non renix to renix transfer case swap info

[james750]

I'm looking at swapping a non renix (1991 and up) NP242 transfercase into the MJ. I already know I need to swap input shafts to make this work with my AX-15. But I also know that non renix XJ's are Electronic speedometer control. Is there a way that I can make this case work with a mechanical speedometer? If not, what would I have to do to convert the MJ to read an electronic signal?

[flint54]

If I understand your question correctly, you are intending to install a newer transfer case into an older MJ.

The transfer case you want to use has an electronic speed sensor, and the vehicle you plan to install it

into uses a mechanical cable. Correct? If so, I think all you need to do is make sure you also get the

right sending unit. The sending unit, either electronic or mechanical, installs into a hole in the output

housing. They are interchangeable, and use the sane pinion gear. My confidence of this is based on today's

experience at the JY where I scored an NP242 from a 1990 XJ. It has a mechanical speedometer, and

my 1992 has an electronic speedometer. Except for the connection (cable vs wire), the sending units are

identical. You probably already know this, but the sending unit has three positions, depending on what range

drive gear you have. 26-31 teeth, 32-38 teeth, or 39-43 teeth. The donor vehicle may have a different

drive gear than what you need and you may need to make an adjustment.

[james750]

That answers my question perfectly, I wasn't sure if the NP242 used a hall effect type sensor on the electronic speedometer versions instead of a gear. I should be able to make this case work then. Thanks!

[Geonovast]

All 4.0 T-cases after 90 should be 23 spline... you shouldn't have to swap any input shafts.

[james750]

Yeah, but the short length 23 spline input was only behind the AX15, and the 242 was only offered behind the AW4 (which has a long length 23 spline) as far as I know. (http://www.novak-adapt.com/knowledge/np ... _gears.htm) Would I have to swap inputs to get the lengths correct?

[Geonovast]

AX-15 and AW-4 used the same length T-case inputs. The AX-4/5 used the long ones.

[ParadiseMJ]

I was thinking about this today, as I had just fixed my speedo cable on my 231. I also happen to have an NP 249 laying around...so I took the sender/gear out of the 249. Other than the sender and connection to the shaft (square end vs. round end), the whole thing looked to be the same length, size etc. So like the others said, just swap your sending unit (mechanical) into your later model TC...should work fine if it meshes with the helical gear INSIDE.

[ParadiseMJ]

The tranny shouldn't make a difference as both senders are in the T-case, not the tranny.

[james750]

The tranny shouldn't make a difference as both senders are in the T-case, not the tranny.

We were talking about input shaft compatibility relating to the tcase, not the speed sender.

 

Weren't the speedo gears for an electronic speedo a different length than the mechanical ones? For some reason I thought that the electronic speedo's used a short speedo gear and the mechanical speedo's used a long gear.

[deziped]

The short speedo drive gears are were used when they went to electronic speedos. But, if you use the old style mechanical cable hookup I would think you could drop a long shaft driven gear in the hole and it would work for cable. You can get more info here with a call. http://www.transmissioncenter.net/speed ... ____va.htm