I've searched....

I'm swapping a TF999 into a 2000 TJ to replace the NV3550. I've read that I need the correct input shaft length on the NP231 transfer case. I've also read that the input shaft used with the AX15 (on TJs) is the wrong size. Some have used a Teraflex seal extension to fix this.

According to the info here:

http://www.novak-adapt.com/knowledge/np231.htm

The AX15/NV3550/TF999 all use the same NP231 input shaft length. Of course this conflicts with the experience of some who have done the swap with a NP231 mated to a post 1998 or later AX15.

Does anyone know the proper NP231 input shaft length (transfer case mating surface to end of input shaft)?

you should be good to go. as a rule of thumb you should have a minimum spline engagement of the shaft diameter.

Thanks!


Some people mention "engaging" the transmission output seal. I'm not even sure what that means??

Thanks!


Some people mention "engaging" the transmission output seal. I'm not even sure what that means??

In the output of the trans you should see a seal that the input of the tcase slides into. If the input of the tcase does not extend into the trans output seal far enough (engaged) you will leak trans fluid out of the rear of the trans.

When I went from a 5 speed to an auto I had to use a clocking ring and it pushed the input shaft .25" away from the trans seal, which I did not notice until I started puking trans fluid out of the weep hole at the tcase mounting flange.

If you are using a clocking ring or if you are unsure if your input shaft will hit the seal in the the back of the trans you should get a speedi sleeve. You will need Chicago Rawhide part #99193.

Since I installed the sleeve I have no issues with the rear trans to tcase seal.

I love my NV3550 so I kept it in even though I was thinking about swapping in an AW4 with the Atlas 4-speed. I guess I got lucky because my atlas 4-speed came with the same length input shaft as the 231. Even though the 4-speed for was a TJ with automatic. Not sure how exactly that works out. Also, I think some NV3550s don't have a weep hole? Anybody know why some trannys have a weep hole and some don't? For what it is worth my atlas was for a TJ automatic and had an input shaft length of 2.125 from the end to the face of the t-case that the studs screw into.

Thank you wckdyj, I can easily picture what you are talking about with the seal.


tbeede, thanks for the measurement. My input shaft length measures at 2.12" as well so it looks like I'll be good to go when the trans finally gets here.

is there something wrong with your 3550 or did u just want an auto? because im in serious need of a tranny. best way to contact:
gadawgfan54@yahoo.com