what gear oil to use in a stock 8.8? November 27, 2009, 06:58:14 PM Getting ready to swap rears, and was curious if I should use something with an additive, or just regular gear oil...?It's a stock '89 Mustang 8.8 with Trac-Loc.I did search, a lot of guys said they used 90w with no issues...if so, I literally have gallons of that stuff...TIA :D Quote Selected
what gear oil to use in a stock 8.8? Reply #1 – November 27, 2009, 10:09:51 PM 75-90 i believe.I run 75-140 synthetic.You will need a 4oz bottle of posi additive. Quote Selected
what gear oil to use in a stock 8.8? Reply #2 – November 27, 2009, 11:00:23 PM Quote from: dominator;300364You will need a 4oz bottle of posi additive.Yeah, especially if you like to turn corners... When I repl the clutches in mine, it chattered so bad it was scary... At least till I put the friction modifier in it... Quote Selected
what gear oil to use in a stock 8.8? Reply #3 – November 28, 2009, 01:55:51 PM when i do my rear i plan on going the synthetic route too especially since you don’t really change it. I was looking for the extra protection and HP from it. Just put my head in hear to liston up to the oil weight. Quote Selected
what gear oil to use in a stock 8.8? Reply #4 – November 28, 2009, 04:15:58 PM I use Mobil 1 and the modifier. Quote Selected
what gear oil to use in a stock 8.8? Reply #5 – November 29, 2009, 10:29:08 AM I run 80w-90 synthetic blend(they were out of Mobil 1 full synthetic last time). I always thought the friction modifier was manditory, but when I had my rear done a few years ago they said absolutely never use friction modifier...THEY claimed that all it does is allow more slippage of the clutches and they wear more quickly. Mine would chirp the inside tire around tight turns...lasted about 2 days like that then it was good. I had them pack extra clutches in the T-lock and that rear is about as tight as the day it was done.I would be inclined to believe what they said...I've seen guys need new clutches after a year or two after a rebuild using friction modifier...not because they were completely wasted, but because it acted like a 150k mile limited slip.My car will occasionally drag the inside tire around slow tight parking lot manuevers...but ONLY in the rain and when power is being applied.I'm not looking to start a massive debate...just what a reputable Ford shop told me and seems to be working.Good luck,Don Quote Selected
what gear oil to use in a stock 8.8? Reply #6 – November 29, 2009, 02:24:52 PM Yeah, I've read several opinions...I'M not gonna tell you that you're wrong....it seems to work for you I went ahead and used the f/m, and some semi-synthetic oil....the little bit I drove it last night I couldn't hear any abnormal noise, then again..still had just the open headers... Quote Selected
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