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914World.com _ The Paddock _ Time to look for a TBD
Posted by: ww914 Oct 8 2014, 09:34 AM
I have read many posts here regarding TBDs and I would like to hear some comments on both Wavetrac and Guard, or any other product that is working for you. My 914-4, 2270cc, with stiff suspension on Hoosier A6s, is primarily used for auto-cross. Don't care much about ice, snow or rain as this car will not be driven in those elements.
Thanks in advance for any responses.
Posted by: campbellcj Oct 9 2014, 06:28 PM
I have a quaife that has served me well for 10 years...not much I can tell you about it beyond that however.
Posted by: ww914 Oct 9 2014, 07:51 PM
I have a quaife that has served me well for 10 years...not much I can tell you about it beyond that however.
Do you auto-cross the car? And, if so, how does it react to fast in-fast out on corners?
Thanks for responding.
Posted by: J P Stein Oct 9 2014, 09:14 PM
Guard here,,,back in the day. That would be my first and only recommendation.
Invisible going in, throttle on in the corner and it helps you steer around it....kinda tucks in. That is easy to get used to. Catchable when coming out hard.....as you should be.
Posted by: campbellcj Oct 10 2014, 06:22 PM
I have a quaife that has served me well for 10 years...not much I can tell you about it beyond that however.
Do you auto-cross the car? And, if so, how does it react to fast in-fast out on corners?
Thanks for responding.
No autocross, only track, but I do drive on some tight technical tracks (e.g., Streets of Willow, Fontana infield) and the car does turn-in and power-out nicely. Bear in mind my car has a heavily-modified
Posted by: mskala Oct 10 2014, 08:23 PM
Wavetrac. I don't have enough car knowledge to talk vehicle
dynamics. All I know is I autocross with similar car setup to yours
and I no longer spin the inside rear trying to get out of corners. It's
like a TBD but with the addition of some innards that are supposed
to keep the diff working even if a wheel is really unloaded.
Posted by: Randal Oct 11 2014, 03:04 PM
Guard TBD's work great. Only way to go if your running Autox; you can dial out understeer. Same with Hill Climbs, the TBD will put the power to the wheel with the most traction.
Haven't driven the Wave TBD, but Bill Pickering just put one into his 901 for his new 914-6. It a 3.2 liter, so looking forward to trying that differential in the car. Should be a terror.
Posted by: ww914 Oct 11 2014, 04:34 PM
Guard TBD's work great. Only way to go if your running Autox; you can dial out understeer. Same with Hill Climbs, the TBD will put the power to the wheel with the most traction.
Haven't driven the Wave TBD, but Bill Pickering just put one into his 901 for his new 914-6. It a 3.2 liter, so looking forward to trying that differential in the car. Should be a terror.
Matt Monson of Guard says that the Torsen design of Wavetrac locks under braking which is counter to what would be desireable in AX. He says the Wavetrac design is deliberately intended to prevent trail braking, which means that all your rotation in a turn must be done during the coast phase of the turn. Their locking mechanism doesn't release until you let go of the brakes. With the Guard, you can rotate earlier and therefore get on the throttle for exit in the direction you want to go. Anyway, in theory it sounds like a fast enter/exit in a tight turn.
I wish someone would chime in on that who has one and tell us if this is what he/she experiences.
Posted by: Randal Oct 11 2014, 05:24 PM
Guard TBD's work great. Only way to go if your running Autox; you can dial out understeer. Same with Hill Climbs, the TBD will put the power to the wheel with the most traction.
Haven't driven the Wave TBD, but Bill Pickering just put one into his 901 for his new 914-6. It a 3.2 liter, so looking forward to trying that differential in the car. Should be a terror.
Matt Monson of Guard says that the Torsen design of Wavetrac locks under braking which is counter to what would be desireable in AX. He says the Wavetrac design is deliberately intended to prevent trail braking, which means that all your rotation in a turn must be done during the coast phase of the turn. Their locking mechanism doesn't release until you let go of the brakes. With the Guard, you can rotate earlier and therefore get on the throttle for exit in the direction you want to go. Anyway, in theory it sounds like a fast enter/exit in a tight turn.
I wish someone would chime in on that who has one and tell us if this is what he/she experiences.
I've just used the Guard and know it eliminates understeer. YES!
Not a big fan of trailbraking in autoxing, but do see big open courses, like Crows Landing, where it could be used effectively.
Can't wait to drive a big time torque car like Pickering's with the Wave unit. If it locks up under braking, Bill might be happy as that was the one thing that he didn't like about the unit, wanting to use it at the track as well.
BUT wondering how long it takes from brakes off to unlock; whatever that time is will cost you in autox.
Posted by: J P Stein Oct 11 2014, 08:41 PM
Forcing both rear tires to turn at the same rate under decell will cause big time underseer. That's NOT what the torque biasing diffs do. They act the same as an open diff under decel, braking or no. The TBD will cause the inside rear tire to spin *IF It COMES ENTIRELY OFF THE GROUND*.....in which case you have a suspension problem. Normally, the TBD transfers the torque to the tire WITH THE MOST TRACTION. The effect of this in a sweeper (for instance) causes the rear to feel like it's stepping out....or the front is tucking in, due to the unequal torque distribution.....*I think*.You have to feel it to believe it.....I like it. One can keep rolling in throttle. Usually one reaches the exit before anything untoward happens. Then the TDB responds by equally (or so close ya can't tell) applying the torque to the rears. The car turns in and rotates great....even in the tight stuff.
Quaife & Guard (I've never driven a Quaife equipped car),I am told, act the same.
Me? I urge my competitors to buy a clutch type LSD. 
Posted by: Randal Oct 12 2014, 12:37 PM
Forcing both rear tires to turn at the same rate under decell will cause big time underseer. That's NOT what the torque biasing diffs do. They act the same as an open diff under decel, braking or no. The TBD will cause the inside rear tire to spin *IF It COMES ENTIRELY OFF THE GROUND*.....in which case you have a suspension problem. Normally, the TBD transfers the torque to the tire WITH THE MOST TRACTION. The effect of this in a sweeper (for instance) causes the rear to feel like it's stepping out....or the front is tucking in, due to the unequal torque distribution.....*I think*.You have to feel it to believe it.....I like it. One can keep rolling in throttle. Usually one reaches the exit before anything untoward happens. Then the TDB responds by equally (or so close ya can't tell) applying the torque to the rears. The car turns in and rotates great....even in the tight stuff.
Quaife & Guard (I've never driven a Quaife equipped car),I am told, act the same.
Me? I urge my competitors to buy a clutch type LSD.
Got to admit it that JP figured out how effective a TBD was before any of us knew what one was. And he was nice enough to share that information with us, something that most won't do.
Posted by: ww914 Oct 12 2014, 02:25 PM
Forcing both rear tires to turn at the same rate under decell will cause big time underseer. That's NOT what the torque biasing diffs do. They act the same as an open diff under decel, braking or no. The TBD will cause the inside rear tire to spin *IF It COMES ENTIRELY OFF THE GROUND*.....in which case you have a suspension problem. Normally, the TBD transfers the torque to the tire WITH THE MOST TRACTION. The effect of this in a sweeper (for instance) causes the rear to feel like it's stepping out....or the front is tucking in, due to the unequal torque distribution.....*I think*.You have to feel it to believe it.....I like it. One can keep rolling in throttle. Usually one reaches the exit before anything untoward happens. Then the TDB responds by equally (or so close ya can't tell) applying the torque to the rears. The car turns in and rotates great....even in the tight stuff.
Quaife & Guard (I've never driven a Quaife equipped car),I am told, act the same.
Me? I urge my competitors to buy a clutch type LSD.
Got to admit it that JP figured out how effective a TBD was before any of us knew what one was. And he was nice enough to share that information with us, something that most won't do.
I agree with that for sure.
Posted by: J P Stein Oct 13 2014, 08:07 AM
Buying/installing an LSD is a major investment for many of us. Un-doing it is not something someone wants to contemplate.....so get it right the first time, eh? I read the book, saw the movie, & got the T-shirt before I jumped.
The Guard unit is in the "not cheep" category but seemed to be bullet proof......I don't think the same can be said about those Ricer LSDs. I got a real good buy on one and installed it my self or it would have been out of reach for me. Even then ya really gotta want it. One needs tools & a book ( I had an early 911 shop manual) but it's not rocket science.....a good winter project. The good news is here wasn't any bad news.....it did the job with no excuses. That old 901 lasted well beyond what conventional wisdom said it would.
BTW, An LSD for a Mustang is about 1/4 the cost of the Guard unit.....and you can get one on Amazon.
Posted by: naro914 Oct 13 2014, 04:20 PM
I've been contemplating a TBD for Huey for years...just never seem to get to that $$ expenditure. Papa Smurf has a Guards LSD for racing...and he keeps eating into all of Huey's potential budget. maybe next year...
Posted by: Matt Romanowski Oct 13 2014, 07:54 PM
The Guard unit is in the "not cheep" category but seemed to be bullet proof......I don't think the same can be said about those Ricer LSDs. I got a real good buy on one and installed it my self or it would have been out of reach for me. Even then ya really gotta want it. One needs tools & a book ( I had an early 911 shop manual) but it's not rocket science.....a good winter project. The good news is here wasn't any bad news.....it did the job with no excuses. That old 901 lasted well beyond what conventional wisdom said it would.
It probably lasted because it barely gets used. A long autocross is what, 2.5 miles long? 6 runs a day, 2 drivers is only 30 miles per event (and that is generous). How many events a year? 10 would only be 300 miles. I did over 3,000 on the track last year. It takes time to kill a ring and pinion.
Posted by: J P Stein Oct 13 2014, 09:42 PM
It also lasted a year+ behind a 350 hp Subie after 10 years of abuse behind a 2.7L 6. We normaly did about 20 AX per year. Never did hurt the R & P but stripped 2nd gear clean.
Posted by: campbellcj Oct 14 2014, 06:41 PM
It probably lasted because it barely gets used. A long autocross is what, 2.5 miles long? 6 runs a day, 2 drivers is only 30 miles per event (and that is generous). How many events a year? 10 would only be 300 miles. I did over 3,000 on the track last year. It takes time to kill a ring and pinion.
FWIW my John Williamson (Otto) built 901/914 trans has lasted 10 years, some of which saw 10-15 track events (many 2-dayers in there as well.) There are so many factors in this: build expertise, parts quality/condition, maintenance, temps, driving style, power, weight, grip, etc....
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