Let me save you some time and money – When talking about the dodge 4.7L engine – there is a very important aspect for consideration. There is a JTEC and an NGC configuration that must be mentioned when thinking about changing engines…There are a couple of different ways to find out which version you have – don’t use the method I used. First, the differences. These are found on the cam shaft, and crank shaft – JTEC is the older setup and uses a 16 tooth Crankshaft tone ring (for telling the engine computer what position it is in which then leads to firing and fueling the cylinders.
The tone ring on the right is the JTEC 16 tooth tone ring. The 32 tooth tone ring is more precise and allows for better communication with the engine controls and computer system, probably a little better fuel economy and maybe a little better performance. The two are not interchangeable, the computer will not recognize the reading from the other system. Be careful as Mitchel and Alldata is are not necessarily correct in identifying which years and models have which t
one rings. The donor engine for this jeep project came from a 2002 Dodge Durango, and according to Mitchel’s information this Durango should have had the 16 tooth tone ring.
Another difference is the tone ring on the cam shaft (passenger side head). This ring has a bunch of windows that are read by a camshaft sensor and combined with the information from the crank tone ring work with the computer for the running of the enginge.
The tone ring/gear assembly on the top if you click on the image you can see “NGC” stamped on the tone ring (just above the “V8″ which is stamped on the gear). While there is nothing different in the gears, there is a vast difference in the “windows” on the tone wheel. You can see in the picture with the NGC wheel above the JTEC tone wheel – oddly enough the NGC wheel has less “windows” then the NGC – these spaces are what communicate the camshaft position to the PCM – AGAIN, these are not interchangeable, you must have the correct tone wheel on the camshaft/crankshaft/combined with the correct PCM.
The JTEC PCM has 3 harness connections, while the NGC PCM has 4 harness connections. I have read that it is not possible to change these parts over, also have read that it is possible just to change the computer over and then it should work – in theory one could change the PCM over, but the NGC setup has another harness connection on the PCM, this is having to do with the transmission controls module (or something), so if this is the way you would like to go, you would have to look into what that would involve. I didn’t have access to a new PCM, so I decided to pull the engine apart, inspect the condition of the heads/valves/Pistons/cylinders ect. The tone rings can easily come off of each shaft and be transferred over, there are 3 (T40 I believe) fasteners on the crankshaft tone ring and a bolt on the camshaft tone ring that needs to be removed and the tone rings/wheels can be switched over – they cannot be installed in the wrong positions – the crankshaft ring is indexed with its fastener holes, and the camshaft tone ring has a nipple that can only go in one location.
So. After removing the heads, I removed the engine once again, tore it down, removed the crank shaft, inspected the cylinder bores – got the block honed – the machine shop did a great job, they were able to take off only half of a thousandth of an inch in material to get it back to standard sizing (within spec). I bought a kit off of eBay which contained a bunch of parts (new timing kit, new Pistons, rings, gasket sets, valve spring guides, water pump, and oil pump). Because the engine must be taken down so far, it is essentially a rebuild – I am looking forward to getting the thing back together and hearing it run.
As I was unaware of the difference between the tone rings I could have saved myself a lot of hassle. I had the engine apart and before installing the new to me engine…I had the valve covers off, to inspect for sludge, and had I known what to look for would have caught the NGC on the camshaft tone wheel. This being the first major job like this on my own I also should have known when I tried to start it there was something up…Obviously I knew something wasn’t right, but I chased the sensors, wiring, even fuel before coming to the conclusion that something even more basic was wrong – the engine ran before installing the new engine – I had no codes for timing issues…I suppose it could be possible that I had damaged part of the engine harness when removing/installing the engine (which in part was why I was chasing these issues) but more likely that there was a difference/or something wrong with the new engine. That being said, we are where we are today…and it’s onwards and forwards.
Hope this will help someone else someday.