1st gen LSD

dickita15

dickita15

New member
I have noticed as we push different cars around some diffs seem to bind more when turning. I assume that the LSD's in these cars are tighter. Is the amount of preload(is that the right term) different when the diffs are set up. is there a way to measure how effective a rear is. is wear an issue. is it fixable. if it can be quantified is there a rightamount of slip. lots of questions. can someone point me in the right direction.
dick patullo
ner ita 15
 
Dick, the answer to all your questions is YES. I think it was on this site a while back the LSD was talked about.

Another question to you all with respect to the rearend is:

Without talking about racing in the rain would a welded/locked/spool rearend be the best rearend for road racing ? Or with a non-slip rearend & low HP will the car just bog down because of lack of power ?

The reason I ask this question is because Laborday weekend I race Grattan, MI for the first time & the LS opened on 6 of the 15 turns. Then this past weekend at Blackhawk Farms the LS opened in 3 & 6. Having not taking the LS apart at this time it would be my belief that two things are causing the LS to open. One the LS clutches/plates are worn & my capability (continious learning at driving)of stuffing the car into corners has improved.

Have Fun
wink.gif

David
 
Dick,

I kind of curious regarding your questions too. I'm still running teh stock 3.90 LSD and have been looking for a 4.88. I understand the gear ratio part of the equation but I'm not sure about geometry. Tri link, Panhard bar, Watts Link, sway bars and which is the best or which is over rated I'm kind of stumbling around with these issues. I'll keep watching this post in hopes of getting some insight.

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Mark Jeffery
ITA #92 '85 RX7
MidDiv - Arkansas Region
 
Mark,

Let me first address the issue of rear end ratio. Either the 4.88 or 5.12 is the only way to go (at least in the SE Div). I have tried both a locked (welded) differential and a LSD. The locked setup was great if you tend to throw the car sideways a lot. (but don't try this in the rain unlees you have a good body shop as a sponsor) We don't have enough HP to overcome the push a locked (welded) diff causes. I could get away with it because I do throw the car hard in the corners but on certian sections of the Sebring club course I could feel the car binding up. (not wanting to accelerate until the steering input was lessened) therefore I changed to a LSD. Dropped almost 1.5 seconds in my lap times due to car being freed up in the tight corners due to the LSD.

As to the question of watts link, tri link and panhard rod. I run a modified version of Mike VanSteenburg's tri-link with a panhard rod system of my design. My car is a tad nuetral to oversteer and very controlable in low and high speed turns. I can pick the throttle up so early it's scary and not worry about the rear end wanting to come around. I my opinion, the tri-link designed by Mike VanSteenburg is the only way to go. I have seen the other designs on cars in our region and Mike's design is better, stronger and more adjustable.

I would suggest you call Mike at his shop and discuss it with him or you can call me and I'll be happy to take pictures of my design and send them to you.

Mike Cox
2000 & 2002 CFR IT7 Regional Champion
2001 & 2002 CFR IT7 Citrus Endurance Series Champion

813-927-9011

[This message has been edited by Mike Cox (edited October 17, 2003).]
 
Mike,

I will give you a call next week. Adding a Tri-Link and a 4.88 are projects for this winter. Which, BTW, Starts the day after ARRC.

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Mark Jeffery
ITA #92 '85 RX7
MidDiv - Arkansas Region
 
Dick,

Check out this link. ISC has a test fixture for determining the "Break Away" for LSD's.

Mike,

Does Mike VanSteenburg have a website?

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Mark Jeffery
ITA #92 '85 RX7
MidDiv - Arkansas Region
 
Originally posted by itaracer:
Dick,

Check out this link. ISC has a test fixture for determining the "Break Away" for LSD's.

Mike,

Does Mike VanSteenburg have a website?
Click to expand...

It's my understanding that Mike IS ISC...

They have a fixture, but you'll have to send your diff to them.

Here's a link to their susp page. Their "third link" looks a bit different from Jim Suskos "Tri Link"(G-Force)

http://www.iscracing.net/suspension_2.htm



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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]
 
Dick and David,
Backyard method for checking LSD breakaway (good vs trash) is to jack up one side of the axle while the other side is stil on the ground, put a torque wrench on a lugnut of the raised tire and turn. Note the torque at which the wheel starts to turn. 20lbs and under is bad. 40-60 I believe is desireable.

David, I'd say your improvement has either created or brought out worn/wearing plates.

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Steve
[email protected]
<A HREF="http://www.geocities.com/jake7140" TARGET=_blank>My racing page
</A><A HREF="http://www.geocities.com/elrss" TARGET=_blank>Elkhart Lake Racing_&_Sipping Society
</A>
 
Hmmm...Lime Rock guys may have some opinions here. Between my moments of terror, and my moments of yelling at myself for not getting the best out of the car, I have noticed my revs "popping" over the uphill. When I had an open diff for so many years, this was normal, but it still happens, albeit less, and maybe just recently, as I don't remember noticing it when it was first installed.

I would have a hard time believing that it is BOTH wheels spinning!!! So, who else has noticed this, or am I due for a LSD "tune and tighten"? And if so, how is it done, and who, locally! can do it??

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]
 
Simple method to dial a limited slip at the track:
1) Fill with redline 75w90 NS (NO limited slip additive in the NS oils.) Higher HP cars may want heavier NS oil. Buy a bottle of Redline limited slip additive.
2) If your limited slip is in decent condition, it will now chatter around slow corners, and induce throttle on understeer.
If it spins an inside wheel exiting slow corners, it needs to be rebuilt.
3) Between each session add 1/2 ounce of Redline limited slip additive and drive. When chattering and/or understeer stop, the diff is set up. Do be careful, the pumpkin tends to get pretty hot.
4) If you add too much additive, it's only a $14 dollar mistake (2 qts of fresh oil). A lot cheaper and easier than pulling the thing and reshimming. I use a 30cc syringe to put in the additive.

Depending on Differntial condition, expect to use 1 to 3 ounces of limited slip additive.

Also, I have no particular allegiance to Redline. If another mfg has similar oils, the same principle aplies.

Tak
 
Originally posted by lateapex911:
..I would have a hard time believing that it is BOTH wheels spinning!!! So, who else has noticed this, or am I due for a LSD "tune and tighten"? And if so, how is it done, and who, locally! can do it??
Click to expand...

Believe it or not, both wheels are spinning for that fraction of a second when the car crests the hill. With an open diff, you'll hear the revs pop but with the lsd, both wheels spin which causes the rear(rwd car) to jump sideways there because there is also some lateral g's at the top of the hill which just happens to be the track out point for the uphill turn. With a worn out diff, I got wheel spin exiting big bend and entering onto the back straight. With a godd diff, no wheelspin anywhere except at the top of the hill. NOTE TO WHOMEVER DRIVES LRP. If you don't get wheelspin at the top of the hill, you're not going fast enough
tongue.gif

Ray
PS-Tranny and diff rebuilds are done at Nelsons Automotive in Stamford Ct.
 
Originally posted by moto62:
NOTE TO WHOMEVER DRIVES LRP. If you don't get wheelspin at the top of the hill, you're not going fast enough
tongue.gif

Ray
Click to expand...

(Shaking head)....... Be that as it may, I'm still not going fast enough! @#$^@% Hunduhs!



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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]
 
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