You can use an Xw30 or Xw40 oil, although X should not be greater than 10. I like to use oils with a lower "pour point" index number (X) in the trans, because they work better at start up. I also think 40 weight works better in these cars than 30 weight. And you should be using synthetic (although saab recommends mineral).

So, my recommendation would be a 0w40 or 5w40 synthetic.

Edit - also, don't worry about mixing with the oil that is in there. The oil mentioned above will work fine with what is probably in there (10w30 or 10w40 mineral oil).

 

I'm an old timer who still runs straight 75w

 

*according to a certain saab mechanic on SC* at his dealership they used 10w30, and at a neighboring one they used gear oil; he said the transes using motor oil at his dealership tended to last longer. Just putting that out there.

 

I've had good luck with 75, also seems OK with 0w-40. I agree that its good to have a good low pour index if going with motor oil. I tried 15w-40 once, and it it SUCKED until the car was hot.

 

To be honest, motor oil would be the easier of the two as 75w has gotten expensive and is quite hard to find locally.

 

I can only find 75w90 locally and occasionally some other multiweight gear oils, I think a lot of American cars must use it in the rear end.

 

1qt pennzoil syncromesh, 1 qt red line shockproof lightweight, 2 qt castrol hypoy-c. mix thoroughly and fill.

 

The case probably can't hold that much oil. On a simple refill (without draining primary case) a c900 will only take about 2.5 quarts.

 

i never said use all of it???

*edit*this mixture leaves about 1qt left over in an ng900 trans, and has been shown to help shifter feel and synchro issues several different makes/models of transmissions*/edit*

 

The reason to use those amounts it for perportion. He could probably say .4 qts X, .4 qts Y, and .8qts Z, but you can't buy in those qtys ;-)

 

OK. Shifter feel and smoother synchros are not signs that your oil is helping you. I don't know about an NG900 trans for point a below, but point b holds true for all transmissions.

a:

in a c900 trans, most of the "smoothness" or lack thereof that you feel in the shifter (not grinding) comes from the ball in the rear of the transmission. I would rather use an oil that has a viscosity similar to what saab intended to be used rather than one that lubricates this ball better. Apparently you can take off the rear cover, remove the ball and spring, regrease, and this may actually lead to a smoother feel. Never tried it myself.

b:

And now for a little deductive logic.

Desire 1: I want to have my transmission last a long time without rebuilding.
Desire 2: I want smoother shifting.

Starting from Desire 2...

-I want smoother shifting
-I add an oil that seems to make the synchromesh work better.
-The synchromesh works better because of increased friction in the synchro rings.
-Increased friction leads to increased wear.
-Increased synchromesh wear leads to decreased transmission life.

It appears that our desires are mutually exclusive.

To quote jetman on SC, "Notchy shifting's where it's at."

 

Whenever I think "smooth" I think, "clicks right into gear"...so my smooth = most people's notchy :lol:

 

"clicks right into gear"

haha excellent

if you designed a device to completely remove all shifter feel, you'd make millions.

 

Redline MTL. 2 c900s, 7 years. Any of the SRS c900 guys will tell you that Redline is the stuff to use. Recommended by Scanwest.

 

Redline FTL. 2 c900s, 7 years. Any of the SRS c900 guys will tell you that Redline is the stuff to use. Recommended by Scamwest.

Eh, i'm sure the stuff is OK, but I'm not going to pay extra for a false sense of security.

 

I don't have time to look up pics of the drain plug in a Redline-equipped trans that xassh pulled, but trust me, it was the c900 equivalent of the white house christmas tree.

 

Ok.

I have been running the same 1993 900S transmission since Nov '05 with between 200-300whp and easily 300ft/lbs. I just drained the trans last month, no chunkies. I of course filled it with more Redline MTL.

I realize that this is just one person's personal experience, but who else on here has put down as much power for as long as I have without a transmission breaking?

 

Excellent. Once it's smoother like that, I will really be able to slam through the gears.*

 

Glide* not slam.

 

This is a redline equipped trans after 5-10k miles:

 

Is it possible that after breaking a bunch of transes, you changed your driving style a bit to make it stop?

My trans has been fed synthetic oil of various weights since I bought it, and it's just fine. And this is with a lot of shifting and a good amount of hard accellerating, even in 1st-2nd gears. Probably at least 80% "city miles."

*desparately knocks on wood so trans doesn't blow on me later tonight*

 

I like your marketing.

 

Xassh had a an '86 trans so maybe those shaving are from the pinion bearings. My plug look liked that a week before my bearings went out.

 

how old is your trans?

If it has a lot of miles on it I would stick with whatever is in there, possibly just normal motor oil non-synthetic

If the trans is relatively new I would use redline MTL, MT-90 or their shockproof oil.

I think I have exploded 10 or so C900 trannies & from my experience Redline oils are the only thing that has allowed my trannies to last. Shockproof is what Scanwest suggested that I use on my SPG which does see the occasional track day & has about 280 whp, so far so good...

Synthetic motor oil is so slick & does not have the friction properties to protect the gears & syncros

normal motor oil isn't designed for this type of friction & breaks dows very quick with all the heat these trannies build up, they get VERY hot

The best thing to do for these cars is to add a trans oil cooler. IF you do not ever take your car to a roadcoarse then you can use the OEM oil cooler location. I was shocked by how hot the oil got in my trans even with a oil cooler..... simply driving at 70mph on the highway it gets 300+ degrees really quick

 

I agree with IronJoe.

Redline seems to be a good choice, although expensive. Redline is what they put in Subaru manual transmissions. I am not saying that is what makes it good for a c900, but it shows how the oil stands up to n00b STi drivers.

 

I was thinking about mixing a quart of shockproof with about 1.5 quarts of regular redline to find a happy medium. Thoughts?

 

What are you all going to run this year for winter? I'm a n00b when it comes to oils and it so rarely gets really cold here in southern PA that I've never been too concerned but as the temps have been coming down this year I'm experiencing more lifter noises when I start it up that I'd like to get rid of.

Oh and I have Redline in my transmission and it feels great once its warmed up, that combined with a solid motor mount almost makes it feel like a legitimate shifting transmission.

 

solid motor mount

Makes a huge difference doesn't it! Love it.

 

I am not sure how old the trans is, the car has 209k on it, but it shifts awesome, and doesnt pop out of any gear. Is it even possible that it is the original trans? The fluid looks decient in it, it is just leaking out of the gasket in the very front of the car. When I redo that gasket, I will refill the trans most likely with redline.

 

Your old sig was better.*

 

I am patiently waiting for you to say some more dumb **** before I update again.

 

i use castrol GTX 10-30, and change it every oil change,,, its cheap enough so that i don't care... i think the change interval is more important than the oil itself.

 

With my experience, not true I also did the GTX every 2500 miles & the trans was dead before the 10K mark. I also went with Mobil 1 & I had similar results.... trans dead a little after 5K miles.

I had my best luck with MTL in the winter then MT-90 in the summer & I changed to new MT-90 before a track event. After that trans let go I went with a Scanwest box & they stressed how important a trans oil cooler is & also how great the shockproof stuff is. They told me I can use the shockproof in my trans for years even with doing drivers schools!! I am sure the oil cooler helps out a lot though, I use a gallon of oil now.

With the age of the trans I have seen a few times people post that they have 1XX,XXX miles on their trans, went to MTL & within 5-10K the trans exploded. Thus not sure what to tell ya since trans age isn't known. My best life out of a trans was 55K miles, worst was 1700 miles I beleive

 

I agree with gm and IJ, Redline is very good and has performed well in my recent tranny rebuild. I'm making power in the 250-275hp range. Now that winter has set in, by accident, I found a Harley Davidson Synthetic Tranny Oil 20w-50. The Redline oils are to thick for temperatures lower than -10F-0F, yes they may thin out after some extended driving, but the HD oil has performed very well for me. And yes I have tested it thoroughly. I will admit that I have yet to test this oil at -40F, but the way it "feels" so far this may be the better of oils for these temps yet I have found.

ps