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914World.com _ 914World Garage _ Gearbox oil Minerial v Synthetic
Posted by: neilbardsley Sep 9 2023, 06:42 PM
I recently changed back to using mineral 80/90 GL4 oil from a synthetic 75/90. Seems to shift better with the mineral. I read something about the synthetic being too slippery for the synchro rings? Can someone explain that or point me to somewhere I can read? That isn't intutitive to me
Posted by: Shivers Sep 9 2023, 08:05 PM
This pic shows two rings. One is new with a rough bumpy surface and an old one that is smooth. As I understand it the new ring uses that rough surface to slow down the teeth so the gears can mesh. If it is too slippery the synchro rings can’t slow things down like they are designed to.
Posted by: neilbardsley Sep 9 2023, 11:27 PM
Thank you
Posted by: BillJ Sep 10 2023, 05:42 AM
I recently changed back to using mineral 80/90 GL4 oil from a synthetic 75/90. Seems to shift better with the mineral. I read something about the synthetic being too slippery for the synchro rings? Can someone explain that or point me to somewhere I can read? That isn't intutitive to me
I thought was supposed to be 80/90 gl5?
Posted by: Superhawk996 Sep 10 2023, 06:56 AM
I recently changed back to using mineral 80/90 GL4 oil from a synthetic 75/90. Seems to shift better with the mineral. I read something about the synthetic being too slippery for the synchro rings? Can someone explain that or point me to somewhere I can read? That isn't intutitive to me
I thought was supposed to be 80/90 gl5?
Yes - GL-5 to protect the ring and pinion which needs an EP (extreme pressure) lube due to hypoid gearing.
@http://www.914world.com/bbs2/index.php?showuser=15610
901 transaxle doesn’t use brass based synchros which would be the only rationale for GL-4. Even then, the need to protect the ring and pinion (non consumable) would trump protection of brass synchros (a consumable).
Factory manual
Note for OP: don’t freak out that you’ve been running GL-4. Just switch back to proper lube.
Posted by: neilbardsley Sep 10 2023, 09:37 AM
I recently changed back to using mineral 80/90 GL4 oil from a synthetic 75/90. Seems to shift better with the mineral. I read something about the synthetic being too slippery for the synchro rings? Can someone explain that or point me to somewhere I can read? That isn't intutitive to me
I thought was supposed to be 80/90 gl5?
Yes - GL-5 to protect the ring and pinion which needs an EP (extreme pressure) lube due to hypoid gearing.
@http://www.914world.com/bbs2/index.php?showuser=15610
901 transaxle doesn’t use brass based synchros which would be the only rationale for GL-4. Even then, the need to protect the ring and pinion (non consumable) would trump protection of brass synchros (a consumable).
Factory manual
Note for OP: don’t freak out that you’ve been running GL-4. Just switch back to proper lube.
Noted thank you. I was using gl 5 before. I will find a gl 5 mineral oil
Posted by: 930cabman Sep 10 2023, 10:06 AM
I have been using this one from NAPA https://www.napaonline.com/en/p/SL_SL2473
seems to work well, but we need to remember these gearboxes are old technology and some level of care must be taken
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