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Issues Shifting to 2nd and 4th on Rebuilt AX15

Jeep Wrangler Jeep TJ Jeep 4.0L Jeep how-to AX15

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#1 CJMall

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Posted 06 September 2013 - 10:45 AM

I have recently installed a rebuilt AX15 in my 98 TJ. From the beginning it has been difficult to shift into 2nd and 4th gears. By difficult I mean it requires some strength to pull to engage as if there is a bungee cord opposing the direction I'm pulling. It will engage each time and does not have any noises associated with these shifts. It occurs only while shifting up into these gears. It shifts into all others fine and down shifts into them fine as well. If I have shifted into one of the gears I can shift back into it with no difficulty if I down/up shift momentarily the shift back.

 

The shop I got it from is blaming it on the fact that I used 75W-90 oil at first. They recommended I switch to 5W-30 synthetic and change the oil a couple times to get the gear oil off the syncros. I have since done so with no effect. The local mopar dealer mechanic thinks it is a bent shift rail or fork. Does anyone have any ideas on this? I want to know if it will break in and get better or if I need to tear it down and inspect the parts for bends?



#2 Moses Ludel

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Posted 06 September 2013 - 11:00 AM

Welcome to the forums, CJMall!  Your AX15 transmission issue can be added to the AX15 discussion here at the YJ and TJ Jeep Wrangler forum. 

 

I'll jump into this with a quick question...Since 2nd and 4th are on different shift rails and forks, it's uncommon to have the same symptom on both.  It is not uncommon, however, to have a restriction at the floorboard or matting if your TJ Wrangler has a lift kit with a "dropped" transfer case. 

 

The dropped transfer case (rear of the skid plate) angles the shift lever and shift tower rearward.  The boot, carpet and other obstructions often occur in this configuration, and the two gears affected would be 2nd and 4th.   Check this if you do have a dropped transfer case/skid plate, or in any case, make sure there is no other obstruction to the shift lever.

 

Beyond this, there is a lengthy discussion right here at this Jeep YJ and TJ Wrangler forum on the AX15 and rebuild quirks.  You'll find this of interest, CJMall.  Also, if you're trying to get a better visual on the AX15 internal mechanisms, I have a 209-illustration article at the magazine on step-by-step rebuilding of an AX15 transmission.

 

There are many of us interested in helping you solve this problem.  This is a start, we can go from here...

 

Moses



#3 biggman100

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Posted 06 September 2013 - 04:17 PM

CJMall, welcome to the forums. I dont know if this would apply in your situation, but i heard that having a bad transmission mount, or missing bolts in the mount, or having the skid plate not completely bolted on properly, can cause the transmission to twist a bit on its mount, and that can cause it to not want to shift properly, especially in 2nd, 4th, and reverse. Granted, this is second hand information, but i have heard this from enough people, and after you posted this question, i did a search on it, and several members on other Jeep forums said pretty much the same thing.

 

As for the type of oil to use, most i have talked to recommend either a synthetic 10w-30, or redline MTL, or redline MTL90. One person i talked to, although it was about a Dakota with an AX15, which according to Moses is similar enough to the Jeep AX15 for this purpose, said that even Chrysler/Dodge/Jeep has changed their recommended fluid for all manual transmissions, except the NV3550, to either regular synthetic motor oil, or the redline products. Moses or one of the other members on the forum may have further insight on that.



#4 Moses Ludel

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Posted 06 September 2013 - 06:05 PM

We had a great discussion about AX15 transmission oil at this forum topic: http://www.4wdmechanix.com/forums/topic/47-ax15-transmission-gear-oil/.

 

This should answer some questions...Open for more if necessary...

 

Moses



#5 CJMall

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Posted 10 September 2013 - 06:54 AM

biggman100

 

I have a new prothane trans mount on this application. My skid plate has taken some abuse, but when I had it off I checked that everything was square and not out of alignment. Is this issue associated with the shifter coming in contact with the floor pan as Moses described earlier?



#6 CJMall

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Posted 10 September 2013 - 08:01 AM

Moses, I have no lift on my jeep. I could have sworn that I checked the clearance of my shifter when I reinstalled the new transmission. I will remove the console and check today. Wouldn't I have the same problems in reverse if this were the case? Thanks for both of your input.

 

I have no clearance issues between my shifter and the floor. I just did a test drive to notice this and discovered something. The problem only happens at high RPMs. It shifts fine if I'm shifting early at lower RPMs. Could this still relate back to a oil problem and the synchros not grabbing properly or should I drop this tranny out and tear it apart to see if the gear hubs and synchros are not mating well enough to cause the braking action?



#7 Moses Ludel

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Posted 10 September 2013 - 11:58 AM

CJMall, you're thinking like a transmission mechanic ("technician") now!  There is a relationship between synchro action and rpm.  And you're spot-on about the braking action of synchros.  Also, as you hint, lubrication can make a difference here.  I like Biggman100's research on the Redline and Amsoil alternatives.  Again, refer to: http://www.4wdmechanix.com/forums/topic/47-ax15-transmission-gear-oil/.  These findings are in step with my skepticism about 10W-30 motor oil, or any motor oil for that matter, working in an EP lubricant environment.

 

Note: When I researched oil options, Toyota's use of the AX15 (Aisin 150 in Toyota parlance) transmission came up with the GL-4 (and we can include the GL-5) findings—straight out of the factory workshop manuals for Toyota trucks like the Tacoma.  I'm drawn to Toyota's findings, they've used Aisin transmissions forever and have huge numbers of these trucks in service.

 

Before taking the transmission out, I would look into two possibilities:  1) the first being the lubricant, and 2) the clutch release.  It's just possible that your clutch is not getting enough release throw.  Simply put, the clutch is not releasing fully with the pedal depressed. 

 

This can happen with the Jeep TJ Wrangler when using aftermarket clutch parts.  (Some clutch kits even come with a spacer/shim that fits between the clutch slave cylinder at the bellhousing and the Jeep TJ Wrangler's slave unit;  this positions the slave piston to adjust the slave rod's travel.)   Not sure which release bearing, disk and clutch cover you have or whether you had the flywheel resurfaced.  Each can be a source of clutch release travel trouble. 

 

3rd gear would seem suspect, too, but the long throw of the shifter between 2nd and 3rd can provide more time for gear synchronization or drop-off of shaft rpm.  A quick check of the clutch pedal engagement point is to note how far off the floorboard the clutch begins to engage.  If very little, you may not be getting full clutch disengagement with the pedal depressed.  Try shifting 2nd and 4th with a conscious effort to push the pedal to the floorboard.

 

On the Jeep TJ Wrangler, the hydraulic clutch ("linkage") travel is not adjustable other than the clutch pedal height (which can dictate slave travel).  Check out the full clutch disengagement possibility...Also, a dragging clutch disk or pilot bearing can prevent the input gear from disengaging with the clutch pedal depressed.  Binding or drag of any kind—like a bad pilot bearing, warped clutch disk, a misalignment of the transmission to bellhousing—can prevent complete input shaft disengagement when you depress the clutch pedal.

 

Consider each of these possibilities before plunging into the AX15 transmission.  This issue could still be internal to the AX15, but if your rebuilding shop/supplier is experienced, let's give them the benefit of the doubt for now...If it narrows to the transmission, we can discuss what to look for inside an AX15...

 

We'll continue to assist!

 

Moses



#8 CJMall

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Posted 10 September 2013 - 04:21 PM

Moses, my clutch still feels to engage at the correct point, and I fully depress it with each shift. I do not suspect it to be the culprit part.  

 

I just ordered a gallon of MT-90 transmission lube. I will post once I have a chance to put a few miles on it after the oil change.



#9 Moses Ludel

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Posted 10 September 2013 - 07:58 PM

Sounds like its worth the oil change.  If that does not provide a cure, you can drain and strain that oil through fresh 100-mesh screen and use it again.  100-mesh is equivalent to vintage automatic transmission fluid guidelines.  As long as the oil is still "new" enough and not scorched, it should maintain its quality properties. 

 

Your oil change will be telling, the results should be of value to members and guests...

 

Moses



#10 CJMall

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Posted 12 September 2013 - 06:14 PM

I just changed the 5w-30 I had in my transmission over to some Redline MT-90. I have only driven it 20-30 miles since, but this new oil has made the symptoms worse. I can no longer shift into 2nd and 4th at lower RPMs. I am getting some gear grinding now as well. 

 

I will be removing the transmission to check the gear hubs once I have time. I want to check the other hard parts now to make sure this company didn't give me any other junk that will shorten the life of my AX15. 



#11 Moses Ludel

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Posted 12 September 2013 - 07:14 PM

Well, CJMall, that's a quick lesson...Use my article as a guide for teardown, inspection and reassembly.  Tolerances are close and critical on the AX15.  If you follow the steps and measurements, you should locate the problem.  We're looking for a cause here, you want a specific problem to crop up.

 

Check the synchro rings carefully for spacing/braking surface.  The measurements on synchro ring gap indicate the wear degree.  Also, be certain the correct rings are in use and at correct positions.  We had a great deal of discussion about these synchro rings for the late Jeep TJ Wrangler AX15 transmissions.  Review the discussions for details, especially this one and the threads and topics related to it:

 

http://www.4wdmechanix.com/forums/topic/57-ax-15-shifting-problem-after-rebuild/

 

In this exchange, I included an AX15 orientation done by a tech college instructor for a YouTube video.  He did an excellent job of explaining how this (Toyota 150 or AX15) unit functions...Coupled with my 209-step how-to, you will have a good perspective for a quality rebuild.

 

Here to answer any questions, CJMall.

 

Moses



#12 Moses Ludel

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Posted 14 September 2013 - 09:28 AM

As a footnote, I'll again emphasize that the AX15 is a complex transmission and rebuilding it requires thoughtfulness and focus.  In our many forum discussions on the AX15 transmission, you will find informative, in-depth information. 

 

These exchanges even deal with nuances that seldom get discussed—like the synchronizer blocking rings that suddenly changed part numbers and design in the late '90s.  Most AX15 "quirks" seem to center around these later transmissions, and the aftermarket parts sources appear to be lagging about the correct replacement synchro rings.  Note the Mopar part number differences discussed at our Jeep YJ/TJ Wrangler forum topics on the AX15.

 

At this forum, you'll find many insights.  The Weber State University instructor's YouTube video (which I embedded at one of the AX15 forum topics) will provide a great overview of the AX15 (Toyota A150) transmission and how it functions.  Take the time to view that 24-minute video and get an orientation to the transmission: http://www.4wdmechan...-after-rebuild/.

 

My 209-step, illustrated how-to article should provide the rebuilding instructions.  That article is in two parts, the first part found at: http://www.4wdmechan...Inspection.html

 

Due to the complexity of this unit, some viewers never get past the first part/page of my article before opting for a rebuilt exchange unit or reaching out for a new AX15 transmission assembly from Advance Adapters.  Whatever you decide to do, CJMall, you've got the support here!

 

Moses



#13 CJMall

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Posted 08 November 2013 - 03:33 PM

Moses,

 

I have finally found the time to break my AX15 down. I have ran into a snag. On my transmission the clip outside the 5th gear spacer is a nut with a crimp in it (see attached picture). How do you back this nut up to remove it? Do I have to cut some notches in the nut to relieve the two crimps before removing it? Also, what do I torque this to once I begin to reassemble?

 

Thanks for your help. 

CJMall

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#14 Moses Ludel

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Posted 09 November 2013 - 06:27 AM

Hi, CJMall...I have some very interesting news regarding the nut in your illustration.  After close research through all Mopar service references from 1989-99, it's clear that this is not a Jeep counter/cluster gear.  All Jeep applications of the AX15 use a selective fit snap ring behind the 5th gear, not a nut. 

 

All Jeep/Mopar parts references to the AX15 transmission also show the use of a selective fit snap ring at this location, not a nut.  The unit in my step-by-step, two part series on the AX-15 is early '90s, and I have a 1998 Jeep TJ Wrangler Mopar shop manual that also shows the snap ring use.  I checked my Mopar TechAuthority subscriber info to see if 1999 uses a nut instead of a snap ring.  Not so for Jeep AX15 transmissions.

 

Here are two PDFs showing 1989 and 1999 parts layouts plus the entire 1999 Mopar parts listing for both the later AX5 and AX15 transmissions for those seeking genuine Mopar parts access for the later TJ Wrangler or XJ Cherokee:

 

Attached File  1989 AX15 Countergear and 5th Snap Ring.pdf   65.09KB   2 downloads Attached File  5th Gear Snap Ring on AX15.pdf   97.44KB   1 downloads Attached File  AX15 1999 Jeep Transmission Parts.pdf   701.48KB   3 downloads

 

As for the nut being there in the first place, I looked further to provide an explanation.  Your AX15 transmission is a "rebuilt" unit, and therefore subject to available parts from cores.  Toyota uses the AX15 as the "150" transmission, and I went into my Toyota OEM shop manuals.  In the 1993 Toyota T100 shop manual, I found the countershaft/cluster 5th gear end with a nut instead of a snap ring.  You apparently have a Toyota transmission countershaft/cluster gear with the 5th gear hold nut.

 

Toyota wants you to use a "hammer and chisel" to open up the staking in the nut.  (If there are two stakes, the nut has been reused.  The current stake in the shaft slot is the one you need to open.)  I suggest making a narrow, wedge shaped pry tool from an old chisel.  Shape the end to just fit into the shaft slot.  With care, you can tap inward with a hammer, which will pry out the indented nut flange without damaging the machined slot.

 

The Toyota torque figure for the re-torque after installation is 94 ft-lb or 127 N-m.  Make sure you stake the nut flange into the slot after torqueing the nut.  If the stake area of the flange is fresh, the nut often gets re-used.  If you want to replace the nut, see your Toyota dealer and not the local Jeep dealership!

 

Will all of this work together?  If the gears and synchronizer assemblies are a matched set and all tolerances match with Jeep or Toyota figures, this can work.  There are apparently interchange possibilities here, as your counter/cluster gear indicates.  However, if tolerances, spacing, gear mesh, synchronizer parts alignment, gear alignment or other problems exist with this parts "mixing", you may have unearthed your shifting problem.  Problems can occur even when mixing strictly used Jeep parts, so rely on actual measurements and the true fit/alignment of parts.  Again, see my two-part article for details...

 

Let us know how the Jeep-Toyota marriage works out.  Check out the parts alignment between gears and positions on the shafts, gear backlash, synchronizer parts fit and for any signs of mismatched or misaligned pieces.

 

Moses



#15 CJMall

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Posted 10 November 2013 - 05:00 PM

I measured the tolerances of my gears and came up with 1st-0.004", 2nd-0.008", and 3rd-0.013". The third is a little out of spec. Is it usually the gear or the fixed thrust washer that wears and needs replaced?

 

CJMall



#16 Moses Ludel

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Posted 10 November 2013 - 08:52 PM

Check the 3rd gear thrust for wear indicated by a "step" at the non-contact surfaces.  Same with the gear contact face.  The thrust is as hard as the shaft and likely the same hardness as the case-hardened gear face.

 

You may have the wrong 3rd gear synchronizer hub snap ring in place.  If that ring does not fill the snap ring groove, the gear can show too much clearance at the thrust face.  The synchro hub snap ring is a selective fit and may be the wrong (too narrow) ring.  It must seat yet be snug in the groove.

 

If there are no overt signs of wear at the thrust face or the gear face, and if the snap ring fills the hub gap completely with the hub seated all the way (see my rebuilding illustrations here), then there could be a mismatch of parts.  When core parts get scattered and gathered, a rebuilt transmission can wind up with a mix of "high" and "low" tolerance parts, and this can produce errors.  In your case, though, I'd first suspect an unseated or damaged synchro hub or an overly thin snap ring.

 

If the issue is just the snap ring, you can source wider snap rings, using the original as your base and increasing the width to just fill the snap ring groove gap completely...Let us know what you find here.  If you need the third gear thrust thickness measurement or snap ring available widths, let me know.  I'll research numbers from Jeep and/or Toyota.

 

Moses



#17 ttippetts

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Posted 15 January 2014 - 09:34 AM

I just wanted to say thanks to you all for all for the knowledge and detail that has been posted for the AX15.  I'm currently in the rebuild phase of my 1999 TJ AX15 and have it disassembled with the exception of pressing apart the main shaft. I find it helpful to now know about the 3&4th synchro change that was made and will most likely not be correct in my "kit" that I have yet to order.  Keep up the good work!


Tracy (ttippetts)


#18 Moses Ludel

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Posted 15 January 2014 - 02:24 PM

TTippetts, you're very welcome, glad the forums work for your projects...Members have been very helpful, and I'm pleased to chime into the discussion.  2014 should be a great year for the groups!

 

The later synchro change is ahead of the parts suppliers in many cases.  You now know what to look for and how to determine the parts differences.  What began as news to many at the forums has eventually helped Jeep TJ Wrangler owners with the late AX15 transmission design.  Let's trust the parts suppliers will catch up here! 

 

Thanks, looking forward to your input...

 

Moses





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