| |
Click on image for the lowdown. 
====
| | | Forums66 Topics128,133 Posts1,056,395 Members48,441 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Mar 2010 Posts: 207 Shop Shark | | Shop Shark Joined: Mar 2010 Posts: 207 | What is safe to put in my 4-speed 1965 transmission? My manual says SAE 90 but good luck finding that and then I see warnings on sites about GL5 so I need some advice.
Thanks,
Tom
1965 Chevy C10, 230 straight six, 2WD, 4-speed manual
| | | | | Joined: Jan 2008 Posts: 4,962 'Bolter | | 'Bolter Joined: Jan 2008 Posts: 4,962 | Originally they were designed for straight mineral oil. Chevron still markets a suitable oil. RPM Gear Oils
Recommended for many automotive or industrial equipment where the equipment suppliers recommend the use of a straight mineral oil. . | | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | Check out the box at the bottom right on this page. "When filling your 420 with gear oil, we recommend that you select a conventional mineral oil or a para-synthetic in lieu of a full synthetic oil. Properly assembled manual gearboxes do not have the thermal strains seen by combustion engines or hypoid gears. Synthetic fluid in these gearboxes, while not harmful, is probably an economic waste.
Hypoid gear oil is sulphurized higher than transmission oil and can be mildly corrosive to the non-ferrous alloys used for synchros, bushings and thrust washers in these transmissions.
An 80W-90, API-GL5 or MT-1 rated fluid is very good. Some claim faster shifts from using a 50W engine oil in their transmission and we do not consider this to be contraindicated unless you operate your vehicle in a very warm environment. " | | |
|
|
| |
