Eagle

In the vehicle, with the factory steering stops on the knuckles, the XJ box (@ 14:1 ratio) is 3-1/2 turns lock-to-lock. The ZJ box (@ 12.7:1 ratio) is 3 turns lock-to-lock. The question is what the lock-to-lock is for a bare box, out of the vehicle, for use when checking a rebuilt box on the parts house counter.

https://www.youtube.com/watch?feature=player_detailpage&v=FPQlXNH36mI#t=6

Are you planning to flat tow it, tow it with a 2-wheel car dolly, or load it onto a full-length, flat-bed auto transporter?

If you have power at the fuse and power at the socket, but no light, ground is a likely suspect. The fact that the turn indicator on the dash sometimes lights up is a clue that the circuit is seeking a ground by back-feeding through the indicator.

Something is very wrong. The XJ never had rear disk brakes -- not in any year, and not on any axle. I'm guessing you found an axle from a ZJ Grand Cherokee. If so, DO NOT BUY IT. It has an aluminum housing that's prone to bending, and the internal parts are not 100% compatible with a "real" Dana 44 axle.

You can get gears up to 4.88 for the D35. Maybe even deeper, but 4.88 is the deepest you can go with a D30 in front, so I've never looked beyond that. Rusty's is not talking about a new housing, they're referring to the carrier. Most axles (including both the Dana 35 and the Dana 44) have a "carrier split," which means gears in one range of ratios need one carrier and the gears in another range take a different carrier. The Chrysler 8.25, however, does NOT have a carrier break -- all ratios use the same carrier, and backlash is adjusted with a set screw. For the Dana 35, the carrier break is divided into 3.31 and lower numerically, and 3.55 and higher numerically. IMHO it isn't worth spending the money for new gears and a new carrier in a Dana 35. Choose 4.10 as your ratio, then go junkyard shopping for a set of 4.10 front and rear axles out of a 4-cylinder Cherokee. Having written that, let's back up and ask about specifics: Is your truck 2WD or 4WD? If it's 2WD, do you plan to convert to 4WD? What size tires are you running now, and what size tires do you plan to run in the future? What engine do you have? (I assume, if you have 3.07 gears, that it's a 4.0L with a 5-speed, but let's be sure we're all on the same page.)

It's hard to find a better spring perch than the ones in the Mopar Performance catalog, and the price is stupid cheap for what you get. I ordered a set several years ago. The price was so low that I couldn't believe it was for a pair, so I ordered two. And I got two -- pairs. Here they are at Jeg's http://www.jegs.com/i/Mopar-Performance/312/P4120074/10002/-1 Part number is P4120074. You may be able to order them from a local Jeep, Dodge, or Chrysler dealer and not pay any shipping.

Do you have the correct speedo gear installed? Your tach should be reading ~2100 RPM with that combination. No, 2265 RPM at 65 MPH is correct. The question is why that's a concern. That's right about on the torque peak of the engine, which is the most efficient cruise speed for the engine, and it's slower than what the original AMC engines were designed for. As I've posted before, over the years, starting in 1966, my family has had a number of cars with the AMC 199, 232, 258 engine, all set up with non-overdrive 3-speed transmissions. They were all geared to run 24 MPH per 1,000 RPM -- which works out to 2500 RPM at 60 MPH, and a 72 MPH cruise at 3,000 RPM. Set up like that, we've seen them go more than 300,000 miles. 2,300 RPM at 65 MPH is not an issue.

Agreed. Red is the next stronger, and that's for things you won't take apart.

70 MPH will be 2500 RPM in overdrive. Not bad at all -- that's what the earlier versions of the AMC I-6 were all geared for in the days before we had overdrive transmissions. Should give you a nice crawl ratio off-road.

4.10s with 31" tires is perfect. 31" tires with 3.73 gears is exactly the same as 3.54 gears with stock tires, so 4.10s is only a small step more in gearing that stock when you run 31" tires. Check the ratio on that AMC 20. A lot of the 2.8L trucks and XJs had 3.73 gears.

Does your MJ have gauges, or idiot lights? If you have idiot lights, is the ALT light on when this GEN light is on? If you have gauges, what does the voltage meter show when running? I've never heard of a GEN light in an XJ or MJ, and I don't have a '91 vintage FSM to look at the layout of that auxiliary light panel. I'm half tempted to suggest removing the bulb from that space and forgetting about it.

What make and model vehicle are we talking about? "GEN" refers to generator, and the MJ doesn't have a generator. Where is this light?

Nope. The 2000 XJ uses coil-on-rail ignition. The '88 XJ head doesn't have the bosses to mount the coil rail to. And then, of course, there's the issue of ports not being the same size, shape, or height.

If the expected resistance is around 100 ohms, why are you using the 20,000 ohms range? Don't you have a 0-2,000 or 0-200 ohms range?

What's your stock tire size? And how fast will you be driving? Just go to the spreadsheet I provided a link to above. Let's assume your stock tire size is 215/75-15. Go up to the top of the sheet, to the section for 215/75-15 tires. Go all the way to the right, to the two columns under the 4.88 axle ratio. You don't have a 5-speed, so ignore the "O.D." column. Your 4th gear is a 1:1 ratio, so just read down that column to find the RPM for various road speeds. If you do that, you'll see that 60 MPH is about 3600 RPM. That's about the same RPM as 80+ MPH with your stock gears. It won't kill you engine, but I wouldn't drive very far or very often much faster than that. Here's my frame of reference. Both the 2.5L and 4.0L MJ engines are descendants of the 232 c.i.d. (3.8L) engine that AMC introduced in 1964. We've had several of them in my family, all mated to three-speed manual transmissions. The 3-speed also had a 1:1 top gear, so the setup is directly comparble to your MJ. They were all geared so that they ran 24 MPH per 1,000 RPM. That meant that 60 MPH was exactly 2,500 RPM, and 3,000 RPM gave us a 72 MPH cruise. 2,500 was sort of the sweet spot for getting the best fuel economy, but they weren't bad right up to 3,000 RPM. Above 3,000 RPM the fuel mileage fell off quickly. At a 3,000 RPM cruise, the engines lasted forever. My brother and his wife had a Gremlin that they drove more than 200,000 miles, then they sold it to an auto parts store where it was used as a delivery vehicle for another 120,000 before we lost track of it. The torque peak is closer to 3,000 RPM than it is even to 3,600, but you're probably okay up to around 60 MPH.

IMHO a 5th gear will be wasted. You'll only be able to use it at freeway speeds, downhill with a tailwind. 60 MPH in 5th will be less than 2200 RPM. The [fuel injected] 2.5L made 117 horsepower at 5,000 RPM and 135 foot-pounds of torque at 3,500 RPM when it was introduced in the 1986 model year. This was raised to 121 horsepower at 5,250 RPM and 141 foot-pounds of torque at 3,250 RPM for model years 1987 through 1990. With 35-inch tires, even with 4.88 gears you would be running FAR below the torque and horsepower peaks in 5th gear, and I don't think the 2.5L engine will enjoy that. The graph below is for the later MPFI version. The throttle body numbers are worse, but the overall shape of the curves is similar. I'm still looking for a graph of the earlier version.

Any monoleaf spring is non-progressive. Leaf spring packs can be made progressive by using slightly different arches for the leaves, such that initially only one leaf carries the load, then as load is added the deflection starts to pick up additional leaves. The extreme example is the overload leaf in an MJ pack.

Refer to my spreadsheet -- it goes up to 35-inch tires. For an AX-4, just ignore the OD column (that's fifth gear for the 5-speeds) and use the "1:1" column (that's 4th gear for the AX-4). https://docs.google.com/spreadsheets/d/1pHFuhGgj6dQDfzyfFJH5z7NCDLW2KX3ABQgAJr3lBvM/pub?hl=en&hl=en&output=html With 35s and 4.88 gears, 60 MPH is 2923 RPM. 70 MPH is 3410 RPM. Scroll up to one of the stock tire sizes (215/75-15) with 3.55 gears (which was the stock ratio behind the AX-4)and you get 2669 RPM at 60 MPH and 3114 RPM at 70 MPH. So with the 4.88s and 35" tires your RPMs will actually be slightly less than the stock setup -- which means the engine will work a little harder, but you don't have to worry about over-revving it.

That makes sense.

Fibreglass -- I don't trust it. I've owned two fiberglass sailboats and a fiberglass canoe. I have the surviving half of a fiberglass extension ladder, and the top rung has partially pulled out and isn't safe to support any weight. There's no way I'd put fiberglass in place of steel springs.

So what's going to control the relay? Wouldn't it be easier to accomplish the same thing just by running a larger wire to the input side of the switch?

How will adding a relay ahead of the switch reduce the current flowing through the switch?

What did you put in? All the front shocks I can remember installing came with new hardware. When I have reused older shocks on "lower grade" XJs or MJs I generally replace the bolts with new anyway, as a preventive measure, and I use abundant amounts of anti-sieze on the threads.

What year MJ are we discussing? The wiring diagrams above are for the 1997-2001 XJ. The older XJs and MJs didn't put the resistor pack in the ground leg, downstream of the blower motor. It was upstream, on the supply side, and the blower motor connected directly to ground. I suppose you could put a single relay between the resistor pack and the blower motor input, but then the heater switch would still be carrying the load of the resistor pack. Putting multiple relays upstream of the resistor pack takes all significant load off the blower switch -- all it would be carrying is the load of a single relay control side.