Limited Slip Diff Selection
Limited Slip Diff Selection
(OP)
I require advice on selecting a limited slip diff for my car.
The vehicle will be used as tarmac rally car, hill climb (twisty, bumpy, tarmac) and on the road in all weather conditions. I wish to fit the unit and forget it. It must be low maintenance and reliable.
The differential unit I am using is a UK Ford 7 1/2" unit. Viscous couplings were fitted by the factory so this would be my first choice. Other easily available units are the Quaiffe (torque biasing) and plate.
Any advice would be appreciated.
Thank you
John
The vehicle will be used as tarmac rally car, hill climb (twisty, bumpy, tarmac) and on the road in all weather conditions. I wish to fit the unit and forget it. It must be low maintenance and reliable.
The differential unit I am using is a UK Ford 7 1/2" unit. Viscous couplings were fitted by the factory so this would be my first choice. Other easily available units are the Quaiffe (torque biasing) and plate.
Any advice would be appreciated.
Thank you
John





RE: Limited Slip Diff Selection
Rod
RE: Limited Slip Diff Selection
How did you find the Detroit locker? Carroll Smith in Drive To Win does not rate them.
John
RE: Limited Slip Diff Selection
Several of the vintage 2.5 Challenge series drivers are using Quaife with no apparant problems. You might check with Jack Knight or Leeson. It's been many years since I raced a "rear driver". Detroit Lockers are very good on the race track but tend to be a bit noisy on the street. They 'click' when you make tight turns.
Rod
RE: Limited Slip Diff Selection
John
PS The diff is going in a space framed Morris Minor.
RE: Limited Slip Diff Selection
Viscous type lsd's work on a speed differential between the wheels, ie the degree of lockup is proportional to the difference in speed of the two wheels - perhaps better suited to soft/loose surfaces than a quaiffe. The quaiffe works on torque input from the pinion. The higher the torque demand, the more lockup imposed across the diff. Great for takeoffs but less effective if one wheel has considerably less traction than the other.
I have to be honest and say I don't know exactly how the locker works, but I have come across a lockup diff on a truck axle which used an inertia system to engage a dog and lock up the axle. This was used on a towing vehicle for slippery slopes, came in with a bang when wheel slip occured and took a bit of skill with the throttle to get it to release aferwards.
dunno if that helps...
RE: Limited Slip Diff Selection
John, I am just now installing a Trannex limited slip on a 4.46 R&P in my new (rolled the last one) 63 Austin Cooper 1380 A+ vintage racer. Never used one in a 'front driver' so I am a bit apprehensive. We'll see how it works.
Good move for the Morris, I have twisted several axels on those buggers. My experience with JK is that they were "bulletproof".
Rod
RE: Limited Slip Diff Selection
"What is a problem is that, when the thing cycles from locked to unlocked and back the car goes from 2 wheel drive to 1 wheel drive on corner entry, and back to 2 wheel when the power is applied. This makes the car jump around in a failry unconsistent pattern, and makes it impossible to place the car with the sort of precision that one would prefer.
Back in "Engineer to Win" he was less kind. Page 228. "Violent and unpredictable." "Given any kind of choice at all, no one in their right mind uses a Detroit locker."
RE: Limited Slip Diff Selection
I used the DL on street courses with tight couners, ie, all off going in and all on coming out. It worked perfectly under those conditions for years. On all other courses I used a totally LOCKED diff of varrying ratios. The car was quite successful with lap records at Riverside International Raceway (1980,1985,1989) and qualifying records at Dallas (1972) and Mexico (1973). I've never been one to follow the crowd.
Rod
PS---Detroit Lockers can still be had www.racerpartswholesale.com
RE: Limited Slip Diff Selection
Pancholin
RE: Limited Slip Diff Selection
Detroit Lockers are definatly still available as they are extremely popular for off-roading. Too bad they are so brutal in a short wheelbase vehicle on the street. Accelerating around turns can lock up the rear and skip the front over, even a spool is generally prefered for the predicability!
There are some other "pocket lockers" available now that maintain the factory carrier and replace the spiders and sidegears, Detroit No-Slip(No-spin maybe?), Lockright, Easilocker etc. These are a cheap but leass durable way to try a locker with having to get gears setup.
Ken
RE: Limited Slip Diff Selection
Carroll Smith talks about the Emco diff. Has anybody had any experience with the Emco unit or know more about it? On their website they talk more about single seaters for their diff.
John
RE: Limited Slip Diff Selection
"Given any kind of choice at all, no one in their right mind uses Detroit Locker."... was a quote out of one of Carroll Smith's books.
I was not sure if you thought I was saying that. I would have phrased it differently, even if I thought it, which I would have no business thinking.
Dan T
RE: Limited Slip Diff Selection
Rod