Guest intrepid Posted December 13, 2013 Share Posted December 13, 2013 Just bought a '65 Riv. Here's my question, what differential oil viscosity is called for, and also, re: ATF I'm going to probably partially change the ATF, to a synthetic. Any comments or suggestions, would be appreciated. Link to comment Share on other sites More sharing options...
Jim Cannon Posted December 13, 2013 Share Posted December 13, 2013 Before you mess with the differential oil, make sure you don't have a posi-trac. See shop manual. Link to comment Share on other sites More sharing options...
Guest intrepid Posted December 13, 2013 Share Posted December 13, 2013 I planned on checking for that as well, when I get it on my hoist, this week. Thanks Link to comment Share on other sites More sharing options...
rocky5517 Posted December 13, 2013 Share Posted December 13, 2013 Why does Posi matter re fluid? Link to comment Share on other sites More sharing options...
RivNut Posted December 14, 2013 Share Posted December 14, 2013 Posi-trac units require an additive that allows the clutches to operate properly without binding when cornering. My '66 Riv with posi-trac used to clunk and jump anytime I go around a cloverleaf interchange until a changed the fluid and added the additive. Link to comment Share on other sites More sharing options...
64Riv-King Posted December 14, 2013 Share Posted December 14, 2013 I highly recommend Brad-Penn Motor Oil: Penn Grade 1 High Performance Oil. Made in Pennsylvania with PA high grade crude oil. http://www.penngrade1.com/Default.aspx Link to comment Share on other sites More sharing options...
RivNut Posted December 14, 2013 Share Posted December 14, 2013 I personally don't like Pennsylvania oil. Every engine I've seen that's been run on Penzoil or some other Penn. oil usually has a gray sludge build up in it when it's been torn down.What you need to do is make sure that whatever oil you use has at least 1,000 ppm (parts per million) of Zinc and Phosphate in it. Without the protection of the zinc, you can flatten your cam. I buy Mobil 1 synthetic 10w40 at Wally World; it meets the zinc requirements for your flat tappet engine. A 5 quart container is less than $30. A NAPA Gold filter (made by Wix) or any other Wix filter is my choice. There are other Mobil 1 products that exceed these minimums. Find the Mobil 1 website and study their chart to see which would be best for you.Ed Link to comment Share on other sites More sharing options...
Guest intrepid Posted December 14, 2013 Share Posted December 14, 2013 Guys, my original post was requesting help with the viscosity choice for the rear end. RivNut, I agree with your comment re: engine oils. The API SN oils have much less ZZDP, than the old SL designation(1200 PPM). Therefore, people need to add an additive containing this, or find an aftermarket oil, that still has it. Anyway, I've decided to go with a 75W90 gear oil, with the Posi additive included, in the product, for the Diff. Also I'm going to drain a couple of quarts, of ATF, and a replace, with a synthetic, in the tranny. By the way RivNut, being new here, I've noticed you go out of your way to help, our fellow Buick owners. Thanks for that. Link to comment Share on other sites More sharing options...
Guest intrepid Posted January 4, 2014 Share Posted January 4, 2014 Just got my manuals, and they list GL-5, 80W90 EP gear oil, for the differential. Link to comment Share on other sites More sharing options...
1965rivgs Posted January 4, 2014 Share Posted January 4, 2014 Ed, the gray sludge you are finding in the motors is probably lead if you are referencing older motors. Dont spread it on your Jelly sandwich.....Jeff, when switching to synthetics you will probably be doing some resealing....good luck, Tom Mooney Link to comment Share on other sites More sharing options...
Guest intrepid Posted January 6, 2014 Share Posted January 6, 2014 Tom, the synthetic will clean up some of the old varnish, if there is any. I've got a diff gasket on order, for just that very reason. The benefits of synthetics, far outweigh, the downside of old gasket replacement. Link to comment Share on other sites More sharing options...
Guest intrepid Posted January 6, 2014 Share Posted January 6, 2014 Ed, the only oils that meet the old ZZDP or Zinc numbers, are oils designated with an SL rating, or racing oils (they exceed the 1200 ppm) All the SM and SN have the reduced amount in them Link to comment Share on other sites More sharing options...
RivNut Posted January 6, 2014 Share Posted January 6, 2014 Ed, the only oils that meet the old ZZDP or Zinc numbers, are oils designated with an SL rating, or racing oils (they exceed the 1200 ppm) All the SM and SN have the reduced amount in themI don't think that you can go by the SL, SM, or SN designations and be sure you're getting what you state. If you look at this chart, some of the SN designations have 1300 ppm for zinc and others as low as 900 ppm. Some SL and SN designated oils have the same ppm for zinc. I don't think a blanket statement for designations can be applicable to all oil, you have to look at each one individually. Mobil 1 has some oils that have a 1750 ppm for zinc. Find a product information chart for each company and compare each viscosity under each brand name. Mobil 1, Mobil 1 High Mileage, Mobil 1 ESP, and their racing oils all come in identical viscosities but each has a different level of zinc (and phosphorous) for each brand name. I'm not promoting Mobil 1, it's just that their website is so easily accessible and informative that it makes selection easy. The only problem with their website is if you choose to let them help you determine which oil is best for you, the farthest they go back is to about 1980.Ed Link to comment Share on other sites More sharing options...
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