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locker rear end by mcguiver3
Started on: 09-23-2013 06:51 AM
Replies: 21 (312 views)
Last post by: mcguiver3 on 09-24-2013 08:41 PM
mcguiver3
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Report this Post09-23-2013 06:51 AM Click Here to See the Profile for mcguiver3Send a Private Message to mcguiver3Edit/Delete MessageReply w/QuoteDirect Link to This Post
Guys and gals,
I am wondering about a locker diff for my autocross car.
Have played with the few LSD units available for the Getrag 5 spd but not impressed with them.
Thinking about eliminating the diff and installing a spool or welding up the diff.
Any thoughts?
My problem is on launching. Still have significant wheel spin on one side.
Loosing a lot of time there.
Can the trany hold up?
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theogre
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Report this Post09-23-2013 10:44 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you weld the dif... You will likely have problem turning and/or the dif/trans can fail.

Real lockers cost $, If you can find one for your trans.
aftermarket "bolt-on" kits that mod's the OE dif have problems depending on the kit.

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DimeMachine
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Report this Post09-23-2013 01:31 PM Click Here to See the Profile for DimeMachineSend a Private Message to DimeMachineEdit/Delete MessageReply w/QuoteDirect Link to This Post
I am not an autocross guy but my thoughts are that a locker and corners is a BAD idea. Am I wrong.
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2.5
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Report this Post09-23-2013 04:05 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
Got the best and right size tires you can get yet?
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dobey
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Report this Post09-23-2013 04:47 PM Click Here to See the Profile for dobeySend a Private Message to dobeyEdit/Delete MessageReply w/QuoteDirect Link to This Post
If your problem is launching, and not wheel spin in turns, then an LSD or locking diff is a waste of money. Get bigger/better/correct tires, and/or don't try to launch so harder.

Also, you didn't specify what engine/trans you have, or what RPM you're launching at.
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mcguiver3
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Report this Post09-23-2013 06:08 PM Click Here to See the Profile for mcguiver3Send a Private Message to mcguiver3Edit/Delete MessageReply w/QuoteDirect Link to This Post
OK, here is the deal.............
I have the LSD from Performance Industries in a Getrag 5 speed box.
The engine is a 2.8 with everything thrown at it. Getting 150 at the wheels according to the dyno.
Even a custom built intake system worth about 15HP (again the dyno says)
Full coil over suspension (custom built) with poly everywhere.
It's at 2250# wet right now
tires, Kuhmo Esxta V710 R Comps on 17" rims (fronts 7" rears 8")
Some of you may have seen the car.
The issue is the launch is spinning one tire but on corner exit it doesn't.
So it appears it is working to some degree but not effective when launching.
Tire pressures are around 26# rear (that's the spot it likes the most).
Here are a couple of pics.





Been doing this a long time, about 20 years with the same car but a work in progress.
Have competitive times but always looking for that elusive .500 sec.

Bob
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84fiero123
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Report this Post09-23-2013 06:24 PM Click Here to See the Profile for 84fiero123Click Here to Email 84fiero123Send a Private Message to 84fiero123Edit/Delete MessageReply w/QuoteDirect Link to This Post
Back tire are to narrow, go down to 15s and run 50s.

Simple

Steve

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fieroguru
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Report this Post09-23-2013 07:04 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
Which side spins and is it always the same side?
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trotterlg
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Report this Post09-23-2013 07:40 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you have too much wheel spin with only 150 hp then I think you have some other problems. Larry
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mcguiver3
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Report this Post09-23-2013 07:42 PM Click Here to See the Profile for mcguiver3Send a Private Message to mcguiver3Edit/Delete MessageReply w/QuoteDirect Link to This Post
Rear tires are 245-45 17
Can't go wider on an 8" rim and a 9" rim will not fit under the wheel well.
Have less that 1/4" space between the rim and coil over shock
Went to 17" to get them over the knuckle as it is.
The rear bearings are an issue to if we use too much offset to let them stick out beyond the fender.
I am only exploring an idea here.
Have a friend with a locker in his 360 Z autocross car and while low speed turning is a chore at speed his car is a rocket on course.
Wanted to find a true gear type LSD but not available?
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84fiero123
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Report this Post09-23-2013 10:29 PM Click Here to See the Profile for 84fiero123Click Here to Email 84fiero123Send a Private Message to 84fiero123Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by trotterlg:

If you have too much wheel spin with only 150 hp then I think you have some other problems. Larry


I was going to say isn't that the original HP rating for the 2.8?

Steve

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and one big pain in the ass when it doesn't



Detroit iron rules all the rest are just toys.

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Report this Post09-23-2013 11:19 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by mcguiver3:
...
Wanted to find a true gear type LSD but not available?


At one time, wasn't there a Torsen available for the HiPo Quad 4 Getrag?

Good luck finding one now, though.
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LornesGT
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Report this Post09-24-2013 12:22 AM Click Here to See the Profile for LornesGTSend a Private Message to LornesGTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Off topic! Why do you head lights stick up in the back?
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Khw
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Report this Post09-24-2013 12:36 AM Click Here to See the Profile for KhwClick Here to Email KhwSend a Private Message to KhwEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by LornesGT:

Off topic! Why do you head lights stick up in the back?


My guess? This is a autocross car not licensed for street use, so track use only. The light covers situated the way he has them would vent air from behind the radiator much like the hood vents many people install. Essentially they are no longer headlights at all, just vents.

[This message has been edited by Khw (edited 09-24-2013).]

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fieroguru
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Report this Post09-24-2013 06:27 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:

Which side spins and is it always the same side?


If it is always the driver side, then replacing the long passenger side axle with an intermediate shaft setup should help. When you launch, you induce a torque into the shafts, the longer one can flex/rotate to a much higher degree than the shorter one, so as torque builds it normally is the first to break loose. By making your axle shafts closer in length from side to side (doesn't need to be perfect), then they will twist in a similar fashion and be more likely to break loose together.
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Report this Post09-24-2013 10:16 AM Click Here to See the Profile for dobeySend a Private Message to dobeyEdit/Delete MessageReply w/QuoteDirect Link to This Post
If tires are 245 wide then they should be wide enough, especially with a good track compound. Like fieroguru suggested, moving to a half-shaft setup for the passenger side axle will help keep it from breaking loose.

You also didn't say what RPM you were launching at, just that you were going for an 0.500 time. I'm guessing spinning the one side doesn't help with that. If you're launching at around 4000, you need to launch at a lower speed. Do you have any form of launch control in the car? You mentioned that you got 150 whp on the dyno. Do you have the dyno chart showing that, and the torque curve as well? Not questioning the validity of the HP numbers, but just wanting the data that can help you. Dyno chart and current launch RPM data (both what you rev to with clutch pedal on the floor, and what it launches at when the clutch engages as you pull your foot off), would be very helpful.

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Report this Post09-24-2013 10:16 AM Click Here to See the Profile for darkhorizonSend a Private Message to darkhorizonEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:


If it is always the driver side, then replacing the long passenger side axle with an intermediate shaft setup should help. When you launch, you induce a torque into the shafts, the longer one can flex/rotate to a much higher degree than the shorter one, so as torque builds it normally is the first to break loose. By making your axle shafts closer in length from side to side (doesn't need to be perfect), then they will twist in a similar fashion and be more likely to break loose together.


Even if you used an intermediate shaft style setup... you are still going to have the same sized shaft in the system that can flex the same as a long axle.


Either way, driver mod will control your wheel spin.. might also want to look into your weight balance under load to make sure one side of the car is not loading up harder than the other.
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mcguiver3
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Report this Post09-24-2013 06:28 PM Click Here to See the Profile for mcguiver3Send a Private Message to mcguiver3Edit/Delete MessageReply w/QuoteDirect Link to This Post
The light covers are vents.
The launch occurs about 4000 RPM but even if I slow it down a bit it still spins the wheel.
I do have the dyno chart but dam if I know how to post that????
The tire are due for replacement and may experiment with Hoosier A6 next season.
The R Comps I'm using now are a bit firm cold. Khumo's like it hot!!!!!!!!!!!!!!
But we can't use any warming techniques.
I have scales and the car cross weight is 49.8 - 50.2, almost perfect.
The coilovers are adjustable.
No launch control, That OBD-1 stuff is not smart enough.
Again, just looking for that elusive .500 sec.
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Report this Post09-24-2013 07:42 PM Click Here to See the Profile for tebaileyClick Here to Email tebaileySend a Private Message to tebaileyEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you're running a limited slip, try adding a degree or two of toe in to the side that's spinning. If the wheel is toed out it could be dis-engaging the clutch packs.
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fieroguru
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Report this Post09-24-2013 07:54 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by darkhorizon:
Even if you used an intermediate shaft style setup... you are still going to have the same sized shaft in the system that can flex the same as a long axle.


The one on my car is nearly 2" in diameter and not near as prone to twisting at the 1" axle shaft.
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mcguiver3
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Report this Post09-24-2013 08:39 PM Click Here to See the Profile for mcguiver3Send a Private Message to mcguiver3Edit/Delete MessageReply w/QuoteDirect Link to This Post
The toe is actually set at zero front and rear.
I was running 1/16" toe in each side front (didn't like it)
Rear was always at zero. and 2.5 deg. neg camber. Tire wear/temps. are spot on at that setting.
Was thinking it might help at launch at less that 2.5 deg but then cornering would start to suffer.
It does turn in great with minimal under-steer.
I do appreciate all the help and ideas.
Been playin with this for the last 3 years. The competition is getting fierce, rivalries are escalating.
Also though about an F23 with the LSD. Could be an alternative.
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mcguiver3
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Report this Post09-24-2013 08:41 PM Click Here to See the Profile for mcguiver3Send a Private Message to mcguiver3Edit/Delete MessageReply w/QuoteDirect Link to This Post

mcguiver3

742 posts
Member since Jan 2012
PS,
Money is no object..............

Yea, right........................

No genies in a bottle
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