[Subscribe to Daily Digest] |
You used Mobil 1's "Truck & SUV Formula" 5W-40 & Amsoil's "European Formula" 5W-40?? Tell me more about what they did in your tranny. (I would NOT use any other M1 or Amsoil oils in the tranny, with the possible exception of M1 15W-50 in a warm-enough climate.)
As for any gear oil, let's take a look at the conditions gear oils are designed to address. Your typical tranny is an inline affair, placed behind the engine & exposed to a decent amount of airflow. The operating temps are far lower than those seen by our design (evidenced by the lower temps gear oil viscosities are measured at), & the additives aren't selected to withstand prolonged exposure to engine-type high temps. Saab's design of grafting the tranny to the bottom of the engine, using the top of it as a hot oil return sump & then blocking all the airflow with the clutch assembly, keeps things cooking in the tranny. This is great for cold weather operation (shifting loosens up faster in sub-freezing temps this way), but requires oil designed for different conditions. Saab knew this when they spec'd engine oil for the tranny.
Oil films are your first line of protective defense, so a better/stronger cushion of oil is always what you look for first. The US manual's recommendation for tranny lube is 10W-30 engine oil first & 75 wt gear oil second. The viscosity of SAE 10 weight engine oil lands towards the low end of SAE 75 weight gear oil, while SAE 30 weight engine oil falls just below SAE 85 weight gear oil (engine oil viscosity is measured at 210°F while gear oil is measured at 140°F). Higher viscosity oils provide better film strength, & synthetic oils provide the best film & maintain it longer.
Your next line of defense is your additive package of boundary layer & anti-wear agents. These come into play when all the oil has been squeezed away & dry surfaces remain. You don't want metal-to-metal contact, so floating these compounds around allows them to take the hit before your parts do. Engine oils contain additives designed to withstand combustion chamber high temps, while gear oils do not.
Unfortunately, most engine oils now also contain substances referred to as friction modifiers. They help an engine's sliding parts slide more easily, thereby saving gasoline. Here's where your choice of engine oils can affect your tranny's operation. DO NOT use any engine oil labeled as "energy conserving," as they contain the highest amounts of friction modifiers. Dual rated oils (gasoline/diesel) contain the least.
A final point is Saab's differing recommendations for oil in the North American market than anywhere else. In Europe, they've recommended dual rated oils meeting ACEA A3/B3 for years (possibly decades?). ACEA A3/B3 is a European oil spec meeting very specific viscosity, wear & deposit requirements, & is much more stringent than anything the SAE, API & ILSAC have produced. It's this type of oil that was available to Saab's engineers when they created the recommendation.
So, based on my research, I feel the best oil to use is a dual rated fully synthetic oil meeting a minimum of ACEA A3/B3. For me, that means Rotella Syn 5W-40, M1 5W-40, Amsoil 5W-40, or M1 15W-50.
I'm not saying YOU should switch from Redline. If you like it, I think that's great. For your application & driving style, it obviously meets your needs. But let me pass along what one local Saab indy garage has told me on several different occassions:
First: they feel Redline is the "absolute best" product for Saab trannies.
Second: even with the "absolute best," I shouldn't expect my Saab tranny to last more than 120k miles. (!!)
Third: when they have a Saab tranny that no longer shifts well using Redline, they switch it over to (better than best) BG Syncro Shift II.
This info comes from a shop that works on many daily drivers, not just racers. But, just because Redline has worked well for you doesn't mean it's the best for me. I'm convinced that a lifetime of 75 wt gear oil is what ALMOST killed my tranny at 140k miles, & that proper cleaning & appropriate oil selection has allowed it to live in a better state than when I bought it nearly 7 yrs ago.
I'm sure most folks on this BB are already using syn lubes throughout their cars. If anyone's interested, here's a link to an article about the gear wear benefits of switching from conventional to synthetic lube. Just remember that our gearboxes operate under somewhat different conditions than most others.
posted by 146.82.1...
Article about synthetic gear oil selection
, Sat, 8 Oct 2005 16:47:34
, Sat, 8 Oct 2005 18:04:46, Sun, 9 Oct 2005 10:04:07, Sun, 9 Oct 2005 13:44:48, Sun, 9 Oct 2005 10:02:34
, Sat, 8 Oct 2005 14:48:30, Sat, 8 Oct 2005 15:40:28
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
