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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

9" rear end question?

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Old Feb 17, 2009 | 01:10 PM
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9" rear end question?

I brought in an old truck or should I say 1/2 a truck and is has the 9" rear in it. The nubers stamped on it are " 3L70". I am thinking it should be a 3.70 ratio, but what about the "L"? Thanks, Mike
 
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Old Feb 17, 2009 | 01:12 PM
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limited slip
 
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Old Feb 17, 2009 | 07:12 PM
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Does that mean the same as a Posi-trac? I have several 9" rears and a couple of them are the 3.70 ratio, but this one has the "L". If it does mean posi-trac, do or would I need any thing special { certain type grease, etc. } if I put this "stump" in another truck? Thanks, mike
 
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Old Feb 17, 2009 | 10:11 PM
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posi-trac, positive traction, limited slip, whatever you want to call it. It's the factory version with the clutches inside the rearend. Get someone to hold one axle while you try to turn the other. If it turns easy, they are worn out anyway. There should be some drag or resistance when one axle is held while the other is turned.

They have a tube of special additive you can buy for it, but I have never figured out what it really does. I had limited slip front and rear on my 80, and a guy gave me a tube of that stuff, but I never got around to putting it in, and I never noticed any problems with it.
 
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Old Feb 18, 2009 | 04:34 AM
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Thank you for the reply, I have worked with many 9's ,but had not came across one like this. I thought that is what it amounted to ,but I like to be sure. Again thank you for the reply, Mike
 
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Old Feb 18, 2009 | 04:52 AM
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Originally Posted by Franklin2
They have a tube of special additive you can buy for it, but I have never figured out what it really does. I had limited slip front and rear on my 80, and a guy gave me a tube of that stuff, but I never got around to putting it in, and I never noticed any problems with it.
The front/rear ends prolly had the additive mixed in. You would soon find out if the additive wasn't there!

XL3 (replaced Ford part number: C8AZ19B546A) .. Friction Modifier Additive-4 oz bottle.

MSRP: $4.99 // FTEpartsguy.com price: $4.49.

Every Ford: Equa-Lok, Traction-Lok, Power-Lok, whatever you want to call it....requires this additive.

Drive without it...it won't be too long before the lined clutches overheat and burn up.
 
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