4.0 to 4.7 HO drivetrain swap - Page 2 - JeepForum.com
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Unread 07-17-2013, 08:42 PM   #16
asatxj
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Not all 4.7s have hydraulic fans. I have two 2000's that don't and an 01 and a 00 with 4.0's that don't.
That said, I have a complete donor vehicle (hit in lt front) harness, computer, transmission and transfer case for a 4.7 swap. I also have a 4.7 that has bent valves due to a mistake changing the timing chains. Grrr!

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Unread 07-17-2013, 09:30 PM   #17
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Yeah I studied a 99 with the mechanical fan for a bit today at the junkyard. Idk I'm kinda agitated with that rudimentary setup although it's pretty much fault proof and would be easy to convert to. The Taurus fan conversion with the high/low switch is attractive but I want some sort of automatic, stock-like function. I'd like to be able to use the PCM's signal for the hydraulic fan solenoid still, hoping to prevent a CEL and have some automatic fan control. I keep reading about people hooking an electric fan up to the hydraulic solenoid harness but I suspect they're just tapping into the power from the downstream O2 relay and not using the control signal.

After studying my FSM, I realized both fans use a PWM signal for fan speed control from the PCM on C2 pin 17. They have different names for this circuit though? (4.7 - ENGINE COOLANT TEMPERATURE, 4.0 - RADIATOR FAN RELAY CONTROL). I'm wondering if I couldn't just retain my current electric fan setup and wire up the signal wire intended for the hydraulic fan relay to my current radiator fan relay. Then I could convert to the mechanical fan and essentially have the stock/dual cooling setup of a pre-01 4.7L. I'm not sure if these signals really are identical or if they are different enough that I'll just end up frying something...
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Unread 07-18-2013, 03:27 PM   #18
rm2001wj
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You are correct about both fans using a PWM signal for speed control. However, only in the 01 FSM can you find a discussion of the hydraulic fan operation. I have attached images of two pages from the 01 FSM that you might fine useful. BTW, you will probably guess correctly that JTEC = PCM for WJs.

I think you are probably correct about using the donor PCM PWM signal to run your 4.0 electric fan. I believe it would work.

For testing purposes, I have heard that removing the engine coolant temp sensor signal from the PCM will turn the fan on max speed. It also stands to reason that varying the sensor temp will give a varying sensor signal and should cause the fan to speed up or slow down. For this the fan doesn't need to be installed, but you do have to be careful.
clipboard01.jpg

clipboard02.jpg

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Unread 07-18-2013, 05:22 PM   #19
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Awesome, thanks for confirming that. It looks like it should work just fine wired up like that. So if the hydraulic fan solenoid operates at 100% without the "engine coolant temp" / PWM signal, the PCM is essentially cutting power to the solenoid with the PWM signal in increments. That's how it knows when that circuit is disconnected or malfunctioning, if it doesn't see voltage on that circuit? So in theory you could satisfy the PCM by just connecting the two wires on the hydraulic fan solenoid? Or better yet in my case put that signal to proper use with the electronic fan relay. Good stuff.

So having deemed the engine cooling roadblock out of the way, I bought the radiator and mechanical fan / pulley from the 99 4.7 WJ at the junkyard today. The only other thing to straighten out with the swap now is power steering since there doesn't seem to be an easy and reliable fix for using the 4.7 pump with the hydraulic fan eliminated. Since the pre-01 P/S pumps are the same for both engines, I should be able to bolt up my pump, although it may need a different bracket, I'm not sure yet. Absolute worst case I will have access welding equipment at my uncles shop and can modify / fab a new bracket if it comes to that.

Everything else seems like it is a go. Looks like the connection to the fuel rail is the same and in essentially the same location on both engines. I decided to add the entire exhaust system to the swap list while we're at it. Other than being newer, the reason being our Jeep is CA emissions, so it doesn't have an O2 sensor bung after the main cat. After studying the 99 4.7 WJ in the junkyard today, everything is identical under the hood, like the EVAP system. The 04 is a bit different so we'll see what if anything I decide to update.

Looks like I've thoroughly analyzed this through... hopefully the auction for the donor car I'm after on Monday stays within my budget and I can win it. Since the front end and interior are pretty much beyond feasible repair it shouldn't get much if any attention. Even if I don't win this one, I'll find another soon. Then nothing to it but to do it!

Last edited by CopperDeer; 07-18-2013 at 08:53 PM..
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Unread 07-23-2013, 03:45 PM   #20
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Got my donor vehicle today - let the swap madness begin. Going to start a new "swap build thread" once things get underway next week.

The logistics on getting the 4.7 HO donor I wanted just didn't pan out, although it's a shame because it only went for $450 winning bid (plus fees out the wazz of course...). Actually got an 04 WJ in much better condition, has the standard V8 though. My power gains are going to be more like 20% than 35%, takes a little of the value out of the swap but we want to run 87 octane anyways. Winning bid was $850, after fees and renting a trailer and fuel costs it's in my driveway for about $1200 into it. Little more than I was wanting to pay, but it's a better parts vehicle as a whole and will yield probably an even higher ROI.

Incredibly clean interior! If it wasn't a barebones Laredo and quite as smashed up I might be swapping parts in the other direction It has 143k, more than I had hoped for but all the fluids look fantastic. The icing on the cake - that hydraulic fan assembly that was such a concern looks like it will be salvageable. It spun freely by hand and didn't get smashed up too hard. In fact the A/C even has full refrigerant pressure still. Luckily I already got a radiator b/c it's toast. I have not had a chance to get jumper cables out and start her up yet, tonight though

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Unread 07-23-2013, 03:52 PM   #21
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Quote:
Originally Posted by CopperDeer View Post
Got my donor vehicle today - let the swap madness begin. Going to start a new "swap build thread" once things get underway next week.

The logistics on getting the 4.7 HO donor I wanted just didn't pan out, although it's a shame because it only went for $450 winning bid (plus fees out the wazz of course...). Actually got an 04 WJ in much better condition, has the standard V8 though. My power gains are going to be more like 20% than 35%, takes a little of the value out of the swap but we want to run 87 octane anyways. Winning bid was $850, after fees and renting a trailer and fuel costs it's in my driveway for about $1200 into it. Little more than I was wanting to pay, but it's a better parts vehicle as a whole and will yield probably an even higher ROI.

Incredibly clean interior! If it wasn't a barebones Laredo and quite as smashed up I might be swapping parts in the other direction It has 143k, more than I had hoped for but all the fluids look fantastic. The icing on the cake - that hydraulic fan assembly that was such a concern looks like it will be salvageable. It spun freely by hand and didn't get smashed up too hard. In fact the A/C even has full refrigerant pressure still. Luckily I already got a radiator b/c it's toast. I have not had a chance to get jumper cables out and start her up yet, tonight though

Looks good! It doesnt look like it should be banged up. And if the fan spins freely than most likely its just fine. I could tweak the plastic on mine when it was out and the fan blades would start whacking the sides. So in my view, if it spins freely its good.
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Unread 07-23-2013, 04:10 PM   #22
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The fact that the condenser held is enough proof for me that it should be gravy. We'll see for sure if one of the lines didn't get kinked up once I get it fired up a little later but I'm very happy and excited for this project.
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Unread 07-23-2013, 05:15 PM   #23
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Took a bit of cranking to get it started initially, probably had to build fuel pressure. Some tail pipe smoke and chatter the first couple seconds but it's been sitting over 6 months so that's to be expected. Runs fantastic. Transmission seemed fine around the culdesac real quick. Quick as hell, our 4.0 must be really jacked because this feels like more than twice the power, not 20% more. Started it a 2nd time with the temp sensor unplugged, heard the fan go ballistic but it started kicking up some broken plastic so I shut the engine down real quick. Small oil leak on dr side valve cover. I think I can manage just that! Now it's time for the real fun...
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Unread 07-23-2013, 08:39 PM   #24
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Dont think any swap is going to be easy.

Remember the 4.0 has completly different PCM, wiring harness and sensors as well as completly different exhaust system.
The transmission in 4.0 is 4 speed auto and the 4.7 has a 5 speed auto with different bolt paterns and mounts.
The 5 speed requires different TCM, wiring harness and speed sensor.

Unless you spend $$$$ and go all aftermarker controls you will basicly have to rewire the entire jeep.
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Unread 07-23-2013, 11:41 PM   #25
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Quote:
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Dont think any swap is going to be easy.

Remember the 4.0 has completly different PCM, wiring harness and sensors as well as completly different exhaust system.
The transmission in 4.0 is 4 speed auto and the 4.7 has a 5 speed auto with different bolt paterns and mounts.
The 5 speed requires different TCM, wiring harness and speed sensor.

Unless you spend $$$$ and go all aftermarker controls you will basicly have to rewire the entire jeep.
Or just swap the engine and transmission harnesses.

OP, that donor doesn't look too bad. Any chance of just rebuilding that one?
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Unread 07-24-2013, 05:55 AM   #26
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I have a 4.0 that's my DD and a 4.7 that's being parted for my son in law. I think that it would be quite doable with them side by side. If you aren't in a hurry and take good notes you shouldn't have too much trouble. One thing you need to know is that you will need to swap the ignition or have the pcm reflashed because the 4.7 pcm will think the 4.0 key is wrong. Plan for that one. Take pictures.
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Unread 07-24-2013, 06:31 AM   #27
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The donor car actually looks a lot better than it is, that's her good side after all . I think it ran over like a Honda Civic or something more on an angle on the driver's side than straight on - the deeper I tear into it, the more damage I'm finding underneath (but the motor / oil pan is fine). Most of the steering / suspension would probably have to be replaced as well as some pretty significant work to straighten out the driver's side damage.

I am using the matching SKIM module with it's key taped to it from the donor car in my car until I can get a key flashed to it's SKIM and cut for my ignition. That will allow me to use the PCM & TCM from the 4.7 no problem.

So far everything is actually looking pretty easy, easier than I ever expected. The only difference is the wiring from 4.0 to 4.7 on the 3 connectors on the harness that goes through the firewall. I believe if using the same year 4.0/4.7 it is the same or very, very close. I'm not concerned b/c I have found more examples of people doing a 4.7L swap lately and not mentioning extensive chassis rewiring. Worst case I have an FSM and will hack up the 4.7's harness to work with my 4.0 chassis.

The condenser and hydraulic fan are 100% fine, just a very tiny bit of the plastic shroud broke off. I already bought a replacement radiator for the 4.7L last week. I'm pulling the drivetrain in my garage and throwing it in the back of the Jeep to do the actual swap in my uncle's shop. The only mechanical/physical differences are the throttle cable(s), vacuum hoses, and fuel line routing.
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Unread 07-24-2013, 07:28 AM   #28
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Those connectors from the drivetrain harness to the chassis might be the kicker. Hawking over the FSM they're mostly the same circuits, power supplys for various sensors and what not... but some are on different wires/pins from 4.0 to 4.7. Maybe 5-10 differences in all. Mostly for the TCM I think. I guess I'll have to study these more and make changes to my 4.7's harness to play nice with my 4.0 chassis/BCM... Not enough of a difference to make swapping out wiring under the dash worth it obv
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Unread 07-24-2013, 10:53 PM   #29
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You could just swap all harnesses, SKIM module, and keep the tumbler keys the same so you don't have to replace the driver's door tumbler keys.
I'm real interested in the swap and I will be looking forward to it's completion. Good luck.
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Unread 07-24-2013, 11:54 PM   #30
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There's a little more wiring necessary then I had thought or hoped, but it's nothing serious. The engine would probably even run without it but the transmission won't be happy, maybe even not functional.

I'm just going to make the necessary changes / additions from the drivetrain harness to the chassis by running a few new wires. There's around 10 mismatched or missing wires, mostly transmission related. I need to get an 04 FSM, I have an 01 FSM and it seems to match my 99 chassis's wiring perfectly but there are many discrepancies between it and the 4.7 engine harness.

I'd love to cut the pigtails I need from a 4.0 at the junkyard + my donor and just build a 4-6" long "conversion harness" with the 4.7 chassis and 4.0 engine connectors. It would be nice to avoid hacking up my WJ or the 4.7 engine's wiring and the next time I want to pull / swap the engine it won't require this process all over again... hopefully that's quite a while down the road but still. Screw it, I'll just cut the connectors for the jumper harness off my 4.0.

Donor drivetrain is almost out. Getting the hoist tomorrow, then it's off to the shop for a week or so tomorrow night. I probably won't be online much but I'll be taking pictures and notes and will start a new "cleaned up" thread with the specifics when I get the chance.
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