1999 MJ Build / LWB

[1999 MJ]

I just bought a 1988 Comanche, 2wd, 4 speed manual transmission, long bed.

 

I plan to find a 1999 Donor XJ, to “update / modernize” the exterior & the interior to what perhaps a 1999 MJ could have / would have looked like.

 

My intent.

Exterior:

• 1999 XJ front end with factory fog lights.
• Front doors switched out to ‘99-‘01 specifications, with power door locks & windows.  I’ll be grafting ‘97-‘01 interior 2 door cards onto front door, 4 door cards to make it look factory.  2 door power window switches.
• I’m thinking a 1999 4.0 engine, with a NSG370 transmission.  I’m starting to lean towards the AX-15 / NV3550….
• I’m thinking a Ford 8.8 rear axle, with Yukon Axles.  Obviously, I’ll have the shock mounts relocated and what not.
• Factory HP Dana 30 for the front axle.

 

Interior:

• ‘99-‘01 Interior with Classic or Limited front seats.  I haven’t decided if I want leather or cloth front seats….  I’m thinking manual seat bases, with the option to hinge them forward, so I can get stuff behind the seats.  I’m even wondering about the “ Renix rocker” seat bases, as found on some older XJ’s.
• I’m wondering on how to cut down the overhead console to make it work inside the MJ.
• Key Parts floor pans.

 

Questions:

• Now that you know my intent / visions.

1).  What gear ratios / transmission & axles?  I don’t plan to wheel this MJ.  It will be a pavement princess / mall crawler / sleep in the back camping trips.  I’d like something with 30 or 31 inch tires on 16 inch rims.  I’d like to have a final drive of 6th (5th gear?) gear at around 2,000 RPMs at 80mph.  Is that too low of an RPM for the 4.0 at 80mph?

2).  What can / should I fill the other 2 console slot buttons with?  I’ll be losing rear window defrost, so I’d like to fill that spot.  Maybe I need a 4 slot center console bezel, so I’d need a 4th switch…..

3).  Overhead console, maybe I’ll remove the “sunglass holder” and install 3 switches up there.  Give me some ideas.

4).  I’m thinking a 3 inch lift kit with the Ford 8.8 rear axle.  Educate me about setting this up.  I read stuff about “Over The Axle” versus “Under The Axle”.   I’m not understanding why one is better than the other.

5).  Best / preferred way of obtaining a 3 inch lift?

6).  Rear overhead XJ speakers mounted above the driver / passenger?

 

Dreams / Ponders / Wondering:

• I’m wondering about putting a hidden winch behind the bumper.  I’m wondering who makes the “extended” top bumper cover to fill the gap, between the grill & the front bumper, since it will sit a little bit forward.
• Custom graphics?
• Custom badges?
• Other modernization ideas?  I’m not looking to do a Pi dash or anything like that.

 

Tips?

 

WTB:

• Guidon Renegade 2 topper for the 7 foot long bed.  

[FXWorks]

Re: Gearing, start here and play:

 

http://www.grimmjeeper.com/gears.html

 

I think you can make the 4.0 happy at any rev range with correct setup. I forget what factory RPM is at ~60mi/h for a late model XJ. Something like 2300 RPM?  I'd be inclined to shoot around there or a little lower. Who cruises at 60 mi/h any more? Could set the factory cruise at 70 mi/h with factory rpms instead. Perhaps the factory PCM is optimized for cruise at 60 mi/h.

 

Also, if you are going to be towing, don't go too deep with the gearing. When towing you will not be in overdrive so your RPMs will be quite high. My built XJ is on 265/75-16 (32") with 4.56 gears. I wish I did 4.10s just because of the towing at highway speeds really winds the engine out in third.

 

People say the 4.0 doesn't mind some RPMs but if you are towing a big, heavy camper 6-10 hours a day at times on the four lanes for that family road trip it gets tiresome IMO.

 

For a pavement princess I don't know that I'd bother with a Ford 8.8. Get a ChryCo 8.25 with LSD. You can upgrade the 9" drums to 10" if it bothers you. Did KJ 8.25s have disks? Having done a roll-yer-own rear disk brake conversion on the Scout 44 in the back of my XJ I wouldn't bother with it again. For me the bang for the buck was WJ front brakes (and steering ofc).

 

Spring over axle causes more axle wrap. If you will be towing a lot of heavy loads it may matter. That said, on a pavement rig I don't think it is that much of an issue, or just deal with it. Spring over will be very hard too keep low without being "non-optimal".

 

Lately for my "fleet" of classics I'm all about getting bluetooth working on the factory head units and upgrading the sound output part of the systems. I don't have a lot of cycles into it though. In the sports cars I've been thinking about bluetooth amps with just a volume knob that connects to my phone. Use the normal HU space for aux gauges (i.e. no AV display - keep the driving experience pure and distraction free). The other idea is a SBC with a 2DIN display running Linux that boots straight into Carplay but it's fiddling time I'd rather spend elsewhere these days.

 

Being of a certain age I find the audio side of car builds don't interest me much any more - would rather invest in good sounding exhaust. I don't know that having the overhead speakers wouldn't be annoying. I have headrest speakers in my MX-5 but in the seven years of owning the car I've never turned on the head unit so can't suggest whether it is a thing worth bothering with (pulled HU last summer for CAN/OBD telemetry gear install for autocross). Perhaps a better approach for the speakers in a Comanche would be a under/behind the seats sub, good quality door speakers, and A-pillar tweeters from a late XJ with upgraded speakers. Hmm, I think that'll be how I do mine.

 

HTH

[1999 MJ]

Awesome, thank you for the responses.

 

I had used the gear calculator.  I understand how to put numbers in & see what it calculates.  I just need to figure out if I’d be lugging the engine down in an overdrive gear at 80mph.  I THINK ideally, I could really use 2 Overdrive gears.  I just need to figure out how to get these “custom” gears, without breaking the bank.  Where I live now (Midwest), I really don’t see much elevation change.  If I did, I’d just down shift to stay in the power band as needed.

 

As for towing / hauling, it would be very very minimal.  If I was towing / hauling, I’d guess I’d be under 1500 lbs most of the time, and this would be less than 10 times a year.  Quick rough numbers tell me I usually have less than a 1000 lbs, to include someone else for hunting/fishing/camping.

 

Definitely considering the WJ front brakes.

 

I’m definitely going to need to read up on SOA versus SUA set ups, for a 3 inch lift.

 

In my XJ, I have a 3.5mm Aux input installed.  Maybe my next factory radio, I’ll add Bluetooth.  I was thinking if the rear mounted ceiling speakers were too much, I could always fade them through the radio controls.

 

This is definitely going to be a “yuppie” truck.  I plan on putting a lot of period correct upgraded factory options, from the XJ.

[FXWorks]

XJ/MJ tows a 1500 lb trailer like it's not there.

[pizzaman09]

You should fill the two extra console switch locations with heated seats switches.  That is my plan on my Truck once I finally manage to source some better seat upholstery.

[1999 MJ]

On 5/19/2024 at 12:55 AM, pizzaman09 said:

You should fill the two extra console switch locations with heated seats switches.  That is my plan on my Truck once I finally manage to source some better seat upholstery.

I don’t smoke, so I’ll be installing heated seats, into the factory (ash tray) location.

 

I’m trying to figure out what to put into 3rd slot or even a 4th slot.  ****  I need to look for a factory looking rocker switch, to fill the 3rd slot.  I’m thinking this rocker switch would be a “bed light” as found on the stock 1988 truck.

[pizzaman09]

2 hours ago, 1999 MJ said:

I don’t smoke, so I’ll be installing heated seats, into the factory (ash tray) location.

 

I’m trying to figure out what to put into 3rd slot or even a 4th slot.  ****  I need to look for a factory looking rocker switch, to fill the 3rd slot.  I’m thinking this rocker switch would be a “bed light” as found on the stock 1988 truck.

I did under bed rail lighting on mine, hooked to the factory fog light circuit that I wasn't using.  If you want more info I can point you towards my build thread.  Ended up mounting them with adhesive backed magnets, turned out super clean and works phenomenally.  

[1999 MJ]

57 minutes ago, pizzaman09 said:

I did under bed rail lighting on mine, hooked to the factory fog light circuit that I wasn't using.  If you want more info I can point you towards my build thread.  Ended up mounting them with adhesive backed magnets, turned out super clean and works phenomenally.  

Please point me towards the build.  Also, the rocker switch used.

[pizzaman09]

12 hours ago, 1999 MJ said:

Please point me towards the build.  Also, the rocker switch used.

Build is linked below.

 

I used the factory fog light circuit and switch that was already there.  Someday I might connect it to the correct circuit such that it can be turned on at any time instead of just when the low beams are turned on. 

 

You might find someone on this forum selling new old stock switches or find used ones on eBay.

 

 

[1999 MJ]

I reached out to an eBay seller that sells aftermarket factory looking switches, for the 1997-2001 XJs.  I asked if they made a switch with the icon / graphic that shows the Comanche truck bed light.  Apparently I’m the first to ask if such a switch exists, and no they currently don’t make one.  Maybe if enough interest is shown, they could make a limited run of switches, with the truck bed light icon / graphic.

 

The eBay seller I spoke with is “GoldCoastDistributing”

[jeff351]

On 5/16/2024 at 11:57 PM, 1999 MJ said:

 

• I’m wondering on how to cut down the overhead console to make it work inside the MJ.                                                                              See mine on page 5 here. It was a fun project to do. I still need to come up with a better way of securing it up against the headliner, currently its not as tight a fit as I'd like. ....https://comancheclub.com/topic/62524-project-scuzzy/page/5/#comments

 

On 5/16/2024 at 11:57 PM, 1999 MJ said:

 

6).  Rear overhead XJ speakers mounted above the driver / passenger?

  I also considered this, but after a quick mock-up, it would place the speaker like 3" from your head.