'88 xj

[sjlplat]

Started a new thread to cover the whole build. I figured it would be a mess to create a new one for each update, so I'll keep everything constrained to this thread as I move forward.

Over the years, I've owned, built, and wheeled a number of different Jeeps. I started off like a lot of others with a bone stock rig, and slowly migrated into the extreme. After moving from New Mexico to Texas and getting married, I sold my 1-ton YJ crawler and fell out of the Jeep life.

For Christmas of 2017, I purchased a 2001 XJ 2wd for my son to use as a daily driver. I had enough experience with the 4.0L that I could help him with most mechanical problems he might experience with an older vehicle. Once I got to wrenching on it, I knew I had to get myself another Jeep; but I didn't want to dive back into something so heavily modified that I needed a fabricator -- something I'd taken for granted in New Mexico -- to maintain it.

I started off with a bone stock '88 XJ Base 4-door with 91,390 miles. It was clean, straight, and unmolested. This would be a perfect platform to build something a little more moderate to accommodate my family and my mechanical aptitude!

[sjlplat]

Gauge Cluster Swap

It quickly became apparent that the base gauge cluster wasn't going to suffice for my needs. I want to know exactly how everything is running, and dummy lights just don't cut it.

I found a complete gauge cluster with all the gauges on eBay for $70, pulled from another '88 XJ. While the cluster was out, I figured it would be a perfect time to replace the incandescent bulbs with LEDs.

The odometer in the new cluster was matched to the original. The oil pressure and temperature sensors had to be replaced, as gauges require different sending units than lights.

[Gotcha-Again-LOL]

Love it!!!!

[sjlplat]

60mm Throttle Body

As I slowly work my way through all the mechanicals, I discovered that one of the bolts that attach the air intake hose to the throttle body had been stripped. After some searching, I came across Leigh Performance Machine. Jeff is a machinist by trade, and has built a pretty crazy stroked Frankenstein of a 4.0L for his '90 YJ. Over the years, he has learned a lot, and developed some techniques to help other Jeepers mod their engines. He offers custom machined Throttle bodies for both Renix-era engines and newer HO engines.

Since I was looking to replace my throttle body, this seemed like a perfect opportunity to gain a little more airflow while I was at it.

[Knighttime85]

More airflow is never a bad thing just ask my Duramax...

[sjlplat]

These Renix engines really suffer from airflow. The factory throttle body only has a 52mm bore, which makes no sense at all considering the plenum is 60mm! It won't be noticeable on it's own, but I'm hoping all the small things add up to a small, noticeable gain.

[Knighttime85]

That XJ looks clean for an 88! I'm looking forward to see what you do with it.

[sjlplat]

I overpaid for it, but the mileage and condition was really appealing to me. I'm no mechanic, so I'm paranoid about making sure everything is in perfect running order before I even consider wheeling it. Most of the early work probably won't be very flashy, but it's absolutely necessary, IMO.

[ZacT]

Very nice attention to detail.

[sjlplat]

That means a lot to hear! When it comes to engine and drivetrain I'm pretty green, so I like to know I'm headed in the right direction.

[ZacT]

sjlplat I a firm believer detail is everything. Sometimes I research the littlest things but you gain the knowledge every time. Looking forward to see what you do next.
I have been trying to find the Bhp per litre for our 4.0 engines and seem to be keep getting the wrong awnsers. I have formulas from college to find brake horsepower per hour for our industrial engines but I am missing something. With that number I am using it to find volumetric efficiency of the 4.0 to redesign a air intake/filter system.
I know it sound silly but engines and detail are my thing.

Let me how that 60mm throttle body works out. I run the 62mm on mine a saw a significant gain.

[sjlplat]

LoL, that's beyond my comprehension. I'm a software developer / data analyst by trade, but I'm accustomed to plugging numbers into pre-existing formulas provided by someone much smarter than I! Give me a boatload of data and I can identify trends and patterns, but geometry and physics are over my head.

I'd love to see some noticeable improvements, but from what I understand, any power change below 10% is generally not "felt". I think injectors and exhaust might get me there, but time will tell!

[denverd1]

nice clean XJ!! What are your plans for it?? I bet it breathes a lot better with an bigger TB

[sjlplat]

I really like the "overland" style. I'm still undecided what I want to do with suspension and axles, but it's a toss-up between a Rubicon Express 5.5" short-arm lift with HP30 and D44 axles or swapping in a set of Volvo C303 portals and keeping the factory-height suspension. Both approaches should provide enough clearance for 35" tires with trimming, and each has it's own pros and cons.

The easy option is a lift and TJ/XJ axles, of course, but finding a rear D44 is pretty tough. The portal option is a little more complex, a lot stronger, offers more diff clearance, better off-camber stability, retains all the factory drivetrain geometry, and may not be any more expensive after you factor in gears, lockers, shafts, joints, and SYE with a traditional drivetrain upgrade.

I'm toying with the idea of a hybrid cage. I don't really want a full exo-cage, but I also don't want to destroy the body if I roll it. I figure a hybrid cage can be built inside the body lines and through the roof, doubling as a roof rack.

As far as the rest is concerned, I'll do the typical heavy bumpers, tire carrier, sliders, rear armor, winch, on-board air, auxiliary lighting, etc.

[ZacT]

sjlplat I like the idea of the portal axles. TJ/XJ axles would be simple but the portals will give you clearance and stand out from all the others.

[sjlplat]

ZacT Yea, the more I think it through, the more sense it makes. Everything above the axles remains factory. No problem with driveline angles, no problem with steep control arm angles, and clearance is improved dramatically at the diff.

What I don't know is if it can pass inspection, or if it will still be streetable. The C303 axles have drums on all 4-corners, and a final gear ratio of almost 6-to-1 with the portal reduction. The gearing is great for the rocks (drums not so much), but the final ratio may be too low for 35's on the highway. I believe the stock tires are between 33" and 34" on the C303.

[Redbird]

That's a clean XJ for an 88

[sjlplat]

Installed the new throttle body and throttle position sensor today. No noticeable difference in power, but throttle response seems better. After adjusting the TPS, idle was perfect, but driving on the highway revealed that I haven't solved some of the gremlins I was hoping to fix with this upgrade.

Here you can see the difference in bore, and the step between the old throttle body and the plenum.

[sjlplat]

Today I picked up a Chrysler 8.25 rear axle and driveshaft out of a '96 XJ for $100 bucks. I'm still holding out hope that the Dana 44 will pop up, but I don't want it to delay my build. This should be an adequate upgrade from the Dana 35, and a disc brake conversion will eliminate the concern with losing a wheel if the axle breaks.

[WJ_Guy]

Great axle. Also carrier adjustments are done without shims. So nice to work with.

[sjlplat]

I'm not an axle guy at all, so this will be a learning experience for sure. Good opportunity to work with it out of the rig, so we'll see if I can do some of this myself. Worst case, I blow it up, right?

[Knighttime85]

Man I was hoping to see some portals, but that 8.25 will definitely be tougher than the D35

[sjlplat]

That might still happen, but not right away. I took out a loan to buy the Jeep, so a portal upgrade will have to wait until the loan is repaid.

[ZacT]

So whats the plans for the 8.25? Gears and locker?

[sjlplat]

Yea, I'll match it up with an HP30 and drop in some gears and lunchbox lockers for now. I don't want to sit on this for years trying to build the perfect rig. In the meantime, I'll be on the lookout for some alternatives. It'll be a little costlier in the long term because I'm doing things twice, but at least I can wheel it.

[ZacT]

sjlplat i understand doing things twice. That is exactly what I do. I would prefer to do it once but I like to wheel. I definitely don’t like my rig to be down for weeks at a time.

[sjlplat]

My biggest fear is being 'that guy' on the trail. I hate holding up a group because my junk broke.

[CDE]

Question on the 8.25. If it's stronger than a D35, why aren't more people doing this swap on TJs? Maybe they are and I just haven't seen any. Seems like these things are everywhere and 8.8s are getting harder to find. I just want to be able to lock the rear end, and I've always heard that you should leave a D35 open.

[sjlplat]

Yea, the 8.8 is definitely a better option if you're willing to do a little minor fab work. Since I'm not a welder, I'd have to pay someone to weld up mounts for me. In my case, the 8.25 is a great alternative to a D44 for a direct swap, as I really don't want to put more into this axle than I have to -- especially given the fact that I got a driveshaft with it. My thought is to eventually drop in something much better - eg. portals, or built 44's/60's.

[CDE]

sjlplat that's how I am. I don't have the time or means to do the 8.8 right now (or an 8.25 for that matter since it wasn't offered in the TJ). Since this is my daily, I need something I can bolt in over a weekend. I'll find a 44 eventually...I'm just getting impatient lol

[sjlplat]

CDE I get that. I've been on the lookout for the rare XJ D44. I've seen a couple pop up, but they're either priced far higher than they're really worth, or I've gotta buy the whole rig to get the axle. For the right price, I'm good with buying a parts rig, but they don't pop up often with that axle, and when they do they're either outrageously priced or gone before I get to them.

On another note: I ran a Lincoln locked D35 with 32's on my first YJ and it never blew up. If you're OK with swapping shafts on the trail (or maybe on the street), just weld it up, carry a few spares, and you're golden.