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This thread is terribly anticlimactic for the time being, but I thought I’d get it ready for the engine build & swap taking place over the next two or three weeks. I’m hoping to have it and the trans installed, broken in, and ready for the drive to Barber Vintage Festival in October. The early ‘80s marked a transition from full-sized, V8 SUVs to lighter-duty offerings based on smaller truck platforms. When Reagan took office, GM was developing the S10 Blazer and Ford the Bronco II, but American Motors lacked a truck smaller than the Eisenhower-era SJ. Only its Concord/Spirit/Gremlin-based Eagle, powered by the ‘60s-era straight six and featuring a legitimate transfer case, slotted in below the venerable CJ series; however, it lacked the capacity and capability of its larger stablemates. As such, the United States’ lit’lest automaker began work on a small SUV that retained off-road capabilities while using components common to its siblings and other manufacturers’ supply chains. This became the 1984 Jeep Cherokee (XJ), a distinctive design that mated a unibody with an integrated ladder structure - indicative of SUV design practices until the “crossover” trend neutered all the good things about everything in the early ‘00s. The XJ was perched atop a four-link “Quadralink” front and leaf-sprung rear solid axle, rounded out with driveline, steering, and control components pulled from existing Ford, GM, Peugeot, and then-parent Renault parts bins.  It's an obvious conclusion. Also, no pants. All this effort notwithstanding, AMC still lacked a compact pickup to compete with the Ranger, S10, and increasingly-competitive Japanese counterparts. The full-sized S/J-series (underpinning the Grand Wagoneer) was twenty years old and the long-wheelbase CJ-8 “Scrambler” had failed to find a market. The solution presented itself in a common platform to be built alongside the XJ in Toledo, Ohio. By developing a high-capacity ladder-frame rear section that slotted into the XJ unibody, AMC retained almost all four-door XJ components from the B-pillar forward aside from floorpan changes required to accommodate the unusual marriage of monocoque and ladder. This Comanche (MJ) was sold in parallel with the XJ for seven model years (’86-’92) and received updates accordingly, including an updated variant of AMC’s early-‘60s straight six after the first model year. Short-wheelbase, six-foot-bed models dominated, while a seven-foot bed offered a Metric Ton payload option for 1987.  Even ads neglected to mention the available GM V6 in '86 When a newly-revived Chrysler purchased AMC for its Jeep and Eagle divisions in 1987, a step-sibling rivalry emerged between the independently-developed MJ and Dodge Dakota. Notable was the fact that “Dakota” entries in Baja were re-paneled MJs, which themselves claimed manufacturer's championship titles under the controls of Tommy & Bobby Archer and Walker Evans for SCCA and SCORE, respectively:   While nearly three million XJs would roll off the Toledo, Ohio, production line by the time US production ended in 2001 (overseas until 2006), the MJ was discontinued after the 1992 model year with less than 200,000 produced. Less than 6,000 featured the '91+ updates. As Chrysler intended to replace the aging XJ Cherokee with the larger, unrelated 1992 ZJ Grand Cherokee, it originally made financial sense to focus on the Dodge Dakota rather than produce an orphaned XJ-based truck. Ballooning sales of the XJ Cherokee cancelled Chrysler’s 1992 euthanization of the platform to the extent that it received minor changes in ’96-’97 before all manufacturing capability was shipped overseas in 2001. I didn’t set out to find an MJ, as I’m already saturated with 4WD XJs. The plan was originally to find a ’94-’96 LT1 Roadmaster wagon, but after looking at flawless, one-owner 30k-mile examples, I couldn’t see myself actually using it for anything aside from long trips and autocross comedy. I wanted a project, not a time capsule, regardless of how smooth and suave the capsule may be. As such, the goal was simple: find a rust-free, manual ‘87+ MJ. The ’86, whether fuel-injected 2.5L AMC I4 or godawful carbureted 90-degree 2.8L GM V6, is undesirable due a firewall incompatible with the long AMC straight six (allegedly the work of an engineer who wanted to see the six phased out). ‘89.5+ examples were preferred since they saw the addition of an Aisin AX-15 in place of the troublesome Peugeot BA-10/5. ’91/’92 models received Chrysler’s open cooling system and a much-needed electrical update, replacing the maligned Bendix/Renault “Renix” ignition system and cable-operated gauges with something befitting the nineties. The rare Renault 2.1 TD was also a strong option, but two exist in pieces spread across three continents. Enter a rust-free 1990 2WD, short-wheelbase Comanche in Charleston, SC. With a build date a week too early to receive the Chrysler updates, it comes equipped with a knocking 4.0L and Aisin AX-15 that won’t shift when hot, but brake lines, calipers, drums, stater, alternator, exhaust, clutch, and other bits are all new - roughly $3500 of parts & labor since August 2011. The owner decided to pass it along when the engine developed a horrible top-end rattle, but remained steadfast in finding a good home dedicated to reviving the truck rather than parting it.   I promptly roped my patient girlfriend into driving my autist rear end many hours to retrieve this blue beast under the guise of fresh seafood and the beach. After picking up the truck, FSM, a thick stack receipts, and documentation from the friendliest, most helpful couple you could ever meet, I trekked off in a truck that wouldn’t shift and made single-digit oil pressures at 2500RPM. People turned and stared at the source of this racket when it passed. At best, a collapsed lifter was the sole problem; at worst, oil pump and bearing clearances had increased to the extent that the top end was starving. Solid bet on the latter.  '80s EFI can't be too bad... gently caress, vacuum lines  Radio promptly replaced with functioning OEM Though otherwise clean, those pop-out vent windows guaranteed a surly find:  Only a few through holes... leaking MC and forty pounds of wet carpet pad didn't help.  Patched and POR-15'd After driving the truck 2500 miles with negligible oil pressure, once adding five quarts of oil to top off the six-quart capacity (rest was in the airbox), the decision was made to pull a junkyard 1994 4.0L with an external-slave AX15 to rebuild while continuing to (ab)use the existing driveline. It made a suitable transport for the 396,000-mile donor:  Ground up the speedo cable with that weight in the bed...  Only looks to be a clean driveline Although a friend offered me an SLP LS1 and T56 pulled from a late WS6 for a pittance, I made the poor decision to stay the AMC course with my ’94 donor driveline.  (In retrospect, the LS swap would have cost roughly the same even after Novak adapters were bought.) This itself bore a surprise, likely explaining why an XJ equipped with a new clutch was sitting in Pull-A-Part: Not my pliers. I'm guessing they were left in there during a clutch job.  Not my carbon. The engine was torn down and dropped off at a good machinist with the intention of using a 258 crank for a stroker. More on that later. Around this point I gutted a junkyard XJ Limited of all its distinguishing interior & exterior bits to create a trim package that never existed. Also found a clean, matching MJ headliner.   "Chrome won't getcha home", etc. Wet spot is somehow not the rear main seal  And stripped & refurbished a nasty pair of XJ bucket seats and tilt column.   Thus far all work has been either cosmetic or only mildly mechanical, but when the year-old internal slave cylinder (the source of my shifting woes) shat itself in a USPS parking lot, the decision was made to use the external slave bellhousing and shift fork purchased previously. This is where the truck sits currently. The plan!: channeling the spirit of the Archer brothers’ SCCA arrangement above while keeping the truck true to its daily-driver, motorcycle-totin’ roots. Throw some lower-profile tires on the 15x7" steelies and autocross it on Wednesday nights. Keep total investment under $4.5-5k.
 So please forgive the Jeep thread  leak while I get my parts in line! It's certainly not as impressive or involved as the majority of folks' projects, but I think it's a unique approach to take with an uncommon truck.
OneOverZero fucked around with this message at 03:53 on Sep 6, 2012 |
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Sep 6, 2012 03:50
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This owns. I'll wish you good luck, but you are so organized I suspect you won't need it.
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Sep 6, 2012 04:01
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The NEAI guys can tell you how I have been moaning for an MJ over the last few months. This thread is going to be really hard for me to take without checking kijiji after every sentence, especially with someone who kicks rear end at actually doing stuff at the helm. I assume you've looked at the GRM $2010 Cherokee by now?
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Sep 6, 2012 04:13
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Even down here in south-land, I might see a couple of MJ's on the road every year. When they pop up on Craigslist they're either beat to poo poo (and apparently worth $5k+) or ... well, beat to poo poo (and asking $8k). Nice find, and good job keeping it all Jeep*
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Sep 6, 2012 04:16
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In on the ground floor, I love MJs so much I let two of them have their way with my wallet  Keeping it 2wd or going 4wd? The WJ brake/steering swap is well documented but non trivial cost and parts/fab wise if going 4wd, but if you are staying with 2wd you can do it much simpler. Also, those are possibly the best bucket seats Jeep ever put in anything.
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Sep 6, 2012 04:26
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I went hog wild in here. Comanches are my favorite trucks, and this one was pulled from the jaws of death.
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Sep 6, 2012 04:49
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A Comanche thread without talk of the worlds fastest Comanche? For shame. http://www.comancheclub.com/forums/viewtopic.php?f=7&t=12248 quote:The worlds fastest Comanche is currently located at a Chrysler building in Michigani. It was built to show the performance of the new 4.0L engine in 1987. It set a land speed record at Bonneville of 141mph and had a top speed of 146 MPH. GM did not take this lying down and hired Gale Banks to set a record with a S15 pickup in 1989. In the 240-261 cid class, the Banks truck went 183 MPH, totally blowing away the Jeep record. Banks continued to compain trucks and came back in 1990 with the Syclone, and set a record of 201 mph with a normally aspriated V6. I believe this was in the 261-305CId class. The Comanche also saw some action with the SCCA. These are sweet trucks and I was hunting for one to build as a rallycross slut, but instead decided to go the boring subaru route. This looks like a great project and I hope your 4.0 build goes better than mine went.
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Sep 6, 2012 22:56
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Good luck with the build, if you ever need another set of AI hands I'm in Asheville as well.
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Sep 6, 2012 23:19
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Sep 6, 2012 23:52
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Slow is Fast posted:A Comanche thread without talk of the worlds fastest Comanche? For shame. For what it's worth, the Syclone they mentioned is sitting in the museum at the Indianapolis Motor Speedway - or at least it was as of May. Jeeps built to be quick on the street, that aren't the over-luxuried SRT8? Hell yes.
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Sep 6, 2012 23:57
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IOwnCalculus posted:Jeeps built to be quick on the street, that aren't the over-luxuried SRT8? Hell yes. *ahem* Street AND trails! 
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Sep 7, 2012 00:23
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Sep 7, 2012 01:50
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I love these trucks a great deal.
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Sep 7, 2012 02:20
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ZippySLC posted:*ahem* What's going on with that rear wheel?
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Sep 7, 2012 02:28
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Thanks for the encouragement. I'm sure I'll need it when I inevitably hose something. Saw this tribute to functionality at work: Seat Safety Switch posted:The NEAI guys can tell you how I have been moaning for an MJ over the last few months. This thread is going to be really hard for me to take without checking kijiji after every sentence, especially with someone who kicks rear end at actually doing stuff at the helm. The GRM XJ was a pretty strong inspiration to actually accomplish something. A friend drove it once a year or so ago and said it was the most fun thing at the track - I won't be going that far, obviously, but it's encouraging to see. The vee'd front is great. kastein posted:In on the ground floor, I love MJs so much I let two of them have their way with my wallet   some texas redneck posted:What's going on with that rear wheel?
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Sep 7, 2012 03:05
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OneOverZero posted:The vee'd front is great. Do you think you'd contemplate doing something that radical?
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Sep 7, 2012 04:44
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Oh AMC, how I miss you and your maddening Renault/AMC combinations. 
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Sep 7, 2012 04:48
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CommieGIR posted:Oh AMC, how I miss you and your maddening Renault/AMC combinations. At least they never put an e-carb in the Comanche.
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Sep 7, 2012 06:41
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some texas redneck posted:What's going on with that rear wheel? Not much, actually. Jeep has set the rear wheels way forward in the well on all the Grand Cherokees. For comparison, this is a bone stock 3rd gen PR photo:  And the 1st and 2nd gen:  Supposedly it allows better travel, but it mainly looks broken and becomes problematic when you want to get a little crazy (but not crazy to the point of Sawzalling body panels).
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Sep 7, 2012 07:34
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Molten Llama posted:Supposedly it allows better travel, but it mainly looks broken and becomes problematic when you want to get a little crazy (but not crazy to the point of Sawzalling body panels). Yeah. That's where it ended up after I lifted it.
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Sep 7, 2012 15:16
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My dad had one of these back in the 90s but it had the GM V6 in it and it died a rusty death in some Connecticut winter. I didn't realize they were so popular.
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Sep 7, 2012 15:41
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rscott posted:My dad had one of these back in the 90s but it had the GM V6 in it and it died a rusty death in some Connecticut winter. I didn't realize they were so popular.
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Sep 8, 2012 01:30
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I'm reasonably certain you could find a way to make the EFI work as well if you wanted, 90s EFI is not really all that complex.
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Sep 9, 2012 22:59
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I always get irrationally excited when I see an MJ on the road, they are my favorite Jeep. Definitely looking forward to updates on this project.
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Sep 9, 2012 23:22
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kastein posted:I'm reasonably certain you could find a way to make the EFI work as well if you wanted, 90s EFI is not really all that complex.
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Sep 10, 2012 01:36
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Left Ventricle posted:The Chevy 2.8L V6. What a turd, especially in that truck. There were a lot of cars/trucks carrying that awful thing. Its a cockroach.
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Sep 10, 2012 01:38
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Not really a cockroach in the XJ/MJ, in fact it's quite the opposite. Those drat things are known, even famous, for spinning bearings and throwing rods well before 100k miles due to oiling issues.
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Sep 10, 2012 01:40
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Conundrum! I forgot to ask the machinist to drill & tap for the Renix knock sensor on my HO block. Shortblock is together and ready for me to finish. Damnit. I have a feeling that this isn't wise on a headless, panless shortblock, so either I tear it back down and ask the shop to do a five-minute machine op or I find an alternate, bolt-on location. It's (I believe) an M10x1.5 thread, probably 6h and down 10mm, located midships just above the pan. Would one of the cast motor mounts (driver's side, inboard of the isolator) be an acceptable location, vibrationally, to place a knock sensor? Or am I courting a piezoelectric disaster? Still debating how I want to go about adapting all the '90 Renix controls to the '94 HO engine.
Here's a Comanche. 
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Sep 12, 2012 05:41
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You generally want it toward the middle (front to back) of the block - so between cyl 3/4 on an I6. The sensor isn't looking for vibration, it's basically a tuned microphone looking for a specific frequency resonating through the block. I'm pretty sure placing it on the motor mount will prevent it from picking up spark knock as effectively, if at all.. If you're just trying to make the ECU happy, you can probably bolt the sensor anywhere with a ground, and just be careful with your timing.
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Sep 12, 2012 06:52
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Agreed. Keep it on the driver side, too, there is a lot more junk in the way on the passenger side (oil pump, cam, pushrods, etc.) As for ways to solve your problem... 1. Tap it yourself. Will cost about 20 bucks, you need some cutting oil (its in the plumbing aisle of home depot sold as pipe cutting oil, in a 1 quart squeeze bottle) and the appropriate tap, which I think is about ten bucks, and a tap T-handle for another 5. Make sure you tap it square with the block and call it a day. This may not work out if the boss also needs to be machined flat still. 2. Put a pan on it, cover the fire deck with poly sheeting cardboard and duct tape, bring it back. Make sure he machines it flat before drill/tapping if it still a rough cast boss. 3. Switch to early HO. You will need an HO head iirc, as well as HO intake, fuel rail, all sensors, wiring, and ECU. A few specifics... I would use a 91-93/94 as it is most similar to your current setup. Auto or manual does not matter. I am reasonably certain you can use just the engine harness if you are ok with some FSM research and wire splicing at the bulkhead connector. Only difference in the gauge cluster that can't be solved by using the relevant sensors from your engine is the tach, based on some calculations I did a while ago, I am fairly certain you just need to retune your renix tach to the 4cyl spec to work with an HO ECU's tach drive signal, but cannot guarantee this till I do some experiments I haven't found time for yet. There's also the possibility that you can simply feed the renix tach the ignition coil drive signal, which is approximately the signal a true renix gives it anyways. 4. Switch to late HO. I would not do this unless you really like headaches or don't care about your tach working. A 96 donor is about the latest I would go, and even that is pushing it unless you really love customizing wiring harnesses. Use the oil pressure and water temp sensors that go with your jeep, every other sensor should go with the ECU/harness. If you like the 96 and later belt tensioner style more, now's your time. Substitute a 96 manifold, tensioner, and power steering pump (possibly also a 96 PS pressure hose), and delete the idler on the fan bracket just south of the ac compressor. You will need to dremel a timing indicator off the timing cover to clear the belt path, or use a timing cover off a 96 and later motor. I would probably either use a 93/94 or 96 donor, or get the block tapped, unless you can do it yourself. The knock sensor isn't overly important unless you are pushing the limits of compression/timing with the grade of fuel you are using, I know many renix XJers who simply taped it off and left the connector hanging after breaking the sensor or swapping a new motor in.
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Sep 12, 2012 14:22
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I dusted off a tap and was prepared to risk disaster... moot point, as a block cast February 9, 1994, and machined shortly thereafter was already prepared for a 1/2-20 knock sensor killed off for the '91 model year. Unexpected yet appreciated. I'm guessing the block's CNC program wasn't changed until the '96 NVH casting updates showed up a dozen or so months later. As someone who does GD&T schemes all day long, I shouldn't be surprised that nobody likes changing machine drawings. I'd be curious to see the voltage curve for that sensor. The few replacements listed online haven't provided any data points. Gives something interesting to do if I can get ahold of a shaker table! I'm guessing that the motor mount would have shifted the frequency signature upward. As such, I'm sticking with '94 block, head, intake/exhaust, fuel rail, and throttle body with the Renix TPS grafted on (maybe '96 intake for the tensioner if the junkyard provides). Renix flywheel for the CPS and Renix-era Motorcraft distributor should leave all signals accounted for. Pulled one of the galley plugs for the coolant temp sensor. Time to spend the rest of my evening tracing through three inches of '87 electrical manual.
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Sep 13, 2012 01:14
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Cool! IIRC it's just a high-impedance piezo type knock sensor, basically a hard mounted piezo microphone.
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Sep 13, 2012 01:42
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I want one of these drat trucks!!
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Sep 13, 2012 01:53
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OneOverZero posted:I'd be curious to see the voltage curve for that sensor. The few replacements listed online haven't provided any data points. Gives something interesting to do if I can get ahold of a shaker table! I'm guessing that the motor mount would have shifted the frequency signature upward. If you really want to experiment, I have an extra ebay knock sensor that you're more than welcome to. It's meant for a Nissan, but I would think most of them work fairly similarly. I can snag a sub-harness/plug for it next time I'm at the junkyard (this weekend). Just cover the cost of postage + padded envelope. Though I don't think a shaker table will do much.
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Sep 13, 2012 07:01
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Sep 13, 2012 12:44
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Eh, this is R/C but gently caress it. My old Jeep Comanche 1/10 scale. I have a second one being painted now.
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Sep 13, 2012 13:30
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ColonelJohnMatrix posted:Eh, this is R/C but gently caress it. My old Jeep Comanche 1/10 scale. I have a second one being painted now. Your baby mj is awesome.
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Sep 13, 2012 15:23
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Post more of that li'l truck. I wanted to make an XJ/MJ pair a while back, but I just need some more incentive. What do you do when a engine needs transportation and your only tiedown-equipped vehicle is out of commission? Borrow a friend's '90 MJ, separated at birth by a few days.  It's the next link in the chain - the engine from my truck will be rebuilt in largely the same way and dropped in this'un with an external slave swap. Fourth 4.0L pull in as many months? Hell, maybe that one should go into an Eagle. Aside from being 4WD, his truck is largely what I'm going for in terms of mechanical updates. We noticed some... accelerated blowby and head gasket leakage on the way back from the junkyard, so these rebuilds are right on time. Hopefully he'll hop in on this thread as well.  Picked up a MC/booster from a '04 WJ with 34k, though I left all the good front suspension bits since I wasn't immediately familiar with what I needed. Should've brushed up before I left. Hopefully they don't go anywhere before Saturday (likewise for the KJ 8.25). The engine is coming along nicely:  0.030" over, balanced rear end'y with ARP rod bolts, Cloyes double-roller timing, otherwise pretty standard. I wasn't entirely on-board with the head gasket and cork valve cover gasket that came in the rebuild kit, so I'm waiting on some Fel-Pro pieces (copper seemed unnecessary for the time being). VC, timing cover, oil pan, and intake should all be tanked and ready for paint tomorrow - hopefully I don't incur bad karma by painting it a shade that isn't quite AMC canon (Chrysler engine blue is more readily available, who knew). That said, the '94 valve cover has a pair of baffles underneath the breathers, each sealed by a metallic gasket, while the '96 has a plate that spans the top of the cover. I'm moving forward with the '94 for the time being. Grommets ahoy.
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Sep 18, 2012 01:41
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I believe you want to go with the valve cover that matches the year of the head you use - not entirely sure, compare the valve cover bolt pattern and gasket surface/shape before installing. I know the stamped vs cast covers use different gaskets but not sure how cover swaps year to year work out. FWIW I prefer the earlier cast cover, with its 90 degree cam style oil cap and lack of grommets over the later stamped cover with the grommets and failure prone ratcheting plastic threaded cap.
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Sep 18, 2012 06:02
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My understanding has been that valve covers are interchangeable between years (at least among HO, and HO VC on Renix head) so long as you use the corresponding gasket - head machining should accept it regardless. (Never changed the gaskets on my '98 or '01, but I imagine they're similar if not the same throughout the HO era.) I guess I'll find out soon enough. That said, I did already goof by buying '94 grommets and PCV valves, which will completely throw off idle speed dictated by the 1.6mm orifice in the '90.
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Sep 18, 2012 22:28
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