NSG370 to AX15 swap

[freedom_in_4low]

starting this thread to document my swap instead of doing it after the fact when my memory is fuzzy.

Background: my NSG370 pops out of reverse. In street use it's tolerable but it's exacerbated when backing against any resistance, such as uphill (like the 8% grade on my driveway) or if a tire has to climb a rock or a log on the trail. This is annoying at best, and at worst could be dangerous or life threatening if on a narrow mountain switchback in Colorado. I had an AX15 in my '99 TJ Sahara, I liked it better, and the cost of swapping is almost the same as a rebuilt NSG370. (this thread is not for the purpose of rehashing the relative merits or issues with either transmission or of changing from one to the other)

Parts Required:
(1) New AX15 transmission. I got mine from Novak (their pn TR-AX15) because it was $50 less to ship here from Utah than from Advance Adapters in California. It comes with the shift tower and a new shift lever that isn't quite the same as OEM. It's straight, seems thicker, and is unpainted. I'll have to bend it to my needs. It also came with a shift knob that looks decent enough but not stock by any stretch, and has Novak's name on it.
https://www.novak-adapt.com/catalog/transmission/transmission-packages/ax15-package/
https://advanceadapters.com/transmission-ax15-4wd-new-unit-750-tip-boxed

(1) Advance Adapters 712590L AX15 bellhousing with 05-06 crankshaft position sensor location. My understanding is the bellhousing comes with both CKPS locations so it's backward compatible. The Advance Adapters bellhousing includes all the stuff that goes inside the bellhousing except for the flywheel, disc and pressure plate. At time of order they gave me an expected ship date of May 17. Based on the backlog they had at the time she seemed optimistic that it wouldn't move out but left open the possibility that it could. Because of course, COVID.
https://advanceadapters.com/4559

(1) Luk clutch kit 05-065. Not technically "required" but at 127k miles it would be dumb to have the transmission out and not replace the clutch. I'll have an extra pilot bearing and release bearing because I couldn't buy the clutch or the bellhousing without them. I'll freshen up my flywheel with some emery cloth.
https://www.amazon.com/dp/B000CICYZ4/?tag=wranglerorg-20

(1) pilot bearing remover tool. if I forget to get it before I start the job I'll use the bread trick. The bread trick didn't work, so I went to the zone and got the pilot bearing tool.

(1) Weatherpac connector for the reverse light switch. The NSG370 uses a Mercedes connector that will be cut off and replaced. I got this 5-pack from Amazon https://www.amazon.com/dp/B076H987BN/?tag=wranglerorg-20, and this tool to crimp them https://www.amazon.com/dp/B071KFLY43/?tag=wranglerorg-20

The AA bellhousing kit came with most of the hardware (9 bellhousing to transmission bolts, 3 clutch dust cover bolts, 2 slave cylinder mounting bolts, 1 05-06 CKPS mounting bolt) but for some reason did not include the following, which I sourced from the local Ace Hardware.

(4) 7/16-14 x 1" bolts to mount transmission mount bracket to transmission. The NSG370 used M10x1.5 here. Get flange bolts if you can, use washers if you can't.
(1) 3/8-16 x 2" bolt for starter (again, NSG370 had a metric bolt here). I got a regular hex head and a washer, and had to grind a couple of threads off the length of it because it was bottoming out in the bellhousing before tightening up. I don't think 1-3/4" would have given enough thread engagement, but maybe if it was a flange head and you didn't have to use a washer.
(1) M10x1.5x50 countersunk bolt. I'm welding this on top of the shift lever after I cut it off as the one that came with the transmission was comically long.

I used two additional hex cap screws to attach a cover over the 97-04 CKPS hole, and it's not listed in the bellhousing kit parts list but I have no memory of purchasing them. I think they were the same thread pitch as the 05-06 CKPS, which would make them 1/4-20, but you'll want to make sure.

What's the same or close enough:
1. Overall length. When I had the two side by side last year I measured them as within 1/4", so my driveshafts will be fine.
2. t-case interface. NP231J's all had the same bolt pattern and clocking for the run of the TJ. My t-case has a long input gear that originally came from an AX15, so in a way it's going home, and my front case half came from a 2000 Cherokee with an AW4, which was an identical replacement for the front half that I broke a bolt tab off of during an SYE install in 2019.
3. clutch slave cylinder.

To be considered:
1. The inner shift boot of the NSG370 is basically at tub level, which I expect will conflict with the enlarged section where the upper and lower shift lever meet. The AX15 boot sits proud of the tub to be above this point. My NSG370 boot is trashed anyway and I'm not gonna buy a new one for $180, but if I ditch the hard plastic outer section for an older one, then I think it moves the mounting point for the front half of the center console, so then I'd need one of those from a 2001-2004 TJ. I like the 06 console better so I adapted a <99 AX15 shift boot onto the hard plastic floor plate from the NSG370. https://www.amazon.com/dp/B01BGJM830/?tag=wranglerorg-20
2. I understand the NSG370 transmission mount will bolt up but will interfere with a couple of bolt heads on the AX15, so I need to notch it out to clear those. No problem.

 

[JMT]

starting this thread to document my swap instead of doing it after the fact when my memory is fuzzy.

Background: my NSG370 pops out of reverse. In street use it's tolerable but it's exacerbated when backing against any resistance, such as uphill (like the 8% grade on my driveway) or if a tire has to climb a rock or a log on the trail. This is annoying at best, and at worst could be dangerous or life threatening if on a narrow mountain switchback in Colorado. I had an AX15 in my '99 TJ Sahara, I liked it better, and the cost of swapping is almost the same as a rebuilt NSG370. (this thread is not for the purpose of rehashing the relative merits or issues with either transmission or of changing from one to the other)

Parts Required:
(1) New AX15 transmission. I got mine from Novak because it was $50 less to ship here from Utah than from Advance Adapters in California. It comes with the shift tower and a new shift lever that isn't quite the same as OEM. It's straight, seems thicker, and is unpainted. I'll have to bend it to my needs. It also came with a shift knob that looks decent enough but not stock by any stretch, and has Novak's name on it.
(1) AX15 bellhousing with 05-06 crankshaft position sensor location. My understanding is the bellhousing comes with both CKPS locations so it's backward compatible. The Advance Adapters bellhousing includes all the stuff that goes inside the bellhousing except for the flywheel, disc and pressure plate. At time of order they gave me an expected ship date of May 17. Based on the backlog they had at the time she seemed optimistic that it wouldn't move out but left open the possibility that it could. Because of course, COVID.
(1) Luk clutch kit. Not technically "required" but at 127k miles it would be dumb to have the transmission out and not replace the clutch. I'll have an extra pilot bearing and release bearing because I couldn't buy the clutch or the bellhousing without them. I'll freshen up my flywheel with some emery cloth.
(1) pilot bearing remover tool. if I forget to get it before I start the job I'll use the bread trick.

What's the same or close enough:
1. Overall length. When I had the two side by side last year I measured them as within 1/4", so my driveshafts will be fine.
2. t-case interface. NP231J's all had the same bolt pattern and clocking for the run of the TJ. My t-case has a long input gear that originally came from an AX15, so in a way it's going home, and my front case half came from a 2000 Cherokee with an AW4, which was an identical replacement for the front half that I broke a bolt tab off of during an SYE install in 2019.
3. clutch slave cylinder.

To be considered:
1. The inner shift boot of the NSG370 is basically at tub level, which I expect will conflict with the enlarged section where the upper and lower shift lever meet. The AX15 boot sits proud of the tub to be above this point. My NSG370 boot is trashed anyway and I'm not gonna buy a new one for $180, but if I ditch the hard plastic outer section for an older one, then I think it moves the mounting point for the front half of the center console, so then I'd need one of those from a 2001-2004 TJ. I like the 06 console better so I'm gonna try to adapt either the Mustang boot I have in the parts bin, or an AX15 boot, onto the plastic boot housing from the NSG.
2. I understand the NSG370 transmission mount will bolt up but will interfere with a couple of bolt heads on the AX15, so I need to notch it out to clear those. No problem.
3. I also understand the reverse switch uses a different connector, so I need to acquire the right connector to put onto my harness.

Following. My reverse is a bit of a bear, but tolerable. Are you planning to regear?

 

[freedom_in_4low]

About: AX15

Manufacturer: Aisin (Japan)

Used in Wranglers from 88 to 99. Same basic platform as the R-series Toyota transmission - in fact, several parts are interchangeable. Rumor has it that a first gear assembly and countershaft from an R151F can be swapped into an AX15 to get a 4.3:1 first gear. I haven't come up with anybody actually running such a mod though.

Aisin was founded in 1949 as a joint venture between Toyota and Kawasaki Aircraft Industries making aircraft engines, and is part of the Toyota group.

Visibly, you can see the similarity between the R series and the AX15 between the bellhousing and the bearing carrier plate. (interestingly, the carrier looks steel on the Toyota but looks aluminum on the Jeep). I'm not saying the housing is the same part, but at the very least it looks like the same casting. The fact that Toyota continued using the R series at least as late as 2017 (maybe still using it?) is likely to thank for the fact that we can still buy a new AX15 with upgraded internals 23 years after they were last put in a Jeep.

Toyota R151F, R156F (used in various Toyota and Lexus 4x4's between 1986 and 2017)

Jeep AX-15

About: Chrysler NSG370
Manufacturer: Daimler-Benz (Stuttgart, Germany)

6 speed transmission used in Jeep Liberty, Wrangler, and Dodge Nitro from 2005 to the phase-out of the JK Wrangler in 2018. Rumored to also be used in foreign market Mercedes ML class SUV's. Uses an integral bellhousing. It likely shares some components with other Mercedes transmissions but it's hard to find out what. The engine used in the 2004+ Chrysler Crossfire is rumored to be an NSG370 "variant", whatever that means.

 

[freedom_in_4low]

Following. My reverse is a bit of a bear, but tolerable. Are you planning to regear?

no plans to regear. Our highways are 75-80mph and relatively flat so I don't think I'll miss the 150-200rpm on the interstate. If I miss the 4.46 first gear, I'd rather get it back in the transfer case.

 

[freedom_in_4low]

the shifter handle has 3/8-24 threads...going back into the CJ days it's only been M10x1.5 or 3/8-16, so it's not easily adaptible to any shift knob that I want (which is a stock one). If I can find a threaded insert that goes from M12x1.25 then I could at least put a Toyota knob on there. I just don't like knobs that are metal, ball shaped, etc. I like the soft feel and texture of leather or whatever blend of rubber or plastic that simulates leather....even without the texture like the stock TJ knob would be fine.

good news though, my credit card was run for the bellhousing, and Advance Adapters shows it's status as shipped. They haven't added a tracking number yet but it looks as though I may be ready a month earlier than anticipated.

 

[freedom_in_4low]

This is the knob that came with it. If I can't find a stock looking knob for 3/8-24 threads I'll try to cut it off and tap it or weld a plow bolt on the end.

I don't like the feel in my hand and the connection looks unfinished. Nothing about it looks at home in an otherwise factory stock interior.

 

[freedom_in_4low]

Bellhousing is here, a month before AA said it would be.

Anybody know if the nsg370 dust cover is still gonna work? The lower three bolts look about right in general location but hard to tell with the transmission still attached.

 

[freedom_in_4low]

Anybody know if the nsg370 dust cover is still gonna work? The lower three bolts look about right in general location but hard to tell with the transmission still attached.

answered: it's the same part number from 1987-2006, so yes.

While perusing the parts book I also found this little grommet (#4) that didn't get used on the NSG370, so I don't have one. They're relatively inexpensive so I picked one up on ebay.

I should be used to this by now with all the Savvy stuff I've put on, but similarly, the instructions are more like "tips and general info" and leave it to me to go searching for torque values, where to use the various washers provided, etc.

I suppose since there are 9 bellhousing bolts and 9 inside star washers that must mean the washers are intended for the bellhousing bolts...even the factory parts book is no use here because they don't appear to have used any washers there.

The other 5 lock washers I guess might go on the 3 bolts for the dust cover and the 2 for the slave cylinder?

I didn't get a pilot bushing, but there's one in my Luk clutch kit, so I'll live. And I have an AX15 service manual so I can get all the bolt torques and other instructions there...though even the FSM omits the type of lubricant recommended for the clutch pivot ball. If it was metal I wouldn't worry about it but I know plastic can have material compatibility concerns so I guess I'll just hope that CV2 is good enough.

 

[freedom_in_4low]

answered: it's the same part number from 1987-2006, so yes.

While perusing the parts book I also found this little grommet (#4) that didn't get used on the NSG370, so I don't have one. They're relatively inexpensive so I picked one up on ebay.

View attachment 323712

turns out, that grommet isn't needed. There's no where to put it on the AA bellhousing. I assumed it would be just like the original AX15 housing but with the CKPS location added. Apparently it's not, so I've started a return for it.

 

[freedom_in_4low]

 

[freedom_in_4low]

I'm about halfway through. No luck with the bread trick so I had to hitch a ride to the parts store to get the pilot bearing puller and lost a couple hours. It's out now, but silly me didn't think to put the new one in the freezer while I waited so now I'm waiting for that. I could mount the transfer case up to the AX15 but I think I'd rather not have the extra 70 pounds attached while I'm trying to stab the input shaft in. I'm using a transmission jack but one thing I don't like about it is it doesn't give me good control over the pitch of the transmission. Last clutch job I did, i actually rigged up a sling out of ratchet straps, across the frame and under the transmission, and laid underneath it using my hands and knees to position it while I watched the input shaft. I'm not as young as I was then though, so I'm not sure I'm up to that.

Another lesson learned, I thought I'd just swap the crank pos sensor over while both transmissions were out, but that ended up a stupid move on my part because while I was yanking the trans and tc assembly loose from the engine and clutch, the CKPS got caught on a heat shield and cracked. Glad the Mopar sensor is available and only about $40.

NOTE: The Advance Adapters bellhousing puts the CKPS in the correct location, but it is rotated about 90° from the factory orientation. This points the connector UP instead of REAR. I have a 1" MML and a UCF Extra clearance skid and had to plug in the CKPS before mounting it because there wasn't enough room, and once installed the harness plug is 1/8" or less from the tunnel.

This is too close for comfort in my opinion, and thinking about someone with a higher tuck, I don't know what you'd do about this. Take a hammer to the tunnel, I guess, but I don't know how I'd ever get a good whack there without pulling the whole works out again. I remember there being some wiggle room in the motor mounts when I installed my MML, and I centered the fan in the shroud. I might loosen those bolts back up and try to shift it over to the driver side to get some more room here. I know @mrblaine has done at least one of these swaps so I'm curious what his thoughts are on this. I don't know why, but I just assume every TJ he touches has a Savvy skid

 

[freedom_in_4low]

Side by side

Looks like my rms leak might actually be a valve cover leak based on the oil residue on top of the bellhousing.

Also, the speed sensor on my JB SS SYE is leaking.

 

[freedom_in_4low]

I know it's supposed to be a generic, bend to fit shifter but what on earth would an Ax15 go into that calls for a shifter this tall.

I'm glad I didn't pay a machine shop to rethread it, because I ended up cutting it off. Gonna weld a M10x1.5 bolt onto it so I have stock threads for a factory looking shift knob.

 

[makorider]

Nice write up.
You guys push me to do things I might otherwise not try!!

I have about 150K on my 05 NSG370. Knock on wood, so far so good, but my second daughter is learning stick as we speak...if she's anything like my first forcing shifts and missing gears ....lets just say I'm knocking on wood.. .hard and often, that she stays as is.

What is 5th gear ratio like in comparison to the 370s 6th? Not that its on the highway that much, but curious.

Didn't Mercedes use the 370 in their light box trucks as well?

 

[freedom_in_4low]

I had to go to California for work so I've been off this for a couple days. Just have to finish up the shifter and boot. I did make sure to put oil in it before I left, just to make sure I didn't get excited and start it up before remembering to do it.

 

[freedom_in_4low]

here's my solution to the shift boot problem.

1. Cut rubber out of 05-06 plastic shift boot floor plate
2. fit AX-15 shift boot as neutrally as possible with the shifter but accept that it's going to sit a little to driver because the center console support post is in the way and it wasn't far enough to justify cutting anything up (other than a little bit of the raised "wall" on the driver side)
3. fill gap with scrap sheet of metal...in my case what was left of the bent up Colorado license plate that used to sit on my front bumper (the same one I used to cover the <04 CKPS opening)
4. rivet together (use backing washers where possible because the rivets like to pull out of the plastic if you pull on them too much)
5. seal with seam sealer
6. regret not donning nitrile gloves before you started trying to get the old dried seam sealer out of the nozzle.

 

[JMT]

here's my solution to the shift boot problem.

1. Cut rubber out of 05-06 plastic shift boot floor plate
2. fit AX-15 shift boot as neutrally as possible with the shifter but accept that it's going to sit a little to driver because the center console support post is in the way and it wasn't far enough to justify cutting anything up (other than a little bit of the raised "wall" on the driver side)
3. fill gap with scrap sheet of metal...in my case what was left of the bent up Colorado license plate that used to sit on my front bumper (the same one I used to cover the <04 CKPS opening)
4. rivet together
5. seal with seam sealer
6. regret not donning nitrile gloves before you started trying to get the old dried seam sealer out of the nozzle.

View attachment 331758

View attachment 331759

You probably could have sold that 05-06 lower shifter boot for $100+. They are becoming hard to find, and expensive. There’s a get around somewhere on the forum for $15. I think it’s a Ford shifter boot. Looking good!

 

[freedom_in_4low]

You probably could have sold that 05-06 lower shifter boot for $100+. They are becoming hard to find, and expensive. There’s a get around somewhere on the forum for $15. I think it’s a Ford shifter boot. Looking good!

the rubber I cut out was actually really torn up, so it wouldn't have had much value. I already have the Ford boot laying around from before I decided to do the AX15 swap and was going to use it to repair this one. But the AX15 upper and lower shift levers attach right where the Ford (and the NSG370) boot rides on the lever, so it would have forced the boot a couple inches up or down out of it's neutral position and probably would have eventually torn. The AX15 boot sits up tall to ride above that point.

 

[freedom_in_4low]

the AX15 is in and I've got about 50 miles on it so far.

Impressions:
Feel: the shifter is SO MUCH more precise. I remember having the same impression when I had my 99 and 06 at the same time and could drive them back to back. I can feel it, without doubt, go into reverse and it doesn't give me that feeling the NSG370 did that it might or might not pop out. Better yet, it doesn't pop out. The shift throw feels shorter in every direction. It started a bit notchy but I suspect it'll smooth out as the synchros break in, and I'm either getting used to it or it is actually already beginning to smooth out. My 99 actually would crunch a little bit into 3rd gear, which I blamed on a previous owner likely using non-yellow-metal-safe GL5 in it, or maybe the water it had in it the first time I drained it. Fortunately this one doesn't do that. I filled it with synthetic 10W30 per Aisin's more recent recommendations.

Gearing: I'm not sure I can actually tell that I'm moving faster idling in first gear, but the engine can, because when I hit the 8% grade of my driveway and try to idle up it the way I did with the NSG370, it pulls the rpm down a bit and the PCM reacts with the IAC valve which makes the rig surge a bit. Haven't had it in low range yet. One thing is for certain...I'm NOT regearing again, so if 1st gear/4 low isn't slow enough, I'll be waiting patiently for a reasonable price on a 241.

 

[JMT]

the AX15 is in and I've got about 50 miles on it so far.

Impressions:
Feel: the shifter is SO MUCH more precise. I remember having the same impression when I had my 99 and 06 at the same time and could drive them back to back. I can feel it, without doubt, go into reverse and it doesn't give me that feeling the NSG370 did that it might or might not pop out. Better yet, it doesn't pop out. The shift throw feels shorter in every direction. It started a bit notchy but I suspect it'll smooth out as the synchros break in, and I'm either getting used to it or it is actually already beginning to smooth out. My 99 actually would crunch a little bit into 3rd gear, which I blamed on a previous owner likely using non-yellow-metal-safe GL5 in it, or maybe the water it had in it the first time I drained it. Fortunately this one doesn't do that. I filled it with synthetic 10W30 per Aisin's more recent recommendations.

Gearing: I'm not sure I can actually tell that I'm moving faster idling in first gear, but the engine can, because when I hit the 8% grade of my driveway and try to idle up it the way I did with the NSG370, it pulls the rpm down a bit and the PCM reacts with the IAC valve which makes the rig surge a bit. Haven't had it in low range yet. One thing is for certain...I'm NOT regearing again, so if 1st gear/4 low isn't slow enough, I'll be waiting patiently for a reasonable price on a 241.

4:1 either way!

You probably saw this

https://wranglertjforum.com/threads/rubicon-transfer-case.62353/post-1123915