Rockfrog

The Guage sender hole was there until at least 95, the 7120 head HO's had a sensor arrangemet much like the Renix. Temp sensor in head and ECT for PCM located elsewhere. In 96 the 0630 head was used but I believe the early versions still retained the rear sensor hole (eliminated in later castings). Unless he used a 97 or newer motor the sender should be there for the Guage and the Renix ECT will fit right into the thermostat hole (if you remove the wires from the harness bundle there should be plenty of length to relocate it, in fact slightly too much if memory serves). Or, just plug it with a 3/8" NPT plug.

Having had the truck for just a month, then having the trans powerflushed ... Could possibly be the root of the issue, the AW4 does not tend to respond well to them. If there was a regular service schedule prior, yes, but if none, it may have caused the issue. But, check the TCU, fuse, and wiring first ... Located as indicated above.

You missed the 4wd Comanche in the first post. Assuming ... And we know how that works ... He has a 4.0, the trouble could be with the TCU (Transmission, Control Unit). Check the fuse and the connector. Is the fluid level still good? How was the fluid changed ... Powerflush or simple drop pan and refill? Or it's low on fluid, or the Torque Converter is going ... Or, or, or ... A lot of ors left without further details.

I just pulled my spare out for the last time and sold it last week. I'm rolling on 32" tires now so no plan to reuse it again, since a 32 is too big to squeeze up in there. It functioned perfectly although it does have some crust. Only problem ... I'm up in Canada. But if you want it, shoot me an offer. Shipping will likely run about $30 or so though. Gov't has to get their cut somehow it seems. I'm at work until Tuesday night but can pull it Wednesday.

FYI - most truck transmissions in the 70's and 80's shipped from the factory with SAE 30W inside. This was the standard lube for the T18 and NP435 at the time. The FSM for the AX-15 equipped vehicles included a misprint specifying a trans fluid, which also included phosphorus/sulphur EP additives which are corrosive to yellow metals. The correct spec fluid is GL3/4 which is the basic 75w90 off the shelf run of the mill gear oil. Nothing fancy about it. Chrysler changed the spec to 10w30 so as to end the confusion over the matter (which they themselves caused, yet never covered as a recall, opting instead to add a slip in addendum page to the owner manuals post 1993 when the issue was finally correctly indentified) more than to actually save the transmissions.

You could wire them directly ... Soldering works best ... But adding a connector make repair works less painful. Grab a weatherpak connector from so place like Napa, or scavenge a good connector from the JY. Or as long as it has some good pins, you could rebuild it as well ... I've rebuilt a few connectors on my MJ and my XJ using parts from better condition harnesses.

Use the cables from a Liberty or an Explorer, passenger side. The Grand Cherokee cables were too short even for my Cherokee, used an Explorer passenger side and I have so much extra length I had to loop it. Should work fine for an MJ (I plan to use the same when I finally convert my Comanche this summer).

The only difference between block and head mating is the 0331 incorporated locating dowels, the use of a couple studs will solve that (I made mine from a pair of old head bolts the first time I swapped a head, didn't bother after that one though - I also put a 7120 on my 88 Renix block). The head mating surfaces are exactly the same, the block you have may even be as old as 98 or more. The only thing you have to sort for sure is the exhaust manifold end of things going with the 7120 head. Put the 7120 next to the 0331 and you'll see why. Was the best peace of mind move I made back in 05 when I dealt with this issue, been going strong ever since. Also had the added benefit of letting the engine breathe better (the 2000 stock use to "wheeze out" on the highway, after it kept pulling right to recline - yeah, I was younger then).

The change you refer to is also a change in the overall block design. In 2000 the 4.0L block was redesigned considerably rendering it nearly incompatible with earlier vehicles. The mounting positions and filter boss locations, along with the addition of a spring tensioner were among the biggest changes. This change was only implemented on the Wrangler (TJ), and Grand Cherokee (WJ) platforms ... with the XJ Cherokee continuing into its final year with the same base block design of previous years. As stated previously ... the water pump from my 2000 XJ was exactly the same as the water pump from my 1988 MJ and it resides there still to this day. I have had no issues with AC DELCO and CARDONE pumps thus far (I've owned my XJ since 2002, and changed the pump three times twice "because I was in there anyway" keeping the pump as a working spare).

Yes, the 93-98 Grand Cherokee 4.0L is the same motor used in the MJ/XJ/YJ/ZJ ... Things got funky after that though. There were even a few AX-15 equipped ZJ's produced in the earlier years.

The intake will fit fine, the issue is the exhaust manifold from the 2000/01 will not seal to the earlier heads due to Port mismatch and location difference. You need to swap to the later manifold and down pipe to use the earlier heads. The 91-95 7120 casting is the best choice for a head with the 0630 being essentially the same minus the temp sender port at the back of the head (the 7120 flows better than the 0630 as well but since it's going on an outdated tractor motor it isn't an issue). The TUPY head was intro'd in 02 to fix an issue ... "That was not an issue" as far a Chryco was concerned. There is actually more material between the 3/4 cylinder to lessen the chance of cracking due to a thinness in the casting at that point after the 0331 redesign. My 2000 XJ has been running a 93 7120 head since 2005 when the original head cracked at normal operating temperatures. Currently the motor has 243K kms and the head cracked at 141K. The only parts I changed were the head, valve cover (because I liked it better) and exhaust manifold with down pipe to the trans crossover. You will aslo need to to reshape the driver side motor mount shield (one straight cut, fold over and rivet together is all pretty self explanatory when you see it). If you use the stock 00 valve cover with the earlier head you need the earlier valve cover gasket to match it. The 0331 valve cover gasket is specific to that head. You will also need to make some simple brackets to hang off the valve cover bolts to hold the coils rail in place (I made mine with a hand drill and a hacksaw out of home Depot aluminum). Or, you can swap to a Viper coil (the 6point coil) and add a set of plug wires, just need to extend the stock coil plug wires to wherever you mount the coil pack (the connector and pinnout are the same).

IIRC ... You have a Renix, the rear nipple/hose assemvly simply pops out. Careful not to snap it. The front one is a molded part of the front Vacuum harness. If you take the valve cover from a later model motor and swap that on ... you upgrade to the later style CCV which was less clog prone (due to larger orifice and hose size). The 96 and later valve covers used the least problematic style with parts still readily available cheaply. Search here for 'Vacuum Harness' and it should bring up a series of Dorman part numbers to order to replace the complete Vacuum Harness/CCV system. A further bit of searching will also net some actual CCV to PCV conversions as well, simple, but no more effective as they both do essentially the same thing.

You can also find similar info looking at 84-86 Cherokee 4.0L swaps as well. The firewall was changed for 87 to make room for the added length of the 6cyl. Even then it's still a tight fit stock. You will have to do some cutting and welding to make it fit.

From what bowels of hell did you pull that XJ from ... !?! Only my header harness plug was that bad and I swapped to the '00 harness plug when I did my header panel swap. I'm afraid to think what the rest of that vehicle is like.

Well, I was swapping wheels on the Comanche and ... Well ... I just couldn't stop myself ... 225/65R18 challenger/charger wheels front, 255/75r17 JK tires on charger 2535's rear. But as for fitment, the 255/75R17's sit right at the edge of the flare, and actually look like they belong there. They do measure out to a 32" tire though. And I'll probably add another Inch to the front lift. I can go grab a good corner shot, should be enough light yet. Got one -

That's exactly where they Crack, when mine went I looked in the fill hole and there was a 'nice' green line, there is no number to be seen in the fill hole. The casting number is on the outside of the valve cover. On the head, not the block. The only head used in 2000/01 was the 0331. The TUPY didn't show up until 2002.

For clarity I run 30psi on the highway, and 10psi off road. The chalk test would have me using just over 27 psi on these tires. Please don't compare me to a street car, it was built for the trail first, and to get me to work second. My methods are tried and true, and have been in use for damn near three decades by myself and others, no tires blew up causing the death of twelve busloads of innocent kindergarten kids. The world did not end, hell did not freeze over, I just got to work periodically, and some trails were conquered. Would I do the same thing on a Honda? No, and currently the MJ is street bound and acts accordingly. And this was 20psi 'cause I was being lazy and didn't want to have to air up later when I drove home.

Yup, pop out oil cap and look down through, that's right where it cracks. Dealt with it on my XJ back in '05. You can replace the stock coil rail with the 6 pack coil from a Viper, and a set of plug wires. Just need to extend the stock wiring to where you mount it. Also helps make diagnosing some issues easier.

I run my 35x12.50R15's on my XJ on 15x7 Ultra wheels ... Performance is just fine, both on and off road, although I do realize I'm not in a Ferrari. And they have held the bead as low as 5psi (actually had one burp down to 2psi before, that got close) although I generally run 10psi. Old school poor man's beadlocks, as hick as hick can be I guess.

Yes.

Me too, too much drink not enough smilies ... All good bud. Never a harmful thought in jeep land. Edit - today I like spell check, took me three retries to get this right.

Yeah, well, I like my mess.Relax, I'm Renix too, I even tried to clean it up and made it messier, so I became one with the mess. Rather have my Renix than HO, far simpler. Is it just me ... Or does that sound like there is a need for a support/rehab group in our future ...??

They are just standard relays, doesn't matter what the label says. That mess is the Renix equivalent of the HO era PDC.

I have the water pump off my 2000 XJ 4.0 block currently cooling my 1988 MJ's 4.0 Renix block. Didn't notice anything different from the one I took off.

That would have been for corrosion reasons, steel and aluminum means the steel will rust and the aluminum will corrode faster ... Although in both cases it is not a quick problem unless you live in the rust belt (if so it's more likely the truck will rust faster anyway).