Eagle

Bench seat -- trash. "Station wagon" steering wheel -- base model truck, idiot light instrument cluster. Cheapie aftermarket wheels. Body butchered. 16-gallon is the small gas tank in a longbed ... and how do you "refurbish" a gas tank? IMHO this truck is NOT worth $2,000

Double-stick foam tape.

Transmission bearings?

Yes, the topic is Right Here But I lost the pictures :eek: So, I reloaded them Here I remember that. I liked it then, and I like it now. I think it would look even better with the fenders and grille updated to the "new" XJ style (1997+).

30" tires are about 6 percent larger than stock, so whatever the speedometer says -- you're going about 6 percent faster. 31" tires are 11 percent larger than stock, so whatever the speedometer says you're going 11 percent faster. That's if you haven't changed either the speedo drive gear or the axle gears, of course.

Why would you do that? Upshifting at those low RPMs means slipping the clutch for every shift. You should only slip the clutch when starting in first gear from a standstill. The sweet spot for upshifting a Renix 4.0L is 2200 to 2300 RPM. For an HO it's about 2500 RPM.

My first guess, before reaching the end of your post, was u-joints.

With 3.07 gears? Yeah start in second if you really enjoy replacing clutches. First gear is there for a reason. Use it. Especially with 3.07 gears.

Sure, but that doesn't show up in a tire size chart. What I'm saying is that every tire/gear chart I have ever encountered (other than mine) bases their calculation on the diameter of the tire, without taking into account sidewall squat that makes the actual rolling radius considerably less than half the mathematical diameter. Once you really know what gears will result in what RPMs at ___ MPH, then you can decide for yourself how much allowance you want to make for heaver tires. I agree that 4.10s are a good choice with 31x10.50s. For reference, as I have posted numerous times, I have 3.73s in my 88 MJ 5-speed. The overall drive ratio is EXACTLY the same as my wife's stock XJ with automatic and stock tires. It's fine for daily driver duty, but 4.10s would be much better off-road, and perfectly acceptable on the street and highway. For anything larger than 31x10.50, I think 4.56 is pretty much the minimum unless money is truly an object and you get a deal on 4-cylinder axles already set up with the 4.10s. But the OP here is asking about tires that are 31.6 inches in diameter. That's equivalent to a 32, not a 31. 31x10.50s typically have an actual outside diameter of about 30.5 ... and 30x9.50s typically run about 29.5, making them barely larger than a 235/75-15. It's important to be certain what your tire size really is before making decisions that are going to cost money and that you'll be living with for a long while.

What chart are you using? The problem with most charts, and with most calculations, is that they are based on the tire diameter as it sits on a rim, not mounted on a vehicle. Once you put it on a vehicle, supporting weight, the actual static radius from the axle to the ground is less (often significantly less) than half the theoretical diameter. When I made up my spreadsheet, I went to tire company brochures and web sites and found their own numbers for actual revolutions-per-mile. Even that's an approximation -- within any nominal size, one company's 31x10.50-15 may have a few different revolutions-per-mile than another company's 31x10.50-15. But it's still a lot more accurate than just calculating a diameter from the nominal tire size and dividing it by two. Look up 31x10.50-15 from any tire company and I think you'll find it isn't 31 inches in diameter. Most seem to run about 30-1/2". 31x10.50s with 4.56 gears is LESS overall gearing than a stock 4.0L with automatic and stock 3.54 gears. For the stock setup, 70 MPH in 4th (overdrive) is 2913 RPM and downshifting to third (1:1) bumps it to 3884 RPM. My wife's XJ is an automatic, and there's no problem climbing most hills on Interstates without downshifting. Any incline that's so steep you need to downshift for it probably won't be the end of the world if you only drive 65 instead of 75. But if you have the right ratio, you won't need to downshift as much on upgrades. This is why I think that factory's choice of 3.08 gears behind the 5-speed was so dumb. I have to downshift a lot even at 60 MPH on highways, and I should not have to do that.

Somewhere around 2250 to 2500 is a sweet spot for normal driving, but if you set up your gears to run those RPMs at 75 MPH then at anything under 60 MPH 5th gear will be useless, and 4th gear will be almost useless. Also don't forget that drag increases exponentially with speed, so to push the same "brick on wheels" down the road at 75 MPH requires a whole bunch more horsepower than pushing the same brick on wheels at 50 MPH. 2250 is the torque peak, but it isn't the horsepower peak. What you're shooting for would be almost exactly the same as stock 3.08 gears and stock tires. That setup runs a bit over 2100 RPM at 75 MPH, and 5th gear is totally useless under 60. Not only that, I have run the same route, one way using 5th gear and the other way using only 4th, and I got as good or better gas mileage NOT using 5th gear. The 3.08 ratio was an idiotic choice by AMC/Jeep, but they did it because the fuel mileage and emissions testing was run indoors on a dynomometer, so there was no aerodynamic drag to be concerned with. In other words, they weren't realistic numbers, and the gear ratio was chosen to beat the test, not because it was in any way a good choice for real world driving. So what you would be doing trying to run 2250 RPM at 75 MPH is to duplicate the stock 5-speed overall drive ration, while struggling to spin much larger and heavier tires. Keep in mind that the 4.0L engine (and the 2.5L) is derived from AMCs old I-6 that was first introduced all the way back in 1964. Back then it was carbureted, of course, but the basic block and engine was the same. And in those days we didn't have overdrive, a manual transmission was "three on the tree." Top gear was third, with a 1:1 ratio in the transmission and 3.08 gears in the axle. In my 1966 Rambler American, that worked out to exactly 2500 RPM at 60 MPH, and 3000 RPM at 72 MPH. They ran forever like that. Mine got 28 MPG highway and mid-20s around town. I was in the Army then and I traded mine in for a new Javelin with my combat pay. My brother had a 1970 Gremlin with the same drive train that went something like 350,000 miles. And he autocrossed it on the weekends. If you set yours up to cruise at 3000 RPM at 75 MPH, you won't be "burning up" the engine, and you'll have a much happier rig.

Sure looks like eaton owns detroit http://www.eaton.com/Eaton/ProductsServices/Automotive/AutomotiveAftermarket/Differentials/PCT_221432 I never knew that. I have a TrueTrac in my '88 MJ. I like it ... a lot.

The disadvantage to 4-door XJ seats is that they don't fold forward. MJ seats, and 2-door XJ seats, do fold forward. You can always swap the upholstery from the XJ seats onto the MJ frames -- you'll just have to cut a small slit for the lever that releases the backs to fold forward. Is that worth $150? I dunno -- that's a very subjective call, and while it might be a good deal for one person, it might not be a good deal for someone else.

In terms of revolutions per mile (which is the only important criterion when matching gears to tire size), the 265/75-16s are identical to 33x12.50-15s (637 revolutions per mile vs. 636 revolutions per mile). Using that as the base, my speed to RPM chart (which is corrected for actual revolutions per mile, not theoretical tire diameter that doesn't accound for sidewall squat), I get the following (in 5th gear): 4.10 gears ==> 2282 RPM at 70 MPH (my chart doesn't go up to 75 MPH) 4.56 gears ==> 2538 RPM at 70 MPH 4.88 gears ==> 2716 RPM at 70 MPH Crunching the numbers, to convert that to 75 MPH we get: 4.10 gears ==> 2445 RPM at 75 MPH 4.56 gears ==> 2719 RPM at 75 MPH 4.88 gears ==> 2910 RPM at 75 MPH You should be changing to 4.88 gears. 75 MPH cruise at 2900 RPM is NOT pushing the engine too fast. Conversely, 4.10 gears isn't nearly enough gear for those tires. Remember, a "31x10.50" tire is NOT 31 inches in diameter -- they are typically between 30.3 and 30.5" overall diameter. So if you're thinking that your chosen tires are close to 31s ... you're wrong. If you're not comfortable with 4.88s, go with at least 4.56 gears. Putting this is perspective, a stock XJ with automatic and 225/75-15s turns 2261 RPM at 70 MPH, so if you go with 4.10s you're getting exactly the same final drive ratio as a stock vehicle ... but you're trying to spin much larger and heavier tires.

The TrueTrac is also not made by Eaton. It's made by the same folks who make the Detroit Locker.

Somebody did that. We had photos of it on here a couple or three years ago.

And reduced backpressure in an exhaust = loss of torque at low and mid-range RPMs. Since I never operate a 4.0 liter higher than 2500 RPM (and rarely even that high) I'll take the torque that I use every day over the 5000 RPM horsepower that I'll never use -- ever.

I believe factory spec is 750 RPM.

Nope.

No, I didn't. &%#&% zombie threads.

The AX-4 4-speed and the AX-5 5-speed are the same transmission. The 5-speed just has some extra internal parts to run the overdrive gearset. I'm not certain, but the long tailshaft on the 2WD 4-speed might be the same length as the transfer case on the 4WD, which would allow you to use the same rear driveshaft. Yes, you have to do something to make the ratio in the rear axle match the front. The 2.5 liter 5-speed had 4.10 gears. Your 2WD 4-speed has a 3.54 rear axle.

Those numbers don't even say what they represent. Is that supposed to be RPM at 60 MPH? If so, is that in top gear (overdrive) or 1:1 ratio (4th in the 5-speed, 3rd in the auto)? Assuming they represent RPM at 60 MPH, they are completely wrong. I compared them to the numbers I worked up in a spreadsheet, using actual tire manufacturers' revolutions-per-mile data, and the numbers in this chart simply don't match up with ANY RPMs in my spreadsheet. The above chart is somewhat useful as a general guide (bigger tires = less RPM, more gear = more RPM), but not helpful beyond generalities.

The tachometer was optional on the Pioneers in '88 and '89. Gauges rather than idiot lights were included with the Pioneer package, but the standard cluster had the large fuel gauge. I've owned two Pioneers (my '88 XJ and an '89 MJ) that had the tachometer. So don't skip over a vehicle just because it's a Pioneer. It could have the full cluster with tach.

Used AALs? Craigslist? There is NO way to know what they are or how much lift they'll produce unless you buy them and install them in your truck. Unless they are VERY cheap, I wouldn't bother.

Any taper flared not bubble flared) brake lines are double flared. DO NOT use a single flare for brakes, and DO NOT use compression couplings. Either do it right, and be safe ... or don't do it at all.