Do I need to add a limited slip additive to Valvoline 75 140?

Hey,
I am changing the diff fluid in my ford nine inch rear end. I was running 80W90 before with CRC limited slip additive. I want to change the fluid to Valvoline 75W 140 which is a full synthetic. The label on the bottle says Limited Slip on the top corner of the label. Does that mean I don't need to add the limited slip additive?
Thanks J

 

You might ask a "tech" at your local Ford dealer........

 

Not having built diffs for a while...Why would you go to a heavier oil, even tho' sythetic? I might suggest maybe Redline or some others rather than putting a heavier gear lube in. Synthetics are great...but check with someone who builds lotsa gears.

 

Valvoline has the addative in it all ready.

 

So no additive! Ok man thanks for the advice.
J

 

Why spend money for synthetic if you're gonna have to take it apart again?

 

We bought 3 brand new ford vans [back when I had a real job] and the rear ends chattered terrible going around corners. I put ford additive in them and they quieted down...you'll know if you need aditive by driving the car.

 

Jim!
The rear end actually is quiet now! By changing the diff fluid from 80W90 to the synthetic 75W140! What a suprise! When I pulled the fluid out it was relatively clean too no metal sparkles or crud! Not too bad at all for a Tuesday!


Rocky
Went around several corners and no chatter! so I guess Valvoline has an additive! BTW I did call the 1 800 number and talked to customer support and they did say there was an additive in there for limited slip!
J

 

There was a discussion on here a couple of weeks ago about the same subject. I used Mobil 1 synthetic that had the LS designation. Nothing additional was needed. GM by the way recommends not going to wide open throttle for a couple of hundred miles to ensure the clutch packs in the rear end a infused with the new lubricant.

I will ask again why does rear end fluid stink so bad!!

 

If you have a locker (trac loc) or similar, yes, you need additional additive. Ford Racing makes a great one, small bottle, at your ford dealer...

If that rear is a Trac Lock, it will go awhile before it starts to act wonky, then you are done... if the rear is just an "open rear".... the valvoline by itself will be OK...

Those bottles that are "limited slip" are not for completely filling a diff, but just for "make-up".......been down that road before on my OT musclecars...
Tom