4+3 gear oil
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Any good GL5 80W-90 gear oil will work fine for the 4-speed portion. The Borg-Warner Super T-10 has been around since the 60's and it has survived all sorts of racing activity and worked just fine with 80W-90 oil. No particular need to use a synthetic oil. For the OD unit, use a Dex III compatible ATF. Again, no real need for a synthetic.
In fact, there was much discussion some years ago regarding the use of synthetic oils in the 4+3 and the consensus at the time was to specifically to not use a synthetic in the OD.
My 87 with the 4+3 has seen lots of autocross and track day use and the trans is working just fine using the factory recommended oils.
In fact, there was much discussion some years ago regarding the use of synthetic oils in the 4+3 and the consensus at the time was to specifically to not use a synthetic in the OD.
My 87 with the 4+3 has seen lots of autocross and track day use and the trans is working just fine using the factory recommended oils.
Le Mans Master
Joined: Oct 2007
Posts: 9,700
Likes: 3,469
From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
2024 C5 of the Year Winner - Modified
2023 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
St. Jude Donor '09-'10-'11
I would recommend one of the following oils:
AMSOIL Severe Gear 75-W90
http://kahunamotorsports.com/svg-product-page.html
or
AMSOIL Long Life Synthetic Gear Lube 75-W90
http://kahunamotorsports.com/fgr-product-page.html
Both are very good oils for the 4+3. The Severe Gear is better if the car is tracked often, but the Long Life oil is designed for extended drain intervals. PM me if you have specific questions about the two.
AMSOIL Severe Gear 75-W90
http://kahunamotorsports.com/svg-product-page.html
or
AMSOIL Long Life Synthetic Gear Lube 75-W90
http://kahunamotorsports.com/fgr-product-page.html
Both are very good oils for the 4+3. The Severe Gear is better if the car is tracked often, but the Long Life oil is designed for extended drain intervals. PM me if you have specific questions about the two.
