The standard Ford-Mercury boxes have a 28- or 28- tooth main driving gear. The Lincoln Zephyr box carried a 25- or 26-tooth main gear. The lower ratios available in the Zephyr first and second, produce a higher gearing and permit a higher maximum speed in first and second, without changing the speed possible in high (or direct). In addition, Zephyr ratios are closer than in Ford-Merc boxes. As a result of Henry Ford's feeling for standardization, Z gears are interchangeable in most Ford and Merc boxes.
Never done it my self but............. There looks to be a fairly complete why, what it takes including part numbers, and how to in the Nov 1951 issue of Hot Rod magazine. Ed
Ok, someone help me clear some cobwebs from my memory. Did I read somewhere that later transmissions ended up with the Zephyr gears as standard? If so, when was it and what is the latest year flatty trans guts that interchange?
Ford Motor Company put the "fabled" LZ gears into their Lincoln transmissions from 1940-48 only. The early Lincoln Zephyrs used the Ford p***enger car gears in 37-39. To the best of my knowledge, Ford never installed any LZ ge****ts in any Ford or Mercury p***enger cars in regular factory production. My statement allows for the possibility that the factory could have built some "special" models for special customers who wanted the LZ gears, although I doubt that even this happened. The only difference between the 1940-48 Ford gears and the 40-48 LZ gears was the tooth counts, making the LZ gear ratio higher for first and second gears. The actual gears themselves were not manufactured to a higher level of durability. Before you consider installing any of the gear ratios available, give some thought to the rear end ring and pinion gear ratio, and the rear tire size going on the vehicle. If you've already installed a low number ring and pinion (say 3.54:1 or 3.25:1) and then you combine that with the high ratio LZ gear set in the trans, you will end up with great expressway gas mileage but a real dog moving out in first gear. Tall tires makes it even worse. The reason those gears worked in the heavier Lincoln was because the factory combined them with the very low ratio Lincoln rear end gears (4.44:1 I think). Many Lincolns were optioned with the overdrive to compensate.
Old ford transmissions were not very srong. My brother used an old Buick top shifter in his 36 ford hemi powered lakes coupe used the ball casting off a ford and drilled and tapped the buick case to bolt it together I haved added more roller bearings to the cluster gear, It is supposed to keep the gears from flexing. After my buddies kept blowing up the flat head transmussions I sold my T bucket, olds with flat head trans, rear end and built the next one with a packard trans and olds rear end
I believe the LZ gears are somewhat stronger just because the lowered gear reduction right at the input. All else equal, the reduced gerr ratio would result in lower loads on the first and sesond gears. I am running the 19/25 ge****t with a 3.25 rear. I love it. I can go up my very steep driveway in second with no problem. I love being able to wind out the gears!
The Jalopy Journal
