vincentmoy Posted March 26, 2009 Share Posted March 26, 2009 Been reading many posts here and other forums. Just got myself 4qt of valvoline synpower 75W-90 since it's readily available @ Schuck's up here. Was going to get the rear diff. oil but wanna ask for some opinion. 1st q: Schuck's here has Mobil 1® Synthetic Gear Lube LS 75W-90, Valvoline 80W-90 Durablend, As well as dino Valvoline 80W-90s. Which would be a better candidate for rear diff.? 2nd q: What kind of both is the rear diff. use? It seems like it's round with a square in the middle. What do you guys call it? FYI, my car is 98 OBS 5MT with 184k miles. Thanks for your help! Vincent Quote Link to comment Share on other sites More sharing options...
ericem Posted March 26, 2009 Share Posted March 26, 2009 Id go 75w-90. Same question what is the square attachment I use to remove the plug on the rear diff?? Quote Link to comment Share on other sites More sharing options...
Rooster2 Posted March 26, 2009 Share Posted March 26, 2009 Use a half inch breaker bar with extension. The tip of the extension fits directly into the plug opening. Suggest using a 3 foot bar that you can slide over the breaker bar handle for added leverage. Use PB Blaster, and maybe some propane torch heat to aid in removing the plugs. I have tried two different times to remove bolt/plugs without success. If your car is like mine, it will be a bear to remove both plugs. Those sob's can be really tight. Be sure to remove the fill plug first, before removing the drain plug. Otherwise, you will be screwed, if you have drained the lube, but then can't pull the fill plug to add new lube. Quote Link to comment Share on other sites More sharing options...
edrach Posted March 26, 2009 Share Posted March 26, 2009 Check your owner's manual. I believe it specifies GL-5 level for the gearoil. 75W90 is the preferred viscosity; getting the heavier gear oil will only make shifting more sluggish (been there done that). For a high mileage car like yours I would suggest Redline's 75W90NS gear oil; works great in reducing synchro grind on our '91 Legacy with over 260K on the car. I wouldn't suggest the NS in the rear diff; but 75W90 should be fine there. Quote Link to comment Share on other sites More sharing options...
vincentmoy Posted March 26, 2009 Author Share Posted March 26, 2009 Check your owner's manual. I believe it specifies GL-5 level for the gearoil. 75W90 is the preferred viscosity; getting the heavier gear oil will only make shifting more sluggish (been there done that). For a high mileage car like yours I would suggest Redline's 75W90NS gear oil; works great in reducing synchro grind on our '91 Legacy with over 260K on the car. I wouldn't suggest the NS in the rear diff; but 75W90 should be fine there. Thanks, but I already got the Valvoline synpower for the transmission already. I'm just looking for the rear diff. oil Quote Link to comment Share on other sites More sharing options...
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