Incommando

I wanted a drive-able but very capable 'wheeler. It is going to be far cheaper to make the CJ7 in my sig into what I want than the MJ. The CJ7 chassis is already heavily modified: reinforced frame, competition cut rear corners with steel "crush panels" installed and a set of the reinforced rocker panels with it, already set up for 1-ton axles with a shackle reversal and out-boarded springs, extended wheelbase. It has 53" Rancho springs on all four corners. It is a proven chassis: the previous owner 'wheeled it in this form but took the swapped-in SBC drive train and axles when he moved to a tube chassie'd/air shocked buggy. Financially I am saving a ton by doing the CJ. I don't really need or have space for 3 vehicles so I am keeping the KJ & the CJ. I will rob the MJ's 4.0 to add to an AW4 and D300 that was originally destined for the MJ & then probably start parting the truck. The body damage on the MJ is pretty severe and pics do not do it justice and it was just more than I wanted to do.

Well, so much for this project. Sold most everything to move on to another project: viewtopic.php?f=24&t=32277&p=320197#p320197

I agree that the charts are pretty generic. I think they work better with an auto tranny than a stick, as well. The difference between the 1st gear ratio's between the two types is pretty extreme in many cases. But I still maintain that the factory gear ratio's are a good compromise for power and efficiency and ton's of people who re-gear agree that going back to a near factory balance is preferable. Isn't there a difference between peak horse power or peak torque and maximum efficiency? The idea is that you need peak power ( of either type) to reach a given speed but less to maintain it. If peak horsepower and peak torque translated to maximum efficiency it doesn't seem like the peaks would be some 1,300 rpm's apart? Just curious. Even if the assertions about spinning the inline sixes near the redline is true, I doubt anyone recommends keeping the RPM's at the 4,600 RPM mark (which is peak horsepower for the chart for a '92 4.0 that I located online) for a 500 mile highway trip for peak mileage. BTW: by switching from a 27.1" tall tire (205/75/15) to a 28.8" tall tire (235/75/15) you changed your 5th gear RPM's at 65 MPH from 1954 to 1834. 4th gear for the same speeds is 2474 & 2322, still very far below peak TQ or HP figures but hardly several thousand (around 1,100 (TQ) to 2,300 (HP)) below. Again, peak does not necessarily = most efficient, either. Under modern testing perimeters a 196" Rambler I6 would probably produce less than 100 hp peak NET ( they only made 138 GROSS) versus 170+ NET for the Renix 4.0, which could really help pull the vehicle at a lower rpm as the 4.0 probably makes considerably more TQ & HP at 1900 RPM than the 196 did even at peak. The low tech carb'ed 196 may be the distant basis for the 4.0, but the injection and ecm alone make them completely different animals. The "one setting fits all drags & rpm's" un-adaptability of a carb, especially an ancient 1 or 2 barrel, versus even the Renix FI system's on-the-fly adjust-ability is a huge difference maker. Move onto the OBD1 4.0 H.O. and your are really talking apples and oranges.

Typo: early MJ's (pre-'91?) had 21 splines. The first mod I would make would be to add a period button to your keyboard. Having a post that is easier to read is more likely to return a bunch of responses. Many just will not bother to read a post that is one run-on sentence. :D If you are going to convert to 4wd, do as suggested and buy a complete donor vehicle. There are so many little parts that are a pain to source if you don't get everything. Trust me on that... :wrench: Your '87 probably has the craptastic Dana 35 rear end that is considered to be a poor axle..but make sure that you verify your rear axle before swapping. Some tow package 2wd's got the Dana 44 and it is a desirable axle. The easiest path would be to find a donor '97 or newer XJ with a 29-spline 8.25 rear and a large-joint HP Dana 30 front to get the best readily available axle set for an MJ. You will need to relocate the rear axle perches to swap the rear axle but other than that the front will bolt right in in place of your 2wd beam axle front. Get the newer AX15 tranny to replace the also unloved Peugeot tranny you have at the same time. A swap to am AW4 auto/231 would also be a worthy upgrade to your current transmission. At least around me the auto XJ's are much more common than the 5-spds and generally cheaper. If you ever wind up near Dayton, OH I have an open 8.25, a welded 8.25, and a HP D30 all with matching 3.55's that I could lay on ya for a song... I'd even throw in a set of high-end M.O.R.E. spring perches for the rear...8)

You are going 180 degrees in the wrong direction for peak highway MPG. Some of the gear sites and 4wd catalogs have a chart listing tire size vs. ratio with it broken down into three sections: Highway MPG vs. all-around performance vs. off-road only. http://www.4wd.com's printed catalog lists 4.10's with a 28" tall tire as returning poor fuel economy but increased towing power. For that tire size they list 3.55's as the best all-around performance and 3.07's for best highway fuel economy. The cheapest way to go for 3.07's would be to find a set of generally cheap axles from a 5-spd XJ/MJ and throw them under your truck. For 4.10's you would have to go to a 34" tall tire to get in the "good highway MPG" range. Remember that peak MPG can be seriously different for around town vs. highway driving. Great highway gears may make your engine work too hard to move the vehicle in heavy light-to-light type driving and driveability suffers. The factory axle gears with a factory sized tire generally offers the best compromise on power vs. MPG and your rig should have the preferred 3.55's in it. Most people who change tire size generally change the gear ratio to duplicate the factory combo's numbers in order to maintain that balance unless it is a towing or true off-road vehicle. The cam can make a difference if it radically moves your power band. Use a chart like

Yep, your front drive shaft attachment point will be down behind the front diff housing where your LP rear shaft will be at the same height and be the first to hit oncoming obstacles because the diff housing isn't in the way. :D I am in no way saying that a HP front isn't better, just that there is nothing wrong with a LP in most applications. Especially when you can find a lot better deals on LP D60 fronts. Mine came from under a drive able truck and ran me 25% of the cost of a HP Ford. Keeping $900 in my pocket was worthwhile for me. Maybe it won't be for others. Like most things, there are trade-offs.

By a cheaper GM D60 ( or even cheaper Dodge D60 ) and then get a spacer ( less than $100 some places) that will allow you to bolt your AX15 or AW4 to a pass drop D300 transfer case = all cast iron case with gear-to-gear operation that is considerably stronger than a 231. You get a D60 front and a transfer case upgrade for less than a Ford front D60. A LP D60 is plenty strong under something as light as an MJ. Everyone looks to tire diameter alone when considering axles and they ignore the vehicle weight factor.

Taking the CJ plunge myself....

Propaganda is propaganda.

I'll pass

:agree:

My first MJ had the towing mirrors in the r.h. diagram. The second has the standard mirrors in the top l.h. diagram. The towing mirrors are significantly better in doing what rear view mirrors are supposed to do... :D.

The control arms are the same. Unbolt your beam axle and bolt in the HP D30. Grand Cherokee Dana 44's are IMHO a hunk of junk. It has an aluminum center section and different internals. Many believe that even the crappy D35 is a better choice. I would get a 29-spline 8.25 from a later Xj...they are stupid cheap and plenty strong. You could spend as much or fab as much as you want to move the shifter.... but the bench seat/auto/4wd MJ's have the little shifter on the tranny hump from the factory. I routinely drove with me and two pre-teen daughters in the cab and the 4wd shifter on the floor was not an issue. You do not need buckets or a floor tranny shifter to have the 4wd lever on the hump. It's your money and time, though.

I don't think I would trust the 2x6 without also running "legs" to the subframe/frame lick a traditional slider bar.

go to the truck section of your local McAuto parts place ( whatever one you have near you) and pick up the Chevy shackle set they have laying on the shelf in their little truck section display. Pick up some 2" front spacers from any number of sources. Should have about $100 in the lift. I missed the 15" rim part and read that as the much more common 265/75/16, which is 31.6" tall- what most tire companies "32's" run height-wise.

Sheeple have to have whatever the marketers tell them is hot right now: the "i" thing is a current one. Just like "HD" was and so you even get cheapo "hd" sunglasses. :roll: Or how adding the term "2000" to any product made it seem cutting edge and new...until 2000 came and went. Apple may have started the "i" fad and gets a pass for that being their marketing gimmick for that reason. But all of the copiers are just going after the hipster doofus's who have to have the "latest"...

Although a good product, Treadwrights aren't really "made" in S. Dakota but are more precisely "re-made" as they only offer retreaded tires. Not knocking them but I think it is something that should be mentioned. The Michelin's wear like iron and will give you plenty of life but IMHO are limited to pavement only. They may be suitable for gravel, IDK. But they come with a high buy-in. Walmart does not make tires or anything else. They use their huge buying power to get products made to their specifications, which is generally just a price point. This does not usually bode well for the quality of their products IMHO. Manufacturer's cannot afford to ignore the huge Walmart market and bow to their pressure even if sometimes the product is not something they they would attach their name to as a stand-alone. I have zero experience with the Walmart-only Wrangler Authority (http://www.walmart.com/ip/Wrangler-Authority/11983156) tires mentioned but note that Goodyear does not offer them anywhere else. And never have. Walmart does offer several other Goodyear tires, though, including Wrangler MT/R's. They are not nearly the bargain that the Wrangler Authority is as they are the same Goodyear's available everywhere else and are not Walmart-only spec. I have had numerous Goodyear's in recent years, including the vaunted MT/R, and have been very disappointed with all of them. I will not buy another Goodyear tire. I have had good luck with ,and have recommended to others, various Cooper tires and never heard a bad word about them. The General Grabber at/2's are another tire with a good rep. and also offer some level of off-road ability.

That is the most desirable rear axle and that is less than half of what I usually see them go for..

Thanks for the info......I'll have to have the rear shaft cut down anyway so I'll just go from there

The 231J I got for my 4wd conversion is a later style with a "boot" on the rear output as opposed to a metal "cone." Will this cause me any issues? Thanks

Most 265/75/16's are closer to 32" . If you are running stock rims i can't imagine them not rubbing at or near full lock, especially going over a higher curb apron or such. My 265/70/16's will and they are about 31"

R.I.P. Joe

D41 sure was a weak link. But those early D44's weren't much better. I swapped in a 225 out of a '67 jeep in my Flattie and it busted rear ends like they were D35's :D

A common issues is that the body side mount for the track bar is wallowed out. I hate doing anything that may point the finger at what many consider a lousy company but make sure you check that out.

I was thinking 3A due to the windshield