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Discussion Starter #1 (Edited)
Hello everybody!

I've been eyeballing this forum for a few years now but haven't signed up until just a couple days ago, because now i have a project!

I own the 2008 Jeep Commander Sport 4.7. It will soon be a 6.1. About a week ago I ordered a remanufactured long block from 3rd Strike Performance, and a number of other parts. I still have more to get but I could use some help. The most I've done on a vehicle was a rack and pinion replacement on a foxbody mustang, I've never taken on a task quite like this one, but I'm mechanically inclined, and I'm a nuclear mechanic in the Navy, so I'm confident I can get it done.

Here are the parts I know I need and/or I'm using:
Long Block (ordered)
Valve Covers
Coilover Covers (ordered)
Fuel Injectors (ordered)
Alternator 5.7/6.1 (ordered)
Compressor 5.7/6.1 (ordered)
Power Steering Pump
ECU 5.7 Commander (ordered)
Wiring Harness 6.1 GC (ordered)
Intake Manifold (ordered)
Exhaust Header (ordered)
Throttle Body
Fuel Rails
Oil Pan 5.7 Commander (ordered)

I've got a little over $2k left in my current budget until I have to start going from paycheck to paycheck. If I'm missing anything or anyone has any suggestions, it would be greatly appreciated. I intend on documenting as much as I can and updating this thread as much as I can with lots of pictures when I start this undertaking. I am serious about this project, it's not going to be a dud where I just say "HAHA! I wanna do a SRT swap, into mah Mander!" and then not follow through. I've wanted to do this for a WHILE, and I can finally afford it. I have read the other SRT swap threads by Saturate and whatnot, and while helpful, didn't have everything I needed. I'd like to know more from a technical standpoint.

Thank you all in advance!
 

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Holy smokes! Ballsy move tackling this project. Hope you keep us updated. Good luck.
 

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Just an FYI, the 4.7 and 6.1 use different transmissions.
But does the 4.7L transmission bolt up to the 6.1L engine? I don't know, I suspect yes, I think they kept the same bellhousing pattern for all the V8's.


As long as they've been doing engine swaps, people have been using transmissions rated for the less powerful engine. Usually with an Automatic Trans, the damage that comes from using more power than its rated for is that the trans wears out much faster.


Definitely add more cooling for the trans.


I'd think the biggest problem may be, can the front drivetrain (driveshafts and axle/diff) handle the power of a 6.1L?


The only option I see, if you want it to bullet proof, is transfer the entire drivetrain of an SRT Grand Cherokee. It had a different XFR case and driveshaft's to handle the 6.1L power, as well as the trans.


The biggest problem that you may encounter is incompatible software and communications between the different control modules for Engine, Trans, Drivetrain and Body.
 

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Discussion Starter #5
But does the 4.7L transmission bolt up to the 6.1L engine? I don't know, I suspect yes, I think they kept the same bellhousing pattern for all the V8's.


As long as they've been doing engine swaps, people have been using transmissions rated for the less powerful engine. Usually with an Automatic Trans, the damage that comes from using more power than its rated for is that the trans wears out much faster.


Definitely add more cooling for the trans.


I'd think the biggest problem may be, can the front drivetrain (driveshafts and axle/diff) handle the power of a 6.1L?


The only option I see, if you want it to bullet proof, is transfer the entire drivetrain of an SRT Grand Cherokee. It had a different XFR case and driveshaft's to handle the 6.1L power, as well as the trans.


The biggest problem that you may encounter is incompatible software and communications between the different control modules for Engine, Trans, Drivetrain and Body.
So my jeep uses the 545RFE trans which does bolt right up, in fact, for many SRT drop in kits sold by many retailers online they will include the 545RFE and I've read that it can safely handle up to 600HP. As for the control modules, this is why I'm using the 5.7 ECU for a mander, still controls the transmission from within, can handle anything else related to my mander, as well as just have a reputable shop just tune it for the engine. Also, my jeep doesn't have 4 wheel drive :frown2:. I bought it when I was 19, it was what I could afford at the time, none the less, I fell in love with my mander and can't imagine getting rid of it at any time in the near future.
 

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That simplifies the swap though, you just have to worry about the driveshaft to the rear. That might be one thing to consider, getting a stronger custom rear driveshaft.


Most auto trans can easily handle more power than they are rated for, but it gets them hot and wears them much more quickly. If the stock 545RFE is factory rated for 450 ft-lbs or HP, what ever, that rating likely means it can handle that power and last 100k miles or more. You increase the power 25% over the factory rating, it might NOT snap anything in the trans, but it ain't going to last 100k + miles. Adding more cooling will reduce the extra heat from the extra power that will shorten the life of the trans as well. Also, fluid and filter changes on the trans more often will help it live longer under the higher stress.


Since the Commander Stock recommends only Synthetic Axle fluid and changing it every 15k miles for severe usage, but lasts the life of the vehicle for normal usage, I'd consider rear axle fluid changes often, and using the best Synthetic Fluid, like AMSOIL in the right viscosity. The pressure on the ring & pinion must be pretty high if they recommend changes that often for severe conditions, and adding a more powerful motor is just going to increase the pressure on the gears.
 

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Oh, and yes, I've seen that strategy about re-using the PCM for the old engine on the new bigger engine, if they are compatible, to keep the communications working properly. Especially if use a tuner program to alter the tables in the stock PCM to adapt it better to the new motor it should work out better than trying to splice a PCM for another vehicle into the data network, you can get yourself into a corner where only a Chrysler lab could develop a fix to get you out of.
 

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Discussion Starter #8
That simplifies the swap though, you just have to worry about the driveshaft to the rear. That might be one thing to consider, getting a stronger custom rear driveshaft.


Most auto trans can easily handle more power than they are rated for, but it gets them hot and wears them much more quickly. If the stock 545RFE is factory rated for 450 ft-lbs or HP, what ever, that rating likely means it can handle that power and last 100k miles or more. You increase the power 25% over the factory rating, it might NOT snap anything in the trans, but it ain't going to last 100k + miles. Adding more cooling will reduce the extra heat from the extra power that will shorten the life of the trans as well. Also, fluid and filter changes on the trans more often will help it live longer under the higher stress.


Since the Commander Stock recommends only Synthetic Axle fluid and changing it every 15k miles for severe usage, but lasts the life of the vehicle for normal usage, I'd consider rear axle fluid changes often, and using the best Synthetic Fluid, like AMSOIL in the right viscosity. The pressure on the ring & pinion must be pretty high if they recommend changes that often for severe conditions, and adding a more powerful motor is just going to increase the pressure on the gears.
This is good info, thank you. Hadn't thought of all this nor did I know about these kinds of things. I already have a transmission cooler, but I guess I could upgrade soon. Just got the 5.7 ECU yesterday. got it for a steal at $65 off car-part. Ordered used fuel injectors (for now) off a website for $120 the other day. I'll upgrade when my budget builds back up. I know I've got to finish the project at hand first, but next year I'd like to supercharge this thing!
 

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Discussion Starter #9
Does anyone know if the odometer info is stored on the gage cluster or the ECU? I hadn't thought about it until a couple days ago, and I hadn't looked up the applicable laws in WA yet about any possible issues.
 

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Hmmm, the PCM does store the mileage in its non-volatile memory. But it varies from vehicle to vehicle, many the mileage in the PCM is just for maintenance and calibration reference. I have swapped out PCM's in a '99 Neon and it did NOT change the mileage in the odometer, but it had a electro/mechanical driven odometer. In most cases its stored in the instrument cluster, but it is possible it could be read from the PCM.


The Dealer has the tools to program the mileage into the PCM, I'm sure they can do the same Instrument Cluster as well. You're going to have to take it to the Dealer or someone with the tools to program those things anyway, so I wouldn't worry about it.


The PCM has an anti-theft measure where it will refuse to start unless the VIN# programmed into it matches the VIN# on other control modules. So, if you do this work yourself, you're going to have to either get it towed to the dealer, or try to drive on the 4.7L PCM controlling the 6.1L hemi motor to the dealer. Just tell them to do the mileage in the PCM and odometer also.


Look at the title transfer section of your title or registration, it usually will talk about the State Law about Odometers. Every state I have registered vehicles, (never WA though) it talks about the penalty of perjury to misrepresent the actual mileage of the vehicle, and an check box option saying the odometer is accurate or is inaccurate.


I take that to mean, its NOT illegal to have the wrong mileage on the odometer of "your" car, its just illegal to state the mileage on the odometer is accurate when in reality it is NOT.
 

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Hmmm, or should I say, in most states its illegal to intentionally alter your odometer; it is NOT illegal to have an inaccurate odometer because of an innocent reason, other than intentionally altering the odometer to misrepresent the mileage of the vehicle, but its still illegal to NOT disclose that the inaccuracy of the odometer during the sale of a vehicle.
 

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Discussion Starter #12
So I contacted my local dealer and they said the Odometer reading IS stored on the ECU, they're gonna get back to me on what I can do. we briefly discussed bringing in my commander in WITH the installed ECU, and they can flash the new 5.7 ECU with my accurate milage and just swap the ECU's then I'll tow the jeep back if I need to. BUT! I'll have accurate mileage on the Jeep.
:grin2:
 

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Discussion Starter #13
Something new I thought of. Spark plug firing order. Would it be the same as my 4.7? what about the coilpacks and wires? should I replace those as well?

And just an update cause it's been a few weeks... I was told a turn around time of 2-3 weeks to receive the long block, aaaaand I still haven't gotten it. I ordered the Mopar cold air intake for the grand cherokee SRT8 though, I hope it fits right! But I will be ON IT when the block gets here. thanks guys.
 

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Something new I thought of. Spark plug firing order. Would it be the same as my 4.7? what about the coilpacks and wires? should I replace those as well?
I thought you were going to use a 5.7L PCM (ECU)?


Have you checked to find if the wire harness is the same between the 4.7L and the 5.7L, I would think they are different and if so, you're going to have to swap out the wire harness with the PCM and Engine.


If the wire harness is the same between the two engines, and the firing order is the same for the SRT motor, then I think you would NOT have a problem. Even if firing order was different between the 5.7L and 4.7L engines, but the wire harness's are the same, then that means the wire harness just completes the circuit between the PCM and coil, thus the PCM will fire it in the correct order.


Thing to worry about is if they changed the firing order between the 5.7L and 6.1L (which I doubt) but if they did, your 5.7L PCM won't work, unless you start swapping pins around on the connectors to the PCM.


I would keep the coils intended for the engine in the vehicle, they are designed to produce the spark strength the engine needs. If you use different coils, they may NOT make the necessary spark strength and thus you might have problems.


I believe the PCM fires the coils by grounding the primary when its needed. And it probably has a constant 12+VDC applied to the primary of the coil. I could be wrong on this, confusing it with the fuel injectors. So, a different coil than the PCM was designed to use, probably won't be a problem.


Of course, I think that grounding is done with solid state driver circuits and they do have a limit in the amount of current they can carry, so although unlikely, its possible a hotter coil might burn out the PCM (in at least the driver for the coil). But that's the risk you take doing a hi-tech engine swap like this.
 

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Discussion Starter #16
I thought you were going to use a 5.7L PCM (ECU)?




I would keep the coils intended for the engine in the vehicle, they are designed to produce the spark strength the engine needs. If you use different coils, they may NOT make the necessary spark strength and thus you might have problems.




Of course, I think that grounding is done with solid state driver circuits and they do have a limit in the amount of current they can carry, so although unlikely, its possible a hotter coil might burn out the PCM (in at least the driver for the coil). But that's the risk you take doing a hi-tech engine swap like this.
1. I am using the 5.7 ECU, still learning engine stuffs,

2. So I SHOULD get new coils for the 6.1?

3. Even if i use my current coils, they could go bad in which case I just buy new coils anyway.

That's what I got.
 

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Discussion Starter #17
oh, and update, I got contacted by my engine seller. The block had a crack in a couple cylinders. They're starting over with a new core. "Hopefully by the end of the month" he says.
UUUGGGHHH.
 

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1. I am using the 5.7 ECU, still learning engine stuffs,

2. So I SHOULD get new coils for the 6.1?

3. Even if i use my current coils, they could go bad in which case I just buy new coils anyway.

That's what I got.
So, I assumed you asked about the 4.7L having the same firing order as the 5.7L, because you plan on using the 4.7L wiring harness?

Is the wiring harness for the 4.7L and 5.7L the same? Have you checked?

If NOT, you will need the wiring harness for the 5.7L, and that's hoping its close enough to the 6.1L to work.

Ignition Coils: NO, what I'm getting at is you should use the ignition coils designed for the 6.1L. If the 6.1L SRT motor uses the same ignition coils as your 4.7L, then great, use them. If the 6.1L uses different coils than your 4.7L or 5.7L, then you should get and use those ignition coils. And if that is the case, you'll need to confirm they use the same connectors as the wire harness you're using.

Coils often last the life of the vehicle, sure, like anything, they can go bad. Honestly, the costs on this project are going to climb a lot, more than you anticipate. So I would NOT buy new coils unless you have too.

Sorry about the delays, that is what I've heard about the HEMI crate motors, delays and problems. People waiting a long time or getting a block or motor, that is NOT right.
 

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Discussion Starter #19
Alrighty, well I planned on getting the 6.1 Harness, from what I hear, the 5.7 harness is only slightly different from it, and I didn't want to dead with it. I had a 6.1 harness lined up, but the guy sold it before I tried to buy it from him. and I don't know the difference in harnesses between years for the 6.1 GC. I'm trying to research that now, but I'm not having much luck. I can get new ignition coils, that's fine, and the money isn't an issue. I accounted for possibly spending more than I anticipated, as anyone should with ANY engine swap.
 
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