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Old 02-11-2009, 09:22 AM   #1
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Synchromesh tranny fluid

I have a 2000 boxster s and grinding issues when I try to shift in 2nd gear. I heard that GM/Pennzoil synchromesh tranny fluid is good stuff for that. I was gonna go out and buy some but I just wanted to make sure it won't damage anything. I think there are friction modifiers in it also. I'm in florida so it has nothing to do with being cold as a lot people report. Also, I heard that stuff is really thin, if I wanted to make it thicker, what should I mix it with and in what ratio. Thanks.

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Old 02-11-2009, 09:57 AM   #2
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Sometimes friction modifiers make shifting worse. The friction modifiers in most gear lubes are in there for limited-slip differentials... so they don't grab and/or wear out prematurely. Your Boxster doesn't have an LSD.

The problem you (most likely) have is worn synchros which means two things: 1) the surfaces of the synchros have been polished by wear and 2) they engage a bit later (and with less pressure) since they have worn.

I suggest you start with a tranny fluid (e.g. Redline 75W90NS) that does not contain friction modifiers. See how it works for a couple of hundred miles. If you still aren't happy, you can add a friction modifier (without having to change the tranny fluid) and see if that improves the situation.

Good luck and report back so others can learn from your experience!
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Old 02-11-2009, 10:29 AM   #3
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i could try theredlineand yai know thats probably the problem but i figured it couldnt hurt. i just picked up some valvoline dura blend tough driving formula(2qt 80w90) and pennzoil synchromesh (1qt). i was thinking of mixing them since im in fl. Havent done anything yet though. is mixing a really bad idea? i dont think sm will be thick enough on its own but i definitely dont wqnt to make anything worse.

What about shockproof? If you think thats good too, then which version? There is superlight, light, and heavy.

I feel overwhelmed about what I should do. Some people say that the 75w90ns is not recommended and to use shockproof instead. I'm really ignorant with this stuff, but I want to get the best thing for my transmission. Some people even say they mix it, like I was going to do with the Synchromesh. I just don't know if these other forums are reliable since I have a porsche and it could be different. Basically, I want something that is high quality so that I know for a fact that I need to have work done on the synchros.

Last edited by Viper5; 02-11-2009 at 11:43 AM.
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Old 02-11-2009, 12:06 PM   #4
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Same thing

I have a 2000 S also. I get a little grind going into 2nd once in while too, especially when the tranny is cold. Usually goes away after the tranny warms up. It feels to me like the synchro is worn. I have to pause a little between 1st and 2nd when I shift until the tranny warms up. The car just turned 100K, and I am the 3rd owner. No telling how the previous owners treated the tranny. I usually double clutch when down shifting into 2nd to minimize synchro wear.
Did you see this thread in the Performance and Technical section?
http://www.986forum.com/forums/showthread.php?t=18785
They have the same problem.
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Old 02-11-2009, 05:55 PM   #5
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Why don't you just use the genuine Porsche transmission fluid and be done with it? Its good for 90k before changing out so the quality and correct weight is not in question.
Care must be taken with aftermarket gear oils as GL4 rated oils are good for the synchro's and not so good for the transaxle gear mesh while GL5 rated oils are good for gear mesh but not so good for synchro life as the fluid tend to be too slippery causing the syncho's to skid.
As far as I know, Porsche have never released the techno details of its gearbox oil.
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Old 02-11-2009, 06:47 PM   #6
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If you email Red Line they are very good about recommending specfic lubes for your car.

Great stuff.

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Old 02-11-2009, 07:41 PM   #7
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Earlier today I decided to return the items purchased at the store and made an online purchase for 3qts of redline 75w90NS. I will report back to let you know how it runs. I read somewhere that redline recommends that for alfa and porsche style transmissions
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Old 02-14-2009, 04:25 PM   #8
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I got my Redline 75w90ns today. I'm surprised how fast it came in. I got it from Summit, and I think they have same day shipping. I will try to do a flush tomorrow and put the new stuff in. Is there something I should about this before I proceed? I've never done it before.
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Old 02-15-2009, 02:42 AM   #9
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It's straightforward, but two pointers...

1) warm the new fluid (float the bottles in a sink of hot water for 15 minutes) and it will pump *much* easier/faster

2) so the fill tube from you pump stays in place, tape it to the bracket near the back end of the tranny

Let us know how the shift feel changes.

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