I'm a little surprised, so can I get a quick answer??? Thanks

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318willrun

318willrun

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As some of you know, I've been putting some time in the '77 Ramcharger and things are going along pretty smoothly. I've changed the Dana 44 differential grease and now I'm changing the 9 1/4 rear end grease. I guess I assumed 3.21 open. When I jacked it up and removed the cover, it's a sure grip. 3.55 sure grip. I've always added the bottle from the dealer to my 8 3/4 or 8 1/4 rear ends.

Question: Will this Valvoline F/S that claims "limited slip" be sufficient for the sure grip unit or should I add the little bottle from the dealer?
thanks in advance.

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It has the friction modifier in it.
Only time i add modifier is in a new limited slip.
 
I shy away from full synthetic in the older diffs. You may find it noisy.

When ford started using f/s in the rears, they was blowing up left and right.
Over haul and fill with conventional...

I’m sure the f/s has improved by now, but i still prefer non synthetic.
 
I usually like adding my own friction modifier. At least that way, you know you have enough. That 9.25 is a pretty big differential. I would be wondering if there's enough friction modifier in the gear oil. It never hurts to have too much, but not enough and you can have chatter and early clutch wear.
 
A have used the Mobil 1 F/S in the last couple of rear ends without issue. I could t hear any noise. My ‘79 Magnum has the 9-1/4 W/3.55’s. That has the F/S. I tried some very long & quite mufflers. Never heard anything from the rear diff.
 
Thanks All. I'll buy the additive for peace-of-mind.
I also have conventional high performance Valvoline 80w-90 with the limited slip protection. I can add the "additive" to that as well.
 
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R4Sedan said:
That's the same exact oil I've been running for years, but I still put either Mopar or Ford additive in it.
Click to expand...
you've been using the Valvoline full synthetic also? I'm a believer in FS lubricants, though I don't always use it in everything.
 
Yes, The last three or four cars I built. I used the Full Synthetic just like you have pictured. It seems as though the Chrysler Friction modifier can be sometimes hard to find. Last time I bought two bottles so I had an extra.
 
A friend of mine had a test report on Harley's and I can't find it now but it said that if you use syn in motors that sit a while it runs off the top end it doesn't stick like conv oil so when you start it its actually dry on the top and they were wearing rockers & valves from dry starts
 
Called the Dodge dealership and they were out of sure grip additive, so I stopped by NAPA and bought this. I like Amsoil in snowmobile products... LOL...

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