Question in the middle of swapping a busted th400/np218 for a working th400/np242

[kestrelnh]

I'm swapping out my busted th400 that had a np218 transfer case on it for a functional th400 that has a np242. I think (we'll find out) I have the right drive shafts, etc., but I have a question I hope you all can help with now that I have both the old and new transmission and transfer case next to each other.

The np242 didn't come with a speedometer adapter. The speedo adapter from the np218 has the drive offset from the center. I didn't see two part numbers in the TM for speedo adapters, so I'm wondering if it will work on the np242, and if so where on the clock face the offset should be?

A followup question is that my truck has 2.56 gears. I bought the red 36 tooth adapter for the np242. Is that the one I should use, or should I re-use the orange gear from the old np218?

Thanks, and there may be more coming as I try to figure this out

 

[kestrelnh]

Getting closer here. It appears that I should set the alignment of the speedo adapter to the mark of where the driven gear in the speedo adapter falls. There are recessed lines on the speedo adapter to align with the raised mark on the transfer case. It looks like the range I'll use is the one that is 32-38 (not labelled, but I assume the units are teeth).

I still wonder if I should use the red or orange gears on the np242

red: 36, orange:35

 

[tage]

Have you read the mwo for the adaption?

 

[kestrelnh]

Have you read the mwo for the adaption?

No, the closest I got was this:

http://psmag.radionerds.com/images/d/d3/PS_Magazine_Issue_565_December_1999.pdf

Any idea where I can find the MWO? My GoogleFu is failing me.

 

[kestrelnh]

Another thing that is bugging me is I ordered a new shift lever to attach to the NP242 t-case. It was NSN 3040013588708 which is different than the one for the np218, but when I lined them up, they look identical. Is this the right one? It looks like it should work, but is pretty close to the cooling lines. The park looks like:

 

[kestrelnh]

Re-checked the TC shift lever, and while the outside shape in the same, the alignment is different, so I think I'm in good shape there.

 

[AOR]

Getting closer here. It appears that I should set the alignment of the speedo adapter to the mark of where the driven gear in the speedo adapter falls. There are recessed lines on the speedo adapter to align with the raised mark on the transfer case. It looks like the range I'll use is the one that is 32-38 (not labelled, but I assume the units are teeth).

I still wonder if I should use the red or orange gears on the np242

red: 36, orange:35

I would suggest driving the vehicle and put a GPS app on your cell phone at 60 mph I think each tooth will change the speedo by about 2mph
I suggest checking out this link I use for the Jeeps it should help you to understand the relationship to the amount of teeth regarding tire size and gear ratio. https://www.quadratec.com/c/reference/jeep-speedometer-gear-tooth-chart