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Need Help with Stick to Auto Conversion

erikwylie

Jealousy Root of all Evil
Location
Las Vegas, NV
Ok, I have 90 Cherokee with AX-15 trans in it that is giving me issues. I have access to an 89 with an AW4 and all the parts needed. Please how do I hook up the computers? Am I gonna have to splice into the main harness and if I do which wires do I connect to.

I have searched but not coming back with anything that I really understand. I am just wondering if this is gonna be just a couple of weekends or am I looking at a major reconstruction.

Any help or links would be great.

TIA
Erik
 
erikwylie said:
Ok, I have 90 Cherokee with AX-15 trans in it that is giving me issues. I have access to an 89 with an AW4 and all the parts needed. Please how do I hook up the computers? Am I gonna have to splice into the main harness and if I do which wires do I connect to.

I have searched but not coming back with anything that I really understand. I am just wondering if this is gonna be just a couple of weekends or am I looking at a major reconstruction.

Any help or links would be great.

TIA
Erik

Make sure you get the TCU and replace the TPS (since the RENIX auto TPS is actually two units in one, while the manual TPS is a single sensor. You can't "split the signal" - since the transmission sensor and engine sensor work in opposite directions.

Apart from that, they're independent systems. I don't recall if all the wiring is already in place on the manual, tho - do you have access to the donor vehicle? I've got a 1990 that's slated for deconstruction (AX-15,) but I've not been able to get to it yet.
 
5-90 said:
Make sure you get the TCU and replace the TPS (since the RENIX auto TPS is actually two units in one, while the manual TPS is a single sensor. You can't "split the signal" - since the transmission sensor and engine sensor work in opposite directions.

Apart from that, they're independent systems. I don't recall if all the wiring is already in place on the manual, tho - do you have access to the donor vehicle? I do have access to the donor vehicle, harness computer pedal all, just a little nervouse on the wireing part as I am color blind, and have a bad shake in my hands for soldering.
I've got a 1990 that's slated for deconstruction (AX-15,) but I've not been able to get to it yet. A direct bolt in is not out of the question either, if I can afford to buy it, so think about it.
 

If you've got the full donor vehicle, the job has just become much simpler - and your being colourblind or having shaking hands should now be a non-issue. Since you've got the full vehicle, you can just replace the subharnesses as required - should be plug-and-pray.

RENIX ran a separate transmission controller (under the PAX side of the dash, methinks...) and you can just look up there in your current vehicle to see if you have the plugs already. Also, check the branch of the engine bay harness that plugs into your TPS - if you see a 4-pole connector that's not connected to anything in the same branch (2x2 square,) you've got that already as well.

The only real engine bay problem I can think of for you is the connection for the NSS (2x4 Deustch, I think) - but if you've got the donor, you can just swap the engine bay harness entire and call it good. The underdash harness would be a bit more difficult, but I'm inclined to think all the connections are there (there's not an awful lot of communication between the RENIX ECU and the AW4 TCU. I'm informed that the ECUs for A/T and M/T have different part numbers, but I need to recheck. Per Hollander's, I think they were the same animal...)

What do you plan to do with the old goodies, anyhow? Just wondering...
 
Thanks again, for the help, haven't thought of what to do with the old "goodies" I presume your refering to the old trans? are you in need of one?
 
erikwylie said:
Thanks again, for the help, haven't thought of what to do with the old "goodies" I presume your refering to the old trans? are you in need of one?

Old pretty much anything - I'm trying to start a "parts exchange", especially for older (RENIX and OBD-I, to 1995) rigs. Sheetmetal and such would be cumbersome to store, but electrics, electronics, and hard parts are all getting harder to find - and I'd like to do my bit to make things easier for all of us (what do you think I plan to do with parts after I finish deconstructing the 1990 I've got? And get done taking measurements and cataloging information?)

So, pretty much anything you're not going to use, I'd like to talk to you about. As far as the transmission goes, what's wrong with it?

Oh - one thing I forgot to mention earlier - count the splines on your donor transmission. Should be either 21 or 23 - the AX-15 uses a 23-spline output. If you need a 21-spline transfer case input, I may be able to scare one up for you - as I recall, it was a mid-year 1989 change from 21-spline to 23-spline, coincident with the changeover from the BA-10/5 to the AX-15 (the AW4 just changed outputs.)
 
The transmission started giving me problems a couple of months ago, we thought it was the clutch, so we changed the clutch and throw out bearing and what not. It was making a noise like the a spring was rolling around in the bellhouseing, so after we changed the clutch, it was still doing the same thing, only worse. now it is having a hard time going in and out of gear. That is the reason for the trans swap.
 
erikwylie said:
The transmission started giving me problems a couple of months ago, we thought it was the clutch, so we changed the clutch and throw out bearing and what not. It was making a noise like the a spring was rolling around in the bellhouseing, so after we changed the clutch, it was still doing the same thing, only worse. now it is having a hard time going in and out of gear. That is the reason for the trans swap.

The bellhousing-end noise may be an input bearing going south on you, which could be a wear issue or the pilot bushing/bearing has been gone for a while (which can also cause an input bearing failure.)

Hard shifting - what gear oil have you been using? AX-15s like using GL-3 - GL-5 (which is easier to find) causes the synchroniser rings to self-destruct after a while. Most people don't know this, and the FSM recommends GL-5 (which it should not...) and you run into trouble that way. Kinda like using ATF +3/+4 in an AW4 - causes clutch chatter, because the friction modifiers are different (the AW4 was designed for Dexron II/IIE/III ATF, as it is a Toyota box - not a Chrysler!)

So, sounds like an input bearing and synchroniser rings - might as well just overhaul the thing from the off...
 
I would much rather convert to an Auto so my wife can also drive it. (might let me wheel more) Plus I believe I already have everything I need in the doner jeep. I am mainly just concerned with the electrical portion of the swap.
 
erikwylie said:
I would much rather convert to an Auto so my wife can also drive it. (might let me wheel more) Plus I believe I already have everything I need in the doner jeep. I am mainly just concerned with the electrical portion of the swap.

D'oh! Forgot about that... That takes care of the input gear issue - just swap the whole transfer case!
 
erikwylie said:
Oh and as far as gear oil, I used 10w30 per the recomendation of a Jeep mechanic.

And we put a new pilot bearing in.

Wow. 10w-30 is way too light for the AX-15. You need to use 75w-90, Redline MT-90 is arguably the best fluid for the AX series transmissions. That mechanic that told you that should pay for any damage done to that transmission due to running the 10w-30.
 
tgoff said:
Wow. 10w-30 is way too light for the AX-15. You need to use 75w-90, Redline MT-90 is arguably the best fluid for the AX series transmissions. That mechanic that told you that should pay for any damage done to that transmission due to running the 10w-30.

That is interesting, I was actually told by more than one guy from Jeep that 10w30 is the way to go. I am now second guessing my self though. I only put about 100 miles on the jeep before I started having the shifting issues. The weird noise was happening even before I put the new clutch in.
 
I'd worry about running something that light in the AX-15. If there were shifting difficulties due to age, I'd probably run around a 40- or 50-viscosity racing engine oil, maybe a straight 30, but nothing lighter. I know a lot of "modern" manuals are designed for 10W-30, 5W-30, and I've even seen one for 0W-20!, but I wouldn't run something that thin in a real transmission.

Unless, maybe, I was down at McMurdo Sound Research Station...
 
I double checked my FSM to make sure and it does call for 75w-90 gear oil for both the AX-5 and AX-15 transmissions. You need to find a GL-4 gear oil which is becoming hard to find now a days in the local parts store. This is due to the brass syncros which will get deteriorated by the GL-5 gear oil sulfer content. I run MT-90 from Redline and highly recommend it. It may cost a little more but the performance in both hot and cold shifts plus the extra protection it offers is well worth it.
 
tgoff said:
I double checked my FSM to make sure and it does call for 75w-90 gear oil for both the AX-5 and AX-15 transmissions. You need to find a GL-4 gear oil which is becoming hard to find now a days in the local parts store. This is due to the brass syncros which will get deteriorated by the GL-5 gear oil sulfer content. I run MT-90 from Redline and highly recommend it. It may cost a little more but the performance in both hot and cold shifts plus the extra protection it offers is well worth it.

I think though it may be too late for a simple oil chang at this point. I would think that damage is already done.
 
For the Renix, there are no connections between the TCU and ECU. Most of the auto tranny wiring is between the TCU and the tranny. The wiring harness from the tranny computer goes through the firewall where most of the wiring ends in the two connectors for the two harnesses (NSS and sensors/solenoids) going down to the tranny. There are another handful of wires that you'll have to splice into the main wiring harness.

From memory: it's constant power, ignition switched power, ground, 3-wires to the second connector on the TPS, wire going over to the extra brake pedal switch, wire going over to the comfort/power switch, a couple of wires to the yellow diagnostic connector (don't bother hooking up), backup wire from the NSS sensor, and a park/neutral wire from the NSS. I didn't bother hooking up the park/neutral sense wire as Jeep starts without it anyway. For the power and ground wires, I just dug in the harness and found matching color wires that had power or ground when they were supposed to.

Also, before you put the tranny up, you'll want to redrill the hole on the xfer case linkage bracket on the body side 2" further forward. The xfer case linkage rod is 3" longer minus the tranny being 1" longer than the AX15.

Short answer is to plan for a long weekend or two as there are lots of misc things to track down such as trim pieces. Being good with wiring will really help. Also keep in mind that the spline counts on the tranny output willl be different so you 'd need to swap over the xfer case as well.

Feel free to PM me if you run into problems.
 
It calls for 75w-90, but if you go into the parts department at your local dealer and ask for it, for an AX-15, and it will supersede to 10w 30 motor oil. I was the guy who told him to run this. I live in hot sunny socal, and run this stuff all year round, I have had no problems with it, and niether have any of the other 100 or so jeeps and older dakota trucks that I have put it in. If you want to see thin fluid, go ask the parts department for NV3500 fluid, it's almost like water, not to mention it's also used in the NV3550, and the NV5600 which is used behind the 5.9l cummins. I have no Idea how many miles are on my AX, I bought it used with around 130k on it, and I really don't know how many are on there now, because my speedo dosen't work. It made the cold shifts better which is why crysler recomends you put it in.

5-90, if you want the information about this supersedence please PM me and I will get you the info, seeing as how you have so much of it availible to others.

Justin
 
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Can you post that info? I've heard of putting in 10W-30 for very cold climates where gear oil would be like molasses, but I'm wondering just how appropriate it would be for a warm weather climate. My instinct tells me that the bearings would be fine, but you'd wear the gear faces and synchros faster. On the plus side, motor oil doesn't have the brass easting sulfurs like the GL4 and GL5 have.
 
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