Eagle

My Verizon contract finally rolled over so I used the renewal to upgrade from my four (or six?) year old flip phone to a Samsung Galaxy SIII. I figured my wife and daughter both have smart phones, it was inappropriate for the guy who pays the bill to be the only one still in the telecommunications dark ages. So now I have it (got it today) -- what do I do with it? What are some must-have apps for the 'Droid platform? Don't worry about music and entartainment apps -- I don't even listen to the radio in the Jeep when driving. I'm thinking more along the lines of what apps would be useful oriented toward driving, Jeeping, and shooting. Also, while in the Verizon shop, I notived they are selling a Delphi vehicle information doohickey that plugs into an OBD-II port and broadcasts vehicle data that can be read by a smart phone or tablet. Has anyone used that? Is it worth the $249 they want for it? Would it tell me anything my Harbor Freight Tools code scanner won't tell me?

According to my research, a 205/75-15 turns approximately 760 revolutions per mile. A 225/75-15 turns approximately 730 revolutions per mile. That's a difference of 4 percent. That means your speedometer would be off by 4 MPH at 100 MPH, or 2 MPH at 50 and 1 MPH at 25. Changing tire size NEVER makes a speedometer read 'X' number of MPH fast or slow at all speeds. It's a proportional difference. Have you checked your actual speed against the indicated speed using a GPS? Do it at different speeds, like 25, 50 and 75 MPH and see what the error is for each speed.

The numbers aren't on the carrier. They're stamped into the outer edge of the ring gear.

ok, what if ya don't know if ya have the right drive gear? Redwolf Then you take out your drive gear and count the teeth, then look it up in a FSM or an on-line chart. However, to look it up you need to know both the tire size and the gear ratio, and IIRC you aren't certain about your gear ratio. So basically the question would be: was your speedometer reasonably accurate before you changed to the 31" tires? If so, you can back into the speedo gear charts that way. The charts tell you which gear to use for an axle and tire combination. If you count the teeth on your speedo drive gear, then you know what and you know the tire size, so you go into the chart and find the block with that number of teeth with your stock tire size, and that should tell you what axle ratio you have. Then you follow down (or across, depending on how the chart is laid out) to the new tire size, and that tells you how many teeth you need on the new drive gear. As a rule of thumb, going from stock 225/75-15s up to 31x10.50s is a jump of 7 percent. If the original tires on your truck from the factory (which is what the speedo gear will be calibrated for) were 215/75s, the jump will be about 9 percent. All speedo gears cover a range of two or three tire sizes, which is why the speedometer typically isn't exactly accurate even from the factory. So you can get close just by counting the number of teeth on your drive gear and choosing a new gear that has +/- 8 percent fewer teeth. Here's a link to a chart. 225/75 tires are 28.3" in diameter, 215/75s are 27.7" in diameter, so call it 28" for your stock tires. 31x10.50s typically run a bit less than a true 31" but call it 31". http://www.quadratec.com/jeep_knowledgebase/article-46.htm So, for argument, lets say you have 3.55 gears. On the chart, 3.55 gears with 28" tires should have a 35-tooth drive gear. 35 less 8 percent is 32.2, so my backwards math method would say you need a 32-tooth gear for 31" tires. Looking at the chart, if we find 31" tires and 3.55 gears, it tells us you need ... 32 teeth.

The 2.8L automatics came with 3.73 gears. The 3.54s could easily have been from the factory behind a 5-speed. AMC typically went one step "taller" in gearing behind the 5-speeds than they did with the automatics.

I wouldn't trust the bumper hitch even for a "light" camper trailer.

There is no way to do it yourself other than swapping speedo gears. That usually gets you to within about a +/- 5% accuracy, which translates to being off by about 2-1/2 MPH at 50 MPH. To get it closer than that, speedometer calibration shops play with the return spring on the needle. But they would insist on having the correct speedo drive gear for the tire size before they even start tinkering with the speedo head.

3.55 (or 3.54) was the factory ratio for a 4-banger with the AX-4 transmission.

^^^^ Agreed. Also, the turbine wheels originally had center caps. The wheel in your photo is missing the center cap. The turbines are 15x7". The spare is 15x6".

I once had a professor who used to say that a lot: "It's exactly the same except it's different." ???

Looks to me like the SSBC unit and the more expensive Wilwood unit are intended to completely replace a stock proportioning valve or distribution block. That suggests to me that the pressure switch isn't for the brake lights, but for the brake system warning light on the dashboard. I don't see any reason to spend the extra money for either of these when it's far simpler to retain the stock distributiuon block, plug the by-pass outlet for the rear, and install the less expensive Wilwood unit in the single line that goes to the rear.

You're looking at the expensive Wilwood valve, the one for disc brake systems. The one for converting MJs is this one: http://www.summitracing.com/parts/wil-260-8419/overview/

I'm not familiar with the SSBC unit. A good friend runs the Wilwood and has been happy with it for many years. I believe the unit sold by Chrysler in the Mopar Performance Catalog is the Wilwood.

I'd say the speedo cable needs to be lubricated.

I think you're making a HUGE mistake. A camper will move the center of gravity a lot higher than it is. A lift will just make that even worse. IMHO what you really should be looking for is a set of metric ton springs -- something to add load capacity withOUT raisng the center of gravity.

Springs cannot push the axle either way, sideways. Lateral location is done by the track bar. The stock track bar centers the axle for the stock spring height. Lift the truck --> get an adjustable track bar.

Double flare. Bubble flares weren't being used by American cars at the time the MJs were being built.

Correct me if i'm wrong, But the res tank is never sealed? So having a leak in that wouldnt affect the water pressure? Sounds more like a radiator cap to me. Since you asked -- you're wrong. The Renix-era 4.0L XJs and MJs used what we call a "closed" cooling system. That plastic bottle at the firewall is not an overflow recovery bottle -- it's a surge tank that is part of the pressurized cooling system. The cap is a pressure cap. As has been noted above, if the bottle (tank) is split and can't hold pressure, then your cooling system has no pressure and will boil the coolant. As coolant gets hotter, it expands. That bottle is not supposed to be full. When the system is cold, the bottle should be filled to the halfway level -- there's a post inside with a notch in it, and you fill to the notch -- no higher.

I'd be game to try some 3" XJ AALs but I'm having a hard time finding them, as I don't want a full kit, just the leafs. Anyone seen these anywhere? I've seen a few that don't state a lift amount or application..... Has anyone here tried bastard packs? Thanks for all the good info guys... this is making more sense now! Try the Rancho 2-1/2" AAL kit. It should give you about an inch and a half.

Maybe I have only seen worn out XJ leaf packs, and non worn out MJ leaf packs, but every XJ leaf pack I have seen not under a vehicle (9 packs from 5 different vehicles, ranging in age from 1990 through 1999) had considerately less free arch than every MJ leaf pack I have seen, including 2 wd ones (10 packs out of 5 vehicles ranging from 1987 through 1990). That's exactly correct. Now go back and read what I wrote. If you take an XJ main leaf, out of the vehicle and out of the pack, and hold it up against an MJ leaf pack IN the pack and IN the vehicle sitting on its wheels with the box empty -- the XJ leaf will just about match the arch of the MJ spring. Since that's the case, it is impossible for an XJ leaf to lower an MJ -- which is what someone else said would happen. Stick the XJ leaf in there, and sitting there with an empty box it won't be doing much of anything -- just taking up space. But ... as you start to add load to the bed, now you have an additional leaf to help carry the extra weight.

I thought CJ leaves were only 2 inches wide ... (Not a CJ guy, obviously.)

^^^ What he said. No "procedure" or "sequence" involved. In fact, the torque isn't really all that critical, but the Jeep FSM has a torque for everything.

Everything will work EXCEPT that the '89 speedometer cable attaches using a plastic clip, where the '86 speedo cable attaches with a metal clip and retaining screw. If you can get the speedo cable that goes with the '89 cluster you should be good to go. Remember that you'll have to swap the oil pressure sender and the coolant temperature sender in the back of the head.

MJ springs are longer than XJ springs, but the more important difference is that XJs come from the factory as spring-over-axle (SOA), whereas MJs are spring-under-axle (SUA). The MJ springs have considerably more native arch built in, so an AAL that produces 'X' amount of lift in an XJ produces less lift in an MJ. For example, the Rancho catalog lists the same AAL for both the XJ and MJ. It says in the catalog that it produces 2-1/2" of lift. I called Rancho and spoke with their engineering department. They acknowledged that the results are not the same for the XJ and MJ, but the marketing department didn't think anyone would be lifting an MJ so they ignored MJs. The correct spec is 2-1/2" for an XJ but 1-1/2" for an MJ. As for using an XJ main leaf in an MJ, there is simply no way it can lower the vehicle unless you install it upside down (arched against the rest of the pack). In fact, the native arch of an XJ main leaf is about the same as the arch in an MJ pack in the vehicle, sitting with an empty bed. That means adding the XJ leaf would not lower the vehicle, but probably would not lift it very much, if at all. It would, however, add load capacity. In fact, I have a couple of XJ packs that I hope to use for making a home-brew pair of MJ "metric ton" spring packs. My goal is added capacity, decent ride, and no lift.

Actually, you're right. Extension is still extension. My bad. However, there is still the issue that the valves may not work properly (or at all) if/when inverted.