One reason the IH Engineers developed a internal and or external brake system can be found in the manual:
Blue Ribbon Service Manual International Cub Cadet Tractors Models 86, 108, 109, 128, 129, 149, 169, 800, 1000, 1200, 1250, 1450, & 1650 GSS-1464 W/ Revision 2 September, 1979
Aside from a safety parking brake, or engine failure on a down-hill slope, the following paragraph under the
Check Valve Service chapter located on page 2-40 states this:
NOTE: Late production tractors are equipped with self-unloading check valves in the hydrostatic transmission. The tractors so equipped cab be identified by the absence of a release lever on the right side of the frame cover. These check valves will dump automatically when the engine is shut off. This will allow the tractor to be rolled.
CAUTION: Any time the engine is shut off the brake pedal should be locked to prevent the tractor from rolling.
Makes perfect sense why IH done what they did! Especially if the model 129 in topic discussion was up-graded to the self-unloading check valves. My personal opinion for my early 1450, is to go with the self-unloading check valves once the current manual check valves can no longer be operational. I find it very difficult to push the 690 pound beast with one arm, and hold the dump lever with the other arm when something prevents the tractor from self operation.
Hope this helps!
