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Discussion Starter #1
just got the 9" back together and back in the '56, I haven't put fluid yet, reason being 2 opinions. The guy who built my C6 told me to run synthetic ARP (I have no reason to doubt his opinion), the guy who set up the 3rd member told me to go with limited slip gear oil, and says that's what the guys at Pro Gear use and he's been using for ever with no problems.

The new set up is 9", 3.70 gears with Trac Lock. What do you guys think? Either way I can't go wrong, just what's better?

All I need is my drive shaft and fluid in the rear and I'm rollin'.
 

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Either way you go, make sure the gear oil says for posi-traction (means clutches) rear ends on the bottle else you will need to get a bottle of the friction modifier from Ford, which wouldn't hurt to add it any way.

I've always ran regular off the shelf gear oil label for posi's with no problems.
 

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Just bought a new 31 spline made buy US gear, the instruction say not to use synthetic fluid, but to use the regular 90wt with friction modifier, synthetic is to slick and makes the cluthes slip on each other is what the owner of the shop said.
 

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Discussion Starter #4
enough said, the guy that set up my rear said I might have to put the addative.

thanks all
 

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I always start with about 1/3 to 1/2 a bottle of friction modifier, if it needs more you can always add some, but you cant take it out. I have had no probs with using 1/2 bottle of friction modifier with my posi`s. and if you have never used it, dont open it untill you have to, that has to be the worst smelling crap ever

dont get it on you or spill it in your garage
 

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Discussion Starter #7
can I get that stuff at the local auto parts store? Thanks for the heads up one the stench...........
 

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With regards to the ford friction modifier
dont spill any of that $#!^ or your garage /house will wreak for a long time , the dealer I work at and many others parts dep. would not even bring it in the warehouse they would leave in the box out back!!hA!!!LOL
 

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Discussion Starter #12
I did locate some for $3.60 a bottle, thanks.

one more question,

how much gear oil should this thing hold, I don't want to buy to much, and I don't want to have to go back to the store.
 

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can anyone say they have had problems with the synthetic gear oil. I have a 9" with a ford traction lock unit. i am running redline synthetic gear oil made for limited slips. i didnt add any of the friction modifier since the gear oil i used was meant for limited slips. i dont get any chatter. was it a bad idea to use the stuff, could i be losing traction?
 

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Discussion Starter #14
I talked to the guy at Pro Gear about how much to get (no more than 4 qts.), he said to get the modifier and use 140 wt. of good stuff, and stay away from the synthetics. I'll give him a call tomorrow and see why not.
I'm sure allot of would like to know.
 

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Discussion Starter #15
F.Y.I.

synthetics kill the clutches, the 2 main manufactures of limited slips state that in their warranty, "do not use synthetics, will void warranty".
I got this info from the guy at Pro Gear, he said they use synthetics in their race car that goes to Bonniville, but they don't care, cause after 6 miles they tear it down.

He said "I've never seen it work well, never, not even Red Line" (quoted)

so there we have it.

This is Slick Mo Fo signing out, my work here is done.
tonight the drive shaft goes in and I'll test this thing out. ADIOS!!!!!
 

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so if i decided i wanted to switch back to regular fluid, would i have to not only drain the synthetic, but clean it out to make sure there is none left, or could i just drain it and put in some regular fluid?
 

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Discussion Starter #17
I don't know,

call these guys @ Pro Gear 1-858-571-1158 I think I talked to Mark.
 

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Discussion Starter #18
got her running lastnight, it took 3.5 qts. w/half bottle of friction modifier. I hope I got the right stuff, 'cause it didn't stink at all, well no worse than the gear oil.

With the new gearing and haveing traction from both tires, it damn near jumped out of it's own skin. very happy with the combo.

Dave, did you call that guy?
 
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