Rx7-88na

Okay -- if anyone read my post on 2nd Gear Grinding you'll know why I started this thread... but for those who dont --

What is the story with synthetic gear oil -- I hear Readline is supposed to be great -- what is your experience with synthetic vs organic... thanks

Mykl

Surely somebody knows...

Cwaters

I had the grindy problem when i first got my car. Replaced the goop that was in there with some synthetic Valvoline and it's been MUCH better. Red Line is touted as being the best but I was ona budget and in a hurry so the car got what the parts store had...

Cory Waters
waiting on that clutch line to come in the mail

selanne8

i replaced the stuff in my transmission with mobil1 and there is a definate improvement in the smoothness of the shifts. dunno about power gains or anything like that since my engine is already on it's last leg...

john

gnat's-ass7

I'll have to try that. What are you guys using in your diffs?
BTW-they're wouldn't be a power gain involved, as you aren't modifying the engine. You might get better power transfer, but I don't know by how much.

mprime

I put redline in both my rear diff. and trans. and I noticed a immediate improvement. Great stuff ordered it from Summit total I think it was 15 bucks.

NJDave

I use Redline in both my transmission (MT-90) and the differential (75W90 Gear oil). Someone above mentioned Mobil 1. Unless Mobil 1 makes a gear oil I don't know about (could be possible) I wouldn't use it. I took my very low mileage 89 RX-7 convertible to the dealer and asked them to put synthetic oil in. They did it and just put Mobil 1 oil in. I noticed my gears started grinding almost immediately, mainly from first to second gear. I can't remember the exact details, but I did some checking and determined that Mobil 1 isn't the best oil for the trans - if I remember correctly, Mobil 1 is a GL-5 oil and the recommendation for the transmission is GL-4.

Whatever the specifics, the bottom line is that once I switched to Redline, the grinding stopped immediately.

Dave

BTW: I also got it from Summit Racing - it was $7.95 a quart - shipping would be on the high side given the weight of the oil.

Mykl

I've got Mobil 1 in the gearbox right now. I have all Summer long.

If felt fine at first, but after a few month my 1-2 shift started grinding. I guess I'll have to order some Redline tonight.

Audiofight

I will be ordering some Redline soon for myself. Fortunately, I work at a Powersports shop and have access to it from one of the OEM maufacturers (can't remember who, I think Kawasaki or Sea-doo) and can get it cheaper.

Yeah for me!

Anyway, Njdave mentioned what weight he is using, what about the rest? Any particular weight to avoid or go to because of advantage/disadvantage?

Answering my questions will be for everyone's benefit, so don't think I am barging in on this guys thread. No offense to anyone

Mykl

MT-90, I think.

Barging in on the thread? If nobody posted anything for fear of that then we wouldn't have a message board.

SaabGuy

Mobil 1, Castrol, Valvoline, I dont care what type... DO NOT USE IT IN YOUR TRANNY. It is far to slick and will burn up your synchros. Synchros need friction to function properly....

REDLINE MTL or MT90 is specially formulated synthetic and actually works wonders in trannies. The oil has a viscosity of 10-30 or 10-40 depending on which one you need, and high a HIGH COEFFICIENT OF FRICTION (same as 70 weight motor oil) which is what you need for burnt/bad/worn synchros. The high friction will allow synchros to sync much faster than any other oil, eliminating grinding and hard shifting.

General synthetic motor oil will ruin your synchros because its friction rating is extremely low, lower than conventional motor oil, you do not want to put it in your tranny. GET IT OUT QUICK



My saab's 3rd gear would always grind when I beat on the car, ALWAYS. After 2 quarts of REDLINE MTL it shifts like butter, doesnt grind, and suprisingly it is very easy to shift into 1st gear at 70 MPH (HOLD CLUTCH!) , try that with normal oil, bet you will never get it in.

skibum9199

Is there a difference between the MTL and MT 90?
How many quarts should I order?


~Jesse

blue 86 na

Mykl

Well, if that's correct then I guess my transmission is fucked. I wish I would have known that when I put the Mobil 1 in the gearbox.

Okay, how exactly does it ruin the syncros? Is it the actual lack of friction that causes them to not function properly? Or does this lack of friction actually cause damage?

If I dumped in some Redline do you think it would help "cure" my problem?

adamlewis

Yeah I love redline...But it has been my experience, and the same with friends, that at first, the gears will grind as bad if not more. But after about a week or so, it will make your trasnmission the smoothest shifting thing youve ever had

flubyux2

dont forget Royal Purple. thats supposed to be good Sh-tuff.

chris

niner

i put in mobil1 in both my tranny and diff. like 2 years ago....
the grinding b/t 1-2 and 2-3 had decreased but it has come back lately. i might switch to redline or royal purple in the tranny.

NJDave

The correct redline products for RX-7s (at least my 89 convertible) are MT-90 (for manual transmission) and 75W90 (for diff). Redline makes two different 75W90 oils: 75W90 and 75W90NS. The 75W90 contains limited slip friction modifiers. However, Redline recommends the 75W90 (not the NS) for ALL street driven rear wheel drive vehicles.

If you want more info or need to find a dealer, go to www.redlineoil.com.

By the way, as soon as I figured out that the Mobil 1 was the wrong oil, I went back to the dealer (Crystal Mazda, Green Brook, NJ) who put the Mobil 1 in the transmission and told them that they put the wrong stuff in. They turned around and told me that Mazda doesn't recommend any synthetics in the car and, therefore, they were only doing what I told them to do. They initially refused to take any responsibility and refused to change out the oil or give me a refund. At no time did a service rep ever tell me that Mazda didn't recommend synthetics in the car. My opinion is that a dealership should tell you if you are going to do something they consider stupid. In this case, they gladly took my money and didn't care if they performed the correct service.

In the end, after lots of arguing, they agreed to swap out the oil for free if I'd bring the new oil in. But I will never give them my car to work on again, even for free. So I paid someone else to change the trans oil.

Now in fairness, if you live in this area, and like to get genuine Mazda parts, I would certainly get them from Crystal. The parts department is fantastic - it's just the service area that is horrible.

Dave

SaabGuy

I am a strong believer in synthetic oils, unfortunately you gotta read up on what type to put in where. Mobil 1 synthetic is great for piston engines but you have to keep an eye on it, it is very slick and can leak out if you have old/loose seals. The purpose of synthetic oil is to lower friction in your engine, unfortunatly transmissions need to friction to the synchros do not slip. REdline MTL, MT-90 and I guess any other synthetic oil specifically formulated for transmissions will be far superior to conventional and normal synthetic.


www.redlineoil.com talks about what a transmission requires for friction.

Thaniel

I have redline in my trans. I see the biggest improvement that I have noticed is when the trans is cold. The redline doesn't seem to thicken at low temps as much as the standard gear oils.

DroptopRX7

iTrader: (12)

Upon purchase of my 160,000 some odd miles 88 convertible, I put Redline oil to reduce the 2-3 gearshift crunch in the transmission and used Redline oil in the rear end. Never a problem. Further, with the limited slip rearend I just got, I'll be putting in Redline as well. Even without having done so in the past, the testimonials I just read indicate that Redline is the way to go.
On another note to Dave, one should be wary when dealing with service organizations. They are not under a legal obligation to preserve your interest. Maybe an argument can be made in regard to a Good Samaritan or moral issue, but certainly there are no Good Samaritan laws as such in the car repair business. Maybe they didn't feel like giving you advice. On the other hand, did you ask to see the Mazda suggestions in WRITING somewhere? That's always my first response when someone quotes "the Law" or "their Policy". Of course I come from a legal frame of mind so take that into account...
Ralf

pd_day

iTrader: (6)

Most brand named oil (castrol, mobil, valvoline.....) sells GL5 stuff. On the label of the oil, it'll say GL5 will work with GL4 application. But in our tranny, it's not the case. GL5 contains sulfate (you'll notice the nasty smell from the sulfate). Sulfate will attack brass, brass is what our synchros are made out of, thus explain for your increasing 2nd gear grind. I found this out after 2 weeks of using Castrol Syntec gear oil. I noticed the 3rd gear grind getting worse. I immediatly swap out the castrol stuff with redline MT90. MT90 is GL4 grade and does not contain sulfate. After 2 to 3 weeks of the redline stuff, my 3rd gear grind dissappeared.

A con I found using the redline stuff is that it needs to be warmed up. It's not as smooth in the morning as opposed to after a highway cruise.

Ryde _Or_Die

How many quarts would you need to change the transmission fluid? I found some redline for &8.50 a quart. Just need to make sure I have enough to fill it back up.

skibum9199

The number five keeps coming to mind, but I'd like to know for sure too. I think the easiest place to get this stuff is probably summit, in case anyone was wondering

~Jesse

Mykl

Look it up in a manual somewhere, but I think it's around three or so.

charger-

iTrader: (1)

My 87 Owners manual says 2.5 liters (2.6 U.S. qts.) for manual tranny, 1.3 litres (1.4 U.S. qts.) for the n/a diff, and 1.4 litres (1.5 U.S. qts.) for turbo diff.