Transmission oil
Thread Starter
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Transmission oil
Hello everyone. I need some info on the 4+3 transmission oil for the manual trans part.
I have been researching this a little bit and found a lot of stuff for Super T-10 transmissions.
These following questions are specifically in regard to our particular 4+3 transmissions.
People have said that using GL5 has additives that will corrode the syncros over time and that you should use GL4. Is this true?
People have said that using synthetic gear oil will cause the syncros to slip during shifts and make shifting harder or grind the gears. Is this true?
I am currently using Valvoline 80w90 GL5 synthetic gear oil in mine and I have not noticed any hard shifting or any other problems with the trans.
Thanks.
I have been researching this a little bit and found a lot of stuff for Super T-10 transmissions.
These following questions are specifically in regard to our particular 4+3 transmissions.
People have said that using GL5 has additives that will corrode the syncros over time and that you should use GL4. Is this true?
People have said that using synthetic gear oil will cause the syncros to slip during shifts and make shifting harder or grind the gears. Is this true?
I am currently using Valvoline 80w90 GL5 synthetic gear oil in mine and I have not noticed any hard shifting or any other problems with the trans.
Thanks.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Use a good grade of SAE 80W GL5 oil. That is what is specified in my '87 Owner's Manual. GM spec'd that GL5 standard back then and I would think that the 84-86 trans would use the same.
IMHO, unless there is some documentation that says synthetics or multi-grade oils are proven to be better, stay with the factory recommendations. YEars ago there was a debate going on regarding the use of a synthetic AFT in the OD unit. The consensus at that time was to not use a synthetic fluid. As I recall there were a couple of OD unit failures that were attributed to a synthetic fluid. Dexron III is still widely available as are the filters..
Make sure that you can remove the fill plug on the side of the case before removing the drain plug!!
IMHO, unless there is some documentation that says synthetics or multi-grade oils are proven to be better, stay with the factory recommendations. YEars ago there was a debate going on regarding the use of a synthetic AFT in the OD unit. The consensus at that time was to not use a synthetic fluid. As I recall there were a couple of OD unit failures that were attributed to a synthetic fluid. Dexron III is still widely available as are the filters..
Make sure that you can remove the fill plug on the side of the case before removing the drain plug!!
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
Some interesting conversations regarding
transmission oils:
https://www.corvetteforum.com/forums...post1563122321
transmission oils:
https://www.corvetteforum.com/forums...post1563122321
Drifting
Joined: Sep 2014
Posts: 1,579
Likes: 59
From: Trieste Italy
Hello everyone. I need some info on the 4+3 transmission oil for the manual trans part.
I have been researching this a little bit and found a lot of stuff for Super T-10 transmissions.
These following questions are specifically in regard to our particular 4+3 transmissions.
People have said that using GL5 has additives that will corrode the syncros over time and that you should use GL4. Is this true?
People have said that using synthetic gear oil will cause the syncros to slip during shifts and make shifting harder or grind the gears. Is this true?
I am currently using Valvoline 80w90 GL5 synthetic gear oil in mine and I have not noticed any hard shifting or any other problems with the trans.
Thanks.
I have been researching this a little bit and found a lot of stuff for Super T-10 transmissions.
These following questions are specifically in regard to our particular 4+3 transmissions.
People have said that using GL5 has additives that will corrode the syncros over time and that you should use GL4. Is this true?
People have said that using synthetic gear oil will cause the syncros to slip during shifts and make shifting harder or grind the gears. Is this true?
I am currently using Valvoline 80w90 GL5 synthetic gear oil in mine and I have not noticed any hard shifting or any other problems with the trans.
Thanks.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The ZF 6-speed manual transmission first appeared in 1989. From 1984 thru 1988, the manual trans was the Doug Nash 4+3 except for the 1988 Callaway twin turbo cars which got the ZF 6-speed. These were two entirely different transmissions.
