[DeTomaso] ZF-Q transaxle

[Ken Green]

      Just FYI,  anything which has been in the public for more than 21 years should be past patent protection.  Basically, you have to file for a patent within 1 year of any public disclosure or sale, and the patent term (presently) is 20 years from the filing date.  (There are some exceptions, and US patent law was changed from a patent term of 17 years past the issue date to 20 years past the filing date in 1995 to prevent abuses of "submarine" patents where issuance was intentionally delayed to extend the term).
   
        You also don't need to feel bad about copying something after the patent expires.  The patent system is based on trading an enabling description in the patent for a 20 year monopoly.  After the patent expires, you should feel totally free to study and copy any patent.
   
        The ZF parts Lloyd sells are not protected by a patent, they are protected by Lloyd's know how (Lloyd's parts work) and by the limited market.  Anyone can make and sell FZ parts, but it probably doesn't make sense because they will not recover the development costs.
   
  Ken

JDeRyke at aol.com wrote:
  IMHO the 'old' ZF is quite capable of handling 5-600 horses regularly and 
7-800 if the driver takes some care in shifting (and getting out of the throttle 
when airborn!) to prevent shock-loads. I know of two real ZF failures: Jr 
Wilson broke a clutch input shaft by not backing off while getting air-time at 
high revs/200 mph in his 572 inch Boss 429 conversion; the shaft snapped in two 
on landing. And Greg Isakoff somehow broke several gear sets in '04-05 while 
road-racing a 650+ horse Pantera; dunno how 'gently' he shifts. For the rest of 
us with less than $50,000 in our engines, a good tune-up of our ZFs wil allow 
them to do another 35 years on the street & occasional open track. Supposedly, 
the 'super' ZF gearsets are a little stronger- but I have no direct 
experience. 

I've not torn one down, but my understanding is, the Quaife LSD diff is based 
on the mid-'70s Torsen spiral-bevel-gear diff design (which I have torn 
down). These work well, as long as you get one that can take the torque. I have one 
in my garage right now that failed behind a 500+ horse 350 Chev in a 
roadracer. The iron diff case spread, allowing force to move outward to the tips of 
the bevel gears, which then chipped and failed. One problem seems to be parts 
availability; when Torsen's patent (apparently) lapsed, the rights seem to have 
spread across the globe and not all dealers handle all models. I've checked 
four dealers & none can do anything for this particular LSD. Two had never 
heard of the model.
Nothings perfect, or cheap, when you talk of big power- and actually usie it. 
Torsen-type LSDs don't heat up lube like a clutch-type LSDs, so probably do 
not require any sort of diff cooler except maybe for Daytona or LeMans. FWIW- J 
DeRyke
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