Rear diff and manual trans fluid

[LeDevil]

What do all you guys use for rear diff fluid and Trans? I'm wanting to change my trans fluid and my rear diff but I'm not sure what to use for either one. For some reason half my Chilton is missing :confused:

[Cuts metal like mad]

I used 75/90 gl-4 (recommended) for my trans, and 80/90 gl-5 for the rear diff... Valvoline, if it matters.

 

There is some debate that gl-5 can be used in the trans and shifts better, however some say they have had trans failure caused by running gl-5 (supposedly it can cause premature wear on the yellow metals)... I prefer to stay nuetral on this and use what is recommeded by Nissan.

[ggzilla]

My 1972 Datsun owners manual recommends GL-4 spec:

* 75,80,90,140 straight weights

* 80-90 multiweight

 

I recommend the newer 75W140, it will work better at high temps that 80/90 or 75/90. Also theoretically better at cold temps than 80/90. And meets the original GL-4 spec.

[HRH]

For Vancouver, you're definitely going to want 75/80-90. The 140 is waaaay too thick for the cold climate. Will be a bitch to shift smoothly. CA or AZ, 140's great.

 

Ggzilla, how is a heavier weight oil (140) better at cold temps than 80-90?

 

In my Datsuns, I use 75-90 Castrol gear oil when I can find it. Or straight Valvoline 80-90. 75 vs. 80 isn't much of a difference.

[Edz280zx]

What about Redline MTL..I've heard it's good..opinions?

[Cuts metal like mad]

redline? I think when people pay 3x normal price (or more) for a product (a header) :D the end result is usually extraordinary or horrible and usually nothing in between...

 

Take this anyway you like...

[ggzilla]

140 is waaaay too thick for the cold climate

Exactly right. 140 lube is too thick for any climate. On the other hand 75W140 acts like 75 when cold and 140 when hot. So it's good for both hot and cold climates. You want a multiweight since the lube starts cold, but gets hot while driving.

[Edz280zx]

redline? I think when people pay 3x normal price (or more) for a product (a header) :D the end result is usually extraordinary or horrible and usually nothing in between...

 

Take this anyway you like...

 

That's cool, I know what you mean. I'd just heard "stories" about it and wondered if anyone had any first hand experience with it.

[HRH]

Yeah, but there's no point in running a 140 weight oil in the northwest unless you're running constant high speeds, high outside temp (100+ degrees), or getting the diff really hot.

 

A 75-140 weight will overall be a heavier oil at the same warm temperature than a 75-90 weight, which means increased drivetrain stress from trying to turn gears in thicker oil, which is why 140 is not good for cold weather unless you like double-clutching because the synchros can't do their job.

 

UNLESS you use a 75-140 synthetic gear oil, as they tend to run thinner though being the same weight. I wouldn't recommend for Datsun trannies, just because I don't see the need. Then again, I had Redline in the Miata transmission, so I might reverse my opinion on that. I think it was synthetic anyway.

 

Chucks Gear who rebuilds my Datsun trannies, runs 10w40 in all the Datsun trannies he has. Helps them shift better, though my Datsun guru and myself argue in favor of 80-90 weight as there isn't really that much of a problem shifting it anyway.

[ggzilla]

A 75-140 weight will overall be a heavier oil at the same warm temperature than a 75-90 weight,

I believe that is untrue. In an multiweight, the effective weight varies by temperature. It won't get to the 'thick 140' state until is get very very hot -- high speed driving, etc. Yes, sometime I drive 75mph for hours, where the law allows. By contrast, a 90 weight at the same 'very very hot' temperature is now too thin. So you can't lose with a multiweight, it handles either condition.

 

The reason the owners manual didn't list 75W140 is because it hadn't been available back in '72. Compare to the engine oil -- back in '72 Datsun recommended 20W50 oil.

 

Edited December 22, 2008 by ggzilla

[LAYEDOUTB2K]

What about Redline MTL..I've heard it's good..opinions?

 

i havent used the MTL but we have been been using the Shockproof gear oil in everything we have raced for years and love it. when we would swap out gears at different tracks, we would drain it out and pour it back in and be just as clean as when it came out of the jug. for a normal everyday car, i think it might be a little overkill for the price.

[bonvo]

80w90 in both

 

i havent had any hard shifting issues except when its cold after the car warms up some its fine . it seems fine when hot and it hits 110 here on occation in the summer

[ggzilla]

Just remember that the gear oil will be hotter than your 110-degree summer weather. Even in cold places it will get hotter than that inside the differential.

 

If anyone is interested in learning about oil "weights", there are some good technical explanations out there, just use your favorite search engine.

[HRH]

Hmm, I think we'll just have to agree to disagree. I'm going with 80-90 unless I'm in Phoenix. Plus, the Datsun manual doesn't recognize 140 existing, so obviously 80-90 must be superior. :D

 

I decided to check Castrol seeing as it's the only oil I use for the most part, and they had a "Expert Questions" thing, so I sent them the jist of this thread with all my contact information. Should get a reply in a few days, I'll post it when I have an answer.

Edited December 23, 2008 by HRH

[djmoreron]

subscribed. been wondering about this also.

[slodat]

In my 510 I run Redline MTL in my trans and Redline 80-90 with Ford LSD additive in my rear diff.

[datzenmike]

I used 75/90 gl-4 (recommended) for my trans, and 80/90 gl-5 for the rear diff... Valvoline, if it matters.

 

There is some debate that gl-5 can be used in the trans and shifts better, however some say they have had trans failure caused by running gl-5 (supposedly it can cause premature wear on the yellow metals)... I prefer to stay nuetral on this and use what is recommeded by Nissan.

 

Yes, heard the same. Can't go wrong with GL-4 or full synthetic. GL-5 is more than needed in the diff but no brass to worry about so is ok to use there or T cases. Beware, the synthetic can leak past old seals where the original oil wouldn't. Very penetrating and slippery.

 

I use a semi synthetic in my tranny and, yup, the rear seal started to leak and had to change it. I found the oil to be thinner like 10W motor oil. Shifting is easier by far in the winter, and the gears make a nice satisfying 'CLICK' when changed. I like it.

[Cuts metal like mad]

OH... thats reminds me mike... to determine if the fluid is GL-4 or GL-5, look on the back of the bottle... I had my wife stop by the parts store the other night, she wrote down exactly 75/90 GL-4, when she came home she had GL-5 because the idiot at the store "didn't know there was a difference". So I had to go back and get the right shit...

[HRH]

So Castrol wrote back. This is the question I sent.

 

"There is a debate on our forum regarding the proper gear oil in relation to temperature. For an older Datsun (1968-1973 510s to be exact) the recommended gear oil is 80w90, which is what I've always used and haven't had a problem. There is dissenting opinion that 75w140 is better for overall use, even in cold climates, because the oil will still run cooler in the cold, so it will behave more like the 75w, until it warms to 140. I disagree, thinking a 75w140 gear oil will overall be heavier than an 80-90 weight, thus leading to harder shifting in cold. I pretty much consider the Pacific Northwest to be 80w90 material for all older diffs and trannies, but figured I ought to ask the experts, so if anyone at Castrol (my only oil company) could reply back, that would be great. Thanks! -Matt fastdatsun@yahoo.com"

 

And here is the reply:

 

Thank You for Contacting Castrol North America,

 

Castrol always recommends following the guidelines of the original engine manufacturer for the recommended fluid to use in your specific applications.

 

If Datsun recommends the use of 80w-90 gear oil in your application, please do not use another weight as the 80w-90 has been tested to provide the best performance and protection.

 

Castrol Consumer Relations.

 

This is the biggest bunch of lawyering, politicing, cover your ass bullshit I have ever received from a company. And they sidestepped the question.

 

WHICH LEADS me to believe this might be a form auto response? Anyway, I'll be writing back to them or calling as I've been a loyal Castrol supporter for years and things like this are what make me change my loyalty. It's all about the principle.

[slodat]

Like I said, I use Redline.

[Edz280zx]

Like I said, I use Redline.

 

I think I'll be switching over this summer.

[slodat]

I started running MTL in my transmissions and rear diff at the suggestion of a friend (dislexicdime). I have no complaints. It works good. I was just reading RedLine's web site. They have some good info. According to their web page the MT-90 may be more suited to Nissan applications. Not sure what difference it would make. I have been very happy with the MTL.

[Edz280zx]

Well...this will probably sound goofy..I first heard about it on Jay Leno's Garage on his Honda S600 video..He highly recommended it, he runs it in all his cars I believe. I just wondered if any one in the "real" world used it and how they liked it.

[HRH]

This is the email I sent back to Castrol regarding their previous answer. We'll see if I hear back.

 

Dear Castrol,

 

This sort of an answer is unacceptable. I expect more from the company that supplies the oil for all the engines I build. I recommend Castrol to more people than I can think of, and being an assistant manager at a local NAPA auto parts, I'd say that's some pretty good advertising. I'll assume the previous response was an auto-form what-have-you, seeing as it completely dodged the question like a politician being asked his or her stance on campaign finance reform.

 

And while being a loyal Castrol customer, simple issues like this are what make or break partnerships. Valvoline makes a great oil, I have no problem using it. Red line is another great oil. I used it in my Miata gearbox, but haven't yet used it for the Datsun. I choose to use Castrol as I believe it's superior.

 

In the Christmas spirit, I'll give you guys another chance for a heartfelt response indicating the question posed, had indeed been read. I don't expect an answer soon, as it's nearing Christmas. However, if someone there would be kind enough to send me an email after the 25th, or give me a call, I would greatly appreciate it, lest I be led to believe Castrol doesn't have time for little old me.

 

Sincerely,

Matt Albertson

[Edz280zx]

Well written letter..I'm interested in what their response will be.