Posi Clunking When I Make Sharp Turns

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RPMagoo

RPMagoo

Just An Old Motorhead
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Don't crucify Me. This Question is about My Falcon Sprint. -- I recently had the rear rebuilt. It's a Ford 8" - 3.80 ratio - Posi. When I put it back in, I used Castrol 75-90 gear oil. This oil, supposedly, has anti friction material in it, plus I put in a small tube of friction modifier. -- I drove the car around town, plus a 25 mile round trip, and everything seemed OK. -- Yesterday, I drove it a few miles, and every time that I made a sharp turn (both ways) it made a loud clunking noise. -- My assumption is, that there's a problem with the clutches, in the posi, and I'll have to pull the rear, again, to deal with it. -- Your thoughts, please.
 
It's like when you go to the doctor and you tell him it hurts when I do this.... and he says.... well stop doing that.

Stop making sharp turns.
 
We used to do a dozen or so figure 8's in a parking lot to get the friction modifier worked in the clutches. You may need to do that.
 
It's probably not seated the clutch pack yet. I ASSUME it is a clutch pack? Ford was notorious for using the Detroit locker in places you'd never suspect. Are you sure it's not a Detroit unit? That would explain the noise. I've seen quite a few in the 8" units too over the years. Even one in a Pinto with a factory 8". In its defense, it was a V6 4 speed car, but still I consider that mass overkill. If you're sure it's a limited slip (Trac Lok or Traction Lock for Ford) then I simply think it needs more driving.

The figure eight suggestion is a good one. That's how some auto makers recommend breaking in some of these AWD cars after a transmission rebuild. The AWD unit is very similar to a limited slip unit, if it is not the fluid style viscous coupling......or "visious coupling" as we called them when I ran the office at the transmission shop.

Lastly, since the limited slip unit essentially does lock the two rear axles together to some degree, they will never be completely quiet........unless they are broken or worn out.
 
toolmanmike said:
-- We used to do a dozen or so figure 8's in a parking lot to get the friction modifier worked in the clutches. You may need to do that. --
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-- There's a Church parking lot, next door. I'll try that when the roads dry up.
 
oldkimmer said:
As suggested, change the oil and add 2 bottles of the Ford friction modifier. Then do ur figure 8s. Kim
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I agree with this. As stupid as it sounds, the Ford friction modifier is the slap best on the market. Alot of the Chevy and Mopar guys I know use it. It's all I use as well.
 
RPMagoo said:
I used Castrol 75-90 gear oil. This oil, supposedly, has anti friction material in it, plus I put in a small tube of friction modifier.
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My guess, as with others, you didn't put enough friction modifier in it.

Some people confuse what the friction modifier does, it doesn't increase friction like some would think, it actually allows the clutches to 'slip' better so you don't have them catching when turning.

I would try that first, change it out and put the Ford stuff in it. Doing figure 8's might sound silly but that is what is recommended. When I rebuilt my clutch unit I went to a large parking lot and did several figure 8's in forward and reverse.
 
I've got a 9" behind an EFI 350 in a 73 LandCruiser. It's been so long I THINK it's a Detroit Locker, it has always loaded and unloaded sharply in turns, not sayin this is good or responsible to leave it alone but it's lasted close to 30 years with much abuse from Dunes, Off Roading, wading through the Pacific in Mexico many times...
 
Prepare for stink with the Ford Friction modifier. I have an unopened bottle in two zip lock bags and I can still smell it when I walk by.
 
"slap best".. lol..
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oldkimmer said:
-- Did u use the Ford friction modifier? Kim --
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-- I used Valvoline, non-synthetic gear oil, and TransX (K&W) friction modifier. -- All of this, only, has a few miles on it. Will it cause any problems, if I mix-in a bottle of the Ford modifier ? -- I thought that, possibly, I could try this first, with some figure eights, and go with all new, if necessary..
 
There is only 1 way to find out. Idk if I have ever mixed 2 kinds. But I have put the friction modifier in with oil that claimed it had the additive in it. So then I probably mixed 2 kinds. Kim
 
Most gear lubricants have friction modifier in them. but a new install requires a bottle of modifier be added. And the figure 8 is necessary to break in the unit.
All that is avaikable locally is ac delco modifier, so thats what i use.
 
I soak the clutches in the Ford friction modifier before assembling the carrier. That's the only way I have found to make sure you don't have a problem. There is a service bulletin for the Corvettes and the Camaros about noise from the rear on tight turns and they call for figure eights both clock wise and counter clock wise 10-12 times in each direction then change the fluid and do it again. I have just taken a Corvette out in a parking lot and done the figure eights only and then when out on the highway and ran the piss out of it. It has fixed it until the owner drives it around real slow for a couple of months and it acts up again.
 
Could you post a link to a video showing the difference between a clockwise figure eight and a counter-clockwise figure eight please?
 
I’m not the guy that wrote it it’s just how it reads I’m looking to post the original TSB. I will say it’s how you start the figure eight and then change the direction. It feels different depending on how you start out to the left or right
 
hemi446 said:
-- I’m not the guy that wrote it it’s just how it reads I’m looking to post the original TSB. I will say it’s how you start the figure eight and then change the direction. It feels different depending on how you start out to the left or right --
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-- I guess that it's a 50 - 50 deal. -- :) --
 
RustyRatRod said:
I agree with this. As stupid as it sounds, the Ford friction modifier is the slap best on the market. Alot of the Chevy and Mopar guys I know use it. It's all I use as well.
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Agree...I have used the Ford stuff in my MoPars too and it works great.
 
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