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Unread 10-08-2012, 12:34 PM   #1
Rican142
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what's the best tranny?

What is the best tranny to put in my 89 comanche i6 right now I got the ba10. Would the ax15 be the best?

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Unread 10-08-2012, 04:40 PM   #2
USMC_XJ
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The best that is a direct bolt in would be NV3550. Which can in the 99-01 Cherokees with the 4.0 as well as the Wranglers. However, the AX 15 will easier to find and will suit you just fine. The 90-93 ish were internal slave. 94-99 were external. Your choice on which one you want. But, keep in mind that if you get one of those transmissions, your transfer case will have to get modified to have it bolt to the transmission properly. So, best bet is to get a ax15 with 231 from a donor.
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Unread 10-09-2012, 07:41 AM   #3
Rican142
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Do you know what the difference is between the two? And what do you mean by internal and external slave? Is that in reference to the slave bearing? And what's a 231
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Unread 10-09-2012, 11:05 AM   #4
97_4popper
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The slave cylinder for the hydraulic clutch is what he is referring to. A 231 is the NP231 or NV231 transfer case.
External slave is more desirable because it is easier to replace. The internal one requires removing transmission and transfer case and belhousing to replace.

AX-15 will suit you just fine and is more plentiful.
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Unread 10-09-2012, 01:38 PM   #5
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Quote:
Originally Posted by USMC_XJ View Post
The best that is a direct bolt in would be NV3550. Which can in the 99-01 Cherokees with the 4.0 as well as the Wranglers. However, the AX 15 will easier to find and will suit you just fine. The 90-93 ish were internal slave. 94-99 were external. Your choice on which one you want. But, keep in mind that if you get one of those transmissions, your transfer case will have to get modified to have it bolt to the transmission properly. So, best bet is to get a ax15 with 231 from a donor.
Critical Differences:

- The BA-10 has a 21-spline output gear, the AX-15 and NV3550 have a 23-spline. The earlier transfer case may be used, but you will have to replace the input gear. Check with Novak Adapters for this part, or get one from a salvage yard (however, earlier is better - the helix angle on the input gearset was changed ca. 1993-1994, and mismatch of helical gears usually results in destruction in the relatively short term.)

- The YJ/TJ versions of these transmissions use a different "clock angle" for the transfer case than the XJ/MJ/ZJ versions - the YJ/TJ is clocked flatter to improve breakover angle and ground clearance. This would require EITHER a clocking ring OR replacement of the transfer case adapter housing (the three are not compatible across transmissions) OR redrilling the clocking ring. However, in all cases, the transfer case mounting stud pattern is the same.

"Internal Slave" refers to the "concentric slave cylinder/bearing assembly" - it cannot be serviced except by removing the transmission. It was a dumb idea when Mazda came up with it, it remained a dumb idea when Ford did it, and the story has not improved with retelling.

"External Slave" refers to a separate slave cylinder/throwout bearing setup, and the cylinder may be removed without removing the transmission. The T/O bearing is moved about by a fork, instead of direct hydraulic action. The difference is immediately apparent when looking at them.

Note that the "internal slave" setup may be converted to an "external slave" setup, I've posted the hows and whys here before. Likewise, I've also posted donor lists and pitfalls here before, so a search may prove fruitful.
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Unread 10-18-2012, 06:25 AM   #6
Garvin
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The helix angle was actually changed in late '94, early '94 has the older style.

The YJ/TJ clocking can be used but you will need a custom shifter in most cases. I have heard both sides of people fitting it fine and others having to slightly massage the floor to get it in. Either way you can use that clocking pattern. I reclocked mine flatter than the Wranglers and raised it up and was still able to fit the transfer case after banging the floor up in one small section.

Also, between AX15 and NV3550, it's debatable which is really stronger. The NV3550 did get more ribs on the case than the AX15. From personal experience and experience of people I know, the AX15 holds up to a lot more abuse. I have a buddy that blew up 3 NV3550's behind a ZZ4 Chevy 350 and could not blow up an AX15. I'm currently running an AX15 behind my mildy built Chevy 350 (~300hp, ~360 torque, and lots of skinny pedal) and it has not hiccuped once.
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[B]1986 Jeep Comanche 126000+ miles[/B]
Long Bed, Chevy 350 TPI (5.7L V8), AX15, NP231
Roll Bar, 15/38.5R16.5 Ground Hawgs, Bastard lift (Custom 3-link long arm system, 4.5" Rusty's front springs w/ 1.75" spacers and 6.5" RC shocks, SOA rear), Dana 60HP/Sterling 10.25, 4.10's, Recessed winch, more mods to come...

[B]1992 Jeep Comanche 174000+ miles[/B]
Short Bed, 4.0L I6 HO, AX15, NP231
In the process of doing a frame up restoration.

...RIP...
[B]1990 Jeep Cherokee XJ 207774 miles[/B]
4.0L I6, AW4, NP231. Tom Woods SYE and Drive Shaft, Rusty's 8.0" Long Arm Suspension Lift, 36/13.5R15 Super Swamper IROK's, Dana 30 Front, Tube Diff Guard, Dana 44 Rear, 4.56 gears, Ox Locker, disc brake conversion
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