95 YJ, 2.5L 4 cyl manual trans gear oil selection - JeepForum.com
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Unread 08-21-2006, 11:22 AM   #1
merlin2375
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95 YJ, 2.5L 4 cyl manual trans gear oil selection

I have a 95 YJ that desperately needs some new gear oil. It is the AX-5 manual transmission since it is a 95 with the stock tranny.

I have searched up and down and read up and down and here is what I have heard:

Jeep/Hayes manual reccomends GL-5 fluid and that it can eat the syncros (read this in many places)
Many jeepers reccomend redline MTL or MT-90
People use synchromesh (is this synthetic??)
Redline (the company) reccomends 75W90 NS (I called them)
Dealer quoted me a price for a GL-3 lubricant (I called them)

I have no idea, the jeep has 100K on it and I don't know the last time the tranny fluid was changed. My biggest thing is not destroying the transmission. So I am looking for a safe choice that will provide good protection and not eat the brass synchros.

Given the mileage and all this stuff what do you guys reccomend?

Thanks a lot!

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Unread 08-21-2006, 11:50 AM   #2
Brown Dog
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I use 75W90. I really like it, and the transmission has performed flawlessly for over 100K miles.
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Unread 08-21-2006, 12:03 PM   #3
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You will need to use conventional GL3 gear lube or a GL4 rated synthetic. Redline MT90 and Amsoil MTG are two commonly used products in the AX5 and AX15 boxes.
Mobil 1 gear lube or run of the mill 75W90 GL5 sta-lube types are not the right tool for the job.
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Unread 08-21-2006, 01:46 PM   #4
mrobertson
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I've got a bad 3rd gear synchro. I can only shift it by letting the RPM's come down before attempting.

I put synchromesh in and it didn't make 1 bit of difference and it was expensive. I just drained it and put in non synthetic 75W90 and it shifts better than it ever has and was 1/2 the price of the synchromesh.

Take it for what it's worth....


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Unread 08-21-2006, 02:35 PM   #5
Smash209
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Redline works, but I personally like the Dealership oil better. It is expensive, but it is designed for these trannys. My conclusions are that synthetic gear oil like redline and amsoil may protect better, but the syncros need a little friction to work, thats why I've found that the real Mopar oil to be a little smoother to shift.
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Unread 08-21-2006, 03:45 PM   #6
1stJeepyj
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Quote:
Originally Posted by Smash209
Redline works, but I personally like the Dealership oil better. It is expensive, but it is designed for these trannys. My conclusions are that synthetic gear oil like redline and amsoil may protect better, but the syncros need a little friction to work, thats why I've found that the real Mopar oil to be a little smoother to shift.
I didn't realize that?????
I use Redline MT 90 and love it. It smoothed out my tranny.
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Unread 08-21-2006, 03:53 PM   #7
accord387
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I have penzoil synchromesh in my ax5 right now (no local places had the right redline in stock at the time), i have no complaints. When i put in my rebuilt tranny i'll be running redline though. I think it's worth the extra money to get the good stuff on something that doesn't get replaced very often.
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Unread 08-22-2006, 08:32 AM   #8
merlin2375
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thanks very much for the info guys, while I've heard a lot of info, the one thing that is constant is that GL-5 is not reccomended.

Here's what I can say, it definitely seems like 75w90 is the right weight and it's really more about what GL spec the oil meets

Redline
MTL (75w80) is a GL4
MT-90 is a GL4
75w90NS is a GL5
Synchromesh is unknown.

Basicallly I am hearing that GL5 is bad, and that GL4 or GL3 is better. So som e more questions:

1) What do the GL specs exactly mean?
2) Does redline make a GL3 application?

Right now I will say I am leaning towards the MT-90, heavier weight GL4!

Thanks again!
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Unread 08-22-2006, 11:08 AM   #9
Smash209
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GL-1; Specified for spiral-bevel and worm gear axles and some manual transmissions under very mild service. Usually contains rust and oxidation inhibitors with pour point depressants and anti-foamants. Most R&O oils or AW hydraulic oils will suffice here.

GL-2; Specified for worm gear service more than can be satisfied by GL-1. Most R&O oils or AW hydraulic oils will suffice here.

GL-3; Specified for manual transmissions and spiral-bevel axles under moderately severe service. Most Tractor Hydraulic fluids (THF) or AW hydraulic fluids will suffice here.

GL-4; Specified for hypoid gear service under severe service but without shock loading. This classification is essentially obsolete but is still specified by some manual transmission/transaxle manufacturers. Implies an EP/AW additive package that contains 30% to 50% less S-P additives than the GL-5 service classification. Some Marine Gear Lubes fall into this classification, especially the full Synthetic Marine Gear lubes and specialty blenders MT lubes that use high levels of esters.

GL-5; Specified for hypoid gear service but with shock loads and severe service operation. Usually meets Mil-L-2105D and in most cases, is the multipurpose automotive gear oil. Most 75W90 to 75W140 grades meet the GL-5 classification. This grade has a high level of Extreme-Pressure additives that could be mildly corrosive to nonferrous parts, such as brass, bronze and aluminum parts. Most of the modern GL-5 lubes contain metal deactivators that prevents attacks by the extreme-pressure additives. In addition to EP additives, these lubes contain rust inhibitors, defoamants, friction modifiers, thickeners, and Viscosity Index Improvers.

GL-6; Although some manufacturers still specify this lube, it is obsolete as well and was never adopted by the API.
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Unread 08-23-2006, 12:11 PM   #10
merlin2375
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sounds like MT90 it is!
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