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-   -   9" rear in a jailbar truck (https://www.fordbarn.com/forum/showthread.php?t=347350)

GB SISSON 06-19-2025 12:01 AM

Re: 9" rear in a jailbar truck
 

Quote:

Originally Posted by cas3 (Post 2395715)
Sorry I don't have a specific answer, but yes I know there is a small bottle of special additive to use to make the clutch pac happy. Google 9" ford, there are several places that specialize in 9"ers and I would bet the answer is there

Thanks Skip. Yes I've been doing my research and see numerous explanations of how it all works. No or not enough friction modifiers in a limited slip axle causes clutch chatter and vibrations, especially in low speed, low torque cornering. For instance a little old man steering his homemade wooden car into a gas station. The friction modifier, (us limited slip guys just call them 'FM's) :) actually reduce the friction in the clutch packs so the clutches slip smoothly while going around corners. I am confident this is what I'm hearing and feeling on those sharp corners.
Shortening up the parking brake cables was the last difficult task, and I made it more so by having the cable installed into the backing plate with it's ball end in the fork already. This was to assure correct length. All the cable work was done with the clevis/threaded end vice gripped onto the running boards, which I will say, Did make an excellent workbench.

Scotty's 52 F3 06-19-2025 10:00 AM

Re: 9" rear in a jailbar truck
 

Sounds like you got it figured out Gary so maybe you already know this. Throwing it out there anyway.

Some of the gear lubes on the store shelves will have the limited slip additive already added but it will say so on the label. If you filled with oil that does not contain the additive you can buy just the additive and save draining your fresh oil. The additive is pretty smelly stuff.

Even after you add it, it takes a few miles to get soaked into the clutches and start working.

They ARE nice to have over an open diff. And not quite as harsh as a locker.

GB SISSON 06-19-2025 11:44 AM

Re: 9" rear in a jailbar truck
 

Yes, thanks Scotty, I'm getting educated in yet another new realm. Just made a run to napa and got the additive to mix in with yesterday's GL5. I found some photos on line of ford trac-loc differentials and compared them with a photo I posted on this thread after I uncrated the 3rd member fron Lanny. Sure matches up to be a ford trac loc. There is plenty written online about the noise and vibrations when the clutch pack does not have the friction modifier and it chatters on slow cornering. Supposed to add it to warm differential so the cabinet work will have to wait til I go for a warm up, then the mix, then the test drive. Sucks to be waiting for cabinets from Mt Pickett Woodworking... But a guy has to have his priorities straight.

GB SISSON 06-20-2025 07:44 AM

Re: 9" rear in a jailbar truck
 

5:40 am, 2 cups of coffee in and I'm heading down to the cabinetshop to make up for lost time. The additive did the trick and wife and I drove the woodie out to dinner, then up the winding mountain road in the state park, followed by a run down to the old boatyard at Obstruction Pass. Thanks to all who helped make this happen.

51504bat 06-20-2025 08:06 AM

Re: 9" rear in a jailbar truck
 

Sounds like you're all set for the big Fourth of July parade! I'm sure Woody is looking forward to riding on the front grille for all to see.:cool:

cas3 06-20-2025 10:48 AM

Re: 9" rear in a jailbar truck
 

How's the brakes?

GB SISSON 06-20-2025 12:40 PM

Re: 9" rear in a jailbar truck
 

Quote:

Originally Posted by cas3 (Post 2395941)
How's the brakes?

Excellent! considerably larger in the rear and the parking brake holds way better. Gear ratio is the same, so the new axle doesn't bring any new thrill to the ride, but the huge increase in torque from the 221 to the 276 (not to mention the 5 spd tranny that went in with it) still brings a smile to my face every time the old wagon is pointed at a hill! To me the entire drivetrain has now been brought up to modern standards. Which way is the mainland?


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