More questions on manual transmission oil

Hi again, Thanks for the replies to my "hard to shift in low gears when cold". I'm going to change the transmission oil this weekend; is the differential oil the same as the transmisssion oil???? If not what should be used? Is it just like the transmission, in that it's just a drain and replace? Also, from what I've read, either Redline 75w-90 oil or Swepco - 201 oil - is what most of the folks are using?? Thanks again for your time, Patrick

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The Shell transaxle lube you can get from the dealer works great. Smooth and quiet. Cost for 3 liters from the dealer is about $90.00.

Yes, it is the same oil and compartment for the transmission and differential so they call it a trans-axle. You need to have an oil that is good for both the gears and the synchros. What year is your car? Looks like it might be a '99, does it have the LSD? If you have the limited slip you might want to look for a special oil. Your best bet is to get the fluid from the dealer.

I just changed mine Monday night. I finally went with Red Line 75w90 because it was in my 964 race car and did so well and I don't want to have 2 different kinds (inventory issue... principles of lean manufacturing ). I put the regular Mobile from Advance in the 964 and drove it on the track this weekend. I could tell a difference. It did NOT shift as well as it did with the Red Line, prrticularly after getting hot, so I'm changing back to Red Line before I drive it again. Now, back to the 996. I can tell a slight difference in shifting w/the Red Line. It does seem smoother. That might be just because it's fresh and the old had about 80k miles on it. The 996 is my daily driver and doesn't see the track. As far as the changing itsself. It's pretty simple: -Take the fill plug out 1st -Take the Drain Plug out. Mine was hard to break loose and got a chunk of my knuckle! - Fill transmission to just below the fill plug level. I did this by slowly adding until it started dripping out of the plug ON LEVEL GROUND. The trick is how to get the fluid in the gearbox. I took and old Mobile bottle w/the squeeze nozzle on the end. Poured out the Mobile, refilled w/ Red Line and used this bottle to get fluid into the box. I'm going to guess it took right at 3 liters, maybe a little less.

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Lower gear unit hand pump, suitable for replacing the gear lubricant in an outboard motor, is perfect for this. Screws into the top of a quart bottle of gear lube. You can find them for $7 or so in the auto parts stores.

Thanks Doug. I got one of those this weekend. Thankfully Red Line has an odd shaped top so it wouldn't fit Actually, it might have worked. I just defferred to my tried and true method. I'm going to try it again on the 964. If nothing else, I'll find a suitable bottle and pour the RL onto that, then put the pump on.

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Some years ago had the tranny/diff fluid changed in my '02 Boxster. (Don't remember the mileage but it was high.) Afterwards, shifting while tranny/diff cold was worse, but shifting warm was better. (I always let cold engine warm up to point secondary air injection pump shuts off before driving away but even this is not sufficient to put any heat into tranny/diff fluid. Only driving can do that.) Adapted to when cold shifting from 1st to 3rd. Once warmed up shifting from 1st to 2nd worked just fine. Recently, took car to a local Porsche dealership for among other things another tranny/diff fluid change: It's second and with over 185,000 miles on the odometer so due, of course, way due. Service quoted me $45 (approx.) per quart of fluid and the thing uses nearly 5 quarts of fluid. Bit the bullet and went ahead and had service done and was surprised when I got car back how improved shifting was. Even cold I could shift from 1st to 2nd and no longer had to use that skip shift technique until tranny/diff warmed up. I don't know what at the 1st fluid change what transmission fluid was used. Checked receipt and the cost was around $15/quart. This last change Porsche fluid was used and while one can't always assume one gets what one pays for, based on my experience and the improvement in shifting I'd have to say that $45+/quart transmission fluid may just be worth the money. I know others recommend other brands, even synthetic, but I'm sticking with the Porsche fluid based on the improvement I noticed. Sincerely, Macster.

Well crap, I just bought 4 qts of Mobile1 Synthetic 75W90 from Autobarn for like $8.40 a qt....so you all are telling me this is probably no good to use? Even tho I only have 38k on my 2002, that's a long time for the oil to be in there IMHO...maybe I'll be the guinea pig and just end up using it as a flush if I hate it....

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I've never used it in my Boxster (unless it was factory fill or used for the 1st or 2nd tranny fluid change) so I don't know how it compares to what the dealership used or even what the factory used. In fact maybe the dealership used that same lube but just applied the standard Porsche markup... If the owners manual doesn't specifically advise against using a synthetic lube in the tranny/diff and if the stuff meets whatever requirements there are for the tranny/diff fluid use the fluid you bought. If you find shifting cold/warm/hot satisfactory great. If you find shifting cold/warm/hot unsatisfactory, then you can think about what you want to do. In my case, I just assumed the slight but noticable reluctance of the tranny to shift from 1st to 2nd cold was an artifact of the new fluid (and assumed the proper fluid had been used) and since the shifting when hot was better than before the fluid change I lived with the behavior for many thousands of miles. Really, it was no hardship. Had the cold shifting been worse or the hot shifting not improved I would have probably tried another fluid change, at least gone back to the place that did it and complained and see what recourse was available. I would not have been surprised to in this case to be told that with that many miles on it the tranny might need to be 'rebuilt' or replaced. 'course, I would have then almost certainly tried a fluid change just to make sure the fluid (or even an incorrect fluid level, etc.) wasn't the cause of the degradation in shifting. Change the fluid and use the new fluid you have. Give the new fluid a chance. Chances are shifting will be no worse than it was before the fluid change and if acceptable to you then it will be acceptable to you now. Shifting might even be better. At least the tranny/diff has clean/fresh fluid and should last longer and deliver better performance for the remainder of its life, and that's a win. Sincerely, Macster.

Thanks ya'll, "pat056" Redline 75w-90 is what I think I'm going to get...local speed shop has it (with the GL-5 rating) and only $12 a quart! I would use the Porsche oil but I want to do the change this weekend and the local Dealer is about 150 miles away from me! "Macster" thanks for all the information and time you took to answer my questions. My big "Ah-Ah" was the the transmission and diffeerential are one in the same...I though that they were "one of each".... THANKS, Patrick

I can tell you this. Since I changed the fluid Monday, my car has not slipped out of 2nd when cold. Before this would happen almost certainly if I short shifted right after starting down the road...not anymore.