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Ax15 transmission gear oil


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I have found some conflicting information concerning the use of certain gear lubricants in the AX15 transmission.   The factory service manual recommends 75w90 GL-3.   The dealer only supplies synthetic gear & axle lubricant 75W90 GL-5.   It is almost impossible these days to find 75W-90 GL-3.   What I have also found is that GL-3 gear lubricant does not have the sulphur content (EP additives) that GL-5 has that can be damaging to the brass synchros.  My solution so far is a product called MT-90 made by REDLINE. http://www.redlineoil.com/content/files/tech/MTL%20and%20MT-90%20Tech%20Info.pdf  This is a gear oil that is rated GL-4 and is 75W90 gear oil.  What I am concerned about is the sulphur content in the GL-4.  So what I am loooking for is a 75W90 gear oil with low to no sulphur content but also is not going to be to slippery for synchro contact.  There is also rumours that mopar has designated 10W30 as the replacement for the 75W90 GL-3.  What do you think? 

 

Thanks, Jason

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Mopar offered a specific AX5/AX15 gear lubricant with its own part number.  Ask your dealer to check for that number in the Mopar Parts Catalog and see if there is a superceded number.  That should point to the right replacement lube if the AX5/AX15 oil is no longer available. At the magazine, in the lengthy lubrication article, I show a bottle of the Mopar AX5/AX15 lube.  I took that photo in 2004, and the oil was still available at that time...If you hit the wall, ask here again, and I will furnish part numbers for the original Mopar lube...

 

The Aisin transmission synchros are very touchy, and the issue with the Aisin transmissions is exactly what you suggest.  Too much lubricity in the lube, the synchro rings will not brake against the gear hubs—and there will be clash on shifts.  Too little lubricity is also an issue, the unit will run hot, damage bearings and fail. 

 

I learned years ago to match the OEM ratings for that reason...Sounds like Redline is close.  If you do use that lube, make sure there is no clash and that synchros shift okay when cold—or hot.  Again, my preference would be the OEM Mopar AX5/AX15 or exact equivalent lube if available. Mopar's 75W-90 synthetic gear and axle lube sounds more than adequate, but only if the synchros like it. My concern would be the braking action of the synchro rings when cold or hot.—Moses

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Hey fellows,
                  The new specs from Mopar do call for 10w30 in the AX15, although I hear that redline is a very good product. My old transmission has the older style gear oil in it now (75W 90), and as Mr. Ludel was alluding, there can be problems with too much lubricity! My best advice is to figure out the kind of wear that you have on your transmission parts (given mileage, usage, maintenance history, type of driving[off road vs. mostly highway]). Once you do that, and have a look at your old tranny fluid for tell tale warnings, select the oil closest to the OEM that takes those factors into account. I know of guys who run Royal Purple in their transmissions, and some who swear by the heavier Redline... Hope this has been of help!

 

Sincerely,

Pete H.

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Here is a link to the article and part number for Mopar's very own AX5/AX15 oil: http://www.4wdmechanix.com/Jeep-4WD-Lube-Oil-and-Filter-Service.html.  Go to my illustration #29 for details...Ask the dealer for the exact supercede to this part number...Trust this helps clarify...Moses

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Doesn't make sense to me! A motor oil is not an EP oil.  I have heard of motor oil variations for manual transmissions, but this is really a stretch.  I would take your thoughts and the experience of Pete H. and try the Redline.  Follow my caveats about the Redline or any other oils regarding lubricity and synchro ring action. 

 

10W-30 seems way astray from 75W-90 GL-3, -4 or -5.  I'm puzzled about the Mopar recommendation and personally would not go there...Moses

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The reason that my Mopar dealer told me was that the 10w30 was found to protect as well as the older gear oil, without the sulfur that can affect the brass parts found in asian transmissions. I was incredulous, to say the least! I know that the AX 15 and its mates are no Muncie rock crushers, but the shear protection of 10w30 sounds, well, inadequate under load.
Also, as was mentioned earlier, the AX15 stock synchros tend to be, er, touchy. (Thank God they are not as bad as the Peugeot!). The first and second in my experience tend to have problems with hard shifting when cold and the transmission has a few miles behind it. I reckon it's a fault with the AX 15 that was easier to mask by superseding the old gear oil with the new spec. Some I know folks do run the 10w30 in their tranny to ease the problem, and change the oil as if it were in their crankcase, on the order of every few thousand miles. AMSOIL also offers both the Mopar spec, as well as  the "hey that can't be right" 75w90.

Best Regards,

Pete H.

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Toyota has used the AX15 for years.  In addition to authoring the Jeep Owner's Bible, I wrote the Toyota Truck & Land Cruiser Owner's Bible. Jeep and Toyota generously supplied period OEM books for my Bentley Publishers' ventures...

 

I just pulled the '93 Toyota T100 shop manual off the shelf, and guess what?  Toyota recommends API GL-4 or GL-5 and a 75W-90 rating for the transmission lubricant.  Given that Toyota has produced far more trucks with Aisin transmissions than Jeep, let's consider this insight useful. As for which GL-4 or GL-5 75W-90 oil to use, I believe this comes down to lubricity. 

 

Many years ago, when I wrote the "Holy Moses!" tech Q&A column for OFF-ROAD Magazine, I became enchanted with all oils synthetic.  This held true for engine oils and gear lubes, and my Jeep Owner's Bible, from first to third editions, promotes Mobil 1 engine oil...At the same time that I became infatuated with Mobil 1 engine oil, I recommended Mobil gear lube to the readership of the magazine.  Lo and behold, I received a nice letter, tactful and diplomatic, from a Toyota truck owner.  (This was around 1988-89.)  He shared that when trying Mobil synthetic gear lube in his transmission, the unit developed clash on shifting.

 

I deduced that this was from insufficient braking action of the brass blocking rings, and I immediately sided with him, noting that the recommended Toyota lube, non-synthetic in those days, worked better in his gearbox.  The Mobil gear lube had too much lubricity, which simply would not allow the rings to brake properly against the gear hubs during synchronization.  (The rings slipped on the hub rather than grabbing it.)  He changed back to the OEM lube and did not have a problem thereafter...I stopped proselytizing synthetic gear lube as a "universal good thing"—unless recommended for a specific gearbox or axle application.

 

So, that said, I recommend either the original Mopar AX5/AX15 Lubricant (if it can be found in NOS form) or Toyota's recommended API GL-4 or GL-5 in 75W-90—as a non-synthetic choice.  (In 1993, Toyota did not use synthetic gear lube as a factory or dealership service fill.) 

 

Redline may have a specific lube that works well with the AX5 or AX15, so I defer to Redline's experience here.  Ask Redline to be sure.  There is so much buzz about AX transmission lubes that Redline should have this down by now.  Also, Amsoil has a tech line, you might compare viewpoints.

 

When a Redline or Amsoil official recommendation comes forward and gets tested by someone in this forum community, please report back.  Maybe we can put the "AX oil" thing to bed...Moses

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  • 4 months later...

Ok guys, i did a bit of research, as well as talking to a rep at both Redline and AMSOIL, and here is where they directed me to, product wise, for the AX15:

 

AMSOIL recommendation, using a direct quote from the link the rep sent me to: Manual Transmission, AX15 (5-SPD)......GL-5,  All TEMPS......75W-90

 

         SEVERE GEAR 75W-90 Synthetic EP Lubricant (SVGQT)
         75W-90 Synthetic Long Life Gear Lube (FGRQT)
         SAE 80W-90 Synthetic Gear Lube (AGLQT)

 

Redline recommendation, from talking to the rep, and from people i have talked to the last few weeks online and in person: MT-90 75W90 GL-4 Gear Oil

  • Offers quicker shifts, perfect synchronizer coefficient of friction
  • Safe for brass synchros, as it lacks the reactive sulfurs found in most GL-5 oils that cause damage
  • High performance gear protection and longer synchro life
  • Eliminates notchy shifting, even when cold
  • Satisifies the gear oil viscosity requirements of 75W, 80W and motor oil viscosities of SAE 40, 10W40, and 15W40
  • Recommended for GL-1, GL-3, and GL-4 applications, as well as where most special synchromesh fluids are specified
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