Hey guys, I just got back from a trip and my rear end seems to be doing something wierd. As I got home, my rear end started making a wierd vibration and rubbing noise everytime I made a sharp turn while accelerating. I just went out and tested it again, and it only does it when you are giving the car gas while doing a sharp turn. I found an empty parking lot to make a few sharp turns, and it goes away as soon as I release the gas pedal, only to start again as soon as i'm back on it no matter how lightly while turning. Any idea's? I had the rear differential fluid changed a bit ago to Amsoil Series 2000 75w90 like the manual explains. Since Amsoil's Series 2000 gear lube already comes with the limited slip additive, I did not add any limited slip additive since Amsoil says that it's not needed(my old Lightning didn't need it either). Right after the fluid change, I tested it by driving in tight circles, and it never had a problem till now. Any idea's?????????
Wierd rear end vibration and noise while turning
- Thread starter junehhan
- Start date
jgc61sr2002
Contributing Member
Sounds like the limited slip differential clutches. Sounds like a trip to the dealer is in order. Good luck. Keep us posted.
I don't think I like the sound of that. I'll try some additive first, but wouldn't it be chattering instead of making a rubbing type vibration if it needed the additive? Also, if it was the additive, wouldn't it be doing this even when i'm not giving it gas while going around a sharp corner?
Marauderjack
Senior Member
Might be that the Amzoil has "almost enough" additive and just a dab more will fix it!! Get a bottle of the Ford "stinky stuff" and I'll bet it will be fine!! :up:
Marauderjack
imp:
Marauderjack
imp:
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TripleTransAm
Guest
The clutches are supposed to grab, but not excessively... so the friction modifier serves to decrease the amount of friction, just enough to allow proper grabbing when the axles are meant to be 'tied' together, but during cornering, once the clutches break grip, they are then supposed to slide easier, until they get to grip once again, and then it's right back to a good amount of hold.
Tough to describe, but look at it this way:
There are two kinds of friction, static and dynamic. Static is when the two surfaces are stationary with respect to each other (ie. no rubbing, otherwise known as a very boring first date). Dynamic is the friction that occurs when the two surfaces are in movement relative to each other. A good example is pushing hard on a big appliance trying to get it to move... getting it to move involves overcoming the static friction, and once you get it moving, you just have to apply enough force to overcome the dynamic friction. Dynamic friction is less than static friction, in this case.
I suppose that in the case of a limited slip additive, it must change the dynamic friction such that once the clutches ARE slipping, they don't try too hard to grab (ie. much lower dynamic friction) because if they did, the action would be very jerky. Once the two axles are back to equal speeds, the good static friction qualities will hold them there until they are overcome yet again during the next turn.
Since the clutches are soaked in the diff oil (+additive, if that's the case), any deviation from the factory spec will make the clutch material behave differently, and then it's trial and error before you find the good ratio.
Tough to describe, but look at it this way:
There are two kinds of friction, static and dynamic. Static is when the two surfaces are stationary with respect to each other (ie. no rubbing, otherwise known as a very boring first date). Dynamic is the friction that occurs when the two surfaces are in movement relative to each other. A good example is pushing hard on a big appliance trying to get it to move... getting it to move involves overcoming the static friction, and once you get it moving, you just have to apply enough force to overcome the dynamic friction. Dynamic friction is less than static friction, in this case.
I suppose that in the case of a limited slip additive, it must change the dynamic friction such that once the clutches ARE slipping, they don't try too hard to grab (ie. much lower dynamic friction) because if they did, the action would be very jerky. Once the two axles are back to equal speeds, the good static friction qualities will hold them there until they are overcome yet again during the next turn.
Since the clutches are soaked in the diff oil (+additive, if that's the case), any deviation from the factory spec will make the clutch material behave differently, and then it's trial and error before you find the good ratio.
Thanks for the advice and help guys. I've got a 4oz bottle of differential limited slip friction modifier and i'll try half of the bottle first. Today on my way to work, it doesn't seem to be as bad as it was yesterday, although it's still doing it. It seems to do it a bit more when i'm accellerating while making a sharp right turn vs. a sharp left turn. I'll probably put 2oz of the additive in on Thursday since i've got no time till then............
RoyLPita
RWD only fan
Save yourself a trip to the dealer.
This is from the 2004 Ford Crown Victoria, Grand Marquis, and Marauder shop manual:
"With the Traction-Lok differential axle, slight chatter noise on slow turns after extended highway driving is considered acceptable an has no detrimental effect on the locking axle function."
This is from the 2004 Ford Crown Victoria, Grand Marquis, and Marauder shop manual:
"With the Traction-Lok differential axle, slight chatter noise on slow turns after extended highway driving is considered acceptable an has no detrimental effect on the locking axle function."
RoyLPita said:
Hey, thanks for that tip. In my case, it's more of a rubbing/moaning sound than a chattering though. You can kinda feel this rubbing type sensation from the rear end too, usually while making a sharp right turn while hitting the gas pedal. It's still doing it slightly right now, but i'll see what happens after I add 2-3oz of the limited slip additive. When I have the 4.10 gears put in sometime this summer, I think i'm just going to have full synthetic Motorcraft gear lube put in instead just to prevent this since apparantly not all LSD's respond the same to the Amsoil gear lube. I remember when I had the diff fluid changed on my old Lightning, it worked fine on the Amsoil gear lube without having to add anything extra in............
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TripleTransAm
Guest
junehhan said:
Hot DANG... I think I'm gonna call the missus and see if she wants to come home early today *nudge nudge wink wink*...
David Morton
Closed
That's exactly the way they explained it to me at the GM training school in Atlanta 12 years ago. Sticky when static, slippery when dynamic.TripleTransAm said:
You figure all that out by yourself? What's your MM rating? I'll recommend you for OTS.
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TripleTransAm
Guest
David Morton said:You figure all that out by yourself? What's your MM rating? I'll recommend you for OTS.
Okay, you got me... I searched high and low for what OTS could possibly mean and came up with this... http://www.ots.duke.edu/
And MM rating... well, I have ONE Marauder... does that give me a MM rating of 1?
:rock:
Well, I had the limited slip friction modifier put in this morning, and it's still doing it. It seems to do it more when i've come to a complete stop, and accelerate as i'm turning. Should I give it a little more time, or should I go ahead and schedule another appointment with the dealership?
David Morton
Closed
OTS=Officer Training SchoolTripleTransAm said:Okay, you got me... I searched high and low for what OTS could possibly mean and came up with this... http://www.ots.duke.edu/
And MM rating... well, I have ONE Marauder... does that give me a MM rating of 1?
:rock:
1 Stock Marauder=MM1; add 1 Modification (Performance only)=MM1.1; 2 Stock Marauder=MM2, etc.
:up: