Little Trucks, Big World

Lubrication for Transmission Rebuild....GL5 or ATF...

Here's one I was presented with today. I decided to let a professional Transmission house rebuild my FS5W71B 5 speed transmission. They suggested to fill it with ATF, after the rebuild, being as it is very cold up here in Quebec city, and Martin the owner of the company claims that using ATF in the manual transmission rebuilds he does, is working out much better than standard oil. The issue he claims is with lubrication and the cold, the ATF he says works much better, and his customers are very happy as he has had no returns. He says on cold days, that the GL4, and GL5 is too thick, and the bearings & other parts, starve for lubrication, which is causing bearing failure at an earlier interval. What do you think Tiger Racing? and Datzen Mike, and other Oil specialists? Should I go with the ATF? or stay put with the GL4 - GL5 ?  Id' like your input on this...DAttsun Al, 

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Well in very cold climates, I would certainly use a lighter weight gear oil, just as Nissan recommends.  But I certainly wouldn't use straight ATF, it's not designed for the type of gears in these transmissions...  Personally, I'd probably go with a synthetic gear oil or additive like Lucas...  I have been in instances where it was so cold, and the oil so thick, that the transmission was still trying to turn the tires even while in neutral lol...  But the thing is, once it's warmed up, you're not going to have the viscosity you need with ATF...  Not a chance I'd be willing to take myself, not unless he's guaranteeing it will work, or he'll replace your transmission at no cost.  I've heard of people using ATF as an additive, but never using it straight in a manual gear box that wasn't designed for it.

I'm sure Mike and Doug can add something to this since they both live in colder climates.

Well you could run straight 75W if you don't expect the temps to rise above 50F but in Quebec this would mean changing it for the summer again. I use a synthetic blend in mine and it sure looks 'thinner' than the GL4 it's supposed to use.

As to the ATF, many newer cars use it or thinner motor oil from the factory. I see no problem with it for use in the winter. Automatics run very hot in the summer and lubricate the same gears and bearings. It is very detergent and high in anti foam ans anti rust additives.

The biggest difference is that automatics don't really run with the moving parts immersed in oil as there is a hydraulic oil pump and fluid is circulated under pressure. There is enough normal seepage thrown around to lube everything. A standard transmission relies on splash oiling to lube everything. I would imagine that a standard would foam the oil more than an automatic but this isn't a problem like it is in an auto that relies on hydraulics. I found no one saying to NEVER run ATF in their standards.

I agree with Corey's input, as well as yours, about the ATF, I found many guys running it and claim its just fine. With your input, and this, " EP additives can indeed wear away synchromesh materials at a faster rate as wished for. another by-product of EP-additives may actually be friction reduction, which may lead to longer shifting times and possibly overheating of synchros. standard gearbox oils do use a certain amount of EP additives to prevent tooth wear - the art in making a gear oil is to strike the right balance between wear protection of gear surfaces while at the same time not compromising the synchromeshes. usually this is achieved by using less EP additive (API GL-4 level) whereas backaxles usually contain twice as much EP-additives. The latter products should be avoided in gearboxes unless explicitly required by the manufacturer. " found on -- http://www.eng-tips.com/viewthread.cfm?qid=69574  by romke, I will go with the GL4, as indicated by Nissan, in my manual. I'm thinking an 80w according to the temp chart. 

Yes absolutely. GL4 is indicated by Nissan and has been forever. GL 4 does have the correct balance of sulphur additives (about 4%) that won't harm the phosphor bronze synchros. GL 5 contains about 6% and on the face of it 2% more isn't much but it is! That 2% difference is actually a 50% increase in sulphur additives. Transmissions transfer power at along the same axis while the differential gears do so around a 90 degree corner and the gears 'rub' together differently and need more anti scuffing sulphur additives.

Be sure that any transmission oil says 'yellow metal safe' or 'safe for copper/brass/bronze synchros'. Simply saying meets or exceeds GL4 doesn't mean much because GL5 far exceeds GL4 because of the sulphur compounds. GL4 is GL4, so look for it and use it, don't listen to a mechanic born after 1985.

Understood, will do, Thanks Mike, 

Mike I stand corrected, thanks for opening my eyes to the additive issue, I was focused solely on the lubrication standard whereas in many brands GL5 is recognized to meet and exceed GL4...  Interestingly though, the additives are not even part of the GL specification...

I also wasn't aware that Nissan had issued a specific warning about using GL-5 in manual transmissions, but found a reference to it in my research.

The only problem now being that the GL4 specification was retired in July of 2010 by the American Petroleum Institute...  (By a 12 to 1 vote, Chevron being the only no) Which means unless a manufacturer voluntarily complies with the previous standard, there's no guarantee that it will meet those specifications any more, API won't (can't) test samples for compliance.

"Without access to the required tests, additive suppliers and lubricant marketers tend to use one or both of the following methods to support API GL-4 claims, said Buzdygon.
Under the “50 percent treat rate” approach, if API GL-5 quality can be documented for a given treat rate of an additive package, then half the treat rate of that additive package is deemed to provide API GL-4 quality. This approach is not documented in any API, SAE, or ASTM publication, but it is used frequently in the industry, Buzdygon said, and although this approach may have been valid in the past, being based on actual test data, this approach would not necessarily apply to untested additive chemistry.

second method is to document performance by running selected tests that are similar to the original API GL-4 tests listed in ASTM STP 512A. However, technical judgment is required to make a proper choice of test method and test results, and varies greatly within the industry, said Buzdygon."


So this relatively new specification MT-1, which is designed for manual transmissions, would appear to me to be the next best thing to substitute for GL-4 if and when it is no longer available.

I have yet to find an oil with the MT-1 specification, it will be interesting to see if they state they are yellow metal safe...

OK, you've educated me, but then confused me there Mike...  How could ATF possibly be ok considering what you've just said about GL-5?  ATF is not GL-4, it has even higher concentrations of EP additives than GL-5, and it's the wrong viscosity???  Is there any ATF that states it is yellow metal safe?

ATF is fine. In fact, most transmissions today will run great on ATF. I know all about the metals used in the transmissions and the claim that we should only use GL4, however ATF will not harm, corrode, pit or damage these transmissions in any way. The percentage of yellow metal in these transmissions is not high enough to be damaged by ATF. In fact, It will run great and last years and years. To prove this. I promise to only run ATF in my brand new, rebuilt transmission from now on. You will all see, in 5 or 6 years and after a few hundred thousand miles, that my transmission is in great shape and running perfectly. 

Scott, I hear you, and I want to know where you get your data on this? I know ATF is Excellent, that automatic transmissions have many moving parts, planetary gears, and all. Do you have personal experience with ATF in your manual transmission? 

I have only had my 720 for 6 months so I cant say my experience with ATF in this transmission is any longer then that. I know a few transmission re-builders who really are experts on these transmissions. the kind of folks who could disassemble the entire transmission in the dark with blindfolds on and rebuild it with new gears and bearings perfectly. These are people I trust, with years of experience rebuilding manual transmissions. One of them drives a 720 everyday and runs AFT in his.  So, while the data and specifications of GL4 are different then ATF and I know Datsun and Nissan recommend GL4. I am trusting their experience and advise. Trust is earned and these folks have earned my trust, so I have no problem experimenting on my truck. I just had the transmission rebuilt a few months ago. In a few years we will see a real world example of running on ATF. I am sure everything will be fine.

Hey Scott, I admire your trust in your builders.  Its hard to find someone in the automotive service industry to be able to trust like that.  However, it would be interesting to know where these builders got their information, what justified them trying ATF in the first place.  It would be a very big gamble to make, putting something completely different than what the manufacturer recommends into someone else's equipment, unless they had some very hard evidence to back it up (beyond just personal experience).  That would really put them in a bad liability position if a customers transmission fails.  So, why don't we ask these experts to fill us in, and get the story from their perspective, straight from the horses mouth so to speak???  You think you could get them on here to discuss this???  Maybe they know something that isn't common knowledge.

I will ask them to join us on here to discuss... I would love it if they did!





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