Marine1Texas

If your hilly yes a 4.10 would be a good choice. I like the 4.10 all the way around anyway. The one reason I went with 4.10 even on a flat area, it added back what got taken away with the 31's. Are you going to get a d35 with 4.10 or you going to regear? A lot of people are against regearing, since the dana 35 is considered weaker and not worth it. One can make a case either way. If you have the 3.55 in there you can get new ring and pinion gear and bump it up. I think if you can find a dana 35 or maybe even a dana 44 for a good price it will be well worth it, then doing a regear. Not everyone is skilled even who do diffs for a living. I have regeared both of my d30 and d60. My 87 had the d44 from factory, so I just went with a thick gear on it. Took me 5 days to get it just right, so no whiney noise. My 88 had the d35 and we searched for a d44 for 4 months. The 88 has the 4.6 in it so I was for sure not going with another d35. That truck I use to pull trailer with 10 feet tall hay bales from the back up to staging area. If you do have a regear and not a axle swap, Find some one with a good long record at doing jeep diffs. If it is not right, you can get a chipped tooth before you know it, or it can be very noisy. If you plan on regearing try out RWKHausSupply.com. Robert runs it and can get you a good deal. He knows all you will need to know about regearing it.

My 88 4.0 with 3.07 switched it to 3.55 and the mpg went down by 1 or two it not much difference same tires. Now on my 87 4.0 that had 3.31 went to 4.10 when chipped a tooth had 235's to 31 I have a lot of gunt now, however a loss of 4 mpg. I know everyone is a expert, and everyone been doing everything for years, and master mechanics (sarcastic). These are what I have come to in the 6, 4.0's all non HO but renix, for here I need to be above 1850 and below 3000k to stay in half way mpg. I also am in a area that speeds are much fast, less stop and go, that is pretty flat. I had a 1984 XJ 2.8L carbed and it was great at 55mph up hill or flat. it had the 3.55 with A904 and 215's standard from factory. However that $#!& engine blew up at 105k My Wife hated driving it, so slow. In those days the speed limit in Texas maxed at 65 during day 55 at night. 70 was the fastest that thing would go to the floor and it was screaming around the 3k rpms. I just wonder if that thing had a over drive it would of been able to handle 70 easy. since the highest of tq was at 2400 and it dropped off fast at 2800 rpms, the HP kept going all the way up to redline I think 4700 or so. Then again it really was only built to do 55 anyway. I still waiting for the guy who was inquiring to give more updates.

I was thinking he wanted better mpg, that is why I was shooting for lower Rpms. If one is fine at running 3k or slightly higher at 70 mph that is ok and yes it will not burn engine up, if everything is in good working condition. You should be able to find 4.10 very easy. The 3.4 does have a good amount more of torque so you will have better PEP even staying at the 3.55 you have now. Here in N.E. Texas 70mph is what you do on th 75, 35, or 635. You have to do 75 to 80 if your out of the city area or get run over even by the big rigs. More info will get better answers of course. Area where you live. Here it is low altitude and pretty flat. Also looking for better mpg, and how often you drive highway. Around here I spend 50% driving in low 2wd at 5 mph. 25% driving 55 mph local roads and 25% driving 80 mph on interstate. Sent from my ASUS_Z00AD using Tapatalk

Mark if I remember right that 904 is a 3 speed auto, so you should have at least a 3.55 in there. 70 is pushing the rpms on that thing with anything 3.55 and above. you should not be over heating that could be that sprayer and bad cooling flow. you would have to figure that out. If you have 3.55 with say 225/75r15 your running 2950 rpms. If you have 3.07 with say 225/75r15 your running 2550 rpms. However with a auto you going to loose big power on take off if you put 3.07 in there. no recommended. With my 31's a 4.10 and standard 5 at 70 my rpms are 2450 however it is a 4.0 with much more torque then a 2.8 or a 3.4. I know you don't want to hear it, but if you want to cruise at 70 you need a over drive. If your upgrading engine, I would look for a cheap upgrade with a overdrive auto. maybe a wreck one that you can pull everything out of. Around here Comanche's are not common , however XJ's are all over the junk yards, and for sale. You can pick a running one up, wreck for 300 to 600 easy.

^ if you have the dash torn down, yes make sure your heater core is up to snuff.

It will be the same as any other HEI with carb. It can be tied in to the current or new XJ harness. With a HEI you just need to use the power that would go in to the old engines coil and it runs in to the new coil, or Pig tails for HEI. On the other side of the pig tail you have a tac wire that could be spliced in, however going from 6 to 8 your tac on your dash would need to be different. HEI systems are one wire and basically just need the power turned on, just running thru ignition system (key), or a relay kicking on from the ignition system (key) if you want to not overload the wiring. While you have your dash out, you need to look at what gauge and how your going to fit all that in. none of the renix or HO gauges will work with what you have, but the fuel guage can be made to work. You will need to setup electric wiring for speedo ( or cable) tac, and if you want oil, temp, volts tied in. just things off the top of my head

Wiring is simple on any auto ac system. a switch that is on your dash turns a relay on, that then supply's the power to engage the clutch on your compressor. As all systems there is a pressure valve on your drier receiver that opens the circuit if enough pressure exists or closes the circuit between the relay and the clutch if pressure is too low. not much to it at all. The relay also turns the electric fan on and off. The only thing extra is on the inside of a vehicle there is a temp switch that will interrupt if the air gets to cold not all have this. Our mjs are the most basic ac systems you can get, you don't even need a harness per say (one wire running from dash to relay under the hood). A relay that connects to a toggle switch on your dash or to your air controls is all you really need (one wire). Most people have the skills to push the button off if it gets to cold. Pulling the power from the ignition so that when the key is off and toggle or which left on, it is off power to the relay. The power coming from the ignition is very low amps, because the harness under the hood is pulling direct from battery source, and low amps from ignition is just to switch on the relay. Just a 30 amp fuse on the power going in to the relay from battery is needed

before I switched to HEI, I indexed it just like in Cruisers tips. I in fact have index 2 different dizzies one old and a new one neither of them smoothed the idle out. As soon as I put the HEI in and timed it, and set the advance curve I wanted, it idles perfect all the time. I don't take the truck out of state or up real high to worry about the timing. It has never run so smooth in all the years we have had the MJ. Also it does not need the full rotation to stat up, it normally starts on the very next cylinder to fire, or maybe 2nd if it is cold meaning below 32. So I see the starter lasting twice as long. I know people say that HEI is not as good as the computer dizzy, however here on the farm pulling 5k around all the time thru the mud I trust it. For me on this 4.0 I keep the Fuel injection system but with larger injectors, have the large over sized throttle body, capped EGR off, direct cold air intake coming from scoop, and HEI. When it go's out if it does, I will do the 4.5 or 4.6 upgrade like I did on my 88 MJ. I will stay with the fuel injection tho.

they make one for the jeep 4.0/4.2 that just drops right in. at summit they have them in stock and not bad price SUM-850047 is what I got. you will need the pig tails too.

My wife's 2017 Chevy Traxs, wife's previous 2009 Chevy equinox, My sons 2008 Sierra 2500HD all have closed cooling system. My 2001 Dodge 3500, the 2017 corvette Z06, 2017 Nissian GTR, then there are all the BMW's and Mercedes. It is becoming more common now days. All the new systems have a better design because the plastics don't crack like the ones in the MJ's and the flat washer on cap don't go out as easy. That is why a good metal replacement is a good idea in my mind!

I always fill to the top on mine. Expansion is not much to be able to push it of. So probably forgot to put it back on. If you got water in the system, I would flush since, you are going to get bubbles to from because of the water which will cause early demise of the pump. It will cause uneven heat distribution in the pump. that is just my 2 cents....

closed cooling system works great, that is why all new cars are switching to them. My 735i BMW made in the 1992 has the closed cooling system and has never had one single problem, as of my closed cooling system on my MJ jeeps. They work great, because they allow for better expansion then a open system. As of anything, they have to be maintained. Allows for temps to stay near operating temps longer with out cooling lower making the thermostat last twice as long. 2nd the jeep cooling system on the 4.0 can easily over cool the engine if it is allowed to do so. The jeep's 4.0 run a 205 to 210 and that the cooling system is well suited for that....

only thing I can see is when your have a heavy load or pulling. My dually handless way better at pulling. From having a two duallys on my farm, wheel bearing wears faster, and you do get a extra flex on your shafts, so they tend to go out faster.

so it is to tight your saying? Mine is that way after a while, I just use some vise scrips to hold just behind the screw. Then it is good to go after a nudge.

Yea 2nd picture and last picture you can see the 2nd tire.

Disconnect the hose and the electrical connector and go for a drive...report back :-) lol flat on the face as he takes off........

Unless you do a cps mod to push it advanced that is the only way to mess with the timing with the ECU. Even if you turned the dizzy, it will retard it. The only way to get around that is the HEI. There are limits to the HEI, however if your wanting to go out side the specs that the ecu handles that is the only way. They do not make mods for the ecu. I found that in the renix, the best for more power and mpg is; 1.) the bigger throttle body with the bigger fuel injectors . possible HO intake 2.) a better air filter system, like cold air. finally the most expensive 3.) the upgraded 4.0 to 4.5-4.6 with the HO head. A better exhaust flow will help as well, but no big gains. In the end it comes down to what you want to use your mj for. Road, offroading, rock climbing, or combo road and offroading. The extra power you gain on any mode only starts to work as the engine revs higher then 2k, unless you do the upgrade in displacement. So it comes down to gearing. If your offroading and want the power you change the differential ratio's. With 3.07/3.08 standard and 3.55 for auto, you can easily put 4.10 or better. This will give you better power at your low end for rock climbing. Then you can change things around by going deeper and adding new larger tires. I found with the 3.07/3.08 a 29inch is the biggest you want to go before you start loosing at highway speeds. However if you say go to a 4.10 then 31 will do very well for you on the Highway and a nice upgrade for offroading. However once you get over that 29 to 30 inch your brakes are not as good as they once were, and you want to think about upgrading at least the master cylinder booster system. Once you are 32 inch and over you will notice those brakes are not going to cut it!

After doing above, inspect around master clutch, then the line that go's down to the slave. I have had this happen and it always turns out to be in the line starts a small leak. gets hot and a small amount of air gets in and fluid drips out.

yes they are bolt on. you can get the piece by piece now to build it. the kits are no longer made. However it shows you how you can do a tubed cone and go to the firewall, or a snorkel or a scoop like I did. You can still find all the pieces but sold as each.

This is the cowl intake. is go to the fire wall. I used this one with a alter end not going to firewall but to a scoop on the hood, So you get true cold air and a little forced air the faster you go.

CPS

looks like it is a drier receiver. However it sure does not look factory. Normally on top of the drier receiver the in and out with the pressure switch . either this is mounted upside down or something else is going on. never mount a drier receiver upside down if this is the case.

Yes both are 4wd ax15's I did forget about the shifter, we just made those up in the garage here at home. Same with the cross member we just made one, we also made a custom one for under the 242, and 231. We tend to bottom out some times when we are pulling heavy stuff across the acres. kook911 - I would fill in that crack on the 3 bolts with some jb weld, let is set for a few days to get nice and cure since it will be thick fill in.( might even fill in a little wait a day and then fill in again. if that is enough fill, Then tap it to the bolts you need. Would not be ultimate fix, of new but would make it last longer. I forget some times we just make things here, and not buy them :) If it slipped our mind we just get to work and fab something up. nothing better then going thru the old metal scrap pile taking something, bending it in to the right shape or welding something new all together In south Dallas off the 175 they have a guy Stan Hopkins that has a crap load of transfer cases, rear ends and a few trannies. He normally carry the AW4 but not the AX15 or BA10/5. He also make new drive shafts. I would check the pick n pull website. they have 3 or 4 in dfw area, and every now and then see something

if you get the 4wd ax15 you could just swap the spline on your current 231 or 242 with a 23 spline. you only need the slave, clutch, and the transmission mount. The holes in the frame are already there for the ax15 mount to bolt up. I know in southern Texas around San Antonio they have a heap full of parts for the xj and mj's. it is just the 400 to 600 mile drive from dfw. I have 2 BA10's in my shed that have 140 to 200 k on them and they shift like butter still. When we started putting these trucks to heavy work is when we put in the new trannies. They are the back up's if the ax15 ever to go out.

with over size tires you will come in to braking issues is one reason people do the brake upgrade. anything 31 and bigger!