Funny handling after LSD swap
08-22-09, 04:35 PM
#1
Funny handling after LSD swap
So I just finished putting a S2 LSD into my FB, and I have run into some funny handling. I didn't do anything to the car BUT put a LSD out of a EUDM SA (circa 1982, verified by VIN), and have noticed very twitchy handling.
Here is the rundown of my suspension modifications, and afterwards i'll explan the handling quirks.
RB springs all around
Tokico Illumina's set to setting #2 in the front
Tokico Blue's in the rear
Energy Suspension Black Poly bushings replaced factory rubber at the axle connections to the 4 link ONLY (none on the body, none in the swaybars, none in the Watts link)
Rear bar disengaged, passenger front swaybar endlink broken (just found today while bleeding my brakes).
Sway bar setup DID NOT change between old axle and new axle. Suspension setup DID NOT change between old axle and new axle.
In quick transition the back end will become unsettled and slide quite a bit. The way I found this was on a deserted back road, at about 50mph, quickly steering left then right. The back end would step out every time.
In fast sweepers, it feels (and sounds) like the inside rear tire is getting dragged, akin to a dog with a lame leg dragging it's leg around.
The LSD, provided it is the factory LSD that came with the shell I purchased to get the LSD from, has 76k on it. No bearing noise. No gear whine. I did place one wheel in the dirt while stopped and attempted to accelerate hard, and the wheel on the dirt spun, but the car did accelerate (it felt like it was the spinning wheel that accelerated me, not the wheel on the pavement).
What could cause the twitchiness in transition? Is this just a driving quirk of the LSD rear ends that I need to get used to?
Here is the rundown of my suspension modifications, and afterwards i'll explan the handling quirks.
RB springs all around
Tokico Illumina's set to setting #2 in the front
Tokico Blue's in the rear
Energy Suspension Black Poly bushings replaced factory rubber at the axle connections to the 4 link ONLY (none on the body, none in the swaybars, none in the Watts link)
Rear bar disengaged, passenger front swaybar endlink broken (just found today while bleeding my brakes).
Sway bar setup DID NOT change between old axle and new axle. Suspension setup DID NOT change between old axle and new axle.
In quick transition the back end will become unsettled and slide quite a bit. The way I found this was on a deserted back road, at about 50mph, quickly steering left then right. The back end would step out every time.
In fast sweepers, it feels (and sounds) like the inside rear tire is getting dragged, akin to a dog with a lame leg dragging it's leg around.
The LSD, provided it is the factory LSD that came with the shell I purchased to get the LSD from, has 76k on it. No bearing noise. No gear whine. I did place one wheel in the dirt while stopped and attempted to accelerate hard, and the wheel on the dirt spun, but the car did accelerate (it felt like it was the spinning wheel that accelerated me, not the wheel on the pavement).
What could cause the twitchiness in transition? Is this just a driving quirk of the LSD rear ends that I need to get used to?
08-22-09, 09:18 PM
#2
My 7 is my girlfriend.
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Not sure if this has anything to do with your problem, but did you put an LSD additive in the fluid? Not doing so can cause problems with the clutch discs. Namely chattering and abrupt engagement. Even if the gear oil you put in says it is LSD safe, get some additive anyway.
08-22-09, 10:18 PM
#3
Not sure if this has anything to do with your problem, but did you put an LSD additive in the fluid? Not doing so can cause problems with the clutch discs. Namely chattering and abrupt engagement. Even if the gear oil you put in says it is LSD safe, get some additive anyway.
08-23-09, 02:56 AM
#6
. . . Rear bar disengaged, passenger front swaybar endlink broken (just found today while bleeding my brakes).
. . .
In quick transition the back end will become unsettled and slide quite a bit. The way I found this was on a deserted back road, at about 50mph, quickly steering left then right. The back end would step out every time.
In fast sweepers, it feels (and sounds) like the inside rear tire is getting dragged, akin to a dog with a lame leg dragging it's leg around.
. . . ?
. . .
In quick transition the back end will become unsettled and slide quite a bit. The way I found this was on a deserted back road, at about 50mph, quickly steering left then right. The back end would step out every time.
In fast sweepers, it feels (and sounds) like the inside rear tire is getting dragged, akin to a dog with a lame leg dragging it's leg around.
. . . ?
A disconnected front swaybar (broken end link) will also cause oversteer.
A good LSD will spin the inside rear tire during tight turns under hard acceleration.
You say that the swaybar end link didn't change, and I assume from what you wrote that the unsettled rear end happened during cruising, not acceleration. You also say the inside rear tire is dragging, not spinning.
Allowing that you're new to an LSD in your car, I'd do the following:
1) Fix the swaybar end link. You want to do this anyway. Drive it the same way and see if the unsettled rear improves. You probably don't know exactly when it broke.
2) If that doesn't do it, change the rear fluid as already suggested. Be sure to use the LSD additive. This may improve the dragging or spinning.
3) Consider stickier tires. When I went from OE to lower profile performance tires, the spinning of the inside rear tire disappeared.
All this assumes the rear end isn't making any bad noises when driving straight. If it is, you have other issues.
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08-23-09, 09:14 AM
#9
LSDs will tend to cause more oversteer (unsettled rear end) during acceleration.
A disconnected front swaybar (broken end link) will also cause oversteer.
A good LSD will spin the inside rear tire during tight turns under hard acceleration.
You say that the swaybar end link didn't change, and I assume from what you wrote that the unsettled rear end happened during cruising, not acceleration. You also say the inside rear tire is dragging, not spinning.
Allowing that you're new to an LSD in your car, I'd do the following:
1) Fix the swaybar end link. You want to do this anyway. Drive it the same way and see if the unsettled rear improves. You probably don't know exactly when it broke.
2) If that doesn't do it, change the rear fluid as already suggested. Be sure to use the LSD additive. This may improve the dragging or spinning.
3) Consider stickier tires. When I went from OE to lower profile performance tires, the spinning of the inside rear tire disappeared.
All this assumes the rear end isn't making any bad noises when driving straight. If it is, you have other issues.
A disconnected front swaybar (broken end link) will also cause oversteer.
A good LSD will spin the inside rear tire during tight turns under hard acceleration.
You say that the swaybar end link didn't change, and I assume from what you wrote that the unsettled rear end happened during cruising, not acceleration. You also say the inside rear tire is dragging, not spinning.
Allowing that you're new to an LSD in your car, I'd do the following:
1) Fix the swaybar end link. You want to do this anyway. Drive it the same way and see if the unsettled rear improves. You probably don't know exactly when it broke.
2) If that doesn't do it, change the rear fluid as already suggested. Be sure to use the LSD additive. This may improve the dragging or spinning.
3) Consider stickier tires. When I went from OE to lower profile performance tires, the spinning of the inside rear tire disappeared.
All this assumes the rear end isn't making any bad noises when driving straight. If it is, you have other issues.
The front swaybar endlink had to have been broken while I was driving it just before the car was parked due to a leaking rear axle, as I found the broken endlink while bleeding brakes post swap.
The unsettled rear end was at constant throttle, 50mph, with a quick left-right transition. The dragging of the inside rear tire was at constant throttle, 55mph in a left hand bend.
Yes. From disk brake to disk brake, the whole rear end went in.
08-23-09, 06:59 PM
#11
I just got home from hanging out with a potential girlfriend, and noticed another oddity, which seems to be amplified by the LSD swap. While going from I-75 to I-696 at about 70mph, things got very sketchy. Steady state left hand bend, not too sharp, on concrete (not asphalt), with lines cut in the pavement going in the direction of travel, it felt like the rear axle shifted one way, severely unsettling the rear end of the car. I almost put it nose first into the wall it was so bad. It did this twice during the bend. The rear tires DID NOT squeal.
The twitchiness during transition got better after reconnecting the swaybars. It still slides a bit, but it isn't as dangerous. Much more controllable. I think I need to auto-x the car to learn the handling characteristics with the LSD, but the sensation that the rear axle is shifting is a bit scary.
08-23-09, 07:09 PM
#12
Lives on the Forum
You need to have the suspension loaded before you perform the final tightening, otherwise you get all kinds of weird handling issues just like you are describing.
Get it up on some ramps (rear wheels), loosen everything, then retighten everything. And I mean exactly that, loosen everything before you begin tightening again (as opposed to loosen one thing, then tighten it up, then move to the next).
Once you get that done you should be in good shape.
08-23-09, 09:38 PM
#13
This is the key right here. Your rear bushings are binding.
You need to have the suspension loaded before you perform the final tightening, otherwise you get all kinds of weird handling issues just like you are describing.
Get it up on some ramps (rear wheels), loosen everything, then retighten everything. And I mean exactly that, loosen everything before you begin tightening again (as opposed to loosen one thing, then tighten it up, then move to the next).
Once you get that done you should be in good shape.
You need to have the suspension loaded before you perform the final tightening, otherwise you get all kinds of weird handling issues just like you are describing.
Get it up on some ramps (rear wheels), loosen everything, then retighten everything. And I mean exactly that, loosen everything before you begin tightening again (as opposed to loosen one thing, then tighten it up, then move to the next).
Once you get that done you should be in good shape.
08-24-09, 08:52 AM
#14
Lives on the Forum
Jackstands under the axle will serve the same purpose, so no problem there. I don't think it will matter what state the car is in when you loosen everything, so doing it after it is in the air should be fine. Good luck.
08-26-09, 11:40 PM
#16
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I'm having a similar problem with my spec 7.. left handers are a hand full yet it sticks like crazy on right handers.. I'm going back though it this week to see what i can find.. I think i may have a axle bearing onthe pasenger side going and i wonder if that may be binding up on left handers
09-02-09, 03:54 AM
#17
On a non-lsd axle, the wheel to the inside of the turn radius basically free wheels. With lsd, it tries to rotate at the same revolutions as the outer wheel. Since the inner rear wheel is the least loaded wheel during turns, it will break traction first, and yes, in a sense it is dragging since it's trying to turn faster than the path of travel. This is the main cause of snap over steer. Once the inner tire breaks traction all the power is transfered to the outer wheel, allowing that tire to break traction easier.
My FC is non-lsd and it's very hard to induce snap oversteer or even do donuts. It's very easy to with the widebody, even with it'sd much larger tires. In fact, it's quite easy to do donuts from a dead stop with lsd. Just a turn of the steering wheel while dumping the clutch is all it takes. It takes a bit of relearning one's handling techniques with lsd. Once mastered it's sooo much more fun.
From your description, it sounds like you have a good, tight lsd unit. Play with it and have fun. With practice, you can do so much more with lsd than without. Keep in mind the it works during accel and decell. Decell is where many get into trouble. The rear end starts to walk on them, they abruptly let off the gas pedal and before the realize it, the rear has swung around the other way. Best way out of that situation is to feather the throttle and keep steering corrections to a minimum. I've seen too many non-experienced driver's over correct, occasionly with very bad results.
In the rain, I have to be very careful shifting into 2nd gear as the tires break loose easily and the rear end wants to go to the front of the line. If done right, I can swing the car 45* one way shifing into 2nd, then swing it 90* the other way shifting into 3rd, in the rain at low speeds/rpms. throttle input is just as important as steering input. That little trick makes passengers very jumpy.
My FC is non-lsd and it's very hard to induce snap oversteer or even do donuts. It's very easy to with the widebody, even with it'sd much larger tires. In fact, it's quite easy to do donuts from a dead stop with lsd. Just a turn of the steering wheel while dumping the clutch is all it takes.
It takes a bit of relearning one's handling techniques with lsd. Once mastered it's sooo much more fun.From your description, it sounds like you have a good, tight lsd unit. Play with it and have fun. With practice, you can do so much more with lsd than without. Keep in mind the it works during accel and decell. Decell is where many get into trouble. The rear end starts to walk on them, they abruptly let off the gas pedal and before the realize it, the rear has swung around the other way. Best way out of that situation is to feather the throttle and keep steering corrections to a minimum. I've seen too many non-experienced driver's over correct, occasionly with very bad results.
In the rain, I have to be very careful shifting into 2nd gear as the tires break loose easily and the rear end wants to go to the front of the line. If done right, I can swing the car 45* one way shifing into 2nd, then swing it 90* the other way shifting into 3rd, in the rain at low speeds/rpms. throttle input is just as important as steering input. That little trick makes passengers very jumpy.
09-05-09, 12:21 AM
#18
On a non-lsd axle, the wheel to the inside of the turn radius basically free wheels. With lsd, it tries to rotate at the same revolutions as the outer wheel. Since the inner rear wheel is the least loaded wheel during turns, it will break traction first, and yes, in a sense it is dragging since it's trying to turn faster than the path of travel. This is the main cause of snap over steer. Once the inner tire breaks traction all the power is transfered to the outer wheel, allowing that tire to break traction easier.
My FC is non-lsd and it's very hard to induce snap oversteer or even do donuts. It's very easy to with the widebody, even with it'sd much larger tires. In fact, it's quite easy to do donuts from a dead stop with lsd. Just a turn of the steering wheel while dumping the clutch is all it takes. It takes a bit of relearning one's handling techniques with lsd. Once mastered it's sooo much more fun.
From your description, it sounds like you have a good, tight lsd unit. Play with it and have fun. With practice, you can do so much more with lsd than without. Keep in mind the it works during accel and decell. Decell is where many get into trouble. The rear end starts to walk on them, they abruptly let off the gas pedal and before the realize it, the rear has swung around the other way. Best way out of that situation is to feather the throttle and keep steering corrections to a minimum. I've seen too many non-experienced driver's over correct, occasionly with very bad results.
In the rain, I have to be very careful shifting into 2nd gear as the tires break loose easily and the rear end wants to go to the front of the line. If done right, I can swing the car 45* one way shifing into 2nd, then swing it 90* the other way shifting into 3rd, in the rain at low speeds/rpms. throttle input is just as important as steering input. That little trick makes passengers very jumpy.
My FC is non-lsd and it's very hard to induce snap oversteer or even do donuts. It's very easy to with the widebody, even with it'sd much larger tires. In fact, it's quite easy to do donuts from a dead stop with lsd. Just a turn of the steering wheel while dumping the clutch is all it takes.
It takes a bit of relearning one's handling techniques with lsd. Once mastered it's sooo much more fun.From your description, it sounds like you have a good, tight lsd unit. Play with it and have fun. With practice, you can do so much more with lsd than without. Keep in mind the it works during accel and decell. Decell is where many get into trouble. The rear end starts to walk on them, they abruptly let off the gas pedal and before the realize it, the rear has swung around the other way. Best way out of that situation is to feather the throttle and keep steering corrections to a minimum. I've seen too many non-experienced driver's over correct, occasionly with very bad results.
In the rain, I have to be very careful shifting into 2nd gear as the tires break loose easily and the rear end wants to go to the front of the line. If done right, I can swing the car 45* one way shifing into 2nd, then swing it 90* the other way shifting into 3rd, in the rain at low speeds/rpms. throttle input is just as important as steering input. That little trick makes passengers very jumpy.
09-05-09, 01:26 PM
#20
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it should take a little more force to get it to start turning than it does to keep it turning, and once its turning it should be smooth.
09-06-09, 12:23 AM
#21
Dammmm it really pays to cruise threads and read.
I swapped in an entire rearend with polyurathane (sp?) bushings all around and it feels somewhat funny. I thought it might have to do with the adjustable swaybar it came with and I'd try different settings until it felt normal to me again... but now I'm thinking it has to be the tightening everything without the rear being loaded. hmmmmm did not know about that 1.
I swapped in an entire rearend with polyurathane (sp?) bushings all around and it feels somewhat funny. I thought it might have to do with the adjustable swaybar it came with and I'd try different settings until it felt normal to me again... but now I'm thinking it has to be the tightening everything without the rear being loaded. hmmmmm did not know about that 1.
09-06-09, 08:29 PM
#22
Dammmm it really pays to cruise threads and read.
I swapped in an entire rearend with polyurathane (sp?) bushings all around and it feels somewhat funny. I thought it might have to do with the adjustable swaybar it came with and I'd try different settings until it felt normal to me again... but now I'm thinking it has to be the tightening everything without the rear being loaded. hmmmmm did not know about that 1.
I swapped in an entire rearend with polyurathane (sp?) bushings all around and it feels somewhat funny. I thought it might have to do with the adjustable swaybar it came with and I'd try different settings until it felt normal to me again... but now I'm thinking it has to be the tightening everything without the rear being loaded. hmmmmm did not know about that 1.
09-07-09, 08:16 AM
#23
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One more thing to check...Front toe in contributes to squirly handling and the feeling that the rear steps out easily. Make sure the front toe-in is set to spec.
RXDad
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09-07-09, 09:48 AM
#24
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On a non-lsd axle, the wheel to the inside of the turn radius basically free wheels. With lsd, it tries to rotate at the same revolutions as the outer wheel. Since the inner rear wheel is the least loaded wheel during turns, it will break traction first, and yes, in a sense it is dragging since it's trying to turn faster than the path of travel. This is the main cause of snap over steer. Once the inner tire breaks traction all the power is transfered to the outer wheel, allowing that tire to break traction easier.
My FC is non-lsd and it's very hard to induce snap oversteer or even do donuts. It's very easy to with the widebody, even with it'sd much larger tires. In fact, it's quite easy to do donuts from a dead stop with lsd. Just a turn of the steering wheel while dumping the clutch is all it takes. It takes a bit of relearning one's handling techniques with lsd. Once mastered it's sooo much more fun.
From your description, it sounds like you have a good, tight lsd unit. Play with it and have fun. With practice, you can do so much more with lsd than without. Keep in mind the it works during accel and decell. Decell is where many get into trouble. The rear end starts to walk on them, they abruptly let off the gas pedal and before the realize it, the rear has swung around the other way. Best way out of that situation is to feather the throttle and keep steering corrections to a minimum. I've seen too many non-experienced driver's over correct, occasionly with very bad results.
In the rain, I have to be very careful shifting into 2nd gear as the tires break loose easily and the rear end wants to go to the front of the line. If done right, I can swing the car 45* one way shifing into 2nd, then swing it 90* the other way shifting into 3rd, in the rain at low speeds/rpms. throttle input is just as important as steering input. That little trick makes passengers very jumpy.
My FC is non-lsd and it's very hard to induce snap oversteer or even do donuts. It's very easy to with the widebody, even with it'sd much larger tires. In fact, it's quite easy to do donuts from a dead stop with lsd. Just a turn of the steering wheel while dumping the clutch is all it takes.
It takes a bit of relearning one's handling techniques with lsd. Once mastered it's sooo much more fun.From your description, it sounds like you have a good, tight lsd unit. Play with it and have fun. With practice, you can do so much more with lsd than without. Keep in mind the it works during accel and decell. Decell is where many get into trouble. The rear end starts to walk on them, they abruptly let off the gas pedal and before the realize it, the rear has swung around the other way. Best way out of that situation is to feather the throttle and keep steering corrections to a minimum. I've seen too many non-experienced driver's over correct, occasionly with very bad results.
In the rain, I have to be very careful shifting into 2nd gear as the tires break loose easily and the rear end wants to go to the front of the line. If done right, I can swing the car 45* one way shifing into 2nd, then swing it 90* the other way shifting into 3rd, in the rain at low speeds/rpms. throttle input is just as important as steering input. That little trick makes passengers very jumpy.
I have a LSD rear on my autocross car... When I dump the clutch, it lights up both rear tires. Problem is sometimes (not always) when I am autocross racing and in a tight turn, under full throttle, and coming off a rise in the pavement (IE. the worse case scenario) I spin the inside wheel.... Not bad, not enough to disrupt handling.....just spin.
Do you think my rear clutches might be getting weak? I replaced my gear oil with Royal Purple synthetic and no additive. (additive makes the plates slide easier).
I am considering rebuilding my LSD if it gets worse.
Oh and to the OP, you must really be driving the **** out of your car to disrupt the handling so bad....I can tell you, the difference between driving a car with an LSD and a peg legger is the difference between night and day.
Yesterday I was driving my SA22 in the rain (peg leg rear) it would spin 1st, 2nd, 3rd gear straight as an arrow.... try doing that in my 84 with an LSD....soon you will be driving with your tailights going FORWARD!!
09-07-09, 10:47 AM
#25
Absolute Power is Awesome
On a non-lsd axle, the wheel to the inside of the turn radius basically free wheels. With lsd, it tries to rotate at the same revolutions as the outer wheel. Since the inner rear wheel is the least loaded wheel during turns, it will break traction first, and yes, in a sense it is dragging since it's trying to turn faster than the path of travel. This is the main cause of snap over steer. Once the inner tire breaks traction all the power is transfered to the outer wheel, allowing that tire to break traction easier.
My FC is non-lsd and it's very hard to induce snap oversteer or even do donuts. It's very easy to with the widebody, even with it'sd much larger tires. In fact, it's quite easy to do donuts from a dead stop with lsd. Just a turn of the steering wheel while dumping the clutch is all it takes. It takes a bit of relearning one's handling techniques with lsd. Once mastered it's sooo much more fun.
From your description, it sounds like you have a good, tight lsd unit. Play with it and have fun. With practice, you can do so much more with lsd than without. Keep in mind the it works during accel and decell. Decell is where many get into trouble. The rear end starts to walk on them, they abruptly let off the gas pedal and before the realize it, the rear has swung around the other way. Best way out of that situation is to feather the throttle and keep steering corrections to a minimum. I've seen too many non-experienced driver's over correct, occasionly with very bad results.
In the rain, I have to be very careful shifting into 2nd gear as the tires break loose easily and the rear end wants to go to the front of the line. If done right, I can swing the car 45* one way shifing into 2nd, then swing it 90* the other way shifting into 3rd, in the rain at low speeds/rpms. throttle input is just as important as steering input. That little trick makes passengers very jumpy.
My FC is non-lsd and it's very hard to induce snap oversteer or even do donuts. It's very easy to with the widebody, even with it'sd much larger tires. In fact, it's quite easy to do donuts from a dead stop with lsd. Just a turn of the steering wheel while dumping the clutch is all it takes.
It takes a bit of relearning one's handling techniques with lsd. Once mastered it's sooo much more fun.From your description, it sounds like you have a good, tight lsd unit. Play with it and have fun. With practice, you can do so much more with lsd than without. Keep in mind the it works during accel and decell. Decell is where many get into trouble. The rear end starts to walk on them, they abruptly let off the gas pedal and before the realize it, the rear has swung around the other way. Best way out of that situation is to feather the throttle and keep steering corrections to a minimum. I've seen too many non-experienced driver's over correct, occasionly with very bad results.
In the rain, I have to be very careful shifting into 2nd gear as the tires break loose easily and the rear end wants to go to the front of the line. If done right, I can swing the car 45* one way shifing into 2nd, then swing it 90* the other way shifting into 3rd, in the rain at low speeds/rpms. throttle input is just as important as steering input. That little trick makes passengers very jumpy.
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