Transmission fluid swap
02-12-2020, 02:21 PM
#16
Rennlist Member
I have yet to drive my new fill of Redline 75W 90 NS any large distance but will soon do a 3,000 mile road and track trip and report back.
It’s a pity there’s no easy way to create a video for this site but I have a spare guide sleeve, syncro and gear set that allows me to see how they work and that gave me the impetus to change fluids.
The syncro’s job is to help two moving items in the box to be at the same speed so they can mesh together smoothly. It synchronises speeds.
It does this with a surface on the synchro that matches a surface on the gear set. As they move together the synchro progressively engages with the gear, like a clutch. It’s ultimately metal on metal contact. When the gears are synchronised, the power is going through the linked gear not the synchro.
The transmission oil has a difficult job. It has to lubricate but also allow the synchro to engage with the gear. If it is too slippery, then the synchro doesn’t work as well and the shift is notchy. However the oil also has to protect the transaxle which is a different requirement. It appears that Porsche had complaints and changed its recommended oil to two specific ones, not just the GL5 spec.
Before I rebuilt the box I tried Redline as my synchros were on the way out. It did not work. This is different as I have near new synchros and gear sets in my box. There is no discernible metal in my oil. I’m just trying to find an oil that works with my synchros so they can do their job. Those reading this with a tired box many have no improvement changing oil.
It’s a pity there’s no easy way to create a video for this site but I have a spare guide sleeve, syncro and gear set that allows me to see how they work and that gave me the impetus to change fluids.
The syncro’s job is to help two moving items in the box to be at the same speed so they can mesh together smoothly. It synchronises speeds.
It does this with a surface on the synchro that matches a surface on the gear set. As they move together the synchro progressively engages with the gear, like a clutch. It’s ultimately metal on metal contact. When the gears are synchronised, the power is going through the linked gear not the synchro.
The transmission oil has a difficult job. It has to lubricate but also allow the synchro to engage with the gear. If it is too slippery, then the synchro doesn’t work as well and the shift is notchy. However the oil also has to protect the transaxle which is a different requirement. It appears that Porsche had complaints and changed its recommended oil to two specific ones, not just the GL5 spec.
Before I rebuilt the box I tried Redline as my synchros were on the way out. It did not work. This is different as I have near new synchros and gear sets in my box. There is no discernible metal in my oil. I’m just trying to find an oil that works with my synchros so they can do their job. Those reading this with a tired box many have no improvement changing oil.
02-12-2020, 03:25 PM
#17
I have yet to drive my new fill of Redline 75W 90 NS any large distance but will soon do a 3,000 mile road and track trip and report back.
It’s a pity there’s no easy way to create a video for this site but I have a spare guide sleeve, syncro and gear set that allows me to see how they work and that gave me the impetus to change fluids.
The syncro’s job is to help two moving items in the box to be at the same speed so they can mesh together smoothly. It synchronises speeds.
It does this with a surface on the synchro that matches a surface on the gear set. As they move together the synchro progressively engages with the gear, like a clutch. It’s ultimately metal on metal contact. When the gears are synchronised, the power is going through the linked gear not the synchro.
The transmission oil has a difficult job. It has to lubricate but also allow the synchro to engage with the gear. If it is too slippery, then the synchro doesn’t work as well and the shift is notchy. However the oil also has to protect the transaxle which is a different requirement. It appears that Porsche had complaints and changed its recommended oil to two specific ones, not just the GL5 spec.
Before I rebuilt the box I tried Redline as my synchros were on the way out. It did not work. This is different as I have near new synchros and gear sets in my box. There is no discernible metal in my oil. I’m just trying to find an oil that works with my synchros so they can do their job. Those reading this with a tired box many have no improvement changing oil.
It’s a pity there’s no easy way to create a video for this site but I have a spare guide sleeve, syncro and gear set that allows me to see how they work and that gave me the impetus to change fluids.
The syncro’s job is to help two moving items in the box to be at the same speed so they can mesh together smoothly. It synchronises speeds.
It does this with a surface on the synchro that matches a surface on the gear set. As they move together the synchro progressively engages with the gear, like a clutch. It’s ultimately metal on metal contact. When the gears are synchronised, the power is going through the linked gear not the synchro.
The transmission oil has a difficult job. It has to lubricate but also allow the synchro to engage with the gear. If it is too slippery, then the synchro doesn’t work as well and the shift is notchy. However the oil also has to protect the transaxle which is a different requirement. It appears that Porsche had complaints and changed its recommended oil to two specific ones, not just the GL5 spec.
Before I rebuilt the box I tried Redline as my synchros were on the way out. It did not work. This is different as I have near new synchros and gear sets in my box. There is no discernible metal in my oil. I’m just trying to find an oil that works with my synchros so they can do their job. Those reading this with a tired box many have no improvement changing oil.
Have you had any issues with your shifter cable?
02-12-2020, 03:51 PM
#18
Rennlist Member
I have a C4 which is a more direct linkage than the C2. There are a few bushes to replace and I have done the major ones. Neither version have cables. What I did incorrectly is leave a washer off the bolt in the last linkage before the box. However, that’s just introduced a bit of slack, not impacting on the synchros action.
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Tsmith5150 (02-12-2020)