deuce_fc

hey fellas im gonna change my tranny fluids but im not so sure which type of oil to use. can i just use regular mt90 tranny fluid??? or can i use honda oem tranny fluids?? the reason i suggested the honda mt fluids is b/c my bro in law works at a honda dealership and i can get it for free, lol. thanks in advance fellas.

HOZZMANRX7

iTrader: (43)

Search my wankel friend. S E A R C H!!!

There are a number of threads on this subject, one in particular with some great insight from IceMark.

KhanArtisT

iTrader: (2)

I used Royal purple 75W90 and noticed smoother shifting when cold and warmed up. My rough first gear engagement problem after warmup actually completely went away after I refilled with Royal Purple. And then I blew first gear out of the trans...lol this is a NA-T on stock trans though.

93rx74lyfe

iTrader: (1)

I'm going to go out on a limb here but dont use honda fluids.

HOZZMANRX7

iTrader: (43)

And IceMark demonstrated that Royal Purple is NOT the best choice for our RX7 trannys.

SEARCH

I'll give you one tip, again courtesy of Icemark. GL4 Start there.

deuce_fc

thanks fellas.

SpikeDerailed

iTrader: (7)

Most hondas use a nd 10w30 for their mtx boxes, that isn't acceptable for the FC transmission. I have become a fan of shell, rotella in the engine and 75w-90 in the trans and diff.

HOZZMANRX7

iTrader: (43)

Jeezzz. I gave you everything you needed. Ok, I can't stand this. I guess I'm in a mood. But, just to close this out,I put "oil" in the Key Words box, and "Icemark" in the User Name box, and look what popped up after 20 seconds of effort?!?!?! Note the Royal Purple rating on the chart:

Quote:
<TABLE cellSpacing=0 cellPadding=6 width="100%" border=0 itxtvisited="1"><TBODY itxtvisited="1"><TR itxtvisited="1"><TD class=alt2 style="BORDER-RIGHT: 1px inset; BORDER-TOP: 1px inset; BORDER-LEFT: 1px inset; BORDER-BOTTOM: 1px inset" itxtvisited="1">For the trans I would use Redline MT, or MT-90 or Amsoil Manual Trans fluid (GL-4),
for the diff, I would recommend the Redline or Amsoil gear lube. Lots of guys use the Mobil one gear lube with good results as well. I recommend you stick with a GL-4 lubricant in the transmission, while using a gear oil designed for LSD in the diff. Maybe Icemark will give us his opinion of transmissions and diff oils. </TD></TR></TBODY></TABLE>
I would agree with that, with the RX-7 tranny's GL-4 oils are going to be your best choice and I have used both MT-90 and Amsoil Manual Trans fluid.

Lets talk a little about tranny/gear lubes, and (I will cover rear end lubes later) about that GL rating and how it works.

API (American Petroleum Institute) service classifications range from GL-1 through GL-5, with the number indicating level of service severity. GL-1 is the least severe, and its requirements are normally satisfied with motor oil. GL-2 requirements are met with rust and oxidation inhibited oils. GL-3 through GL-5 require the addition of extreme pressure (EP) additives, with higher GL numbers indicating a higher level of EP additive. That is the only difference.

GL-4 gear lubes have half the extreme pressure additives of GL-5 lubes... it does not change anything with how slippery a gear oil is.

According to the API: GL-4 is spec'd for Manual transmissions, spiral bevel and hypoid gears in moderate service, while GL-5 is spec'd for moderate and severe service on hypoid and other types of gears and may also be used in manual transmissions.

EP additives work by forming wear-resistant compounds with the metal of the gear tooth surface. As the gears mesh, these compounds shield the gear teeth from direct metal-to-metal contact that would cause wear and damage to the gears. If too little of the active additive is present, proper protection would be compromised. Too much of this additive could cause excessive chemical corrosion of the gear surface. If an API GL-5 gear oil is used in a application where API GL-4 gear oil is called for, chemical corrosion of "yellow metal" components may occur, such as bronze synchronizers, brass bushings, etc. This may lead to shifting difficulties or shortened equipment life.

Now where that hits us, is that the both the Mazda M type (most non turbo RX-7's from SA through FC models) and the R type (RX-3,REPU, and all Turbos) transmissions have brass or bronze syncro's. So using a GL-5 in our transmissions will result in chemical corrosion of those syncros. Also toss in that gear oil that overheats (such as 250F+) most of the gear lubes start breaking down, creating high amounts of sulfuric acid entwined in the lube- a GL-5 oil and overheated gear lube means a tranny that won't shift without grinding in short order.

So now lets look at brands and how they hold up. Because the trannies and rear ends have metal to metal contact, it is important that the gear lube has sufficient shear strength through out its life. This is the thin film that protects the metal from actually rubbing on a microscopic level. A poor film shear strength and the gear lube does not protect anything.



What this shows:

Ideally a good quality gear oil will be in the gray area before and after the test. Lucas 75/90 Synthetic, at 22.35 cSt, and Royal Purple Max-Gear 75W-90, at 19.32 cSt, both exceed the maximum 18.49 cSt initial viscosity (red), failing the SAE J306 requirements for SAE 90 gear lubricants. All other gear lubricants were within the required high-temperature viscosity range prior to the KRL Shear Stability Test.

Viscosity measurements following the KRL Shear Stability Test revealed that seven gear lubes sheared down below the minimum viscosity requirements (orange), failing the shear stability requirements of the SAE J306. The two gear lubes with the largest viscosity loss, as reflected in the following graph, were Royal Purple, losing 40.6% of its viscosity, and Torco SGO Synthetic, losing 35.2% of its viscosity. Royal Purple was the only gear lube to fail both the initial viscosity requirements and the shear stability requirements. It started out too thick and ended up too thin.

So in other words, after 20 hours the royal purple and Lucas failed miserably and the Pennsoil, Mobil1, Mopar and GM oils, and Torco all lost so much viscosity that they really were not even the same weight oil anymore.

Full test here: http://www.amsoil.com/lit/g2457.pdf

So for a RX-7 tranny, I am looking at either Redline MT-90, Amsoil Severe for synthetics and for a non synthetic Castrol Hypoly (since the Valvoline are GL-5).

Anyway, a few things to remember:

All better quality gear lubes need a break in period (usually 50 to 150 miles-depending on driving conditions). It take a bit to squeeze the old oil surfaces out and to impregnate the new oil surface in.

It is not like engine oil that is constantly being forced to circulate, gear lube must be lifted into the gears by other gears that are typically submerged.

That is why I am always skeptical about people that claim Brand X oil solved all their shifting issues or rear end noise issues as soon as the changed it and just drove around the block.

Evil Aviator

You can't go wrong with Red Line MT-90. However, you can check to see if you can get some free GL-4 75w-90 or 80w-90 from your brother, preferably synthetic.

deuce_fc

thanks fellas, got the redline mt 90 in the tranny. thanks for all the info.

awddrift4

wow.. todays a good day, i found what i was about to search for lol

Gregory Casimir

iTrader: (8)

wow this was really helpful

Frostycrowd

iTrader: (9)

Great information.

Evil Aviator

For the last three of you to reply about the greatness of the information in this thread, what about it was so great? If you are more specific then maybe one of the moderators could add that information to the FAQ so it helps out more people.

86NA7XR

The thread helped me decide exactly what trans fluid, diff lube. It's great!!

So much information and yet the thread still gives choice as well

eage8

iTrader: (9)

If you get specialized oils you shouldn't use the same oil in your transmission and differential.

I use:
Transmission: Redline MT-90 (only for transmissions)
Differential: Redline 75w90 (not 75w90NS, the normal 75w90 has friction modifiers in it for differentials, it's even recommended by Redline for the torsen I'm about to put in because it keeps temps lower than the 75w90NS)

87 t-66

iTrader: (133)

or

jake1191

iTrader: (1)

Mt-90 for the trans and if it is a car that gets beat put Redline Heavy Shockproof in the rear ive had it for 3000miles and im loving it. in fact im about to put it i my TII when i get around to it.

86NA7XR

Even more help, and reviews lol, thanks! I think the drivetrain has 16x,xxx miles, Doubt that the previous owner changed the fluids besides engine oil.

FelixIsGod29X

iTrader: (50)

The greatness of the thread is how there is a review of different brand diff fluids and how they break down. Ive never seen this before so its something good to know. This thread pretty much shows the few kinds of diff fluids you can use that are known for its quality. Thus helping others choose the right fluids.....including me. : )

1990_fC3C_t2

Am i right in thinking you can put redline super light weight shockproof in the tranny and diff??

jake1191

iTrader: (1)

^ I would put heavy in the diff and the medium in the trans. or just mt-90 in the trans and heavy shockproof in the rear

1990_fC3C_t2

(icemark)
I have been using super lightweight shock proof for about a year now, in all my car's rear ends as well as have put in a couple of FC manual trannys.

The super light shock proof is about a 75W90 that flows like ATF.

I can without and regrets say that super lightweight shock proof is the best choice for any FC in both the rear end and the tranny. I swear it is worth a couple HP back from driveline losses as well.