LSD Expertise Needed

2381 Views 33 Replies 21 Participants Last post by BiteTheBullitt0793, Jan 25, 2009

Kirk

Discussion Starter · Jan 1, 2009

I have a small patch of ice on my driveway. When I pulled slowly onto the driveway the right rear tire rolled on to the patch of ice. The left rear was on dry concrete. As soon as I got on the ice the right rear started spinning and the car stopped moving forward. I gave it a little gas (3K rpm max) but the car stayed put.

My question is: Shouldn't the LSD help out in this scenario and put power the left rear tire that is on dry concrete if the right rear is spinning freely? I expected to be able to roll right across the ice patch but didn't. Is this normal or is there something amiss with my LSD?

Any info appreciated.

1 - 20 of 34 Posts

bmsjr

· #2 · Jan 1, 2009

Kirk
I am far from an expert on LSD, but as I understand it, the Ford LSD has to have some traction on both rear wheels in order to limit the slip. If 1 wheel has no traction at all (on ice), the spring in the LSD cannnot create enough force to make the other wheel turn. If you jack up 1 rear wheel and leave the car in gear with the emergency brake off you will find it rather easy to turn the wheel that is off the ground by hand. Ford says that it takes 25 ftlb to turn the wheel. If you have one wheel on ice, try applying the brake. This will cause the spinning wheel to need more force to turn and then cause the clutches to tighten up and apply power to the wheel that is not on ice. If anybody can explain this better, or if I'm wrong, and I may be, please correct me.

Bruce

pylonracer

· #3 · Jan 2, 2009

BMSJR
sounds like good advice (applying brake) I had the same problem with my RX8 stuck on 1 mm of snow!, so I turned TCS off and it also helped.
My poor baby is covered in snow so I have to car pool with the misses :-(

Dillo Dave

· #4 · Jan 3, 2009

I should have known on a car forum, this was NOT the LSD I was thinking of.:shock:

BiteTheBullitt0793

· #5 · Jan 3, 2009

the other LLLLLLLSSSSSSSSSDDDDDDDD

hey dave,
i hear you! i figured as many "children of the 60's" as we have around here that this thread would take a side road very quickly. personally, shrooms were more to my liking. :lol: :lol: :lol:

Bullitt 736

· #6 · Jan 3, 2009

Dillo Dave said:
I should have known on a car forum, this was NOT the LSD I was thinking of.:shock:

Doc may have seen the title and is having a flashback. :lol:

first ford

· #7 · Jan 3, 2009

window panes ,brown dot , orange sunshine , sugar cubes , purple osley oh it all comes back to me now the 70s i think seemed to pass real quick and hard to remember rotflmao.

steelfalcon29

· #8 · Jan 3, 2009

Dillo Dave said:
I should have known on a car forum, this was NOT the LSD I was thinking of.:shock:

I was thinking the same thing. :lol:

Kirk

Discussion Starter · #9 · Jan 4, 2009

Well, I see I have received more info than I had expected here.

Thank you Bruce for your answer. :smile: I feel better about my car now.

To the others who posted....

Thanks for the, eh... info? I feel better about missing out on the 70's. :wink:

DDT

· #10 · Jan 4, 2009

QUOTE=first ford]window panes ,brown dot , orange sunshine , sugar cubes , purple osley oh it all comes back to me now the 70s i think seemed to pass real quick and hard to remember rotflmao.[/QUOTE]

Too funny! The 'best' I can 'remember' was ORGANIC (yup way back then) chewy gooey cooked peyote packaged in horse pill capsules. Always for sale at the corner of Mexico, Texas and New Mexico on the Rio Grande (levy) by the guy with a hook on one hand.

SniperStang

· #11 · Jan 5, 2009

hey, old timers...

Lucy called, she wants her Diamonds back.

shaun

Jimbob

· #12 · Jan 5, 2009

SniperStang said:
hey, old timers...

Lucy called, she wants her Diamonds back.

shaun

Far out, man!

See less See more

Dave and Julie

· #13 · Jan 5, 2009 (Edited)

The amount of torque a limited slip axle transmits from one side to the other depends on the torque bias ratio. With a friction type limited slip the torque bias ratio will decrease over time, but when it is new let's say it is 1.5 to 1. If the left side can support 10 ft/lbs then it can transmit 15 ft/lbs to the right side. But if the left side can support zero ft/lbs, then the right side will also have zero ft/lbs since 0x1.5=0.

Even my mechanical gear type Torsen LSD in my Ranger will not get up the driveway if one side is icy for the same reason. Set the parking brake and drive through, or go through faster and drag the brakes while you drive. You will notice more tracion with the brakes on than off.

An open axle has a torque bias ratio of 1 to 1. Whatever one side supports, the other side has available. When you break one side loose, and it can only get zero ft/lbs to the pavement on the right side, then that is all you will get on the left. People often misunderstand open axles and think they only spin one side. When you look at the equation, you can understand better how it works.

Then there is preload which the Ford LSD has like was said, maybe 25 ft/lbs. That's not a lot, and apparently not enough to get you up your driveway. Some of the racier LSD's have torque bias ratios of 2 to 1 and much higher preloads. Just because you have LSD doesn't mean you will spin both tires all the time. Only a locker or spool can do that.

Also, when you are in that situation do not spin one side of the axle. You will quickly wear out the clutches and be left with an open axle and/or a degraded torque bias ratio.

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Kirk

Discussion Starter · #14 · Jan 6, 2009

Dave and Julie said:
The amount of torque a limited slip axle transmits from one side to the other depends on the torque bias ratio. With a friction type limited slip the torque bias ratio will decrease over time, but when it is new let's say it is 1.5 to 1. If the left side can support 10 ft/lbs then it can transmit 15 ft/lbs to the right side. But if the left side can support zero ft/lbs, then the right side will also have zero ft/lbs since 0x1.5=0.

Even my mechanical gear type Torsen LSD in my Ranger will not get up the driveway if one side is icy for the same reason. Set the parking brake and drive through, or go through faster and drag the brakes while you drive. You will notice more tracion with the brakes on than off.

An open axle has a torque bias ratio of 1 to 1. Whatever one side supports, the other side has available. When you break one side loose, and it can only get zero ft/lbs to the pavement on the right side, then that is all you will get on the left. People often misunderstand open axles and think they only spin one side. When you look at the equation, you can understand better how it works.

Then there is preload which the Ford LSD has like was said, maybe 25 ft/lbs. That's not a lot, and apparently not enough to get you up your driveway. Some of the racier LSD's have torque bias ratios of 2 to 1 and much higher preloads. Just because you have LSD doesn't mean you will spin both tires all the time. Only a locker or spool can do that.

Also, when you are in that situation do not spin one side of the axle. You will quickly wear out the clutches and be left with an open axle and/or a degraded torque bias ratio.

Excellent info here! Thanks a lot for your explanation. I learned something today! :goodvibe:

Park Ranger

· #15 · Jan 7, 2009

DDT said:
QUOTE=first ford]window panes ,brown dot , orange sunshine , sugar cubes , purple osley oh it all comes back to me now the 70s i think seemed to pass real quick and hard to remember rotflmao.

Too funny! The 'best' I can 'remember' was ORGANIC (yup way back then) chewy gooey cooked peyote packaged in horse pill capsules. Always for sale at the corner of Mexico, Texas and New Mexico on the Rio Grande (levy) by the guy with a hook on one hand.

Far out, Man!?

[/QUOTE]

cdynaco

· #16 · Jan 7, 2009

Geez... I had it backwards all these years. I always thought limited slip meant the rear end was constant posi-traction but the clutch allowed slippage when making turns.

[PS: I admit to nothing! :lol: ]

BiteTheBullitt0793

· #17 · Jan 8, 2009

which one is it?

Limited Slip Differential is the phenomenon of performing a task and only being able to use one side of your brain to perform said task. basically, one side of your brain is just spinning it's wheel.

Limited Slip Differential can be thought of as a result of a shortage of properly functioning codons in the dna. Limited Slip Differential is most commonly caused by the ingestion of too much LSD "back in the day" as it is commonly referred to.

now since the biochemical bodily response experienced from taking LSD is the turning on of codons in the dna which usually remain dormant, the real questions to be asked are.... is your Differential in a state of Limited Slip as a result of the ingestion of too much LSD? or is your Differential in a state of Limited Slip because you came from the factory this way? hmmmm

cdynaco

· #18 · Jan 8, 2009

BiteTheBullitt0793 said:
Limited Slip Differential is the phenomenon of performing a task and only being able to use one side of your brain to perform said task. basically, one side of your brain is just spinning it's wheel.

Limited Slip Differential can be thought of as a result of a shortage of properly functioning codons in the dna. Limited Slip Differential is most commonly caused by the ingestion of too much LSD "back in the day" as it is commonly referred to.

now since the biochemical bodily response experienced from taking LSD is the turning on of codons in the dna which usually remain dormant, the real questions to be asked are.... is your Differential in a state of Limited Slip as a result of the ingestion of too much LSD? or is your Differential in a state of Limited Slip because you came from the factory this way? hmmmm

you instructed edgewood dintya?

woah! :neutral:

boozerar223

· #19 · Jan 8, 2009

I miss Marty Feldman... R.I.P. Man!!!

jymontoya

· #20 · Jan 8, 2009

first ford said:
window panes ,brown dot , orange sunshine , sugar cubes , purple osley oh it all comes back to me now the 70s i think seemed to pass real quick and hard to remember rotflmao.

Cocaine did that to a lot of people in the 70's!

1 - 20 of 34 Posts

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