NP242 reliability behind 5.9L Cummins

[95Z28A4]

I'm new to this forum. Googling led me here.

How is the HMMWV NP242 holding up behind the Cummins converted HMMWVs?

I have a 12 valve Cummins and 47RE that I plan to install in a 2004 Suburban. I want to keep the full time/part time 4 wheel drive capability of the factory Suburban transfer case while having 2WD capability and a manual shifter. I am considering a NP242WJ transfer case from a 4.7L 2002-2003 Jeep Grand Cherokee with an upgraded 6 gear planetary. The NP242WJ comes from the factory with the 1.25" wide chain and 32 spline output shaft. It is my understanding the only difference between a NP242WJ with an upgraded planetary set and an HMMWV 242 is the HMMWV 242 oil cooler and the absence of 2WD with the HMMWV. The NP242WJ has a 2WD mode.

Thanks for the help!

 

[TOBASH]

Why not google 242 behind the Jeep Grand Cherokee Diesel engines? Might be a better comparison.

 

[frank8003]

I'm new to this forum. Googling led me here.

How is the HMMWV NP242 holding up behind the Cummins converted HMMWVs?

I have a 12 valve Cummins and 47RE that I plan to install in a 2004 Suburban. I want to keep the full time/part time 4 wheel drive capability of the factory Suburban transfer case while having 2WD capability and a manual shifter. I am considering a NP242WJ transfer case from a 4.7L 2002-2003 Jeep Grand Cherokee with an upgraded 6 gear planetary. The NP242WJ comes from the factory with the 1.25" wide chain and 32 spline output shaft. It is my understanding the only difference between a NP242WJ with an upgraded planetary set and an HMMWV 242 is the HMMWV 242 oil cooler and the absence of 2WD with the HMMWV. The NP242WJ has a 2WD mode.

Thanks for the help!

GEE, You have been at the studies!

 

[95Z28A4]

Why not google 242 behind the Jeep Grand Cherokee Diesel engines? Might be a better comparison.

I may be mistaken, but I do not believe the NP242 was available behind the Grand Cherokee 3.0L Mercedes or VM Motori diesel engines. It was available behind the 2.8L VM Motori 4 cylinder diesel in the 2005-2006 Jeep Liberty. I know this because I own a 2006 Jeep Liberty CRD diesel with a NP242. Behind the 2.8L diesel and 545RFE transmission, the NP242 is holding up fine. But.......the 2.8L VM Motori is not in the same class as the Cummins. I know this because I also own a 1998 Dodge Ram 2500 with a 12 valve Cummins. To install the NP242WJ behind a 47RE, I'll have to replace the input shaft with a shorter 23 spline input from a 42RE equipped vehicle. Just so happens I have a shaft from a 3.7L/42RE/NP242 equipped Liberty. I also have a 6 gear planetary from a late 1990's NP241C which fits the NP242.

GEE, You have been at the studies!

You could say that. I've been wrenching for over 40 years - cars, trucks, jeeps, motorcycles. I'll be retiring at the end of February. The diesel Suburban will replace my wife's 5.3L GMC Yukon.

 

[jkcondrey]

Sounds like you have all the parts to figure it out. Slap them together and tell us how it works lol.

 

[TOBASH]

If you're that worried, use a beefier transfer case like an atlas.

 

[95Z28A4]

If you're that worried, use a beefier transfer case like an atlas.

I may be mistaken, but I believe the Atlas is 2WD and part time 4WD. It does not have full time 4WD capability.

When I converted my 1998 Dodge Ram quad cab diesel from 2WD to 4WD (frame swap, converted NV4500 from 2WD to 4WD, etc), I used a NV271F from a 2006 Ford F250 Superduty. The NV271F is stronger, easier to acquire and less expensive than the NV241DHD that came from the factory in the Cummins powered 2nd gen Dodges. It does not have PTO capability like the NP241DHD, but I don't need it. Unfortunately, the NV271F does not have full time 4WD capability. If I'm not convinced the upgraded NP242WJ can handle a stock 215HP/440 lbs/ft Cummins, I will use a NV271F or NV271D. But......I really want to retain the full time 4WD capability for my wife.

 

[95Z28A4]

Sounds like you have all the parts to figure it out. Slap them together and tell us how it works lol.

Based on my experiences, it's a bit more difficult than slapping them together. I joined this forum seeking first hand experience with a NP242 behind a Cummins converted HMMWV. I do not believe this is the correct forum for a GMT800 Suburban diesel conversion build thread.

 

[Retiredwarhorses]

Based on my experiences, it's a bit more difficult than slapping them together. I joined this forum seeking first hand experience with a NP242 behind a Cummins converted HMMWV. I do not believe this is the correct forum for a GMT800 Suburban diesel conversion build thread.

lose the R4 transmission and install a 4L80e with the 242. It’s a common conversion....anyone who knows enough
about transmissions and diesel engines knows better than to install an R4...but heck, what do I know.

 

[95Z28A4]

lose the R4 transmission and install a 4L80e with the 242. It’s a common conversion....anyone who knows enough
about transmissions and diesel engines knows better than to install an R4...but heck, what do I know.

Are you referring to the 700R4 transmission? Thank you for that sound advice. I too am not a fan of the 700R4/4L60/4L60E transmissions. While they have improved a lot since they were first introduced in 1982, I still don't like them and I've had a few of them. Among other things, the gear spacing between 1st and 2nd is too wide. In my opinion too wide for a low RPM diesel engine. I do like the 4L80E behind a gas or small diesel engine. Personally, I think it's a little on the light side for 5.9L Cummins, but probably OK for a 3.9L Cummins.

As stated in my first post, I will be using a 47RE transmission. The 47RE transmission was factory installed in the Dodge behind the 5.9L Cummins from 1996-2003. With the introduction of the 5.9L HO, the 47RE was replaced by the 48RE. Why the 47RE over the 4L80E? The 47RE bolts directly to the Cummins/Dodge flywheel housing - no additional expense for a special adapter plate/flex plate/starter. The 47RE has a higher overdrive ratio than the 4L80E - 0.69:1 vs 0.75:1. I own a working 47RE from a 1999 Dodge diesel. The NP242 will bolt to the 47RE with the correct input shaft and I happen to have that input shaft.

If I were to use a General Motors transmission behind the Cummins, it would be an Alli$on. But, I can't justify the additional expense and complexity of the Alli$on over the 47RE for a vehicle that will be primarily a people mover with light occasional towing duties. As an FYI, Alli$ons were installed behind Cummins in medium duty trucks using a SAE 3 flywheel housing.