Limited Slip Diff Selection 1

[innovator]

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

 

[evelrod]

Quaiffe seem to be the most common here in SoCal. I no longer race a Ford product (Minis these days) but I used Detroit Lockers for 28 years in a Lotus Cortina (still have one on the shelf with a 4.44 R&P) Never failed in race car service.

Rod

 

[innovator]

The Quaiffe seems perfect except for one aspect and that is if one wheel is in the air or totally looses traction then all the drive goes to that wheel, not ideal.

How did you find the Detroit locker? Carroll Smith in Drive To Win does not rate them.

John

 

[evelrod]

There is a pretty good chance I bought it before Carrol wrote his book (a little old folk humor). Actually I bought the last one from Bob Winkleman in 1966 or 67 if memory serves. I used it on the 4.44 for street races like the Palm Springs Grand Prix, short straights and lots of ninety degree corners. For longer tracks like Riverside or Willow Springs I used locked 4.12's and locked 3.9's. Only two tracks , Mexico City and Texas World, did I use locked 3.7's. Lotus Cortinas are quite quick but aerodynamically they are a brick, just a step above my Mini.
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

 

[innovator]

The Jack Knight is a cam and pawl which seems to be a very good diff, but it wears quite quickly and therefore requires rebuilds. I help run a hill climb / sprint Mini here in the UK and we use a Jack Knight cam and pawl but it probably only runs for about 1 hour a year. It replaces a Quaiffe which suffered from inner wheel spin, due to it lifting, but could that be due to poor suspension setup?

John

PS The diff is going in a space framed Morris Minor.

 

[shabba]

I suppose in rallying the type of diff you use is determined by the type of surface youre driving on.

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...

 

[evelrod]

Shabba, you have successfully described the basics of a Detroit Locker. The lockup events are moderated by 'slip rings' and only manafest themselves in a negative fashion in 'street' use. I used mine in road racing only with no problems. Being a 'locker' they present no heating problems and are tolerant to all lubes.

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

 

[Tmoose]

C. SMith mentioned it In my copy of "drive to win" page 7-34 he talks about the detroit locker. He uses words like "Noisy," "upsetting," "effecitve, cheap, reliable and available." He also says "not an optimum device" referring to what happens if the driver plays with throttle setttings on corner exit.

"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."

 

[evelrod]

Tmoose---"Given any kind of choice at all, no one in their right mind uses Detroit Locker."... If you have followed my posts in Eng Tips over the last three years...You have successfully described ME!

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

http://www.racerpartswholesale.com

 

[Pancholin]

It sounds to me like Shabba described the GM Govloc diff. where if one wheel went about 5 MPH faster than the other a series of weights and pawls caused a clutch pack to lock up. And it stayed locked until deceleration or reverse happened. Unlocked it was an open diff. It worked well in sand or pavement, but since one wheel was already spinning it did lock up with a bang. If I came to a sandy spot I would purposly gently spin just to get it to lock up on my terms instead of waiting until I was nearly stuck then locking up with a bang so that both wheels would spin. Now I have a Detroit Locker and the only complaint I have is that it is nearly impossible to turn on pavement without the inside tire squeeling since the inside tire is the driving one on turns. There is also quite a lot more free play between accelerate and decelerate which cause my cruise control to oscillate on downhill areas.
Pancholin

 

[Slowzuki]

The govloc is an eaton product actually! As far as Quaiffe torsen or non reversing worm gear types, Tru-Trac is another type with various torque bias available.

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

 

[innovator]

My car is short wheel base and will be used on tight twisty courses so I require a good turn in. I understand that an open diff will give better turn in than a partially locked or locked diff. This therefore points towards a torque biasing diff or a plate diff with 85 degree ramps on the coast side.

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

 

[DanT]

Hi Evelrod !

"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

 

[evelrod]

I am not offended by the truth, Dan. Caroll Smith is a great source for automotive/racing information, just not the only source. That old 1966 DL diff is still out in the shop after probably 50 races and it is still in workable condition which I cannot say about some of the other diffs I have used. In fact, I think one of those lap records and several wins were on that DL. How any piece of equiptment functions is variable---installation, operator, environment----you know?

Rod