adrial

Now, with dino 75-90 it is a tiny bit notchy at times if I don't rev match it nicely. However, if I run the car hard through the gears, the car will shift perfectly smoothly after that...so to me that means that the gear oil I'm using right now is too thick.

However...it'll be warming up and the car will see track events, so I'm wondering if 75-80 would be too thin?

I'll be going with either Redline MTL or MT-90 (for those that are wondering, yes I did just change my trans fluid not long ago).

The car has LSD & oil cooler.

thanks,
Adrial

Franco44

Adrial,

Try the Redline MTL. Mine was kind of tough and I put that stuff in. Much better. I've also used it in the past in a BMW as well with good results!

Tabor

I would go with the MTL. It works fine in my car. I think they are both "75-90" rated, but the MTL-90 is "specially formulated" for cars that originally called for SAE90. However, our cars originally called for SAE80.

Edit- The MTL is only 70w80, the MTL is 75w90.

Tom Pultz

[quote]Originally posted by Tabor Kelly:
I would go with the MTL.<hr></blockquote>This would be a mistake. MTL is only 75W80 and is not GL5 rated, which if you look in the workshop manual is what Porsche now recommends... or they recommend straight 80 wt, not a 75W80. MT90 is just a heavier weight MTL. What you really want is Red Line 75W90 gear oil since this is formulated for LSD transmissions. Read all about it at the <a href="http://www.redlineoil.com" target="_blank">Red Line Oil</a> web site.

Tabor

From the Redline site "Red Line MTL may be used in transmissions which recommend 70W, 75W, 80W, or 85W GL-4 gear oils."

The 944 fits in this catagory.

I admit that the GL5 may work better with adrial's LSD, but I have heard horror storries about using GL5 rated fluid in the 944 transmission.

Tom Pultz

[quote]Originally posted by Tabor Kelly:
From the Redline site "Red Line MTL may be used in transmissions which recommend 70W, 75W, 80W, or 85W GL-4 gear oils."<hr></blockquote>Actually, I misspoke before. MTL is only rated 70W80. Since the factory workshop manual calls for 75W90 GL5 in addition to the straight 80 wt. GL4 hypoid gear oil, I would not be very comfortable running a 70W80 in my car. If the workshop manual only called out an 80 wt oil then I'd say, yeah, maybe give it a try, but it doesn't.

I once spoke with German Transaxle of America in Bend, OR regarding 944 transaxles, and they told me they used Swepco at one point, but it was too viscous and blew out the breather. They then changed to MTL but it wasn't heavy enough and they were getting warranty returns for broken ring and pinions. They switched to 75W90 gear oil and that solved the problem. This was a few years ago so who knows what they are using now.

[quote]I admit that the GL5 may work better with adrial's LSD, but I have heard horror storries about using GL5 rated fluid in the 944 transmission.<hr></blockquote>May work better? No, it WILL work better. MTL and MT90 do not contain limited slip additives so they are not suitable for use in LSD transmissions.

I've never heard of any horror stories with GL5. I've been using it for 50K miles and couldn't be happier. What have you heard? Synthetic gear oils made by Red Line, Mobil 1 and Amsoil all seem to work well.

adrial

Tom, redline MTL is 75-80 not 70-80 if that makes any difference.

Keep the information flow comin!

thanks,
Adrial

SGOGT4

I have been getting some chatter in first gear as I let the car decelerate on its own. I originally was getting it in 1st and 2nd, then realized the the PO let the transmission oil get down to half full. Once I filed it up everything in 2nd was fine, but I still get the chatter in first. Any insight? Should I be using a different type. I don't have a LSD in my n/a.

Thanks

Andy S2

I'm currently running Redline 75W90NS synthetic gear oil in my 1991 944S2 and I must say it's very good, the gear change is still a bit stiff when cold , but once it's warmed up it's slicker than snot!!
The NS stands for Non slip as this oil is for non LSD transaxles. If you have the LSD you need the 75W90 gear oil which contains limited slip friction modifiers.
Its also very expensive and hard to get hold of here in England , I paid the equivilent of nearly $70 for 3 quarts!!! <img src="graemlins/c.gif" border="0" alt="[ouch]" />
I've no doubt than someone is going to make me really sick and tell me how much it is in America now.

adrial

I've read that GL5 will corrode the syncro's..
Just how long does it take for them to significantly corrode (to the point that shift effort is increased)?
Wouldn't the extra slickness of the GL-5 counter act the fact corrosion? What I mean is that GL-4 may inflict more wear on the syncro's because its not as slick? Is that even true, that GL-4 isn't as slick as GL-5?

I've read theories about GL-5 corroding syncro's..but are they any facts out there? The only facts I've seen have indicated that GL-5 (specifically redline) fluids are great...any reports to the contrary?

thanks,
Adrial

Tom Pultz

[quote]Originally posted by adrial:
<strong>Tom, redline MTL is 75-80 not 70-80 if that makes any difference.</strong><hr></blockquote>Not according to the Red Line web site, which says it's 70W80

Tom Pultz

[quote]Originally posted by adrial:
<strong>I've read that GL5 will corrode the syncro's</strong><hr></blockquote>If that's true, then why would Porsche spec a GL5 fluid for the 944? The Internet is full of misinformation. Just check out eBay

Tabor

Tom,

The Redline site talks about GL5 being bad for synchros. Maybe Porsche used it because it was the only way to get a LSD to work well. I don't really know. But I do know a racer at PIR who swears that GL5 Redline 75W90 killed his transmission.

Paul C 944

I just put in mt 90 last week the car shifted much smoother it seems to make a big difference ,very happy with results.MT 90 is75w90 gl4.Paragon reccommended this,good enough for me.

Tom Pultz

[quote]Originally posted by Tabor Kelly:
<strong>Tom,

The Redline site talks about GL5 being bad for synchros. Maybe Porsche used it because it was the only way to get a LSD to work well. I don't really know. But I do know a racer at PIR who swears that GL5 Redline 75W90 killed his transmission.</strong><hr></blockquote>The Red Line site says "Most manufacturers of manual transmissions and transaxles recommend an 80W or 90W GL-4 lubricant. GL-5 gears oils which are required in hypoid differentials are not used in most synchromesh transmissions because the chemicals used to provide the extreme pressure protection can be corrosive to synchronizers, which are commonly made of brass or bronze. Typically, the use of a GL-5 lubricant in a synchromesh transmission will shorten the synchronizer life by one half."

Notice that a "hypoid differential" requires GL5 protection according to Red Line. The Porsche workshop manual says to use "80 wt hypoid gear oil" or 75W90 GL5, so a normal GL4 really doesn't satisfy the "hypoid" requirement.

Regarding Corrosion Protection of their GL5 gear oil: "The extreme pressure chemistry used in many gear oils can be corrosive to brass and bronze used in synchronizers and bushings. Most gear oils are corrosive at temperatures of 200°F. Red Line Gear Oils are non-corrosive up to 300°F and the MTL in excess of 350°F. A corrosive gear oil can shorten synchronizer life by half and can also contribute to rust problems. Red Line Gear Oils are designed to provide synchro and bushing compatibility and to prevent rust even when water is present."

GL5 gear oil sounds fine to me.

As for the guy that claimed Red Line killed his transmission I think the key word is "racer." Who knows how the trans was treated.

Bottom line: I'm sticking with GL5 gear oil. YMMV.