I want to buy an MJ, Need Advice

Hi all. I've been a jeep guy for the last ten years. I've had a really nice YJ and XJ in that time. My needs have changed and I need a pickup and thought a Comanche would be a good option. I'd like to have a High Output 4.0, so 91' or 92'. I know the 91' has a renix ECU and lacks a check engine light, does the 92' have a check engine light? I definatley want a 4x4. Does the MJ have a NP231 or does it have a fulltime tcase? I'm on the fence as to whether or not to get a long bed or short bed. Could I fit a dirtbike in the shortbed with the tailgate down? I'm a welder/fabricator and I will eventually build it up, but I plan on keeping it stock for a while. Thanks for any advice

I like not having a check engine light.

My MJ has a 231, I like the short bed. I think a bike would fit in a short bed with the gate up. I carry a quad in my 6' camping trailer, tight but it fits.

I've spent a year just getting my MJ running and back to stock, it's good now but it'll be great when I swap trannys. After running an XJ for 5-6 yrs. I really like the MJ.

I have not named it Suzy and I don't call it him/her...but it is my favorite Jeep.

Actually.. 90 is last year for renix, so 91 is first HO..
And the short bed is standard 6-6.5' IIrC so should fit.
5-spd = 231 for sure. Auto could go either way. Not 100% if MJ's had 242 option.

You could probably get one of those "bed extender" racks and drill some holes and bolt it in.
an old co-worker of mine did it on his 92 ranger with one of the newer racks.

ParadiseXJ said:

I've spent a year just getting my MJ running and back to stock, it's good now but it'll be great when I swap trannys.

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You sig says an 88, so I'm guessing you have the Peugot turd of a 5-speed. If you're looking for a 5-speed, you want the AX-15 which started mid-year 89.

check out the comanche club forum....

Renix ended 1990

BA10 ended mid 89.

All 5spds got 231's, some autos got 242s, it was an option.

5spd gearing is 3.07 for the 4.0, 3.55 for the auto

Things to check that are different than the XJ:

Rear load sensing valve, usually rusted or disconnected by now.
Brake lines that run above the fuel tank are ALWAYS rusted. Tank has to come out to repair. J-bolts and straps for the tank are no longer out there, so you've got to come up with replacements if yours are all rusty.

The top of the fuel tank rusts for the same reason as the line, tanks are terribly expensive, make sure it's good before you buy or plan on a few hundred dollars (A fuel cell was cheaper than a LWB tank)

Longbed is 7Ft, shortbed is 6, that's from the front of the box to the tailgate, measure your bike.

Shortbeds got 18 gallon tanks, some longbeds got 18 gallon tanks, there was an option for a 23 gallon tank with the longbed, usually on the upper models (Mine was a pioneer)

Column shift was an option for the autos, also haven't seen too many of those.

5spd w/No AC doesn't come with an electric fan, at least for the Renix years.

ground for the fuel pump is drivers side tail light harness. Check and clean it.

Other than that the normal buying a 20 year old vehicle stuff.

Edit: If you plan on wheeling it get a shortbed, the LWB brings the suck off road, especially the extra rear overhang.

lawsoncl said:

You sig says an 88, so I'm guessing you have the Peugot turd of a 5-speed. If you're looking for a 5-speed, you want the AX-15 which started mid-year 89.

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Yes, I have a BA/10-5. I have an AW4 waiting in the wings, and I'm looking for a 23 gear/spline 231 or 242. So far the Peugot is doing OK just driving around town and a lil bit of hiway.

Great! Exactly the advice I was looking for. Thank you all for your thoughtful responses.
So far I think I'm going to go for either a 91' or 92' , HO 4.0, manual (ax-15), 4x4(np231), shortbed. Blue Book on this is ridiculously cheap, something like $1500. I think I can talk a private party seller down to around $2k. We have a few really good jeep pick a parts in San Diego, so I should be able to get it ship shape for cheap.

87manche said:

Rear load sensing valve, usually rusted or disconnected by now.
Brake lines that run above the fuel tank are ALWAYS rusted. Tank has to come out to repair. J-bolts and straps for the tank are no longer out there, so you've got to come up with replacements if yours are all rusty.

The top of the fuel tank rusts for the same reason as the line, tanks are terribly expensive, make sure it's good before you buy or plan on a few hundred dollars (A fuel cell was cheaper than a LWB tank)

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Everything else you said was 100% correct. J-bolts are no longer available but tank straps are, for a fairly reasonable price. Tanks aren't expensive, 120-150 apiece for a Spectra one on rockauto, I got lucky and a friend was selling one brand new in box for 75. The fuel level sender assembly that the pump straps into is pure unobtainium though, so be VERY nice to it while removing it! The retainer lockring and gasket for it are the same as the XJ ones though and run like 6 bucks.

XJdePlato said:

Great! Exactly the advice I was looking for. Thank you all for your thoughtful responses.
So far I think I'm going to go for either a 91' or 92' , HO 4.0, manual (ax-15), 4x4(np231), shortbed. Blue Book on this is ridiculously cheap, something like $1500. I think I can talk a private party seller down to around $2k. We have a few really good jeep pick a parts in San Diego, so I should be able to get it ship shape for cheap.

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I got my total rotbox piece of crap auto 2wd MJ for $800. Previous owner, a friend of mine, got it for $600 and dumped 2-300 bucks in parts before selling it to me (I know, because I installed said parts.)

MJs are fairly rare in the pull a parts around here, when you see one, pillage it. Anything MJ specific should be removed and stored or sold to other MJ owners... before the thing gets crushed and turned into a chinese washing machine.

kastein said:

Everything else you said was 100% correct. J-bolts are no longer available but tank straps are, for a fairly reasonable price. Tanks aren't expensive, 120-150 apiece for a Spectra one on rockauto, I got lucky and a friend was selling one brand new in box for 75. The fuel level sender assembly that the pump straps into is pure unobtainium though, so be VERY nice to it while removing it! The retainer lockring and gasket for it are the same as the XJ ones though and run like 6 bucks.

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Well I'll be damned, I couldn't find anything other than the Dorman one that was $260 + shipping when I was looking. Spectra wasn't making the 23 gallon jobby then I guess.


Not like it mattered, my tank needed to get moved out from under the bed anyway.

If you wheel a longbed, with the 23.5 gallon tank, make sure you protect the tank, it's very vulnerable and the front hangs down below the framerail. Factory skids are stupid rare, so plan on fabbing your own.

Agreed.

I got my factory SWB fuel tank skid from a friend after installing his replacement fuel tank for free :thumbup:

By the time I am done with it, this MJ is going to have all factory skids on it.