Eagle

If you don't change the axle gearing from 3.55 to 4.10 the 5th gear will be completely wasted.

You won't be running even in 4th gear -- except for downhill with a tailwind you'll be in third gear most of the time. If you have a 4-cylinder with the 4-speed manual, you will NOT be happy with 31s. Don't think that lower RPMs are always better. Pete already said it, but I'll repeat it. I have history on my side, being old enough to have grown up before most cars had overdrive. When I graduated from college, my first new car was a 1966 Rambler American with a 3-speed manual transmission (and no overdrive). The engine was a 199 cubic inch version of what later became the 4.0L Jeep engine -- and the 2.5L Jeep engine. The gearing and tire size worked out exactly to 25 MPH per 1000 RPM, so 60 MPH was exactly 2500 RPM. This was verified -- I ran a tachometer in it, and verified the speedometer. I got 28 MPG for gas mileage. Your 4-speed, 4-cylinder Jeep on 30x9.50-15 tires will be turning 2496 RPM at 60 MPH. You won't be hurting anything at that engine speed. It's just over a fast idle (sort of ...).

Unless you really NEED 31s, go with the 30s. Yes, in diameter they are only a hair larger than a 235/75-15, but they are wider, both in cross section and at the tread. You can run 31s on OEM Jeep rims with a stock suspension, but the rubbing on the lower control arms will be worse, and you don't really gain anything. Especially with a 4-banger, you will NOT be happy trying to spin 31" tires through stock gearing. The 30s, IMHO, look just about perfect on a stock-height MJ.

The tachometer was optional on the Pioneer and Chief (I know, because I bought the option when I special ordered my '88 XJ Pioneer) and standard on the Limited. They ALL had the 85 MPH speedometer. The ONLY speedo that went higher was the one used in XJs that were ordered by police departments. Good luck finding one of those.

No flaming involved, but you cannot identify the model by the options, because in the AMC days everything was optional and available on just about every model. Post the VIN and that should tell us what model you have.

AMC 20 drum brakes should be the same 10" x 2-1/2" that were used with the D44 in the XJ and MJ.

^^^ That was my first guess.

I've never seen an MJ with anything mounted in the switch panel to the left of the steering wheel, but most XJs have something there. Hit the junkyards and get an XJ panel for the left side.

My 1988 Chief has a cloth bench seat and a non-leather 3-spoke steering wheel. No cargo light, no Dana 44 rear axle. No tilt wheel, no cruise. All those things were options. The tow hooks were part of the off-road option package.

Still needs a compressor. An electric all-in-one spray gun os going to be a lot cheaper to buy, although a compressor is a long-term investment.

A key point to remember is that 31x10.50-15s on factory 15x7 rims with 5-1/4" backspacing, will tuck up inside the wheelwells when the suspension is compressed, which is why we can run 31x10.50s on stock rims with no trimming of the sheet metal or flares. ANYTHING that moves the tires farther out (less backspacing and/or wider rims) results in the outer shoulder of the tire (or the tread itself) making contact with the bodywork when the suspension compresses, thus requiring trimming. There are no aftermarket rims offering 5-1/4" backspacing. Even in 15x7, a rim with 4-1/4" backspacing puts the tires 1 inch farther outboard. Then add another inch for 15x8 rims, and now the outer sidewall and shoulder will ride 2 inches farther out than stock. In states that require the fenders to cover the tread of the tires (which, I think, is just about every state), that 2 inches is enough to make your new tires and wheels illegal.

I have an Acer Aspire One, and I love it. It isn't my primary computer, but it's trying hard to replace my notebook as my secondary. Even with the OEM standard 1GB of RAM it runs the full Microsoft Office suite, and even runs my old version of AutoCAD LT. I use an external CD-ROM drive for installing software. But it is a bit slow. I have seen conflicting reports -- can the Aspite One be upgraded to 2GB, or even 4GB? If so, is the upgrade an additional module, or does it replace the OEM module?

The tire foam products I've been using (STP and another I can't recall at the moment) have silicone in them. Silicone is good for rubber.

Sorry, this is incorrect. The Pioneer level was trim only. Carpet instead of rubber floor mat, cloth seat instead of all vinyl, 3-spoke "sport" steering wheel, and gauges (but no tachometer) instead of idiot lights. The off-road package was optional. Tachometer was optional. Anything other than the base 15x6 steel wheel was optional. 4WD was optional. Most other features were optional. In 1988 even a radio was optional. You can't generalize about Jeep's trim levels. Almost every feature was available on the lower levels as an extra-cost option, and it was rare to see a base or SporTruck that didn't come with at least a couple of options ... which leads to much confusion as to what was standard in each line.

The XJ had the exact same jack and handle, stowed under the rear seat. If you can't un-stick your jack, just pick up an XJ jack from a junkyard.

^^^ This.

I don't know about the most common, but I do know it's getting more and more difficult to find ANY 15" tires suitable for a Jeep. I thought Goodyear had completely dropped the original Wrangler Radial, then I discovered that Wal-Mart still has it ... only in size 235/75-15. And it is still listed on the Goodyear web site ... in only that size. I think that the original is far better than several of the newer Wrangler XYZ series tires that Jeep has been using as OEM, so I just grabbed a set from Wal-Mart while I could get them, and put them in the garage rafters until Spring. As soon as I can afford it, I'll gather up another set of decent OEM Jeep alloys and buy another set before Goodyear discontinues the 235s.

You're even more of a purist than I am, then (at least in some ways). My excuse is that I have a fleet of multiple MJs and XJs, different years and different models. It's just easier all around to standardize as much as possible on wheels and tires so I can swap across vehicles without upsetting the balance of the universe.

If his is the inline 6-cylinder, the transmission will not bolt up to your 4-cylinder.

Too many people don't understand how that works. All other factors being equal, the most economical engine speed is the speed (RPM) at which it produces maximum torque. In a real-world vehicle, various drag factors increase as road speed increases but, in general, the 4.0L engine will not produce maximum fuel efficiency when run below 2000 RPM. Somewhere around 2500 RPM at highway cruise seems to be the sweet spot.

Who has 27" tires? That's a 205/75-15. Yes, that was the base tire in the early years, but most Mjs and most XJs probably came with 225/75-15s, which are slightly larger than 28".

I agree completely. Same with my '88 Cherokee, which I bought new. The difference is that I bought mine with a tachometer, so I always knew how slow the engine turns, and I have always treated it as a 4-speed except on the highway. Even on highways, I have to downshift for passing if there's any traffic. And that's with stock tires. With 31s, 5th gear becomes almost useless. With 31" tires and 3.07 gears, in 5th gear at 65 the engine is only turning at 1696 RPM. That's several hundred RPM below the torque peak. Even 70 MPH is only 1827 RPM. 3.55s are better, but still not "good." IMHO the minimum ratio for 31" tires is 3.73, and even that only gets you to the equivalent of stock tires with an automatic. 4.10s is what I think is the optimum ratio with 31s.

This is incorrect. I have had the light come on when the CAD was not functioning. Loss of power could mean a failing catalytic converter. It could also mean, especially if the truck has been sitting, that a mouse family has taken up residence somewhere in the exhaust system and the nest is restricting exhaust flow.

The guy is jerkin' your chain. Maybe he's just ignorant, but I don't think so. I bought a Cherokee new in 1988. It was ordered in late 1987 and delivered to my dealer mid-January of 1988. All the paperwork said AMC/Jeep. Chrysler didn't "take over" until several months later in 1988, and there were no Chrysler production changes until the 1990 model year. For both the Cherokee and Comanche up through 1988, the FSM is actually the 1986 FSM and it includes in the main book the 2.5L 4-cylinder (carburetor version), the 2.8L V6, and the diesel. There were add-on, separate books to cover the 4.0L engine, the BA10/5 transmission, the NP231 transfer case, the NP242 transfer case, the AW-4 transmission, the 4.0L fuel injection system, the 2.5L fuel injection system, and the electrical wiring.

An '87 with a junkyard engine in it really isn't worth all that much. The body on yours isn't totally trashed, but it's not exactly showroom mint, either. It's a Chief, which means at least it's not a base model and has guages rather than idiot lights, but the most valuable part of the truck as it sits is the roll bar. The Dana 35 rear axle is also not a "must have" choice. The wheels aren't from an '87, and they also aren't alloy so it sorta makes you wonder why somebody even bothered to put them on. I paid $500 for an '88 Chief in better condition with lower miles, and I paid $600 for an '87 Pioneer in better shape with lower miles. Both of those were around 100,000 miles when I bought them. The sad truth is that you have a truck that is realistically worth between $500 and $750. If you have twice that much in it and don't want to sell for less than what you have invested, I believe you have yourself a long-term investment on your hands. I know I wouldn't pay $1,500 for it, and I'm not saying that to be insulting. What matters to me is the body, interior and chassis. I can do mechanical work -- I'm not good at body work. I sympathize with your situation. At this point, I have invested between $3000 and $4000 in my $500 '88 Chief, and it doesn't run because the clutch rusted to the flywheel. I don't have the time to fix it, the frame is developing a crack, and I should sell it -- but I'd have to give it away and I'm not quite ready to do that just yet.