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Cool, but you're not alone in this. Going straight is where you'll be most likely to do that. Going in a turn at low speed is where it's most likely to do a one-wheel-peel since the weight of the car is transferred to one side; if the inside wheel loses traction, then that indicates an open diff or worn out clutches.

If you're not willinng to take our word for it, you're going to have to yank the cover and look inside the pumpkin - no other way around it. The tag, door code etc. all point to an open rear.
Never said I was "alone in it". Seems like you're getting worked up and jumping to conclusions. When you say "not willing to take our word for it" I don't know you are referring to because I never implied anyone was lying.

If you can't explain why an open rear end will spin both wheels when going straight, then no hard feelings. I was just curious.

By the way, I've driven many different rear wheel drive vehicles over the years of different makes, eras and with different types of "Posi" "Limited Slip" "Trac-Loks" or whatever unique word manufactures want to call them, none of the ones I drove with open rear ends had the characteristics of this one, this is new to me.

To be clear, I'm not implying I have Trac-Lok, as a matter of fact, I'm still leaning towards not having it.

As far as taking the diff cover off, I already mentioned that in post #39.
 

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The independent rear suspension isolates the diff from the twisting force. In a solid rear axle car, when the power goes into the diff, the whole axle wants to twist, which in effect adds weight to one wheel and lightens the other. With an open diff, a solid rear axle car will almost always spin only one wheel. With the IRS, that twisting force is isolated to the diff, and never makes it to the suspension or the wheels. This means that on flat level ground, both wheels have similar amounts of traction, and so both can spin evenly.
 

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With the exception of zero traction situations, like doing donuts in a snowy parking lot, I've never seen an open diff spin both wheels when going straight on a dry surface, solid or IRS axle. Just one track without even a chirp from the other side. But that's just me.

Al
 
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The Parts Guy
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Lol. I used to get my open 3.08 diff to spin both regularly via brake torquing when I was a 16-year-old hooligan. It wasn't hard to do.


44552
 

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The Parts Guy
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Also, an unloaded LSD without a pre-load spring, with a weak pre-load spring, or with worn clutches will often spin the opposite tire in the opposite direction when conducting the "up in the air" test described earlier. The LSD can still function quite well under power in these circumstances, as the side gears are then loaded. If you really want to know for certain what carrier you have, pull the cover.
 

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I see what looks like water on the pavement, so that would be a zero traction situation. Did that car have air shocks?

I can't say I've done many brake torques in my MN-12's. My current one has the infamous Trac-lok, so it would likely wheelhop until it shot drivetrain parts out. Or maybe after 15-20k miles the Trac-lok is already shot, it sure seems like it sometimes.

Al
 
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The Parts Guy
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Good lord.

Yes, in that photo there was bleach on the pavement. I could dig through old boxes to find video cassettes showing the same performance on bone dry pavement as well. That car had Airlift air bags in the rear coils.

Again, in my youth, brake torquing was ubiquitous. Nowadays, there is no need to touch the brake pedal to create a smoke show.

44553


If your Traction-Lok is "shot" after 15k miles, it wasn't assembled properly. I've abused this one for nearly 18k miles and the clutches are still in great shape (just checked them a few months ago).
 

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The trac-lok was new old stock, so brand new. It's never performed the way I think one should perform, but I've only had one other Ford with one (Crown Vic with solid axle).

I carry too many one wheel peels out of turns. I don't dare do a straight shot brake torque because it's wheel hopped ever since I installed it. I could use a couple of bushings replaced back there, but the springs and shocks are new.

Al
 
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The independent rear suspension isolates the diff from the twisting force. In a solid rear axle car, when the power goes into the diff, the whole axle wants to twist, which in effect adds weight to one wheel and lightens the other. With an open diff, a solid rear axle car will almost always spin only one wheel. With the IRS, that twisting force is isolated to the diff, and never makes it to the suspension or the wheels. This means that on flat level ground, both wheels have similar amounts of traction, and so both can spin evenly.
I had a hunch that it being IRS had something to do with it. Your explanation makes sense.
 

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1991 Mercury Cougar LS 5.0 in restoration
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With disregard for staying the same thing again, I had an open 2.73 rear in my 5.0. straight, and fairly even surface, I could spin both wheels. Of course it was brake torque like Rod states above. Try to spin the back around and it wasn't happening. One wheel peel all the way around.

Switched to 3.73 w/LSD and I lit then both doing either thing ( I was young and dumb). Then again when my car is back together there could be a few tasteful burnouts here and there😁
 

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Guys, it's easy to tell. Go do a donut; if you can slide the rear directly sideways, rotating around the engine, in a donut, its locking. Both tires slide, and it will go straight sideways.
Lazarus will do a donut with one front tire going one way, one the other, in a donut, without 'slinging' the rear end around.
I'evwon bets with newer mustangs with unkillable traction control. :D
 
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Traction control means learning to control your right foot better. :)
 

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Exactly!!
I do not want the car telling me what to do.
Thats why none of my cars are abs or FBW.
 

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Discussion Starter · #54 ·
Looks like I have a LSD then. I was able to do a 45 degree turn with just my foot and no steering. I don't think you can do that in a open diff without weight transfer.
 
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