Recommended transaxle fluid?
07-30-2016, 01:11 PM
#16
Rennlist Member
I don't want to turn this into another oil thread, but there may be some confusion on friction modifiers.
Mobil Delvac Synthetic is an oft-recommended gear oil for our cars. It was designed for heavy-duty trucks where there is a very high load factor, kinda like flogging a GT3 on a track, I suppose.
Mobilube PTX is a synthetic designed specifically for Porsche transaxles. The kinematic viscosity is about same at operating temp as Delvac but it's lower at cold temps. PTX contains friction modifiers (confirmed by Matt at GT) which REDUCES LSD slippage. PTX, of course, costs more as the base esters are derived from crushed porcupines. OK, maybe not, but it does cost more.
The first time I used Mobil 1 in my '81 Honda CBX (wet clutch) I discovered the need for friction modifiers and changing to a motorcycle-specific Mobil 1 oil with the modifiers stopped the slippage.
I suspect that the factory fill is PTX, but that's really speculation on my part.
Matt from GT, or Jim Morton, if I'm off on any of this, please chime in.
Bob
Mobil Delvac Synthetic is an oft-recommended gear oil for our cars. It was designed for heavy-duty trucks where there is a very high load factor, kinda like flogging a GT3 on a track, I suppose.
Mobilube PTX is a synthetic designed specifically for Porsche transaxles. The kinematic viscosity is about same at operating temp as Delvac but it's lower at cold temps. PTX contains friction modifiers (confirmed by Matt at GT) which REDUCES LSD slippage. PTX, of course, costs more as the base esters are derived from crushed porcupines. OK, maybe not, but it does cost more.
The first time I used Mobil 1 in my '81 Honda CBX (wet clutch) I discovered the need for friction modifiers and changing to a motorcycle-specific Mobil 1 oil with the modifiers stopped the slippage.
I suspect that the factory fill is PTX, but that's really speculation on my part.
Matt from GT, or Jim Morton, if I'm off on any of this, please chime in.
Bob
08-01-2016, 12:05 PM
#18
Rennlist Member
Thread Starter
FYI LvDell posted this awhile back, but when doing fluid R&R, it seems smart to throw away the original nasty internal "allen key" fill plug and replace with and external hex head plug.
porsche P/N 90012402001
Thanks for the pointer KK2.
Craig
porsche P/N 90012402001
Thanks for the pointer KK2.
Craig
Last edited by cgfen; 08-04-2016 at 12:18 PM.
08-01-2016, 03:47 PM
#19
Three Wheelin'
But I love oil threads!
08-03-2016, 05:57 PM
#21
" PTX contains friction modifiers (confirmed by Matt at GT) which REDUCES LSD slippage " Does this mean if Delvac is used a friction modifier needs to be added for the LSD to function properly?
08-03-2016, 08:30 PM
#22
Rennlist Member
No, friction modifiers are 'noise' reducers.
Delvac does not have them
For optimal performance you do not want friction modifiers
Delvac does not have them
For optimal performance you do not want friction modifiers
08-04-2016, 03:54 PM
#23
Rennlist Member
I think they are more than noise reducers. Depending on type they can have a significant effect on shock loading of the wear surfaces. For LSD's they are smoothing the transition (eliminating chatter) but once the transition is made they should have no effect. I don't know if the friction modifiers used in PTX are sacrificial, like a FM such as ZDDP.
08-04-2016, 06:05 PM
#24
Nordschleife Master
I guess it's time for my to clarify my position on these things since I've been misquoted here. The PTX factory fill has friction modifiers in it, but they aren't really there for the benefit of the LSD. They are there to aid the steel synchros in cold start shifting when they can be balky. It makes a marginal difference in LSD chatter and lock up but not much.
Spyrex is kind of quoting me, correctly, when he says that LSD additives are noise reducers. I call them an NVH item. Most oem LSDs and a number of the cheap aftermarket LSDs are really grabby and chattering. They offer very inconsistent locking behaviour and act like an on-off switch with very little progression to their behaviour. A friction modifiers smooths this out. And makes the thing less clunky. It doesn't do a whole lot, if anything for LSD performance.
With my LSDs, or a car rebuilt using my plates, I tell people to avoid friction modifers like you can buy in a bottle from GM or Redline. It will not only reduce the lock up of my LSD, reducing the performance on it, but we have seen it increase wear on our clutches and make things wear out more quickly. I tell people to avoid the additives and to avoid LSD specific gear oils.
Now keep in mind, I deal with racecars and track cars, and what I am about to say absolutely needs to be taken within that context. Please do not ever put Redline oils in your gearbox if you are going to track your car heavily with my products in it. Even their NS, which is supposed to stand for not slippery, in my experience is too slippery. Some people love the Redline in their street car because it gives buttery smooth cold start shifting. Cool. Go for it. But if you track your car with it, not only will your LSD wear out more quickly, but I've seen it really increase synchro wear and on hot days in a long session sometimes shift quality goes into the tank when the oil overheats and gets even more slippery.
If you do run Redline stick to NS or MTL. Under no circumstances do an "Uncle Scotty's" and mix some Shockproof in with it. That stuff is horrible for our transaxles. I've seen a lot of ring and pinions fail on cars with shockproof in them.
Spyrex is kind of quoting me, correctly, when he says that LSD additives are noise reducers. I call them an NVH item. Most oem LSDs and a number of the cheap aftermarket LSDs are really grabby and chattering. They offer very inconsistent locking behaviour and act like an on-off switch with very little progression to their behaviour. A friction modifiers smooths this out. And makes the thing less clunky. It doesn't do a whole lot, if anything for LSD performance.
With my LSDs, or a car rebuilt using my plates, I tell people to avoid friction modifers like you can buy in a bottle from GM or Redline. It will not only reduce the lock up of my LSD, reducing the performance on it, but we have seen it increase wear on our clutches and make things wear out more quickly. I tell people to avoid the additives and to avoid LSD specific gear oils.
Now keep in mind, I deal with racecars and track cars, and what I am about to say absolutely needs to be taken within that context. Please do not ever put Redline oils in your gearbox if you are going to track your car heavily with my products in it. Even their NS, which is supposed to stand for not slippery, in my experience is too slippery. Some people love the Redline in their street car because it gives buttery smooth cold start shifting. Cool. Go for it. But if you track your car with it, not only will your LSD wear out more quickly, but I've seen it really increase synchro wear and on hot days in a long session sometimes shift quality goes into the tank when the oil overheats and gets even more slippery.
If you do run Redline stick to NS or MTL. Under no circumstances do an "Uncle Scotty's" and mix some Shockproof in with it. That stuff is horrible for our transaxles. I've seen a lot of ring and pinions fail on cars with shockproof in them.
08-04-2016, 06:14 PM
#27
Thank-you for sharing 
I guess it's time for my to clarify my position on these things since I've been misquoted here. The PTX factory fill has friction modifiers in it, but they aren't really there for the benefit of the LSD. They are there to aid the steel synchros in cold start shifting when they can be balky. It makes a marginal difference in LSD chatter and lock up but not much.
Spyrex is kind of quoting me, correctly, when he says that LSD additives are noise reducers. I call them an NVH item. Most oem LSDs and a number of the cheap aftermarket LSDs are really grabby and chattering. They offer very inconsistent locking behaviour and act like an on-off switch with very little progression to their behaviour. A friction modifiers smooths this out. And makes the thing less clunky. It doesn't do a whole lot, if anything for LSD performance.
With my LSDs, or a car rebuilt using my plates, I tell people to avoid friction modifers like you can buy in a bottle from GM or Redline. It will not only reduce the lock up of my LSD, reducing the performance on it, but we have seen it increase wear on our clutches and make things wear out more quickly. I tell people to avoid the additives and to avoid LSD specific gear oils.
Now keep in mind, I deal with racecars and track cars, and what I am about to say absolutely needs to be taken within that context. Please do not ever put Redline oils in your gearbox if you are going to track your car heavily with my products in it. Even their NS, which is supposed to stand for not slippery, in my experience is too slippery. Some people love the Redline in their street car because it gives buttery smooth cold start shifting. Cool. Go for it. But if you track your car with it, not only will your LSD wear out more quickly, but I've seen it really increase synchro wear and on hot days in a long session sometimes shift quality goes into the tank when the oil overheats and gets even more slippery.
If you do run Redline stick to NS or MTL. Under no circumstances do an "Uncle Scotty's" and mix some Shockproof in with it. That stuff is horrible for our transaxles. I've seen a lot of ring and pinions fail on cars with shockproof in them.
Spyrex is kind of quoting me, correctly, when he says that LSD additives are noise reducers. I call them an NVH item. Most oem LSDs and a number of the cheap aftermarket LSDs are really grabby and chattering. They offer very inconsistent locking behaviour and act like an on-off switch with very little progression to their behaviour. A friction modifiers smooths this out. And makes the thing less clunky. It doesn't do a whole lot, if anything for LSD performance.
With my LSDs, or a car rebuilt using my plates, I tell people to avoid friction modifers like you can buy in a bottle from GM or Redline. It will not only reduce the lock up of my LSD, reducing the performance on it, but we have seen it increase wear on our clutches and make things wear out more quickly. I tell people to avoid the additives and to avoid LSD specific gear oils.
Now keep in mind, I deal with racecars and track cars, and what I am about to say absolutely needs to be taken within that context. Please do not ever put Redline oils in your gearbox if you are going to track your car heavily with my products in it. Even their NS, which is supposed to stand for not slippery, in my experience is too slippery. Some people love the Redline in their street car because it gives buttery smooth cold start shifting. Cool. Go for it. But if you track your car with it, not only will your LSD wear out more quickly, but I've seen it really increase synchro wear and on hot days in a long session sometimes shift quality goes into the tank when the oil overheats and gets even more slippery.
If you do run Redline stick to NS or MTL. Under no circumstances do an "Uncle Scotty's" and mix some Shockproof in with it. That stuff is horrible for our transaxles. I've seen a lot of ring and pinions fail on cars with shockproof in them.
08-04-2016, 06:21 PM
#28
I don't understand why people keep trying to reinvent the wheel. Put in Mobil 1 Delvac 75/90 and call it a day. It's proven stuff and cheap.... I'm pretty sure Matt has recommended this countless times...
08-04-2016, 06:22 PM
#29
09-19-2018, 02:45 PM
#30
Rennlist Member
Thread Starter
Howdy.
When I did pipe pinning this past winter, I drained the Redline NS that I had installed 16 months earlier and re-filled with Mobilube PTX.
Why?
Just to experiment and go to what Matt @ GT gears recommends for my application.
Works fine, no complaints.
Cheers
Craig
When I did pipe pinning this past winter, I drained the Redline NS that I had installed 16 months earlier and re-filled with Mobilube PTX.
Why?
Just to experiment and go to what Matt @ GT gears recommends for my application.
Works fine, no complaints.
Cheers
Craig