Traditional Limited Slip vs. Torque Bias, Please eduficate me! Options

[SirAndy]

Purpose of the car, in order:

Spirited street driving, occasional AX, occasional track days.



Here's what i think i know (IMG:style_emoticons/default/biggrin.gif)

LSD
- Always locks wheels together under acceleration and deceleration.
- Introduces understeer in slow corners.
- Generally considered the better choice for the big track.

TB
- Only locks wheels under acceleration.
- Acts like a open diff if a driving wheel is off the ground.



So, the question is, what should i get for my 915???

The car will never be a dedicated track car, it's mostly driven on the street.
The TB seems to be easier to drive on the street.
However, the slow corner understeer of a LSD could probably be tuned down with suspension settings.

The TB loses it's magick if one wheel is off the ground. In an AX setting, the suspension would need to be pretty stiff to keep both wheels on the ground at all times, would a LSD be the better choice here?


Anyone compared the two back to back in a 914?
(IMG:style_emoticons/default/idea.gif) Andy

[Matt Monson]

Hello Guys,

It's been a while since I logged in. I just happened to be looking for some information today and came across this fine thread on my other search.

Andy,

I am going to side with the guys who are telling you to go with a torque biasing differential. For all but a dedicated track car I really feel that it's the best option for a 914. It's what I personally run in my own 914. I think it's the way to go for the vast majority of us 914 owners, whether it's got a bone stock 1.7 Type IV or a monster 3.6 swap. It's just very well suited to the chassis dynamics of the car.

Part of why so many 911 owners swear by a true LSD is because of the rear engine design. With all that weight out on the rear end, there's that infamous 911 tailwag under hard braking. Because an LSD locks under braking it helps to make the car much more stable as you bring it down from speed. The midengine design of the 914 makes it inherently more stable under those same conditions. That stability isn't needed in the same way with the 914.

Aside from adding those comments, I don't really see much of anything that I will disagree with in the conversation going on here. Though there is one thing that I do want to mention, and that's regarding the service life of our LSDs. Every time this topic comes up there's a lot of discussion about the cost of rebuilding the LSD and the fact that it does need service over time. This is a practical reality of LSD ownership but it's not something that is a deal breaker for most people. The service life of the internals for our LSDs are about the same as the service life of the clutch or synchros. This isn't something that you're going to be ripping out every year or two and rebuilding, even if the car is a dedicated track car. People get years and years of use out of these things between rebuilds.

Just a couple of examples from recent experience. Last month I rebuilt an early GT LSD. This LSD was so old it still had a welded cap and wasn't CNC billet. The owner had purchased it new from Paul and it was well over a decade old. It was from a 911sc running a hot rod 3.2 engine on carbs that was mostly street driven with a couple of DE/track days a year. The owner said he drives about 5000 miles a year. This was the first rebuild on it. Or, there's Pat Williams' personal 400whp 930. He's been running the GT LSD for 4 seasons of dedicated PCA club racing now. He checked his before he put the car on the track this year and said that he wasn't even close to needing it rebuilt. So, there's a couple real world examples from different applications and levels of abuse. The short version is they hold up and stay together a good long time between services.

I'll try to come aroud more. This used to be one of my favorite P-car boards and work just kind of drew me away. Maybe we should even look at becoming a site sponsor. We've got some new products coming out that are appropriate for the 914 and you would be a good group of people to offer them to.

Regards,

Matt Monson
Guard Transmission LLC

[PeeGreen 914]

Hello Guys,

It's been a while since I logged in. I just happened to be looking for some information today and came across this fine thread on my other search.

Andy,

I am going to side with the guys who are telling you to go with a torque biasing differential. For all but a dedicated track car I really feel that it's the best option for a 914. It's what I personally run in my own 914. I think it's the way to go for the vast majority of us 914 owners, whether it's got a bone stock 1.7 Type IV or a monster 3.6 swap. It's just very well suited to the chassis dynamics of the car.

Part of why so many 911 owners swear by a true LSD is because of the rear engine design. With all that weight out on the rear end, there's that infamous 911 tailwag under hard braking. Because an LSD locks under braking it helps to make the car much more stable as you bring it down from speed. The midengine design of the 914 makes it inherently more stable under those same conditions. That stability isn't needed in the same way with the 914.

Aside from adding those comments, I don't really see much of anything that I will disagree with in the conversation going on here. Though there is one thing that I do want to mention, and that's regarding the service life of our LSDs. Every time this topic comes up there's a lot of discussion about the cost of rebuilding the LSD and the fact that it does need service over time. This is a practical reality of LSD ownership but it's not something that is a deal breaker for most people. The service life of the internals for our LSDs are about the same as the service life of the clutch or synchros. This isn't something that you're going to be ripping out every year or two and rebuilding, even if the car is a dedicated track car. People get years and years of use out of these things between rebuilds.

Just a couple of examples from recent experience. Last month I rebuilt an early GT LSD. This LSD was so old it still had a welded cap and wasn't CNC billet. The owner had purchased it new from Paul and it was well over a decade old. It was from a 911sc running a hot rod 3.2 engine on carbs that was mostly street driven with a couple of DE/track days a year. The owner said he drives about 5000 miles a year. This was the first rebuild on it. Or, there's Pat Williams' personal 400whp 930. He's been running the GT LSD for 4 seasons of dedicated PCA club racing now. He checked his before he put the car on the track this year and said that he wasn't even close to needing it rebuilt. So, there's a couple real world examples from different applications and levels of abuse. The short version is they hold up and stay together a good long time between services.

I'll try to come aroud more. This used to be one of my favorite P-car boards and work just kind of drew me away. Maybe we should even look at becoming a site sponsor. We've got some new products coming out that are appropriate for the 914 and you would be a good group of people to offer them to.

Regards,

Matt Monson
Guard Transmission LLC

New stuff (IMG:style_emoticons/default/aktion035.gif) do tell more (IMG:style_emoticons/default/beerchug.gif)

[Matt Monson]

New stuff (IMG:style_emoticons/default/aktion035.gif) do tell more (IMG:style_emoticons/default/beerchug.gif)

Let me talk to management around here before I go too deep down that path. I don't know how you guys are around here with the vending thing, but I don't want to step on any toes. Regardless, I personally am not fond of the very commercial approach a lot of guys take and prefer to participate on a more informational level.

But I'll give you a hint. It starts with 901 and ends with ears... (IMG:style_emoticons/default/confused24.gif)