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Putting 4.7 V8 from 01 GC into 03 GC

10K views 59 replies 5 participants last post by  Gus9890 
#1 ·
I have a wrecked 01 Grand Cherokee with a perfectly good 4.7 V8, and I am soon to acquire a nice 03 Grand Cherokee with a bad engine, and I am going to put the engine from the 01 into the 03. They are both Limiteds with Quadra-Drive. Until today I didn't think I was going to have any problems with interchangeability, but somebody at work got me thinking that there might be differences between these two years in the engine management systems. Sure enough, poking around on this forum, it turns out there are two different ones, JTech and NGC, and the 2003 might have either. Does anyone have experience with this situation? I have the VIN numbers for both vehicles, can you tell which engine management system it has from the VIN?
 
#2 ·
Can´t help you out with the VIN number, but indeed there can be a difference in the tone wheels of these engines. One uses a 16 teeth tonewheel, while the other uses a 32 teeth wheel. The JTech has a separate PCM and TCM, while the NGC has one controller where all PCM and TCM functions are inside one box.
My jeep (a WG though) is from 2004, but still is JTech.
 
#4 ·
As far as i know there should be no problem in swapping when both are JTech and non HO. Just keep the PCM with the jeep it was in, otherwise the PCM has to be programmed with the new VIN.
 
#5 ·
And a surefire way to tell whether you have JTech vs NGC is the separate transmission control module (TCM) next to the coolant reservoir, like in the middle of the attached picture from my wrecked 01 that will be the engine donor. If it has one, it's JTech. Right? So I just need to look under the hood of the 03 that I will be putting the engine into, and if it's also got the separate TCM, and it's non-HO (which it is, based on the VIN number), then it's smoooooth sailing.
 

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#10 ·
I bought it!

Based on the fact that I know the engines will interchange, I closed the deal on the 03 GC. It's now sitting in my driveway next to the wrecked 01 GC. Today, I removed the radiator assembly from the 01 and put it on jack stands, then I just spent a lot of time looking at it to figure out what all needs to be disconnected. Then it got really cold and I quit for the day.

Hopefully tomorrow I will get out there and start removing the transmission cross member, the shifter linkages, the exhaust system, the engine mounts and the fuel line. Then all I have to do is unplug the various sensors and take it out. Very soon I hope to have the engine/transmission/transfer case assembly out and sitting on the floor of my garage.

Any tidbits of knowledge that others have obtained in the course of doing something like this would be greatly appreciated.

I am both nervous and excited.
 
#11 ·
All right, I've hit my first bump. I need to disconnect the exhaust pipes from the exhaust manifolds. It's got the typical impossible-to-remove rusted-on exhaust system bolt problem, just like any car, compounded by a lack of access. I don't care about the exhaust system in the car I'm removing it from, so I could just cut through the pipes close enough to the engine so they don't interfere with taking it out, but I'm going to have the same problem in the car that I'm putting it in, and I don't necessarily want to destroy that car's exhaust system. Any suggestions? Or is this just a good time to put in a new Y-pipe? I haven't checked prices on that yet . . . .
 
#14 ·
I can't even get a socket on it. The nut is on top, and as far as I can tell, there's no way to access it. I don't know how I would even spray PB Blaster on it, let alone put a wrench on it.The donor car has 192,000 miles on it. Most likely it's got the original exhaust system in it. As much as I hate to spend the money, this might be the right time to replace the cats and the O2 sensors.

Also, I was just out there removing all the sensors, ignition coil wiring, etc. Then I looked over in the vicinity of the transmission control module, and there's a huge wire plug near it, and another electrical connection bolted onto the TCM. After I get the engine out, I bet I'm going to find out that I could have just disconnected the entire engine/transmission wiring harness right there instead of unplugging everything from the engine.

Also, I don't know how anybody can reach the rear spark plug on the passenger side without removing the engine. Also a good time to change those, and put in the absolute longest life plug available, whatever that might be.
 
#15 · (Edited)
I did remove mine a few months back. Didn´t gave any problems to me, but 1 1/2 year ago they where removed as well during the first tranny rebuild and we don´t have cold winters with salt on the roads.
Did you put some PB blaster on them and gave it enough time to soak?
The nuts have a small plate to them, so they won´t turn.
The plugs are not that bad to change. You need a ratched, plug socket, extensions and a flexible joint.
I did change the valve seals a year ago and man, i can tell you that thats real fun, especially cylinder 7 and 8. I made the valve spring compressor myself after i couldn´t get something suitable. The worst thing was to get the valve locks back in place with one hand, while compressing the spring with the other, half laying in the engine bay. I have no idea how many liters of sweat i had lost and how many bad words i´ve said ( or at least thought about some), but i finally succeeded.
Perseverance is the word:headbang:
 
#16 ·
Wiring harness is removable!

So I was in the junk yard yesterday and there was a 99 WJ with the engine removed and a lot of other stuff under the hood ripped out. The wiring harness had been cut at a lot of points from the engine, presumably to help the engine come out, but it had also been unplugged from the vehicle wiring at a few points. It looked like there were about 5 main plugs that would need to be disconnected and the wiring harness could come out with the engine/transmission assembly. I may try this when I remove the bad engine from the 03. It was hard to get some of the connectors on the 01 engine off without breaking them, especially at the fuel injectors. It might be nicer to transfer the harness from one engine to the other when they're both sitting on the floor of the garage.
 
#17 ·
The small red locking tabs from the fuel injector connectors are well known to break, they get brittle due to the high temperature environment. But they are a second lock, so it doesn´t matter that much if they break. Probably the same for other connectors in that same area.
 
#18 ·
Yes! I broke at least two of those red sliding locks when I was taking the connectors off the fuel injectors on my donor engine because they were so brittle. As you say, they are a second lock so I wasn't going to be too upset if they broke off in the recipient vehicle.
 
#19 ·
I think on my jeep most of them broke when i wanted to unlock them. I even searched for new locking tabs, but couldn´t find them and left it as is.
 
#20 ·
Rockauto.com sells replacement connectors for about $17 a piece, which is pretty pricey. From the picture of the item, I can't even tell if it has the red sliding locks or not, but the red sliders appear to be "belt and suspenders" and are not entirely necessary anyway. However, the part is apparently applicable to the following vehicles, so I guess you could find as many of these as you want at the local junkyard.

BUICK (2005 - 2007)
CADILLAC (2000 - 2007)
CHEVROLET (2002 - 2009)
CHRYSLER (1998 - 2008)
DODGE (1998 - 2006)
FORD (2000 - 2007)
GMC (2004 - 2009)
HYUNDAI (2006 - 2007)
ISUZU (2005 - 2006)
JAGUAR (1999 - 2007)
JEEP (1999 - 2005)
KIA 2006
LINCOLN (1999 - 2007)
MAZDA (2000 - 2007)
MERCURY (1999 - 2007)
OLDSMOBILE1990 - 2003)
PLYMOUTH (1998 - 2001)
PONTIAC (2004 - 2006)
PORSCHE 2005
SAAB 2007
 
#21 ·
Success!!

So it turns out that the exhaust pipe bolts were not as hard to remove as I feared. I went out and bought a 1/2" drive 6 point 15 mm socket, so I could apply more torque, and a little U-joint swivel extension, and used my breaker bar and various extensions to reach the bolts, and they came right out. The biggest problem I had was that, after removing the first bolt of the pair on either side, the donut was too loose to keep the self-retaining nut on the top of the connection from turning, so I had to pull the donut down while I turned the bolt. Frustrating but not horrible.

I did spray PB Blaster on it, but I fully expected to snap those bolts, I didn't have any hope that they would actually unscrew, so I didn't give it too much time to work. I literally sprayed it on right before I started loosening the bolts, kind of cursorily. Maybe it helped, maybe it didn't. Right after I finished taking the bolts out on the donor vehicle, I tried to spray a bunch on the recipient vehicle. It will be a few weeks before I get that engine out, so it should have plenty of time to work.
 
#22 ·
Disconnecting transmission and transfer case

So there are a bunch of annoyingly inaccessible electrical plugs on the transmission, three on the driver's side and three on the passenger side. One on the passenger side is almost impossible to reach, and it appears to be connected to an O2 sensor.

On the driver's side are three hard-to-detach connectors, including the mother of all connectors, apparently the main connection to the Transmission Control Module (TCM). Just like the red sliders on the fuel injection connectors, there always seems to be some initial unlocking of every connector that needs to happen before you can get it off, and getting it off involves squeezing the outside of the connector, either near the plug or away from it, depending on whether the tab from the connector is hooking onto the plug from the inside or the outside. You usually don't know what you should do until it's off and you can look at it and say, oh, that's how it was supposed to come off, and hopefully by that time you haven't already broken it getting it off by sheer dumb luck. Any tips or "war stories" on getting these connectors off?

Also, I have no clue how to take the shifter off of the transfer case. On the transmission, the shifter cable appears to snap onto a ball, so it can just be pried off. On the transfer case, there is a much more serious looking clip with a hole in it that fits over a light-colored plastic pin, about 1/4" in diameter, that looks like it has a slight taper. Any tips on how to get this off?
 
#24 ·
Unfortunately I do not. I should check on eBay for one. A part number book would also be nice, so if I break something I can check around for price and availability.

On a good note, I did figure out how to detach the main transmission connector plug and the input speed sensor plug on the transmission. I removed the bracket that held the shifter linkage cable. It was probably going to have to be removed anyway because obviously the shifter is going to stay in the car when I pull the engine/transmission/transfer case assembly. With the bracket out of the way, the input speed sensor came right off. As I noted in an earlier post, I just had to take a guess as to what was involved in removing the main transmission connector. There was kind of a handle that you have to swing away from the connector and down, with it making horrible cracking and breaking noises the whole time, and then the plug slid right off. Despite the sounds, nothing looked broken, so I guess that was the right way to remove it.

Next thing is to remove a similar bracket at the rear of the transmission that holds the transfer case linkage and is blocking the removal of the output speed sensor, and hopefully the transfer case linkage will come off easily after that. Then, it's remove the driveshafts, unplug the fuel line from the fuel rail, disconnect the A/C system (I'm going to use the A/C compressor from the donor engine because the one on the recipient vehicle looks like it's leaking green goo, which I'm guessing is dye that is showing a leak, so I have to break open the A/C system), perhaps disconnect the starter (I'm not sure if I have to), then unbolt the engine and transmission mounts and take it out. I'm targeting this Saturday, March 2, to have it out.
 
#26 ·
Not exactly knowing how the plugs should come off and on top of this the dirt that has collected on the plugs over time, is not making it easy to remove them. I removed my tranny some months ago, but i didn´t had any problems in removing the speed sensor connectors, no brackets in the way on mine.
I had no problems in removing the cable end from the T-case lever. It only has a split pin to keep the cable end in place.
I didn´t see it in your description, but you will have to split the engine/transmission/T-case to get it all out, isn´t it?
 
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