• RME Gear & Apparel

The Rubi Q Build

UNSTUCK

UNSTUCK

But stuck more often.
Ok, I did a bit of research. The JKs, at least, used a 2:1 241j transfer case. This is a very promising idea. It uses the same 4x4 switch, and the same shift pattern I need. As Mike said, I can swap the input shaft to 32 spline and run it. It also does not use a slip yoke so that is a plus right there. The only down side I can see at this point is that it does not have a VSS. I could just pull from the signal the transmission generates, but that would not give me what I need in 4lo. I could easily build a 3 ppr tone ring and sandwich it between the rear output flange and driveshaft. Them mount a VSS to a bracket that hangs off the rear seal housing.
 
zmotorsports

zmotorsports

Hardcore Gearhead
Vendor
Location
West Haven, UT
UNSTUCK said:
Ok, I did a bit of research. The JKs, at least, used a 2:1 241j transfer case. This is a very promising idea. It uses the same 4x4 switch, and the same shift pattern I need. As Mike said, I can swap the input shaft to 32 spline and run it. It also does not use a slip yoke so that is a plus right there. The only down side I can see at this point is that it does not have a VSS. I could just pull from the signal the transmission generates, but that would not give me what I need in 4lo. I could easily build a 3 ppr tone ring and sandwich it between the rear output flange and driveshaft. Them mount a VSS to a bracket that hangs off the rear seal housing.
Click to expand...

Technically the 241OR is in itself it's own case. You can easily recognize this by the larger front section due to the larger primary planetary for the 4:1 ratio. To be honest, this works well for the lower HP rated Jeep/Chrysler engines and provides a good crawl ration but more importantly, helps with the lower powered engines and under-geared transmissions.

Personally, I feel this is the weak link in a higher HP/torque powertrain such as with the V8 with approx. 400 HP and more importantly, not needed.

With the much lower (4.02:1) first gear of the 6L80 transmission coupled with a 2.72:1 transfer case gives you a 11:1 crawl ration without factoring in final drive ratios. Whereas a stock 42RLE for example with a 2.80:1 first gear ration coupled with a 4:1 transfer case ratio will be roughly the same ratio at 11.2. However, with the V8/6L80 combo you will have nearly double the HP and torque so therefore you don't really need the deep crawl ration and in some instances such as snow and/or sand the deeper ration can be more of a con than a pro as it limits wheel speed.

The other added benefit of the 6L80 with the deeper lower gears and taller overdrives is that it allows a taller final drive gear to be used in the axles.

I have found with my setup I don't need 4LO nearly as much as I did with the smaller displacement engine and seldom use it unless actually on an obstacle. This also nets me much improved fuel economy offroad and better drivability manners. For example, in the sandy washes such as in Moab or the Swell I had to use 4LO just to keep the 6k pound Jeep propelled through the sand but now it easily pushes the Jeep through these same washes in 2Hi thus greatly improving my range. I was averaging around 8 MPG when off-road with my V6 powertrain and now I seldom ever dip below 10 MPG.
 
UNSTUCK

UNSTUCK

But stuck more often.
zmotorsports said:
Technically the 241OR is in itself it's own case. You can easily recognize this by the larger front section due to the larger primary planetary for the 4:1 ratio.
Click to expand...
That’s why this is becoming funny to me. A quick image search for 241OR showed every tag I saw saying 241j and 4:1. Sounds like there may be some actual tags out there that say 241OR, it’s just rare. Bottom line, if the tag says 241j it may be 4:1 or 2.72:1. In my 06 Rubi, my 241j is 4:1. In your 241j it’s 2.72:1. In that case you can easily tell if it’s 2.72 by the smaller housing at the input shaft, as you said.

Anyways, I think I will look for a JK 241j 2.72 case and add a vss tone ring and sensor along with a new input shaft and yokes. Seem like the easiest and cheapest way. Thank you for the information.
 
anderson750

anderson750

I'm working on it Rose
Location
Price, Utah
UNSTUCK said:
That’s why this is becoming funny to me. A quick image search for 241OR showed every tag I saw saying 241j and 4:1. Sounds like there may be some actual tags out there that say 241OR, it’s just rare. Bottom line, if the tag says 241j it may be 4:1 or 2.72:1. In my 06 Rubi, my 241j is 4:1. In your 241j it’s 2.72:1. In that case you can easily tell if it’s 2.72 by the smaller housing at the input shaft, as you said.

Anyways, I think I will look for a JK 241j 2.72 case and add a vss tone ring and sensor along with a new input shaft and yokes. Seem like the easiest and cheapest way. Thank you for the information.
Click to expand...
I have a 2.72 case laying around.
 
UNSTUCK

UNSTUCK

But stuck more often.
Thanks to @zmotorsports for the JK 241 info. I found one locally and picked it up for a good deal. The case is way more beefy than my 241c case. I think this thing will be perfect for me.

IMG_4663.jpeg

IMG_4664.jpeg

IMG_4665.jpeg

Now to modify it to make it work. I need a 32 spline input shaft. I think I may have two options here. One of two sizes of bearing. I think iI need the .940 wide bearing, but not sure. Mike?
After that I need a 32 spline 1330 CV yoke for the front output and a 32 spline flange yoke for the rear. I’ll look for one that has the mounting holes for the different sized flanges for future larger driveshafts.
The next item will be a mount for a tone ring and VSS. How do I do this? It will be easy to built a bracket that bolts to the rear output housing. I’m wondering about the tone ring. Do I build one out of, say 1/4” and sandwich it between the output yoke and the DS flange? Do I machine three teeth into the yoke and use it? Should I use only the Jeep VSS and split the signal to the GM ECM or mount a GM VSS as well and program it for 3 PPR? The tone ring will be larger than stock which will make the three teeth larger as well. This will make the Speedo show slower than I’m actually going. I’ll have to figure out how to tune that.
 
RockChucker

RockChucker

Well-Known Member
Location
Highland
When I originally did my 5.3 swap I took the 3 pulse signal off the factory rubicon case and converted it to a useable signal for the gm pcm via a Dakota digital converter. It might make your tj rubicon case less desirable to sell, but you could always steal the rear case half, output housing etc and put the factory tone ring in it as it is in your Jeep now. Or try and find a case half etc to do the same thing. I THINK this would work.
 
UNSTUCK

UNSTUCK

But stuck more often.
As much as I would like to have a VSS inside the housing I don’t want to butcher my 241j and don’t want to invent something, as much as I can help it.

I forgot to mention a clocking ring in my last post. I assume I need one?
 
I Lean

I Lean

Mbryson's hairdresser
Vendor
Location
Utah
The size of your tone ring won't affect the speed shown. 3 teeth is 3 teeth no matter what diameter it is.
 
UNSTUCK

UNSTUCK

But stuck more often.
Think so? The larger diameter tone ring will make each tooth longer. The sensor picks up a tooth for a given amount of time before it drops off. The slower you go the longer time the sensor is picking up one tooth. So the longer the tooth the slower the ecm will think I’m going?
 
I Lean

I Lean

Mbryson's hairdresser
Vendor
Location
Utah
UNSTUCK said:
Think so? The larger diameter tone ring will make each tooth longer. The sensor picks up a tooth for a given amount of time before it drops off. The slower you go the longer time the sensor is picking up one tooth. So the longer the tooth the slower the ecm will think I’m going?
Click to expand...
Each tooth is longer, but it's also moving faster. Think of it in degrees of rotation.... if the teeth and the gaps are evenly spaced, you will have 60° of rotation per tooth no matter how large or small the ring is.
 
glockman

glockman

I hate Jeep trucks
Location
Pleasant Grove
UNSTUCK said:
Thanks to @zmotorsports for the JK 241 info. I found one locally and picked it up for a good deal. The case is way more beefy than my 241c case. I think this thing will be perfect for me.

View attachment 165640

View attachment 165641

View attachment 165642

Now to modify it to make it work. I need a 32 spline input shaft. I think I may have two options here. One of two sizes of bearing. I think iI need the .940 wide bearing, but not sure. Mike?
After that I need a 32 spline 1330 CV yoke for the front output and a 32 spline flange yoke for the rear. I’ll look for one that has the mounting holes for the different sized flanges for future larger driveshafts.
The next item will be a mount for a tone ring and VSS. How do I do this? It will be easy to built a bracket that bolts to the rear output housing. I’m wondering about the tone ring. Do I build one out of, say 1/4” and sandwich it between the output yoke and the DS flange? Do I machine three teeth into the yoke and use it? Should I use only the Jeep VSS and split the signal to the GM ECM or mount a GM VSS as well and program it for 3 PPR? The tone ring will be larger than stock which will make the three teeth larger as well. This will make the Speedo show slower than I’m actually going. I’ll have to figure out how to tune that.
Click to expand...
I have a 32 spline input from my NP241C. I can measure it tonight and tell you which bearing width it is. It's yours if it will work.
 
  • Like
Reactions: DAA
UNSTUCK

UNSTUCK

But stuck more often.
I Lean said:
Each tooth is longer, but it's also moving faster. Think of it in degrees of rotation.... if the teeth and the gaps are evenly spaced, you will have 60° of rotation per tooth no matter how large or small the ring is.
Click to expand...
I didn't think about it spinning faster as well.

glockman said:
I have a 32 spline input from my NP241C. I can measure it tonight and tell you which bearing width it is. It's yours if it will work.
Click to expand...
I think you just need to match the bearing to the input shaft and that they fit in the housing either way. That's mostly a guess though. If you don't mind measuring though and I'll research a bit more on my end. Thanks.
 
  • Like
Reactions: DAA
UNSTUCK

UNSTUCK

But stuck more often.
glockman said:
I have a 32 spline input from my NP241C. I can measure it tonight and tell you which bearing width it is. It's yours if it will work.
Click to expand...
After researching it some more it looks like either input shaft will work. One uses a double row ball bearing that’s .940 wide. The other uses a single row ball bearing that’s .625 wide. Bigger is always better but it looks like either shaft could have been used on small or large drivetrains. So, yes, I’ll take it!
 
You must log in or register to reply here.
Top