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Old 04-05-2008, 06:28 PM
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Next time I change my transmission oil, I'm thinking about perhaps going to a mineral oil formulation as we don't seem to have a ton of luck with the synthetics. Does anyone have any experience using the conventional mineral oil gear lubes?

Also, what about Synchromesh oils? We seem to be having issues with the synchros spinning up to speed and Synchromesh would seem to be just the ticket to solve that. Perhaps a half or full quart cocktail mixed into our gear oil would be a solution?
Old 04-05-2008, 07:37 PM
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Originally Posted by Charles R. Hill
We're talking about transmission and differential fluids right now, idiot.
You are, not me, Mental midget!
Old 04-06-2008, 01:29 AM
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Old 04-06-2008, 02:11 AM
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Originally Posted by LionZoo
Next time I change my transmission oil, I'm thinking about perhaps going to a mineral oil formulation as we don't seem to have a ton of luck with the synthetics. Does anyone have any experience using the conventional mineral oil gear lubes?

Also, what about Synchromesh oils? We seem to be having issues with the synchros spinning up to speed and Synchromesh would seem to be just the ticket to solve that. Perhaps a half or full quart cocktail mixed into our gear oil would be a solution?
You can just go for MT-90 I think. I have it, but havent had a chance to put it into my tranny yet. It should be good for Synchros, but ppl said the shifting quality suck.
Old 04-06-2008, 02:19 AM
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I used MT-90 as my first oil change and the shift quality went right out the window - slow like mollasses in January.

Mixed about 1/3rd 'MTL' with the 90 weight for a silky smooth shift.

I hear the RP and Syncro stuff is a little thinner, right out of the bottle......


S
Old 04-06-2008, 07:54 AM
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I have RP, Shifting has been silk ...

So maybe I should mix it down with a bit of MT-90 ?
Old 04-06-2008, 08:25 AM
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My favorite oil.......

My favorite oil, now don't beat me up over this, take it in the spirit in which it was meant. My favorite oil is, are you ready for this ??????? Here goes...................................Extra Virgin Olive Oil. ( pun intended )
Old 04-06-2008, 08:37 AM
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Mazola FTW !
Old 04-06-2008, 01:15 PM
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Originally Posted by nycgps
You can just go for MT-90 I think. I have it, but havent had a chance to put it into my tranny yet. It should be good for Synchros, but ppl said the shifting quality suck.
I have MT-90 and do not like it. I also have tried RP MaxGear and while I liked it a bit more, it's still far from OEM. You should know this by now...
Old 04-06-2008, 01:26 PM
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Originally Posted by LionZoo
I have MT-90 and do not like it. I also have tried RP MaxGear and while I liked it a bit more, it's still far from OEM. You should know this by now...
RP Max Gear 75w90 is a GL5. It worked great for a while. However after a while each time I changed transmission fluids the issues with 3-4 upshift grinding at high rpms got gradually worse till my transmission was replaced by Mazda. By that time, it would grind anywhere around 4.8k rpm. When the issues first started, it was intermittent at close to 7k rpms.

I have no plans to ever use maxgear in my transmission again. Maxgear is still in my diff however.
Old 04-06-2008, 11:02 PM
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Originally Posted by mysql
RP Max Gear 75w90 is a GL5. It worked great for a while. However after a while each time I changed transmission fluids the issues with 3-4 upshift grinding at high rpms got gradually worse till my transmission was replaced by Mazda. By that time, it would grind anywhere around 4.8k rpm. When the issues first started, it was intermittent at close to 7k rpms.

I have no plans to ever use maxgear in my transmission again. Maxgear is still in my diff however.
At this point I don't want to use either MaxGear or MT-90 when I do my next tranny oil change.
Old 04-06-2008, 11:09 PM
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Originally Posted by StealthTL
I used MT-90 as my first oil change and the shift quality went right out the window - slow like mollasses in January.
Yeah, when I did my first change at around 50k miles, using MT-90 really didn't improve things over the old oem fluid. Going to probably go a 50/50 mix of MT-90/MTL next time.
Old 04-07-2008, 02:06 AM
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If i take my 8 to the track about 7~9 days a year (probably every other month or so), and wanting to stick with amsoil, what do you recommend, jax_rx8?
according to teamrx8's previous post in this thread, using a 50/50 mix doesn't seem like a good idea if i'm pushing the car at the track. I'm not racing like he is, but i know track days can be hard on the car.

i'm guessing, amsoil svg(gl-5) for the rear diff. and mtg(gl-4) for the trans?


Originally Posted by Jax_RX8
AMSOIL Severe Gear is a GL-5 lubricant that is great for your rear diff - and will absolutely, over time kill the syncros in your trans.

For your trans, you want AMSOIL MTG (Assuming you want to use AMSOIL products)

http://www.amsoil.com/StoreFront/mtg.aspx

or for better shifting, you can mix 50/50 with AMSOIL MTL

http://www.amsoil.com/StoreFront/mtf.aspx

As for your other question on trans fluids, Charles is right in that GL-5 fluids do not have the right "grabbiness" (a technical term) for syncros to work efficiently - they do tend to be too slick as they have many Friction Modifiers (FMs) in addition to the EP additives.

But the real issue with GL-5 fluids in a trans with syncros is that syncros use softer metals and GL-5 fluids have way too much Extreme Pressure (EP) additives that actually wear out these softer metals over time, reducing the ability of your syncros to function properly until they just eventually fail.

GL-4 fluids, like the ones I linked above, have some EP adds, but tend to be formulated for the "right" friction for the syncros to work properly and also have much less EP additives (usually different ones as well) to keep from prematurely wearing out the syncro soft metals.

Also, there are many GL4/GL5 combo fluids, like RPs Max Gear, BG Ultraguard, etc, etc, that claim to work in manual trans and diffs. Some use and seem to have successwith these fluids in manual transmissions, but I would shy away from these combo fluids in a manual trans as they will still have too many EP and FM additives (which are required to meet the GL5 spec) for good syncro operation and wear - not all agree with this, but I would rather be safe than sorry as trans rebuilds are not cheap as most of our trans failures seem to be from the syncros failing (or being so slow in operation that we grind the trans gear teeth or break them off completely).
Old 04-07-2008, 06:46 AM
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Originally Posted by trustbuddy
If i take my 8 to the track about 7~9 days a year (probably every other month or so), and wanting to stick with amsoil, what do you recommend, jax_rx8?
according to teamrx8's previous post in this thread, using a 50/50 mix doesn't seem like a good idea if i'm pushing the car at the track. I'm not racing like he is, but i know track days can be hard on the car.

i'm guessing, amsoil svg(gl-5) for the rear diff. and mtg(gl-4) for the trans?
I agree with Team if you are tracking or Auto-Crossing - your choices are right on IMHO.

You could even consider AMSOILs Severe Gear 75W110 for the diff as well for that little extra protection (I assume you were referring to the 75W90), with your tracking and especially if you are in a warmer climate zone
Old 04-07-2008, 09:14 AM
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Originally Posted by mysql
RP Max Gear 75w90 is a GL5. It worked great for a while. However after a while each time I changed transmission fluids the issues with 3-4 upshift grinding at high rpms got gradually worse till my transmission was replaced by Mazda. By that time, it would grind anywhere around 4.8k rpm. When the issues first started, it was intermittent at close to 7k rpms.

I have no plans to ever use maxgear in my transmission again. Maxgear is still in my diff however.
For some reason, the Tranny whine that I got 2 weeks ago is now *gone*

Have been using RP Maxgear in my tranny since 5K miles

hmm ... but still I think I will try MT-90 b4 I go try Amsoil or anything else
Old 04-07-2008, 09:17 AM
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Originally Posted by nycgps
For some reason, the Tranny whine that I got 2 weeks ago is now *gone*

Have been using RP Maxgear in my tranny since 5K miles

hmm ... but still I think I will try MT-90 b4 I go try Amsoil or anything else

no doubt the maxgear feels better / smoother than the stock oils. If you search my old posts under mysql101, you'll see I recommended maxgear for many years too.

The issues started up after ~20,000 miles with maxgear in the transmission. And it wasn't a constant thing, the grinding happened once in a while. Infrequent enough that I thought I wasn't clutching far enough. It's also interesting that with each oil change (I changed tranny fluids once a year) it seemed to get worse. Perhaps results would be different if I only changed the oil once every 50k miles.

My personal recommendation is to switch to something else ASAP.

Last edited by mysql; 04-07-2008 at 09:19 AM.
Old 04-07-2008, 11:33 AM
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Originally Posted by mysql
no doubt the maxgear feels better / smoother than the stock oils. If you search my old posts under mysql101, you'll see I recommended maxgear for many years too.

The issues started up after ~20,000 miles with maxgear in the transmission. And it wasn't a constant thing, the grinding happened once in a while. Infrequent enough that I thought I wasn't clutching far enough. It's also interesting that with each oil change (I changed tranny fluids once a year) it seemed to get worse. Perhaps results would be different if I only changed the oil once every 50k miles.

My personal recommendation is to switch to something else ASAP.
I agree.

This is the problem with GL5 or combo GL4/5 gear oil use - everything can seem fine for quite a long time as the additional wear to the syncros happen slowly, but surely.

By the time the symptoms start showing from the additional wear, it is too late and the damage is done. Then you are left with nursing the trans as far as you can until your eventual rebuild.
Old 04-07-2008, 11:52 AM
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I finally decided to drop the cash for Redline MT-90 for the trans, and Redline 75w90 Gear Oil for the diff.
Old 04-07-2008, 11:52 AM
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Originally Posted by mysql
no doubt the maxgear feels better / smoother than the stock oils. If you search my old posts under mysql101, you'll see I recommended maxgear for many years too.

The issues started up after ~20,000 miles with maxgear in the transmission. And it wasn't a constant thing, the grinding happened once in a while. Infrequent enough that I thought I wasn't clutching far enough. It's also interesting that with each oil change (I changed tranny fluids once a year) it seemed to get worse. Perhaps results would be different if I only changed the oil once every 50k miles.

My personal recommendation is to switch to something else ASAP.
I did read your thread (come on, u think I made 6817 post/being a member since Jun 2005 for nothing? )

Originally Posted by Jax_RX8
I agree.

This is the problem with GL5 or combo GL4/5 gear oil use - everything can seem fine for quite a long time as the additional wear to the syncros happen slowly, but surely.

By the time the symptoms start showing from the additional wear, it is too late and the damage is done. Then you are left with nursing the trans as far as you can until your eventual rebuild.
I have RP in my gear for over 35K miles already. Still alive but ... "its better be safe than sorry" ... I should change it out.

Ok, Im gonna change The tranny fluid out this wednesday to Pure MT-90. (I have to change my winter tires out + Autoexe Under brace in anyway )

Lets see how shitty the shifting will be lol

Last edited by nycgps; 04-07-2008 at 11:54 AM.
Old 04-24-2008, 01:22 AM
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The NB 6-speed guys seem to like the Motorcraft Full Synthetic Manual Transmission Fluid quite a lot. Since that tranny is a close cousin of ours, I'm wondering if it'll work well for us as well. It's very expensive though, but if it's a good cure it might be work it. Jax?

Thread here: http://forum.miata.net/vb/showthread.php?t=270393
Old 04-24-2008, 07:32 AM
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I have MT-90. No problem.

Shift Quality ? I think it feels about the same if not better. it feels *tight* hahaa
Old 04-24-2008, 07:37 AM
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I'm using Redline Heavy Shockproof for the tranny. It has film thickness similar to a 75W250 grade, while providing the same low fluid friction as an SAE 75W90. Also, it looks like a strawberry smoothie. A couple of other members here uses the same thing and it feels great.
Old 06-25-2008, 07:13 AM
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This blows. After a while of silky smooth shifting with MT-90, it's starting to feel rather knobby and hard to shift.

**** this. I'll need to swap into something else as soon as I get back from my summer vacation.

I've read all the recommendations till now..., and quite frankly, it's left me more confused than before. Everyone has their own "trick" and "secret".

So do tell me if you think my new choice is gonna cause problems.

I'm going to try Redline MT-90 again, except this time I mix it 1/3 with MTL.
Old 06-25-2008, 07:36 AM
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^ won't be a problem.. I'm using about a 60/40 ratio MT-90 / MTL.. shifting is great.

Also, the first tranny change with a certain fluid is basically a rinse cycle- on the 2nd one you'll see most of the benefits
Old 06-25-2008, 10:53 AM
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I have MT-90 for couple of months and it shifts just fine.

I came from Royal Purple's Maxgear.


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