gearbox oil

I have been using the Redline 75-90 NS for years and never had problem with 2nd gear shifting when cold but, next gear oil change, I will try the MTL and see if I can tell the difference.

What is the ideal gear oil change interval, once a year, once every two years, or by mileage?

 

I've changed my transaxle oil twice on my (relatively new-to-me) 308 QV. I used Redline 75-90 NS the first time and noticed a bit of funk on tight corners. Second time I used Redline MTL and the funk went away. (Plus MTL smells better.)

I've never experienced 2nd gear problems, but that may be because I skip 2nd until the engine warms.

Isn't this one of those situations where the adage "if it ain't broke, don't fix it" applies?

 

I think Brian changes once a year.

I realize trans fluid isn't under the same stresses and combustion by product crud as engine oil but keeping it fresh helps to keep moisture contamination away.

At least I think that is the reason.

 

Is the MTL that your referring a 75w 80 or am I looking at the wrong product?

 

Brian, since MT90 is simply a slightly heavier version of MTL and since Redline says that MTL is lighter than recommended, why MTL over MT90? Not arguing, just curious.

 

So does driving the car regularly and up to temperature

 

Apologies, I likely reversed the mix for my post, I used the forum standard ratio when I used those products. Either way, MTL still gave better shift quality/feel and even easier 2nd gear access when cold.

 

And which way around would the engine /transmission oil mix were the seals to leak?
If the MTL is slightly lighter would this make the potential issue worse, or is engine oil always likely to leak into the transmission?

 

Yeah, but for those that don't..

 

I would think negligible amount should leak either way unless the seal is gone and needs replacement.

Although in theory if the crankcase breather were bunged up with crud I would expect this to cause pumping of engine oil into the gearbox big time owing to raised crankcase pressure. Not sure if this armchair theory is borne out in practice though.

 

With respect to changing oils and being able to tell the diffenence, as someone who tested oils and manufactured/sold them in another life, a single change does not do much to films/additives left by the prior fill, you need to use the same oil for about 5 changed prior to getting rid of most of the effects of the prior fill... Either that or taking things apart and washing each part with solvent and reassembling. If you feel a big difference otherwise is placebo or effect of over/under filling IMHO

 

Having spent close to 40 years dealing with cars that have a very great sensitivity to the lubricants used I can not disagree more.

Even barring the experience of a considerable number of people I have worked with or supervised with the same experience, not to mention client feedback, when a transmission holds from 5 to 10 quarts of oil, the several ounces left from the old oil is such a small percentage of the total I do not think that position is supportable.

 

^ I can't argue with experience
But, many of the additives actually change the surface of the metal, and these effects persist microscopically (and their benefits or lack of) for at least a few oil changes. I did bench testing, had first hand data and microscopic images that showed this.

 

My experience with other cars, and my 308, is that it takes 1,000 miles+ for the fluid change with a different characteristic fluid to become noticeable - that seems to be how long it took for the old coatings on the synchronizers and gears to be worn off and substituted with the new coatings.

 

brian: what's a reasonable change interval if you use mtl?

 

Just another data point...

I've been doing the Red Line cocktail mix for 20 years, but decided to try straight MTL a couple weeks ago...immediate improvement on feel and engagement. I've got 119k on the drivetrain and still going strong.

 

It is GL4. It was what Ferrari called for until 94 or so. Now that GL5 is around it is what we have all been told to use but it is becoming more and more a topic and as it turns out GL5 has been causing a lot of trouble.

 

Brian and Tommy - thanks for your posts and I am going to put MTL GL-4 into my '85 QV.

Just being hyper-cautious, so could you kindly confirm that I should use 75W90, "MT-90", quart part #50304. (Note, for GL-4 trans oils, Redline also sells 75W80, "MTL," #50204 and 75W85, "MTL-85," #50504.)

Do you know if it's coincidental that the modifiers MTL GL-4 contains for the synchros happen to work for the limited slip diff? Or if Redline specifically addressed LSD needs in the MTL GL-4 formulation? Just curious on this one.

Thanks very much.

 

Would like an answer like I was a 12 year old...1980 308 GTSi...What gear oil?...please give me a potential brand..weight...and does it require an additive, pleeeease! Simple three word answer!! Even the manual doesn't spell it out

 

People have used both. Redline changed the name and added products to the line so it confused the issue.

GL4 is currently marketed by almost every manufacturer as transmission oil. I know of no product containing a limited slip additive. I have used the product in many client cars and my own for some time and I have never had a need to add anything. But then I also understand limited slips suffer nothing additive or not so I personally don't care if it makes a little noise. Not one person has made a comment or complaint of noise.

 

Uhhhhh 3 words, please...brand, type, weight...here is what you get when you google GL4. Can anyone tell me if any of these are correct..."Type" would require a one word answer...synthetic or natural? Why are all these choices synthetic? Did my car come with synthetic gear oil?
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I present information. Hand holding is not in my job description. The book clearly tells you what weight to use. The entire thread discussed positives and negatives of different specifications of products and at least in my case I said quite clearly what I use.

I really don't know how much more I can do. If after all of that you do not know what to do I suggest hiring it done.

 

Well, Rifle, you continue to be an ass... Wanting to start fights...But that's cool, you've made it your job. Now, exactly where does it state "synthetic or not" in the manual? Show me that and I will drive up there and hand you $1,000. P.S. I've been doing it longer and am a better mechanic than you ever thought of being...I just like to give others straight forward answers instead of conjecture and argument...P.S.S. You're so arrogant and insecure you think I was directing my question to you! Maybe a little chill pill would do you some good...In the future when trying to help others with some advice I will add, "except Rifle" that way we won't have a problem again!

Now...if anyone with a clue wants to answer my question, that "has a clue" I was being sarcastic about a three word answer, I'll be glad to hear from you...Thanks

 

Perfect response - thanks. I'm going with MT-90 75W90 GL-4 Gear Oil. Part #50304 (qt) or #50305 (gal).

To tinterow: check it out on Redlineoil.com. It is fully synthetic. (Owner's manual says Agip SAE 80W/90, which is non-synth, but that's over 30 years ago and we know not the best for shift smoothness. Can I get your $1000?)

 

No $1000...because it doesn't mention synthetic in the manual...that was my point...Hehehehe P.S. Now stop bothering me y'all..I have a 348 waiting for a cam belt change