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How to definatively test your rear end positraction

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  #1  
Old 04-01-2005, 10:35 AM
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How to definatively test your rear end positraction

Jack up the rear end (both sides). Have a buddy hold
one tire and you try to turn the other. If you can turn
it pretty effortlessly, you need new clutch packs in the
spider gears in the differential.

I did mine last night. The clutch packs were about $190
and about $100 for labor (Prolly cause I helped he charged
me double <grin> !)

But I sure learned a LOT about rear ends during the process.

My clutches had ZERO material left on them and the steel
plates were chewed all to he!!. What a difference with the
new ones. I figure I was losing about .2 or so in the 1/4
just to slippage. And on the roadcourse, I was always
spinning the inside rear tire. (And therefore destroying the
tire back there)


We'll see how the beast moves now.

C.
 
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  #2  
Old 04-01-2005, 10:51 AM
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I'm speculating.. but from back in my stang days I thought you were supposed to put it in neutral, jack up one rear tire, and with a torque wrench turn the lifted wheel. It was something like 45ft lbs to move wheel? Any less and it was time for a overhaul.

Rich
 
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  #3  
Old 04-01-2005, 10:54 AM
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SVT_KY: How many miles did you have on the rear end?
 
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  #4  
Old 04-01-2005, 04:10 PM
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Originally posted by wydopnthrtl
I'm speculating.. but from back in my stang days I thought you were supposed to put it in neutral, jack up one rear tire, and with a torque wrench turn the lifted wheel. It was something like 45ft lbs to move wheel? Any less and it was time for a overhaul.

Rich
would that not be basically the same thing he was talking about?...instead of your buddy holding the tire, the ground is, and instead of a torque wrench turning it, you are manually... but maybe im wrong
 
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  #5  
Old 04-01-2005, 04:23 PM
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imurhuklbery,

Well... that "shadetree" method would tell you something. But how would you know what's good or what's bad?

Remember it is a limited slip diff. There are springs applying a force to clutch plates and friction disks. Unless your arms and brain is calibrated to know the differance between say 30ft lbs and 45 ft lbs. how would a guy know? (or what ever the actual TQ value is)

A quantitative value is best to keep from throwing money at something that might not be broke in the first place.

Rich
 
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Old 04-01-2005, 04:40 PM
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thats what Sal did for me about a month ago....my truck feels a lil quicker now than before too. He charged me the same too
 
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  #7  
Old 04-01-2005, 06:14 PM
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Where can i buy these?
Do you guys have a website where i can order one?

My truck is about 28000 miles do you think i have to replace these?


thanks
Johnathan
 
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  #8  
Old 04-01-2005, 06:15 PM
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Originally posted by Tim Skelton
SVT_KY: How many miles did you have on the rear end?
53K, Tim
 
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Old 04-01-2005, 06:16 PM
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Originally posted by johnathanh
Where can i buy these?
Do you guys have a website where i can order one?

My truck is about 28000 miles do you think i have to replace these?


thanks
Johnathan
Any Truck shop
 

Last edited by SVT_KY; 04-01-2005 at 06:19 PM.
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  #10  
Old 04-01-2005, 07:01 PM
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wydopnthrtl,


i see what your saying, thx for clearing that up
 
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  #11  
Old 04-12-2005, 11:10 PM
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Just as a measure to help future searches. I just looked up the OEM Ford specs for testing a Gen 2 limited slip diff.

Use a torque wrench with the capacity of at least 271 Nm (200 lb-ft) to rotate the axle shaft. Be sure that the transmission is in NEUTRAL, and that one rear wheel is on the floor while the other rear wheel is raised off the floor. The breakaway torque required to start rotation must be at least 27 Nm (20 lb-ft). The initial breakaway torque may be higher than the continuous turning torque.
This is measured with the torque wrench centered on the axle. They spec a special tool but a simple steel strip with one square hole in the middle (for your torque wrench) would work too. And the strip needs to be long enough to span between some studs.



I just knew I was right about how to check it. I just thought the breakaway torque would be higher. 20lbs ain't much and would explain why I see so many gen 2's doing one wheel peels with slicks.

Rich
 
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Old 04-12-2005, 11:20 PM
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ah very nice thread
thanks for the info SVT-KY and wydopn
 
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  #13  
Old 04-12-2005, 11:27 PM
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Originally posted by wydopnthrtl
. . . 20lbs ain't much . . .
Which makes me ask why in the hell "a torque wrench with the capacity of at least 271 Nm (200 lb-ft)" is required. I can make 20 lbs-ft with a 3/8" wrench.
 
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Old 04-12-2005, 11:41 PM
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Originally posted by Tim Skelton
Which makes me ask why in the hell "a torque wrench with the capacity of at least 271 Nm (200 lb-ft)" is required. I can make 20 lbs-ft with a 3/8" wrench.

I was thinking that myself. lol.

I think the answer is that it gives you an excuse to tell the Mrs. on why you need to go spend another 100+ on tools.

-Kimball
 
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Old 04-13-2005, 07:10 AM
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Originally posted by wydopnthrtl
Just as a measure to help future searches. I just looked up the OEM Ford specs for testing a Gen 2 limited slip diff.



This is measured with the torque wrench centered on the axle. They spec a special tool but a simple steel strip with one square hole in the middle (for your torque wrench) would work too. And the strip needs to be long enough to span between some studs.



I just knew I was right about how to check it. I just thought the breakaway torque would be higher. 20lbs ain't much and would explain why I see so many gen 2's doing one wheel peels with slicks.

Rich

Sounds like 20 is the minimum passable ... Any idea what the
setting is when you replace 'em ??? It was on the sheets that
my mechanic had but I can't remember ...
 
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