57 differential fluid

[drof75]

What kind of differential fluid should be used in a 57 rear end? I am guessing 90wt with no friction modifier.

Buz

[JimNolan]

Anything with Friction disks IE Track-Loc, Equi-Loc should use friction modifiers. Anything not using friction disks IE Tru-Trac, Detroit-Locker or regular non-limited slip differentials use oil without Friction Modifiers. Jim  PS  At least that's what Mosier and Just Rear Ends told me.

[gasman826]

Everytime I hear discussions about friction modifiers, I have always listened and was still wondering at the end of the discussion.  I understand that friction modifiers are added to the lube to help reduce limited slip (clutch) rear ends from clutch 'chatter' during normal turns.  Why would you want a limited slip differential to slip easier?  I guess its just me.
I have had several Traction-Loks with different ratios.  When I was a kid, I changed them just for the weekend.  Never used any modifiers.  Didn't know there was such a thing.  I don't change ratios so often anymore but I have a 3.00 gear for long trips.  I put a 4.11 in now and then for fun.  I usually run a 3.50.  The 3.00 gear is on a Traction-Lok.  The others are Detroits.  I guess that if I enjoy the clatter from a Detroit, a little chatter from a Traction-Lok with no modifier in it will be welcomed.  I have used 90W, 80-140W, and synthetics.  I don't see much difference.  Synthetics are more expensive and they leak easier.  I buy axles and rear end components from Strange.  They recommend organic lubes.

[drof75]

I am pretty sure it's an original 57 differential. Do these require the fiction modifier?

[JimNolan]

If it's a 1957 Differential use regular organic 90W gear oil. There's no limited slip differentials made in 1957 for Fords. No, don't use friction modifier. Jim

[JimNolan]

Gasman826,
   You brought up a question about too much friction modifier being used. One company said too much caused too much slip, another company said it didn't. All company's said nothing directly about having a weaker limited slip differential by using their product. They say it gives a better transision from locked to slip function and produces less chatter during that time.
   I broke an axle with a Equi-Loc and using 90W organic gear grease. The rear end was from a 62 Ford and I talked to the guy that put it in during the 70's. The 90W gear oil didn't hurt the friction disks any. It's still a good rear end.
   I remember when Synthetic oil first come out for airplane engines. Everybody said it was the greatest thing ever produced. Kept dirt suspended better etc. Synthetic oil had a problem though. If you let the airplane sit without flying it, say, over the winter. The oil won't cling to the metal, then you get rust. Rust on camshafts act like sandpaper. Pretty soon you're making metal. Mobil 1 pretty near went bankrupt buying airplane engines. They proved it was no good unless you used the airplane every day. Guess who doesn't make straight Synthetic engine oil for airplanes any more. No one does. They make blended synthetic oil now, half organic/half synthetic. Jim  PS  Guess why I wouldn't use Full Synthetic anything.

[Frankenstein57]

I had a detroit locker in a dirt car for several seasons before the synthetics came along, we just ran 90W. Pounded them pretty hard with no failures. Kind of cool during track packing we would go the opposite direction, in the turns the rear end would do a little wiggle when it locked up.  Mark

[drof75]

Thanks Jim.