Reply to "ZF Synchro Repair Discussion"

You may thank Ford for some of the confusion on gear-cones. In the original GT-40 and most Mangusta transmissions, the gear cones were smooth and the synchro rings were grooved to hold lube. ZF changed that to the present backwards groove design, along with an almost complete redesign of the ZF transaxle in the ZF dash-2 variant. This was to placate Ford's fears of vast warranty problems. Per several ZF memos to Ford circa 1969-'70, the design differences between a Dash-0 or 1 (GT-40 & Mangusta) and a Dash-2 (Pantera) transaxle were:

1)- rotate gearbox 180 degrees (on bellhousing flange) and move ring gear to other side of differential case.
2)- relocate shift mechanism on same side of car as at present (left-hand side) in spite of the 180 degree gearbox rotation.
3)- Increase OD of bellhousing flange by 30mm. New bellhousing required by assembly rotation has one large view/ventilation port, rather than two smaller ones at 45 degrees to each other. The new bellhousing is also die-cast (smooth) rather than sand-cast (rough) as previously.
4)- revise internal lubrication & ducts as req'd for new position of gear assembly.
5)- increase front hole-mounting pattern from 4 to 6 bolts (+ 2 dowels).
6)- Use new clutch spline size (1-1/16" in dash-2 vs 1-1/8" in dash-1 and dash 1.5)
7)- replace aluminum axle side-plates with cast iron for strength.
8)- Relocate unit attach points from (iron) differential side covers/bellhousing to (iron) tail cover. Note- In 1972, the single rear attach point again moved to two points on the transmission case sides via new subframes & mounts.
9)- Transmission (1st, 3rd & 4th) & R&P gearing substantially changed & Ford-recommended gear steel used.

In addition, the dash-1 Mangusta differential case (& interim dash-1.5 pushbutton Pantera case) is 4 lbs lighter than a dash-2, and the mainshaft is 1/2" shorter than in a dash-2. Dash-1 and dash-1.5 transmission mainshaft needs extended pilot bearing/bushing holder. Dash-2 does not. Clutch pivot shaft in dash-2 bellhousing runs in caged needle bearings rather than bronze bushings (dash-1 & 1.5) and is 1-1/4" longer than dash-1 & 1.5 shaft. Cross-shaft OD is larger, too. Throwout bearing release fork is also larger in all dimensions in dash-2.

Max input torque (dash-2); 325 ft-lbs @ 2153 lbs axle load (650 kp); Max engine rpms- 8000
Wt of ZF dash 1 type= 132 lbs (no oil or bellhousing)
Wt of ZF dash-2 type= 144 lbs (no oil or bellhousing)
Dash-1 holds 2.1 liters/3.5 pints 80W lube.
Dash-2 holds 3.5 liters/7.3 pints. Both can be hooked up to lube cooler via cast bosses.
Dash-1 (and dash-0) has ZF cam-type (sprag) self-locking (LSD) differential. Dash-2 has clutch-type. Dash 1.5 may have either type LSD.

And as far as 'brass' or 'bronze' synchro rings, I've never seen one from ZF or Butfoy. They are all non-ZF; there are dozens of types of brass or bronze formulations- aluminum-bronze, phosphor-bronze, red-bronze etc. No reason to expect them to be the same from various sources, possibly explaining the variant in lifespans reported for 'bronze' synchro rings.

Another subject mentioned by Lloyd Butfoy decades ago: 2nd gear synchro wears faster than all the others because in a street Pantera, the car spends most of its running life starting in 1st and quickly going to 2nd.... where it stays until the next stoplight when the sequence is repeated. 2nd gear is good for 70 mph with stock gearing & tires. The altered lube system noted above by ZF engineering for the upside-down Pantera ZFs may not be a perfect substitute for the original, either. The 2nd-to-neutral (or 2nd-to-1st-to neutral) shift is less stressful than upshifts and often is done at lower rpm. 2nd gear synchro is therefore used far more than the others, hence that cone & ring wear more.

Interesting that the so-called Super-ZF (M-1 type) got a redesigned 2nd gear synchro just in time to sell the whole ZF design & tooling to RBT. Thanks for that tidbit, Ron- I've never worked on one. Because M-1 shafts and bearings are also larger, piece-parts cannot be swapped into earlier ZFs. I'm told that with case machining, the entire M-1 gearset can be transferred to a lighter & less-strong early case, but it's not simple- nor cheap.