the advice. Back to the drawing board!

front hitch (makes huge difference).

While my pipe dream has burst, you piqued my interest. How does a front hitch make a huge difference?

I did a zz6 350, 405 hp/ 405 pd-ft tq.

I just searched on that engine. Wow.

I put a supercharged LS3 in mine. It is a bit absurd, but fun fun fun! With a 6L80e transmission.

Best of luck with your endeavor! You really can’t go wrong with an LS. Tons of people have done it so you don’t need to invent much and GM made millions and millions of those engines.
You will get at least double the horsepower and at least 50% more torque and better gas mileage.

Supercharged LS3 is a bit more than I was thinking! The popularity of the LS is why I was leaning that way.

 

[Jim Malcolm]

Sorry splitz, been busy either enjoying it or prepping to enjoy it... Home for a day and then back out for another week

In one word, "stability". At 3.5"-4", who knows anymore, and no attempt to fix the steering other than to center the axle with an adjustable track bar, it drives like a Jeep... Right turns pull you in, left turn push you out. Now add almost another XJ, in my case, back there pushing your around, "Trailer Steer". "Trailer Steer" + "Bump Steer" is a whole lot of hold on and keep 'er straight... This XJ still has a stock bumper on it, so adding the tow hitch really stiffened up the front end. Never really realized how stiff my front end is w/ unknown springs (came on my other XJ), 5100s and the big sway bar until I put the front hitch on and made the suspension do it's job. Took almost all of the dash creaks away, big difference. They recently installed speed bumps, I mean fixed, the road to the boat launch and it's quite the ride with the peddle floored along the level, straight stretch from where I turn onto the road to the base of the big hill. I get 'er up to about 55 before the hill eventually pulls 'er down to 20mph in 1st gear for 100 yds or so before the grade lessens a bit and on we go... With the front hitch installed, it's much, much stable now. The chassis stays much more stable and the suspension does it's job. My XJ is well bump stopped front and rear; I'm sure that helps as well...

At the end of the day, part of it comes down to the size of your brass balls. My buddy has 20 yrs on me, most of it driving professionally, and he'll push the line a whole lot further than I will. I followed him once taking the "easy way" and going down another PA "mountain", the rear of his ZJ was swaying back and forth like a flag in the breeze. Got there and I told him he was "Nucking Futs" and he just kind of smiled and shrugged...