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Discussion Starter #1
I'm new to participating in the forum. Using this COVID-19 lock down as an opportunity to do some much needed Jeep work. I'm tackling the most ambitious Jeep project I've ever tried. I'm converting my 1994 Wrangler YJ from the stock AX5 transmission to the more robust AX15.



Thought I would document the process here to share what I'm doing (parts, costs, challenges, etc) and hopefully learn from others experiences. I'm not a auto mechanic, so bear with me.


Current status: 1994 2.5L Jeep Wrangler. Previous owner installed oversize 33's, then sold it to me. The differential gearing is good for the 33's, so no problem there. BUT, those 33's destroyed the AX5 transmission very quickly! Lost 5th gear, then 2rd gear, so that drove me to the decision to make the conversion (No way I'm going to do this much work and keep that crappy AX5!!).



I know what I don't know, so that leaves me very uncomfortable. No question, I don't know everything that's needed, so I'm taking it slow. Wanted to get the transmission out and have the core ready, before ordering the replacement transmission.



That's where I am, just removed the transmission this morning. You can see in the photo.



Transmission Removal: NOTE: YouTube is your friend. This video is awesome, I just followed the steps. I did it by myself in a few hours. Couple bolts fought me pretty hard, but overall it was pretty straight forward and "relatively" easy. Only difference with my YJ, was I had to remove the muffler assembly, which added about 45-min, what a PIA.





So far so good, now I'm getting ready to spend some real money and can use some help/opinions before buying (If I didn't ask the right question, feel free to offer advise!):)


Major Decision: Transmission

I didn't want to do all this and reinstall a used non-rebuilt transmission, just too many things could go wrong. So looking at re-manufactured/rebuilt.



So now which transmission? Advance adapters -$1,632.12(New and obvious advantage), or XP Precision -$795.00 (rebuilt says it has may improvements/fixes), or Midwest-$1000 rebuilt, etc. Obviously, rebuilt can save a lot of money. Any recommendations?



Note: 96-99 Dakota 2.5L bell housing: Connects R154 to any Jeep 2.5L L4.
So, I bought a 1998 Dodge Dakota Bell Housing ($140) when I first started thinking about the conversion to adapt my YJ 4 cylinder to the AX15 transmission. Thought that might take a while to find, so I bought the first one I found. Tried it on and it fits-up well to the 2.4L engine.



I do have one concern, the Dakota bell housing (7-7/8") adds about 1" in length from the stock AX5 Bell housing (6-7/8"). The AX15 has a 7-1/2" stick-out with 1-1/8" spline length and 3/4" tip. The Clutch spline is about 2" into the bell housing, so that allows the splines on the stick-out to overlap the spline in the clutch by about 3/4". Is that enough or am I missing something?


Also, still unsure how the input splines are converted. AX5 has 14 splines and the AX15 has 10 splines. Any input on that aspect?


Next planned purchases from Advance Adapter:


1 INPUT GEAR-NP231 23 SPLINE SHORT PRE 95 W/716325A (NP231 Transfer Case converts the 21 spline AX5 output to the 23 Spline AX15 output) - $195.57

1 Kit 715545 NP T/C LINKAGE BRKT - $43.30

1 Kit 715545C NP231-AX15/NV3500 LINKAGE ROD KIT - $30.39

1 Kit 716099A SQUARE STYLE NV3550 SHFT HANDLE - $26.15



If I use the Dakota Bell Housing, will not need 1 Kit 712563 AX15 TO JEEP 4CYL B/H EXTERNAL ($473.56)



Its going to be a slow process, but I appreciate any help offered.
 

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Buy the new trans or a good used... stay away from 'rebuilt'.... a bunch of used parts from multiple trashed transmissions.... while there ARE good ones out there, there's also a fair chance of getting a lemon...
 

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Novak or advance adapters for new. I wouldn't buy a rebuilt unless it was working mostly right before a rebuild. I've seen many transmissions that were "rebuilt" but the rebuilder obviously never checked clearances, shaft runout or other important things reputable shops do.
 

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Ok First I want to do this also. I also have a midwest rebuilt transmission that sticks in second gear and wont come out. I changed the oil and it was full of metal shavings. I called and they said it was out of warranty. I bought the jeep at the end of the warranty period and not putting good money after bad. So a ax15 is a good choice. I will be following.
 

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Splines only need to match the clutch disc so have to get one that patches the splines


Sent from my iPhone using Tapatalk
 

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Discussion Starter #6
Thanks Digger84, that makes sense. So I'm reading this to simply replace the clutch with 4.0L clutch to work with the AX15 10-spline input. Then that makes input 10 spline and on the other end, the adapter makes output 23 spline. All good.
 

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This is out of my wheelhouse, but I'm thinking check Flywheel too for clutch surface area.
 

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Don't spend $200 on an input gear...
Call davies jeeps and get one for like $20
 

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I don't know if you need a linkage bracket but if you do, get it from davies...
Really doubt you need the linkage

Can't see any reason you'd want a nv3500 shifter for an ax15... won't fit
 

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Discussion Starter #10
Status: Transmission is out, stripping off the Transfer Case, Bell Housing, clutch release, and removing the Clutch Assembly
Next Issue: Clutch and Flywheel

Issue: The AX5 has a 9-1/8" disk with a 1-1/8" 14-spline input and the AX5 flywheel accepts a 0.59" tip. The AX-15 has a 10.4" disk with 1-1/8" 10-spline input and the I6 flywheel accepts a 0.75" tip.

Solution:
Clutch: Advance Adapters makes a 9-1/8" disk ($78.95) with 1-1/8" 10-spline input and 0.75" tip that can be used with a standard AX5 clutch cover (reuse or purchase new from any auto parts store). Novack offers a clutch assembly for the conversion with the 9-1/8" disk, 1-1/8" 10-spline input and 0.75" tip ($144). Don't forget a clutch tool!
Flywheel: Both Novak and Advance Adapters make a Bushing to fit the AX5 Flywheel and the AX15 Transmission. Requires the a special tool (Puller) to remove the old, then insert the new. I think I can get the puller on loan from our local auto parts store. Though it might be a challenge with the lock down.

Everyone has limited response capability, so moving forward will get slower. Once I place the orders, I'll update.
 

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Discussion Starter #11 (Edited)
New Issue: Clutch Release Arm.
Question: Can I reuse the AX5 clutch release arm with the AX15 transmission. Anyone know for sure?

New Issue: Clutch Slave Cylinder
Question: Can I reuse the AX5 External Slave Cylinder with the AX15 transmission. Anyone know for sure?
 

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Discussion Starter #12
Update on the Dakota Bell Housing: Earlier I was not sure if the extra length of the Dakota housing would create any problems. Confirmed, no issues. So highly recommend starting your search for a 96-99 Dakota 2.5L bell housing as soon as you can. Or, your other choice is to reuse the AX5 BH and buy a $475 adapter. These Dakota years used the AX15 transmission with the I4 engine. Makes a great conversion BH.
 

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Update on the Dakota Bell Housing: Earlier I was not sure if the extra length of the Dakota housing would create any problems. Confirmed, no issues. So highly recommend starting your search for a 96-99 Dakota 2.5L bell housing as soon as you can. Or, your other choice is to reuse the AX5 BH and buy a $475 adapter. These Dakota years used the AX15 transmission with the I4 engine. Makes a great conversion BH.
You could have also just gotten a clutch kit and all needed parts for these years of dakota's as they have the same 2.5l I4 motor as jeeps.
 

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Discussion Starter #14
You could have also just gotten a clutch kit and all needed parts for these years of dakota's as they have the same 2.5l I4 motor as jeeps.
I thought so as well, but they all have a 14-spline input that doesn't work with the AX15 10-Spline input. I found this article that confirmed, they used the same parts EXCEPT the 2WD has a 14 spline and the 4WD has a 10-spline AX15 transmission input.
 

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You don't need any special tool to remove the pilot bushing, just pack it full of bread and drive a punch in more bread and repeat until it comes out
Really just regular old bread like you make a sandwich with and a punch that's fairly close to the size of the hole in the bushing
 

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Measure the tip of your transmission input shaft and buy a wooden dowel as close to that size as you can find. (Naturally a larger one won't fit into the opening in the pilot bearing). Cram the hole in the bearing with white bread (best) but most any bread will do., Compress the bread by pounding on the dowel. Add bread as necessary until the bearing comes out. A bolt can work in lieu of a dowel, or anything similar. The bread is the trick.

Good Luck, L.M.
 

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I thought so as well, but they all have a 14-spline input that doesn't work with the AX15 10-Spline input. I found this article that confirmed, they used the same parts EXCEPT the 2WD has a 14 spline and the 4WD has a 10-spline AX15 transmission input.
It can't be a 2wd vs 4wd difference since I have used cherokee/wrangler/3.9l dodge dakota ax15 inputs interchangeably regardless of 2wd vs 4wd. Dodge must have used the same 14 spline pattern clutch disc that the ax5 had with the 2.5l dakota ax15 to cut down on clutch costs. That means the dakota 2.5l ax15 has the 14 spline input. Never paid too much attention to that and I've rebuilt many of them....
 

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Discussion Starter #18
I decided to go with a used transmission. Ordered it yesterday from "Deadjeeps". The cost of new was putting this AX5 to AX15 conversion price tag to almost what I paid for the jeep. So I'm going with a combination of new/used parts:
Used:
AX15 Transmission
Used Shifter and handle w/spring twist lock
Used AX-15 4x4 Shifting linkage, bracket, linkage rod, shifter and handle

Finalizing the New parts order with Novack. Publish once ordered.
 

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Discussion Starter #19
Next Issue: I was going to used the "bread method" to get the pilot bearing out, but its actually mounted behind the flywheel. So now I'm removing the flywheel, then the pilot bearing. That will mark a milestone where I'll finish the tear-out part and I'll now officially start the rebuild portion!!
 

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Next Issue: I was going to used the "bread method" to get the pilot bearing out, but its actually mounted behind the flywheel. So now I'm removing the flywheel, then the pilot bearing. That will mark a milestone where I'll finish the tear-out part and I'll now officially start the rebuild portion!!
Please post a pic. I can't picture in my mind how the flywheel can block access to the pilot bearing.

Good Luck, L.M.
 
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