[DeTomaso] Final Drive Gear Question

[Rob Dumoulin]

Car #2 in Michael's scenario is mine. Until the Summer Summit a few
weekends ago, my car has never been out to play with any other Panteras
since I've owned it and only a few true Pantera folks have ever even seen
it.  I don't know much of the car's history before it was parked for eons
until I bought it, but it is refreshing to hear people point out upgrades
to the car that I would never have been aware of. So far, I've got an
upgraded Hall radiator, a presumably upgraded master cylinder, the middle
dash vent added, different window lift motors, a red interior, and a Hall
front hood latch system. I hesitate to think that the master cylinder and
lift motors are 'upgrades' because the both suck right now.

I've got rain bans of Tropical Storm Debby soaking us right now but I hope
to run some RPM/MPH numbers when it dries up.  Does anybody else have
higher gears like me and if so, what are your numbers?  Who did this type
of swap 15 years ago or longer?  Would it be safe to assume my ZF is safety
wired?

Rob

On Sat, Jun 23, 2012 at 1:29 PM, <MikeLDrew at aol.com> wrote:

>
> In a message dated 6/23/12 10 11 29, michaelsavga at gmail.com writes:
>
>
> > Here are the facts:
> >
> > Two Panteras
> >
> > Both with 335/35/17 rear tire wheel combos.
> >
> > 1) One believed to have a stock geared ZF Turns 3,000 rpms at a GPS
> > measured 70 mph.
> >
> > 2) The other with a questionable/unknown final drive geared ZF turns
> 2,100
> > rpms at a GPS mrasured 70 mph.
> >
> > A) does car #1 seem about "right" in relation to all other Panteras?
> >
> >>>Yes.   70 mph is about 3000 rpm in most cars.
> >
> > >B) what replacement final drive R&P ratio would account for the 900 rpm
> > reduction in engine rpms.
> >
> >>>That's a huge jump.   The real question is, what's the rpm delta in 4th
> gear?
>
> If the two cars turn the same rpm at the same speed in 4th gear, then the
> unknown gearbox car has a 4.22 ring and pinion and a taller 5th gear.   If
> they turn different rpm, then the unknown gearbox car has a different ring
> and
> pinion, but it might ALSO have a taller 5th gear.
>
>
> >
> > >C) If #2 does indeed have a replacement R&P ratio of X, what would the
> > theoretical top speed of Car #2 at 6,000 rpms.
> >
> >>>That's simple math (which is NOT so simple for me--I SUCK at math!).
> But I can figure this out.
>
> If it turns 70 mph at 2100 rpm, that's 30 rpm per 1 mph.   So 6000 rpm
> divided by 30 rpm per mph, equals 200 mph.
>
> Your tall-gearbox car either has a very tall ring and pinion, or a tall R&P
> plus taller 5th gear.
>
> 4th gear will tell all.
>
> I'll send you a ZF gearbox calculator spreadsheet that you can play around
> with.
>
> Mike
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-- 
Rob DuMoulin
904.476.8744
rob at dumoulins.net