ZF Gear Speedo Ratio /1 and /2

The two different types of speedometers are stencilled in green ink with the gear ratios they support (revs per mile). This is true for both Panteras and Mangustas, so instruments with the same stencilled number will swap between Panteras and 'Gooses. Then there is the speedo's threaded end- early speedos used different threads which require that specific speedo cable to thread on, and the same is true for the right angle drive assemblies.

You really need a copy of the Tech Service Bulletins (TSBs) to sort out fussy little details like this. All the Pantera vendors sell paper reprints, or it's available for free download as a pdf for POCA members- along with myriad other manuals.

There are two variants of speedometer for miles per hour and kilometers per hour with "1210 revs per mile" and "1610 revs per mile" marked on the rear of the speedo. Then there are four right-angle adapters with two cable styles. Early drives are usually Veglia-Borletti while later ones are VDO. Either comes in a 1:1 or 1.11:1 ratio stamped on the drive.

bulletins attached

Good info. Explains why the Borletti drive I got from Wilkinson now makes my speedo read lower. I guess I should be glad I could get one at all, but now the speedo has to be re-calibrated to the drive.

Many thanks for all the replies with the helpful info! I was not aware that there were different speedometers installed.

I recalculated the above tables with wheel diameters and diff ratio. The 1200 speedo from an early 71 needs a 5 teeth worm gear on the ZF output shaft (2,4 ratio on the tag), a 1.1:1 90° drive. The later need the 6 teeth worm gear (2.0 ratio), 1:1 and a 1600 speedo.

Now it is clear, that my currently mounted 1:1 gear is obviously wrong on a 71 pantera and I need find a 1.1:1 in order to get the correct speed.

I have one in hand 50-080  (50311-049)

OK I know it is a Borletti ( not sure if it is 1210 or 1610)

Denis, if that reads 50.0806, the bulletin above points to 1200 rotations/mile...If 50.0804, its for 1610 speedos. But both show for the  DS1 (assuming the '058 means the DS1).

 Claus, calibrating the speedo is one thing, getting the odometer to count correctly will take the right worm drive gears in the speedo. I have no idea if that is easy to sort, even though they are easy to swap....As you'd guess, Fiats used the same basic mechanism around this time (fiat 850) but 1690g/m (revolutions per mile...really meaning rotations per rotation!) so may be very close to this pic I have of a metric speedo (1.67Msomething....Pantera or Longchamp or...?). 

If your speedo is way off (30% no matter what real speed you are going), its probably wrong drive gearing. If just offset (10mph slow whatever the speed) its just a bump of the needle...Lee

Denis, you can easily check the ratio of the drive by turning one end 1 full rotation and check at the same time the output rotation. If it is as well 1 rotation its a 1:1 ratio, means a 50.0804.

My speedo reads approx 10%-15% too high speed, so fits to a 1:1 drive instead of 1.1:1.

The angle drives can get pretty spendy if you can find one, I may have 1:1.1 around somewhere as my GT5 was imported from Europe and converted to mph. 

An alternative is an in line gear reducer available in a wide range of corrections once you figure out what you need.

Cua, Looks like it is a 1:1 drive