Aftermarket or Factory LSD?
05-10-2010, 12:18 AM
#1
Three Wheelin'
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Aftermarket or Factory LSD?
I have determined that I am in the near future probably going to need a LSD. I want to try and make the car go forward and not spin.
I have determined that I could go for a Turbo S factory transaxle which would give me hardened gears (do they help much?) and an LSD. However, with the mileage of most transmissions, I think many of the friction plates would need rebuilt.
The other option is a Guard transmission torque biasing type of differential. I think GT also makes a standard LSD.
I guess which is the better buy? I probably really dont need the lockup on deceleration as I dont race the car. I just want the car not to spin the tire when i push the gas pedal down. Could the hardened gears be installed in a normal transmission?
Any way, if the transmission is apart, to make 3rd gear stronger?
-Dana
I have determined that I could go for a Turbo S factory transaxle which would give me hardened gears (do they help much?) and an LSD. However, with the mileage of most transmissions, I think many of the friction plates would need rebuilt.
The other option is a Guard transmission torque biasing type of differential. I think GT also makes a standard LSD.
I guess which is the better buy? I probably really dont need the lockup on deceleration as I dont race the car. I just want the car not to spin the tire when i push the gas pedal down. Could the hardened gears be installed in a normal transmission?
Any way, if the transmission is apart, to make 3rd gear stronger?
-Dana
05-10-2010, 01:39 AM
#2
Bannana Shine
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The Quaife's always worked great for me (also an ATBD like the Guard). Everything has its advantages and disadvantages, but in general I'd rather have a torque biasing differential than a clutch type (or viscous, for that matter).
05-10-2010, 02:22 AM
#4
Rennlist Member
It would depend on what your useage is. In other words, is the car for the track, street, or both? How much tracktime do you see and how hard do you push it?
My experience was that I had to get the factory LSD rebuilt a couple of times before I bought a Motorsport race LSD 50/80.
Some people are concerned that this will create too much push understeer, especially on the street. I have no problem with this.
My advice is to just bite the bullet and go for the real deal.
My experience was that I had to get the factory LSD rebuilt a couple of times before I bought a Motorsport race LSD 50/80.
Some people are concerned that this will create too much push understeer, especially on the street. I have no problem with this.
My advice is to just bite the bullet and go for the real deal.
05-10-2010, 10:26 AM
#5
Rennlist Member
If you're getting into push understeer situations on the street, you're driving way too fast. I honestly don't care how the car reacts on the street, as I'm nowhere near the limit. I save that for the track.
05-10-2010, 10:28 AM
#6
Three Wheelin'
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It would depend on what your useage is. In other words, is the car for the track, street, or both? How much tracktime do you see and how hard do you push it?
My experience was that I had to get the factory LSD rebuilt a couple of times before I bought a Motorsport race LSD 50/80.
Some people are concerned that this will create too much push understeer, especially on the street. I have no problem with this.
My advice is to just bite the bullet and go for the real deal.
My experience was that I had to get the factory LSD rebuilt a couple of times before I bought a Motorsport race LSD 50/80.
Some people are concerned that this will create too much push understeer, especially on the street. I have no problem with this.
My advice is to just bite the bullet and go for the real deal.
-Dana
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05-10-2010, 11:44 AM
#8
Interestin topic - been wondering the same thing. I autocross my 951 and it drives me nuts when I light up the inside rear tire every time I hit the throttle. At almost $1800 for a Quaife unit (and I have no idea how much a Guard is) I haven't jumped in yet... this will probably be on my "winter project" list. I figure while I'm in there I might as well pick up a turbo-S trans to get the hardened gears - though I too wonder if it's really worth it. How many ppl here run around with 300+hp on stock non-tS transmissions and don't have problems?
05-10-2010, 11:59 AM
#9
Burning Brakes
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I still have a stock '87 951 non cooled, non LSD trans in my car (350rwhp, but i'm at elevation...). No problems, and i have 285's in the back.
I think both the 951 and "S" boxes (i.e. 944S, S2) had hardened 1-2nd gears. The "Turbo S" (AOR) transmissions had 1st and 2nd gears that were also shot-peened. Maybe the R&P was polished or something too? Regardless, it's a fairly minor difference and (IMHO) not worth the price of admission.
The 951 boxes hold up just fine to lots of power. Ultimately the failure is usually of the pinion gear backing out of the case, which can be solved by bolting a 3/8" steel plate behind the pinion gear, trapping it between the case. Long story short, the 951 trans is very strong to begin with, and can be built to be bullet-proof fairly easily.
As for LSD options, i'm all ears! I wish there were a more budget-friendly alternative, though. $2000 is a bit steep!
I think both the 951 and "S" boxes (i.e. 944S, S2) had hardened 1-2nd gears. The "Turbo S" (AOR) transmissions had 1st and 2nd gears that were also shot-peened. Maybe the R&P was polished or something too? Regardless, it's a fairly minor difference and (IMHO) not worth the price of admission.
The 951 boxes hold up just fine to lots of power. Ultimately the failure is usually of the pinion gear backing out of the case, which can be solved by bolting a 3/8" steel plate behind the pinion gear, trapping it between the case. Long story short, the 951 trans is very strong to begin with, and can be built to be bullet-proof fairly easily.
As for LSD options, i'm all ears! I wish there were a more budget-friendly alternative, though. $2000 is a bit steep!
05-10-2010, 05:09 PM
#10
Race Car
A few points:
1. I can only speak for myself, but around Road Atlanta, I use second gear entering turn 7, and that's it. I already have to shift before I track out (yes, I know.....BAD), but many, many 951 guys who are (much!) faster than me can keep it in 3rd.
2. You might post this in the DE/Track forum. Some folks have some very different opinions about the clutch versus torque biasing setup, and it has to do with braking. I am pretty sure the factory Cup cars all use clutch style diffs, so if you like to benchmark........
1. I can only speak for myself, but around Road Atlanta, I use second gear entering turn 7, and that's it. I already have to shift before I track out (yes, I know.....BAD), but many, many 951 guys who are (much!) faster than me can keep it in 3rd.
2. You might post this in the DE/Track forum. Some folks have some very different opinions about the clutch versus torque biasing setup, and it has to do with braking. I am pretty sure the factory Cup cars all use clutch style diffs, so if you like to benchmark........
05-10-2010, 11:21 PM
#11
Rennlist Member
The Turbo S AOR trans and the S2 AOS/AOT transmissions use the same hardened input shaft - the 1st and 2nd gear drive teeth are machined on the input shaft and these were what was hardened.
Only other difference with the AOR & AOT transmissions from earlier units is the LSD guts. Thicker friction discs, thinner pressure cups, and dry film lube on the spider gear shafts.
I am not aware that these changes were extremely significant in either strength or wear resistance, probably more of a slight or incremental improvement.
Only other difference with the AOR & AOT transmissions from earlier units is the LSD guts. Thicker friction discs, thinner pressure cups, and dry film lube on the spider gear shafts.
I am not aware that these changes were extremely significant in either strength or wear resistance, probably more of a slight or incremental improvement.
05-10-2010, 11:51 PM
#12
Rennlist Member
Sorry, yes Duke was right. I was referring to an aftermarket clutch type LSD. Guards get some of theirs made down here in Australia. We pay more here for them than we could buy them from Guards in the US. Go figure. Mine cost in the vicinity of $3500au but well worth it. It's all relative. A good stock 951 will start at about $25k down here so there you go. 968CS are selling for $50k plus.
If you are going to use your car on the track (as opposed to Auto X) then go for the clutch type as they engage on backoff. Some people say that the Quaiffe type torson ones are suited to Auto X or street so it depends on what you want.
There is also a Japanese company that do LSDs I just can't remember their name. Some seemed to think these were worth consideration.
If you are going to use your car on the track (as opposed to Auto X) then go for the clutch type as they engage on backoff. Some people say that the Quaiffe type torson ones are suited to Auto X or street so it depends on what you want.
There is also a Japanese company that do LSDs I just can't remember their name. Some seemed to think these were worth consideration.
05-11-2010, 05:59 AM
#14
Rennlist Member
05-11-2010, 06:08 AM
#15
Nordschleife Master
Interesting, so they are also coming with a 944 variant?
OS Giken's 944 LSD is supposed to be released now or very soon. Seems like a super nice product from what I've read.
OS Giken's 944 LSD is supposed to be released now or very soon. Seems like a super nice product from what I've read.