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7 members (JW51, TUTS 59, 3800GUY, Otto Skorzeny, cmayna, 52GMC35424JD, 1 invisible),
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Mod | | | Forums66 Topics128,065 Posts1,055,863 Members48,428 | | 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!
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For helping keep this great
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| | | | Joined: May 2008 Posts: 88 Shop Shark | | Shop Shark Joined: May 2008 Posts: 88 | Anybody know what the best grade of oil to use in the stock rear end on a 59 3800, and how much to put in?? | | | | | Joined: Apr 2005 Posts: 1,107 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 1,107 | sae. 85-90 is what i use in my rears. | | | | | Joined: Nov 2008 Posts: 544 Shop Shark | | Shop Shark Joined: Nov 2008 Posts: 544 | what about the transmission?
I'm most likely looking at filling both my rear end and transmission with synthetic when I get it all back together. Just curious if you guys are using the same weight in the 4 speed tranny as the rear end as well as what the collective thoughts are on synthetic. | | | | | Joined: Jul 2005 Posts: 581 Shop Shark | | Shop Shark Joined: Jul 2005 Posts: 581 | I run 85-90 in both. I believe I added some Lucas oil treatment to the tranny. Couldn't tell you if anything feels different or "smoother" | | | | | Joined: Jul 2009 Posts: 23 Wrench Fetcher | | Wrench Fetcher Joined: Jul 2009 Posts: 23 | As Workmaster says, 80/90 works for both. Fill till it starts to run out of the fill hole. If you go with synthetic, which will keep the heat down on the hot days and flow better on the cold ones, you will probably end up using a 75/90. | | |
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