OK, so I bought 4 qts of valvoline full syn 75w-140. I have a 4.10 limited slip diff. On the bottle it says "limited slip" so I thought it had the addative in it, but now after test driving my truck after changing the fluid, I don't think it did. I hear and feel a bump/grind/pulseing when I turn. The bottles don't say explicitly if it has addative in it like the other brands did, like royal purple. I wanted to ask people on here to see if someone had this issue before. I don't want to add addative yet til I know for sure because I read on here too much will cause the limited slip parts to not function properly. If I need to I can call valvoline, but I'd rather not. Here are some pics of the bottle, again it doesn't explicitly say it has the posi traction addative in it like the other brands did, just says "limited slip". Also read the back label. It says its reccomended for use in limited slip diffs or something like that. Thanks

 

When I changed differential fluid and used the Valvoline synthetic, I saw the same problem. Added 1/2 of a bottle of Ford limited slip additive and the chattering went away.

Lou Braun

 

Thanks! Figured someone in here must have had this happen to them. I'll buy some tomorrow and mix it in

 

It's funny that the fluid manufacturer wouldn't say that on the bottle. Instead they give you the impression that it's in there and it's not. You always add it anyway.

 

According to Valvoline, additive is not required. Here is their product information sheet.
http://content.valvoline.com/pdf/synpower_gear.pdf

Interestingly, the Ford Chemicals and Lubricants catalog, which lists their SAE 75W-140 Synthetic Rear Axle Lubricant, which has the same specification number as the Valvoline product, has this to say:

<table border="0" cellspacing="5" cellpadding="0"><tbody><tr><td valign="top"></td><td>Note: For a complete drain and refill, some limited-slip axles require addition of Friction Modifier, Part Number XL-3 meeting Ford specification EST-M2C118-A. Refer to Workshop Manual or Owner’s Guide

Since they are the same specification number, I would suspect the Valvoline product would perform the same way, in spite of their product information sheet.
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Same here, I always add no matter what gear oil use, just saves the hassle of having to add it latter. BTW- if you use the Ford additive, do not get it on bare skin, it smells to high heaven and does not wash off. Not sure if the others smell.