LSD or Locked Diff? Options

[twin356]

Looking for OPINIONS on locker or LSD for914/6 about 200hp.

[J P Stein]

Looking for OPINIONS on locker or LSD for914/6 about 200hp.

I put in a Guard TB diff in my 200hp+ 914 and never looked back.
A clutch type LSD or locked diff may well cause U steer on corner entry.

[Cracker]

I'd ask first what you are intending to use the car for? I can't think in any use that you would really be happy with a locker. I have had a Guard TB and have currently a Guard LSD. I prefer the LSD but I also use my car on road courses. If you A/X (which I do not), I hear the TB is more compatible. Out of my realm there...my friend who bought my TB and only runs on Road courses is looking at switching to a LSD someday. He likes the TB but would prefer the LSD. All I know...best of luck.

Tony

[Randal]

In 222 I first ran first a Guard LSD and then later changed to a Guard TB differential.

For autoxing or hillclimbs the TBD works best. If you use a LSD autoxing you'll find that it's difficult to impossible to dial out understeer, i.e., the front end pushing. Slip in a TBD and the understeer is gone, saves time in every tight corner.

On the track the LSD works great, especially in braking areas.

I haven't run a TBD on the track, but will be doing that with the DSR, which has one. It will be interesting to see the differences.

[6freak]

TB DIFF (IMG:style_emoticons/default/smile.gif)

[brant]

I loved my locked diff
it required a completely different driving style
it was literally dangerous on a dirty track or wet track as the required style was full slide

but no one will ever out brake you on the track with a locked diff
tire wear goes up, tranny temps go down

On the current race car I'm running a TB
paul guard and I had a conversation once upon a time, where he admitted that a TB can be faster on a track in a mid engine car, vs- an LSD

our tranny builder (amazing driver) did some testing between different diffs in a 914 and also recommended the TB based on lap times

[twin356]

The car is strictly a Race Car, vintage. Highly doubt ever Auto X. My 356 race cars were always ZF LSD. Past 10 years I drove a sports racer with open Diff. Now back to Porsches, and mid engine.
Thanks for the responses.
Scott

[Cracker]

Brant - Very interesting. Thanks for sharing.

[campbellcj]

Same here; mine has a Quaife TBD which was recommended to me over a conventional LSD or spool (locker) for this car/application. It has worked out great.

[Cracker]

Chris - That is interesting. The conventional wisdom associated the LSD is that it assists under deceleration/braking - calming the rear and stabilizing it under threshold braking. You and your car look great so obviously your TB works well.

T

Same here; mine has a Quaife TBD which was recommended to me over a conventional LSD or spool (locker) for this car/application. It has worked out great.

[campbellcj]

Originally my plan was to use this current box for short technical tracks and have a bit taller-geared one for big tracks; that one would have a conventional LSD, probably a Guard. I just haven't gotten around to this plan yet... and the car is reasonably stable under braking as it sits now - it was much worse at some points in the past.

[Woody]

Guard TBD. So pretty too.

[Cracker]

Cool Woody.

Here is the difference between OEM and my Guard!

T

[jd74914]

How well does the TB unit work on really bumpy courses? Do they have lots of preload to prevent freewheeling when one wheel lifts?

Are the references to LSD above to a salisbury (clutch and ramp-type) or clutch-type? I'm just curious.

[Cracker]

http://www.guardtransmissionllc.com/produc...-differentials/

Mine is a 60/40...

Tony

How well does the TB unit work on really bumpy courses? Do they have lots of preload to prevent freewheeling when one wheel lifts?

Are the references to LSD above to a salisbury (clutch and ramp-type) or clutch-type? I'm just curious.

[Randal]

I've got to add a point of clarification to my earlier post.

I talked to Matt at Guard and told him my understanding of how a TBD worked was that power would always go to the wheel with the best traction. He said, right, but added the qualifier “until the limit” is reached. He described the limit as 20% friction. So anytime you find or create a situation that falls below the 20% limit the differential will go open.

So drive wheel lift on tight corners should be dialed out by adjusting your suspension. Lifting a drive wheel is not good.

[stownsen914]

I've used a locker in my 914 racecar since I built it. 250 hp with wide slicks. I did it mostly for budget reasons since I was pretty $ constrained when I built the car - basically just had the stock diff welded by a local welder. Aside from some push in very tight turns, I've been happy with the handling. Though admittedly that's probably because it's all I know - 90% of my seat time is with this car and my driving style has probably adapted to it. Forget autocrossing with a locker, and for what it's worth, maneuvering the car in tighter spaces like loading on the trailer in the driveway is a pain in the butt.

One thing worth noting - a risk with using a locker is if you break an axle or CV (usually under power), you can lose directional control of the car. I broke a CV on the front straight at Lime Rock a couple years ago, and even in 5th gear nearly lost control of the car at 100+ mph. Not fun. With a clutch type LSD or TBD, you would just lose most or all drive power in that scenario.

Scott