Hi Rick..same way I felt--- but thrust pins in thrust block in 8 3/4 diff discussed in other email are in fact brass. Someone noted maybe only in sure grip..do not know, but do know in several I took apart they were there. And important functionally. = ? Matter of degree? GL-5 eats brass if you believe article. (due to sulphur lube in it) That link is a great reference..main point is synthetic anything in oils is plain better than non synthetic, ---but have to watch additive packages. Same as motor oil, and flat cams. ….. SAE test/paper I saw / read about had older 350 camaro, I think it had 85k miles, running mobil 1, lab test every 1000 miles, oil still OK at 18000 but had lost additives unacceptably by then ; made me feel Ok about 10 k mile change with Mobil 1. Drove JEEP 4.0 330 k miles on this idea , engine still perfect . 4.0 a great engine anyway, but you get it. (99-01 not so good --head cracks,-- however) .Understand all those who are happy with old arrangement. Your call. New oil IS better. Air cooled Onan generator I take care of, now equivalent of 1,000,000 miles at ~ 60 mph, (1800 RPM<) off grid island summer camp, circa 1950, (60 + years!) loves Mobil one and Harley synthetic/Mobil 1 ; much more tolerant of inherent air cooled high temps, better compression, lower running temp, more electricity, by about 10%, before slowing down. Stuff shines at high temps. And cold. Used to use 20-50 racing Valvoline in it, in fall , hard to crank/start, and it burned oil. No more. I believe, but more than opinions, there are real reasons . John From: BARJAM300@xxxxxxx [mailto:BARJAM300@xxxxxxx] Sent: Saturday, August 02, 2014 11:49 AM To: rixpac@xxxxxxx; jkg@xxxxxxxxxxxxxxxxx; jymopar@xxxxxxxxxxxxxxx Cc: chrysler300@xxxxxxxxxxxxxxx Subject: Re: [Chrysler300] Amsoil synthetic gear lube study For anyone interested, Amsoil had a third party conduct an in-depth study on synthetic differential gear lubes. The study can be found at www.syntheticwarehouse.com/brochures/g2457_gearlube_study.pdf Please note that there is an _ (underscore) between "2457_gearlube_study" that does not show up in the webaddress. Jim Bartuska Club Stores In a message dated 2014/08/01 05:33:37 P.M. Eastern Daylight Time, Chrysler300-noreply@xxxxxxxxxxxxxxx writes: Do not worry about using GL-5 in our differentials. For decades there has been sulphur in gear lube being it is an anti scuff/anti-weld additive. GL-5 has almost 30% more anti scuff protection as compared to GL-4. Note; Our transmissions do not use gear oil as lube. I could understand why the oil would cause shifting problems, being it would not allow the syncro to clutch quickly and or correctly. Rick Post Script; I cannot think of any brass in our 8 3/4 rear axles. I have had many of these apart for rebuild or repair Re-clutch power lock sure grip and limited slip 1957 to 1973. _____ To: jymopar@xxxxxxxxxxxxxxx CC: chrysler300@xxxxxxxxxxxxxxx From: Chrysler300-noreply@xxxxxxxxxxxxxxx Date: Wed, 30 Jul 2014 10:45:26 -0400 Subject: [Chrysler300] gear lube Found out some interesting ,-- could be important ---stuff. In Auto Restorer; GL-5 gear lube has sulphur and other additives that attack brass, so not for use on manual transmissions or rear axles with brass / bronze parts ; GL-4 OK ; I know 300F has brass thrust bearings in Axle center (Timken style rear wheel bearings) , many cars of our vintage had brass transmission syncros , brass bushings in diff, etc . I have been using synthetic 75W Mobil 1, not sure now if GL-5 or 4; GL-5 made for all 100% steel bearings, like ball bearings etc typical of new cars , EP additives help those, are in GL-5 Heads up! John Grady, PE [Non-text portions of this message have been removed] ------------------------------------ Posted by: "John Grady" <jkg@xxxxxxxxxxxxxxxxx> ------------------------------------ To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx To unsubscribe from this group, send an email to bob@xxxxxxxxxxxxx or go to http://autos.groups.yahoo.com/group/Chrysler300/join and select the "Leave Group" button For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm For archives go to http://www.forwardlook.net/300-archive/search.htm#querylang ------------------------------------ Yahoo Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Chrysler300/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/Chrysler300/join (Yahoo! ID required) <*> To change settings via email: Chrysler300-digest@xxxxxxxxxxxxxxx Chrysler300-fullfeatured@xxxxxxxxxxxxxxx <*> To unsubscribe from this group, send an email to: Chrysler300-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo Groups is subject to: https://info.yahoo.com/legal/us/yahoo/utos/terms/