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Unfortunately, I don't believe they are serviceable so you'll likely need to buy a replacement, but check what caused it, perhaps a binding speedo cable?
Thanks Larry. New part ordered. $337 ouch!
Speedo cable is fairly new and spins freely. Not sure what might have caused the failure.
It looks to me like you have a Borletti angle drive. There is an alternative to a new angle drive. You can send your speedometer to a speedometer shop such as North Hollywood Speedometer or Palo Alto Speedometer and have it converted to electronic operation. Then replace the angle drive with a VSS or drive the speedo with a GPS sender and cap off the angle drive mount on the ZF. Other than eliminating the speedo cable, an added benefit is the ability to easily calibrate your speedometer.
Thanks David. Interesting idea! I think I'll stick with old skool for now. 
Watch it! I ordered one from Wilkinson. #34. Threw my speedo off by 20 MPH. When I reported it to him, nope, nothing wrong on his end, and that was the only Borletti. I had the wrong speedo..LOL. Funny it was perfect before. I used it until I found one on E-Bay, now perfect again.
@rrs1 posted:Watch it! I ordered one from Wilkinson. #34. Threw my speedo off by 20 MPH. When I reported it to him, nope, nothing wrong on his end, and that was the only Borletti. I had the wrong speedo..LOL. Funny it was perfect before. I used it until I found one on E-Bay, now perfect again.
There are two ratios 1:1 and 1.1:1 for each of the two manufacturers angle drives, because the speedo internal ratios depend on whether it as Euro (kph) speedo or US mph speedo.
Understood, but if it was a Euro drive, then the speedo would have read higher, it was lower.
I have successfully repaired a dozen or so Borlotti angle drives that use skew gears. Drive-tab breakage comes from installing the big double-thread mounting nut such that the drive tabs only touch by their very tips on the short ZF extension shaft inside the tranny. This then fatigues the tips after 40 years or so, even with the light loads of cable & speedometer.
You're correct- both types of angle drives are not made to be serviced and the assembly grease used when they were built 50 yrs ago has usually turned into a brick. You can soften the 'brick' up by soaking it in penetrating oil or brake fluid for a week or so, but re-greasing the sealed assembly is a real challenge.
The VDOs including on Mangusta & pushbutton ZFs use right angle crown gears, and what usually happens to them is the cast gear teeth wear out or chip after the factory lube goes away. Haven't found a source for the tiny gears yet.
@bosswrench, would you mind describing the proper way to install the angle drive?
Do you want the broken one for any reason?
I wonder how many US cars had the wrong drive installed in them. My early car speedo has always read high saying I am going 100 when I know I am not. it is off by about 20 MPH. Do the drives have the ratio stamped on them somewhere? Mine says 50-0804 on the top and a 2 and H and looks to be a Borletti never replaced from original. Also, my speedo rests at 10 MPH. it has never gone to 0.
Mine is a '73 (#5423) too is a 50-0804 was dead on vs. GPS speed. The stop pin on mine is at 10mph.
thanks. I never realized in 31 years of ownership there is a stop pin.
Jmardy, send your broken drive to
J DeRyke
1520 Brandi Rose Way
Minden, NV 89423
And I'll see what I can do. When I fix them, I add a zerk fitting so the poor thing can then be serviced annually. The repair is not expensive as I'm really not in business- more of a hobby.
MOTORHEAD FUN WITH THE ZF TRANSAXLE
1.) To install a speedo angle drive correctly, screw that big dual-thread nut all the way onto the angle adapter until it bottoms (by hand). Then screw the other end of the big nut onto the ZFs threaded adapter (again by hand), which requires un-screwing the big nut a little, as one set of its threads are backward but it has no swivel. The assembly may not be very tight at the end, but that's OK, as transaxle lube is sealed with an internal o-ring, not by the tightness of the nut's threads.
2.) If you do get a small lube leak, things get tricky. Before doing ANYTHING ELSE, clamp a Vice-Grip pliers to the drive tang sticking out of the ZF. This is vital, as the tang is the back end of a 4" long steel drive extension off the ZF mainshaft. If you remove that innocent little 10mm bolt next to the assembly without having hold of the drive tang, the extension shaft will slip down inside the transmission and you'll need to disassemble the whole ZF to get it back! If this happens to you, DO NOT DRIVE THE CAR AT ALL UNTIL THE LITTLE SHAFT IS REMOVED!
There's very little extra room inside the cases, and a spinning transmission gear will snag the now-loose extension shaft and RAM IT THROUGH THE ALUMINUM CASE! This is a $1000+ disassemble-and-TIG-weld repair job, AFTER you remove the ZF and ship it to a specialist. It also assumes the transmission gear didn't break a tooth- more $$$$! All this is not exactly a design flaw but is the result of our ZF being originally designed to run upside-down in the earlier GT-40 and Mangusta (as a 5 DS-25/1 model). Ford (correctly) decided the Pantera needed more ground clearance for public streets than the racers did on manicured tracks, so ZF in Germany simply rotated the castings and flipped the ring gear to the opposite side for the Pantera's 5 DS-25/2 ZF model.
Worked perfectly and gave an extra 3-1/2" of road clearance, but now instead of the speedo extension shaft sliding out on the ground when the retaining bolt is removed, it slides inside the cases unless gripped. Once that 10mm bolt is removed, the threaded boss AND SHAFT can be pulled out as an assembly from your ZF by hand. The sealing o-ring can then be R & R-ed. You really need the illustrated 50-pg ZF Overhaul Manual to understand what's going on inside. For POCA members, a free downloadable copy is in the POCA Archives via the Web, along with dozens of other manuals & info. Or reprints are available from all the vendors or from PI Motorsports (who sponsor this forum).
That stop-pin in the speedo at 10 or 20 mph is not unusual in mechanical speedos that go to 200 mph. In 41 yrs of driving, its only caused us a problem a few times, once during a time-and-distance rally where a 2 mile long section ran through two school zones and we were required to proceed at 10 mph.... Judy had to drive slowly until the needle flickered, then slow again. And due to public perversity, there's a section of narrow road in the hills near Saratoga, CA that has a posted speed limit of 9 mph! Both of these were encountered pre-GPS.
The Pantera SI uses a tiny electronic generator on the angle drive, eliminating the cable. The $300 Autometer 5" OD 0-200 mph white-face speedo that some use in their Panteras eliminates both the cable and the angle drive and runs directly off the ZF extension shaft tang. You have to assemble the $100 electronic speed generator from a second source (details in the archives). It wasn't worth $400+ to me to eliminate these parts.
Yes- that looks fine.
Thanks! I think I took it on and off 20 times! 