Transmission oil - not GL5 but use ?????

Could ANYONE :helpme: please specify for me in direct & clear words what oils spec. I shall use on my AX15 ?? (Must I use a GL3 ???)

Please use format as follows

# Mnfc...........Prod. Name........SAE.........API...........other info
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Check my website, Tech section.

API spec is GL-3 - lower content of sulphur, which is better. Sulphur in liquid at elevated temperatures is antagonistic to yellow metals (copper alloys) - like your synchroniser rings. If you've ever driven a really old stick shift, you know what it's like (ever have to double-clutch anything?)

As far as brand, just stick to something you like. I tend to stick to Valvoline, Castrol, or Sta-Lube.

Hint - I usually end up using the same thing in my axles and manual gearbox - the SAE viscosity spec is actually a bit less important than the API EP lube spec (that's what the GL number is - it goes from 1 to I think six, from "no" sulphur EP lube to loads,) and there's some overlap anyhow. I'd have to check (and I honestly don't feel like doing it right now...) but I seem to recall that I've got a load of Valvoline 75W-90 GL-3 out there with the LSD modifier already added (I've got one OEM LSD, and it doesn't hurt anything if you don't need it) to keep things simple. I like keeping logistics simple where I can - I've got enough complicated crap to deal with already (I spent the last few days organising in-flight oxygen support for my MIL to fly out to OKC on Monday. If Mike thinks she's not staying out there for a few months after I've gone to all this work, I'll have to harm him severely...)

But yes, you must use a GL-3. Or lower (GL-1 or GL-2 will work - GL-3 is about as high as you can go without running into trouble. If your oil is gold when you drain it, you're doing it wrong.) Unlike the API specs on engine oil, the GL specs are not backwards compatible!

Hell, the new API SM "Energy Saving" spec is bad enough - and it should be avoided for our rigs. The SM spec contains a much lower proportion of ZDDP anti-scuff additive, and that means cam/lifter failure in relatively short order. SL or older - prefereably with a Diesel spec as well - or you'll have to get an additive like GM's EOS.)

I thought they used ATF.

what about this Quaker State oil, type Syncromesh ?
(I'm located in Europe and GL3 is hard get).

Oh. Didn't see that.

API being "American Petroleum Institute," I can see why it would be difficult to find that spec. However, you are still going to go mainly by the content of Extreme Pressure (EP) lubricant - which is typically sulphur or sulphur-based. You want a moderate, low, or no sulphur content - as I'd said, having too high of a concentration of sulphur EP lubes can literall dissolved yellow metals in relatively short order.

While I can't read most of the page you've linked, it is fortunate that the linked .pdf datasheet is in English. I'm not entirely sure what the "GLS" specificiation relates to over here, but the "Excellent Yellow Metals Compatibility" line is what you're primarily looking after. This means that it should not dissolve anything, which is the important bit.

@Ron - nope, AX-15 uses real transmission fluid. You know - thick and brown as opposed to red and runny! It's the really new light-duty manual gearboxes (particularly transaxles) that use Dexron - transfer cases have been using it slightly longer. While the switch to ATF for lubricating manual gearboxes has been driven by the desire to save energy, pumping losses, and driveline parasitic drag; I think you'll find that anything that is meant for towing or hauling is going to want something a bit sturdier for lubrication - and gear oil has more "cling factor" or "stiction" (call it what you will) for metal surfaces than ATF ever will. Very important for splash lubrication - that's why I still haven't seen a live axle that takes the stuff (not even the Viper - and it's fairly common to mount an electric pump to cycle the stuff through a cooler!)

Thank you for your complete facts 5-90. Think I'm going for this "syncromesh" and x fingers and hope for the best.

Rgds Tom

For the last 6 years I have been running Redline MTL in my AX-15. It seems to shift smoother and run quieter with the Redline fluid.

Whatever you do, DO NOT let Jeep or any other aftermarket source tell you GL5 is OK in an AX-15. This is false. Years ago, Jeep had an error in their books. Stated the AX-15 used GL5. This was bad info. Jeep corrected it, but never acknowledged they made a mistake.

TJ Rat said:

For the last 6 years I have been running Redline MTL in my AX-15. It seems to shift smoother and run quieter with the Redline fluid.

Whatever you do, DO NOT let Jeep or any other aftermarket source tell you GL5 is OK in an AX-15. This is false. Years ago, Jeep had an error in their books. Stated the AX-15 used GL5. This was bad info. Jeep corrected it, but never acknowledged they made a mistake.

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That's why I explained it the way I did - he's across the puddle, so the API spec probably doesn't mean anything to him. However, finding gear oils that are "Yellow Metal Compatible" is doable just about anywhere (all you need is a datasheet,) so I made sure to explain that - and why it was so.

(One might get the - quite correct! - idea that I've been doing a fair bit of this...:read: :read: :repair: :repair: )

Oh - and the GL-5 mistake is probably a carryover from using the Peugeot gearbox. I've torn four of those apart - there's not a speck of "yellow metal" in that case. The synchronisers are aluminum, which is half of the problem of why they don't last worth a damn. The other part? The gears are made too hard - I checked. HRC 55-60 is decent for a knife blade or a bearing race, but too hard for a gear tooth (should be down around HRC 40-44 or so.)

5-90 said:

@Ron - nope, AX-15 uses real transmission fluid. You know - thick and brown as opposed to red and runny! It's the really new light-duty manual gearboxes (particularly transaxles) that use Dexron - transfer cases have been using it slightly longer. While the switch to ATF for lubricating manual gearboxes has been driven by the desire to save energy, pumping losses, and driveline parasitic drag; I think you'll find that anything that is meant for towing or hauling is going to want something a bit sturdier for lubrication - and gear oil has more "cling factor" or "stiction" (call it what you will) for metal surfaces than ATF ever will. Very important for splash lubrication - that's why I still haven't seen a live axle that takes the stuff (not even the Viper - and it's fairly common to mount an electric pump to cycle the stuff through a cooler!)

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I could have sworn I heard that.

Looking it up in the manual I find:
AX-5 Mopar 75w-90 API GL-3
NV3550 ONLY! Mopar Manual Transmission Fluid PN/ 4761526
AW-4 Dextron IIE/Mercron (not Dextron II as can cause clutches to chatter).
30RH Dextron 3 (not Dextron II)

It's a 2001 manual, no mention of a AX-15.

I think you sell ATF short. The TF-999 or the modern 30RH contains a number of gear assemblys. On top of it, the fluid must withstand lubricating the entire assembly, the torque converter innards, and be able to be compressed at will, and withstand high temperatures. The transfer case also uses ATF and it transfers all the power from the transmission to the shafts. You rairly hear of an automatic transmission or a Jeep T-case failing for lack of lubrication.

If there is any reason a transaxle uses a high viscosity fluid, it is not because it sticks better to the parts, but because the higher viscosity provides a larger cushion layer between the moving parts, high clearance parts which are being subjected to a large side load such as a pinion and ring gear.

I do know that the T5 requires ATF, and it was explained to me it is only because the overdrive is in the extension housing, thinner fluid to reach it I guess.
And yes, put ATF in your transfer case
Now I have to go and find out if my 84 has the AX5 or the T5

Zuki-Ron said:

I could have sworn I heard that.

Looking it up in the manual I find:
AX-5 Mopar 75w-90 API GL-3
NV3550 ONLY! Mopar Manual Transmission Fluid PN/ 4761526
AW-4 Dextron IIE/Mercron (not Dextron II as can cause clutches to chatter).
30RH Dextron 3 (not Dextron II)

It's a 2001 manual, no mention of a AX-15.

I think you sell ATF short. The TF-999 or the modern 30RH contains a number of gear assemblys. On top of it, the fluid must withstand lubricating the entire assembly, the torque converter innards, and be able to be compressed at will, and withstand high temperatures. The transfer case also uses ATF and it transfers all the power from the transmission to the shafts. You rairly hear of an automatic transmission or a Jeep T-case failing for lack of lubrication.

If there is any reason a transaxle uses a high viscosity fluid, it is not because it sticks better to the parts, but because the higher viscosity provides a larger cushion layer between the moving parts, high clearance parts which are being subjected to a large side load such as a pinion and ring gear.

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No argument - I've seen quite a few hydraulic systems (industrial!) that use Dexron for fluid instead of conventional 10-vis hydraulic (or 20-vis, which seems to be about as high as that goes. It's typcally a bit lower - 5-vis or 0-vis.)

But, gear oil is more designed for "splash" lubrication, while ATF likes to be circulated with a pump - note that small pump and pickup assembly in our NP231/NP242 cases, vice the D300 - the D300 is splash-lubed, so it requires fluid with more "stiction" than ATF (that's also why the D300 can be safely flipped, while the NP231/NP242 cannot. Since it requires a pump to circulate, you'd have to redesign the pickup to grab fluid from wherever the new bottom ends up.)

As far as the NV3550, I'll have to check - I thought that, like the NV4500, it had its own funky spec synthetic lube that it liked, although Redline and/or AMSOil had something else that would work as well. Perhaps I'm just getting a wire crossed there (I'm fairly sure about the -4500, but not the -3550.)

Automatics in general contan several planetary gearsets, but there is a pump in the automatic that circulates the fluid around, and the planetary gearsets have a constant supply of fresh fluid. Yes, higher viscosities provide more "cushion" between moving parts (gears and the like,) but I don't recall there being a lot of "slipper" or "oil-film" bearings in transmissions spec'd for gear oil, while you're likely to see some in transmissions spec'd for Dexron (there are probably bushings made of bronze or Oilite, but that's not the same sort of thing.)

Oh - and the 30RH spec isn't "Dexron 3" - it's "Chrysler ATF +3" - you may want to recheck that. The typical Dexron spec is Dexron/Mercon, Dexron II/IIE/III, Mercon V, or something similar - while the 3xRx and 4xRx slushboxes usually seem to want ChryCo ATF +3/+4 (different friction modifiers. Transfer cases don't care, and there has been a good deal of headache caused by using +3 in the AW4, which is spec'd for DII. You can therefore use Dexron II/IIE/III/Mercon V in that, since ATF specs are reverse compatible.)

Your 2001FSM gives GL-3 as the spec for the AX-5? I wonder when they corrected that (you don't use GL-5 in any of the Aisin AX-series boxes - all for the same reason.)

As far as fluid types, I just coped what was in the manual, and though I used my own language for their cautions, that is what was printed.

Sure Automatics have a circulation system and the bearings the drum gear rides on are presurized, but the gear sets are all splash oiled from overspray. Same thing with the Transfer cases. The main bearings are pressurized and everything else is splash oiled.

I was sure I heard somewhere that ATF was OK'd for use in AX-5 transmissions, or maybe it was 30W. However, what is in the book is gold to me.

You have to get away from this "sticktation" idea you have. It's all about viscosity. If you have two surfaces that you want to lubricate, you need to provide separation. A high volume of a low viscosity fluid, is a good sub for a high viscosity-low volume fluid if you can do it. The problem with unsubmerged gears, like an axle, is that there is no way to contain the surface like there is a surface bearing and you can't build pressure, so that's why they chose a high viscosity fluid, not "sticktation".

AX-5 gear cases are pretty much submerged in fluid, so I would think that ATF or atleast a lower viscosity fluid would be OK.

Honda has been using 30W oil in transaxle cases since their 1200 Civic day without a problem. Imersion, tighter clearances, and not loading the transaxle directly allows them to run a lower viscosity fliud and not have wear related failures.

Zuki-Ron said:

As far as fluid types, I just coped what was in the manual, and though I used my own language for their cautions, that is what was printed.

Sure Automatics have a circulation system and the bearings the drum gear rides on are presurized, but the gear sets are all splash oiled from overspray. Same thing with the Transfer cases. The main bearings are pressurized and everything else is splash oiled.

I was sure I heard somewhere that ATF was OK'd for use in AX-5 transmissions, or maybe it was 30W. However, what is in the book is gold to me.

You have to get away from this "sticktation" idea you have. It's all about viscosity. If you have two surfaces that you want to lubricate, you need to provide separation. A high volume of a low viscosity fluid, is a good sub for a high viscosity-low volume fluid if you can do it. The problem with unsubmerged gears, like an axle, is that there is no way to contain the surface like there is a surface bearing and you can't build pressure, so that's why they chose a high viscosity fluid, not "sticktation".

AX-5 gear cases are pretty much submerged in fluid, so I would think that ATF or atleast a lower viscosity fluid would be OK.

Honda has been using 30W oil in transaxle cases since their 1200 Civic day without a problem. Imersion, tighter clearances, and not loading the transaxle directly allows them to run a lower viscosity fliud and not have wear related failures.

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I vaguely remember that about Honda - my 1980 Accord ran the same oil in the transaxle as it did in the engine (kept logistics simple, again. I like that...)

Most autos I've torn down have bushings or oil-film bearings for the shafts (like in your engine,) and Torrington thrust bearings for in between (flat rollers arranged in a circle, so that parts don't have to rub against each other.) Torringtons don't tend to require a great deal of lubrication, so they're covered by oil splashing around anyhow.

I can see where some confusion is arising - as I use it WRT oils, "stiction" refers to the surface adhesion of the oil. When you have a dip/splash lubed system (typical manual transmission or drive axle,) lubrication to the entire assembly is essentially provided by the portion that dips down into the lubricant, and the lubricant is then carried up into the rest of the train. "Stiction." Surface adhesion.

It doesn't have much to do with viscosity - it's more to do with surface tension than anything else. The additive that sees to that is a sort of "reverse surfactant" - I don't know what it would be called, but it actually increases surface tension a bit, rather than decreasing it (as a contrast, soap is technicall a "surfactant." It works to make water "wetter" - breaking down surface tension, so that it gets into/around/under more. It's not the soap that removes dirt from your hands - unless it has pumice in it. It's the fact that the water is able to get into more. Gear oil has an additive that does much the same thing in reverse - and engine oil and ATF has the same additive, only to a lesser degree. It's not as necessary when you have a circulating pump.) If you want more lubrication in a "dip/splash" setup, you either increase the fill level (meaning that the distance the lube has to travel "up" is reduced,) or you lower the assembly (same net effect.)

Does gear oil stick to surfaces more than engine oil or transmission fluid? I had a half-full 5 gallon bucket of gear oil upend itself in a work truck once upon a time, and it took me the best part of a month of cleaning at the end of the day to get it out enough to cut the smell down. Had a case of engine oil get caught under the generator when it fell, and I had that hosed out inside of a week. Something is added to gear oil to make it sticky, let me tell you!

Viscosity is largely controlled by the base oil - gear oil comes from a "lower fraction" than engine oil or ATF. When crude oil is run through a cracking tower during refining, fractions can be anything from asphalt to kerosene, and there are a couple of gaseous fractions and a couple called "distillates" that are used as solvents (petroleum distillates are the most common.) Crude is "flashed" into a vapour at high temperatures, fed into the bottom of the tower, and then the various fractions separate/condense out at various levels - with lighter fractions going to higher levels in the tower. It's a fractional distillation process. Gasoline and Diesel, natch, are fractions as well - with Diesel being a "lower/heavier" fraction than gasoline.

Viscosity is largely controlled by base stock, and then modified by the use of long-chain temperature-sensitive polymer additives. Surface action is also controlled by additives - sometimes surfactants are added (intentionally or no. Most detergents added to engine oils and transmission fluids are also surfactants,) sometimes straight viscosity improvers are added, sometimes surface action improvers are added (makes the oil "stickier" than it would normally be, counters the action of surfactants, or whatever,) and any of a number of other things as well. Granted, I only took one semester of O Chem back in 1987, and what I know of petrochemistry comes from research and learning that way, so it's entirely possible I could have something mixed up. However, that's how I've been given to understand it.

Viscosity is what builds the cushion between moving parts, I'll not argue that at all. But, aren't the properties of lubricating oils myriad in number, and compromises to be made? Petrochemists make those compromises in a technical sense all of the time - for me, I have to make compromises in language, since I don't know the words that are supposed to be used to describe what I'm talking about... So, I'm always willing to be corrected - but it does take some doing to prove that I'm wrong. It is possible...

I have a Neon R/T (my poor man's sports car), that community has gone through the "using ATF as manual trans fluid" also.

New Venture, the maker of lots of gearboxes and transfer cases, that have NV- in the front of the trans name; Chrysler using those gearboxes in some other vehicles have recommended their ATF+4 as the fluid to use.

Chrysler, around 2003, switched to ATF+4 for the factory fill for a lot of vehicles and different systems in their vehicles. Including Power Steering Fluid. Most people believe this was a cost savings measures for Chrysler. As far as the NV-Gearboxes in Neons, people reported better shifting and performance when they replaced the ATF+4 with the OEM Manual Trans Fluid used a few years before, or other MT Fluids like Redline or Synchromesh.

Remember, ATF+4 is high quality synthetic ATF that evolved over years from Chrysler trying to correct all its problems with the A-604 automatic trans.

There have been lots of transmissions for other vehicles, that the manufacturer used certain engine oil or certain ATF as the fluid, which adds to the confusion.

Remember, whats recommended for one transmission, DOES NOT MEAN IT WORK IN ANOTHER TRANSMISSION. The smartest thing to do is to use the fluid recommended by the manufacturer, unless of course the manufacturer made a mistake in its documentation, i.e. Recommending GL-5 for AX-5 and AX-15 Trans.

I can't argue with 5-90's recommendations, I use Redline MT-90 in my AX-5, yes its a GL-4, but it is also synthetic and the literature states that the synthetic and its additive package make it a GL-4 that won't become corrosive to yellow metal at more than twice the temperature of other GL-4's, I think the spec was over 450°. I think its safe, there have been lots of posts from MT-90 users saying they have never had any problem.

One last thing, Friction Modifier some Manual Transmission Fluids have them, some don't, NO GEAR LUBE has it. If you have limited slip differentials that use clutches, you have to add Friction Modifier.

Synchros have frictions surfaces, some trans have big honking synchros that don't need the Friction Modifier to engage quickly and smoothly. Some trans have smaller synchros or use materials for the Synchros that DO NEED Friction Modifier.

My little Neon R/T's NV-350 is suppose to have friction modifier for the Synchros. I haven't seen anything saying the AX-5/15 needs friction modifier, and the opinions vary. I'm sure your safe using straight gear lube if you like. But if you use a Manual Trans Fluid with Friction Modifier, you might get quicker and smoother shifting. Redline MTL and MT-90 have lots of friction modifier in it.

I'll second the vote for RedLine MTL (I chose that over MTL-90 as it gets below 0*F in winter here). The difference between RedLine and the bottle of cheap GL3 from Napa was like night and day, especially for the first few 1-2 shifts on cold mornings. I filled with the cheap stuff after I rebuilt the tranny, planning to run it for a week and then change over. It shifted so bad on the GL3 I thought I buggered the rebuild. Put the RedLine in and it shifted fantastic.

I have heard a lot of recommendations for the SynchroMesh, and a few folks swearing by straight 30W motor oil for colder climates.