rumble seat (8/20/2000,5:14:53 PM)

Transmission gears. This will concern `39 thru `48 transmissions only although some `49 up gears will fit and will be included if I remember. Ford used mainly 4 different trans gear sets to obtain different low and second gear ratios. Two are the infamous Lincoln-Zephyr gears and two are Ford/Merc. This was done to permit using a rear end ratio to give a specific area of driving some good performance for the particular combination of engine, weight, etc. Thus they designed a tall first gear for a car with a low rear end ratio that would be driven primarly in town for quick stop light performance and would have good high gear pickup. Or they designed a low ratio first gear for a car with a tall rear end ratio that would be driven primarily on the highway, but, because of the low first gear it would accelerate quickly at a stop light... it just had a big drop from second to high and you`d usually shift when turning a corner. All high gears in these 3 speed trans drive directly through the trans (don`t transmit power through the cluster gear) and, therefore, do not reduce or multiply the ratio.... they all remain a 1:1 ratio. Now let`s get down to some basics. Transmission gears are usually referred to by the number of teeth on the Main Drive Gear (MDG) and the number of teeth on the forward most gear on the cluster gear. There are 4 different gear sets. The 15/29, 16/28, 18/26, and the 19/25. The last two are Lincoln gears. All 4 types use the same low/reverse sliding gear. The 15/29 and the 16/28 use the same second gears. The 18/26 Lincoln uses a unique second gear. As does the 19/25 Lincoln set up. All 4 types use the same synchro drum and block assembly. And the plate type on the `46-`48 is the best and easiest to use and much superior to the earlier years. Reverse idlers are the same for all 4. Out of space so will continue shortly...rumble seat

rumble seat (8/20/2000,5:40:31 PM)

Transmissions II. The 15/29 set has a 3.11 first gear and a 1.77 second gear. Real stump pullers, but will assist when mixed with a tall rear end (like 3.54 gears) to have good performance at a stop light. The 16/28 set has a 2.82 in first gear and a 1.60 in second. Good selection for pulling lower gears around town (like 3.78 or 4.11 gears) and will have good to excellent stop light acceleration. Lincoln gear set 18/26 has a 2.33 first gear and 1.58 second. Good selection for pulling low gears around town (like 4.11 or lower gears) but will sacrifice highway performance. Lincoln gear set 19/25 has a 2.12 first gear and a 1.44 second gear. Good selection for pulling low gears around town (like 4.11, 4.33, 4.44, and lower). If you`re running without and OD, and want to run 3.54 gears or 3.27 (Ford made some I saw in Texas in the early 1950`s) think about using a 15/29 set. This will give good performance at a stop light with excellent cruising ability on the road. If you`re running 3.78 think about running either a 15/29 for rabbit type starts or a 16/28 for even drop with each gear. The 15/29 would be better if your car were heavy whereas the 16/28 would be better if it were light like an early coupe or roadster. Of course engine mods also affect the performance and should be considered. The Lincoln gears are usually too much if you`re running anything taller than a 4.11 or you have big bore and stroke. The 19/25 set produces unGodly speed in low and second, but rpms hardly drop at all when going from second to high. The 18/26 Lincoln gear has less gear drop and is a better gear setup in my opinion. Lincoln gear sets are nearly impossible to find for anything less than $1500 if they`re in good shape. More to follow... rumble seat

rumble seat (8/20/2000,6:07:57 PM)

Transmissions III. I`d run a 15/29 when using 3.54 or 3.27 gears to give good acceleration at stop lights and have a good highway gear. This would be on a light to medium weight car with minor engine mods. Problem is the long drop between second and high. Just have to rev it a little tighter in second. I`d use a 16/28 when using 3.78 gears to give fair acceleration at stop lights with fair highway cruising. This would be for a medium to heavy weight car with minor engine mods. I`d use Lincoln 18/26 when using 4.11 or lower gears to give good acceleration at stop lights, but would sacrifice highway cruising. This would be in a medium to heavy car with minor engine mods. The 19/25 Lincoln gears would be good when using 4.33 gears or lower, but with lousy highway cruising. Again for medium to heavy weight cars. OD`s change all of this and you can gear them in the basement to have an intersection screamer if you want and still have excellent highway cruising. Just remember the more rpms you turn the engine, the more heat it`ll produce. Something to think about if you live in a hot place or you`re going to drive it across a desert from time to time. In my opinion, OD`s are the way to go. More to come...rumble seat

rumble seat (8/20/2000,6:22:16 PM)

Transmissions IV. Ford, and others, mixed cases and gears so you can`t tell what you`ve got until you count the teeth on the cluster and main drive gear. The `39-`48 second/high synchro drum is wider than the pre-`39 units. The second/high shift fork is different too. The pre-`39 cannot be ground wider for use against a `39-`48 synchro drum because the second/high fork has a slight offset the `39 doesn`t have and will push the drum too far forward on the main drive gear (I think that`s correct.... another senior moment!). You have to use the second/high shift fork off a `39-`48. The ones off a three speed floor shift pickup transmission to `51 fit it seems to me (so will the top). The truck 3 speed transmission cases are stronger than the passenger cars. You can tell a pickup trans case by its raised casting from the drain plug towards the front of the transmission. This makes the case stronger. All `37-`39 trans cases are the same, but the shift tops are different. Just be aware the shift top has to match the synchro drum. And the MDG (main drive gear) has to match the top too. Watch for a narrow bearing collar to identify pre-`39 MDG. Basically, use `39-`48 gears and don`t try to mix them with earlier years. It`s a mess. More later.... rumble seat

rumble seat (8/20/2000,6:35:27 PM)

Transmissions V. The cluster shafts and trans cases wear over the years from being torn down. Then they weep gear grease into the bell housing. This will eventually get on your clutch and cause chatter at the very least. A cure I use after trying O rings etc is to use a cheap expansion plug. Remove the throwout bearing collar shaft. Since these cases are very hard (case hardened) take case to machinest and have the cluster gear hole drilled out to 1 inch diameter with an end mill. You want a flat surface at the bottom to seat the expansion plug against. Drill it exactly 0.100 inches deep. Pick up a 1 inch expansion plug. Grind off 0.120 inches off the end of the front of the cluster shaft. Assemble trans. When assembled, coat the expansion plug with #1 Permatex and insert it into the cluster hole against the seat you`ve machined. Now expand the plug with a flat punch. It won`t leak now. Reassemble the cross shaft etc. On `49-`53 Ford cases (not Merc) the trans case is square and has a flat mating surface that goes against the bell housing. Cut a 0.020 inch gasket that is snug (and I mean SNUG) around the MDG bearing retainer and covers the entire front of the trans. I use some upholstry adhesive to hold it in place (can be used several times since this adhesive doesn`t harden). Install trans and the gasket seals the entire front of the trans and won`t leak.... more later.... rumble seat.

rumble seat (8/20/2000,8:32:49 PM)

Transmissions VI. Use half sealed bearings on the MDG an the main output shaft. These restrict the oil flow and will lessen leaks out the front and back. The end play between the main shaft and the output bearing shouldn`t be more than 0.015 inches. The main shaft is the shaft the low/reverse slider, the second gear and the synchro hub assembly are installed on. This is measured between the bearing and the teeth the low/reverse slider travels on. If there is excessive end play, it will cause the trans to creep out of gear on compression and/or power. Speaking of this, the internal teeth on the synchro drum should be diamond shaped and pointed. If their not diamond shaped, they can be made pointed again with a Dremel or something similar. This helps synchronize the shifting and it also helps keep from jumping out of second on compression. On the trans top you can deepen the rail sockets the balls sit in to also help popping out of gear. You have to remove the rails to do this and take it easy when grinding them. If you get them too deep the trans top will lock in gear and not shift. Grind a little and test them. This really helps to keep them from jumping out of second under compression. I also remove the spacer between the rails on `39 floor shifters and replace it with the spring and detents from a `37-`38 top. This requires grinding new receivers in the inside of both rails directly opposite the ones on the outside. Grind these less than 1/3 of the way into the rail. Stretch the spring 1/2 inch and reassemble. This also prevents jumping out of gear, but does make them a little harder to shift until everything wears in. More later....rumble seat

rumble seat (8/20/2000,8:40:16 PM)

Transmissions VII. Cluster gear bearings are caged up through `48 Ford. 1949-`50 Mercs are also caged and are interchangeable. The cluster gears also interchange as do the MDG and their caged bearings. The `49-`50 Ford is not like their brother Mercs. They use needle bearings and different spacers that are installed using heavy grease and a dummy shaft. But they will work with any MDG `39-`48 if the teeth count is matched for the number of teeth on the cluster. The MDG from a `49-`50 will not work in these early trans. More later..... rumble seat

rumble seat (8/20/2000,9:04:26 PM)

Transmissions VIII. In 1951 Ford changed their gears completely. They went to diamond shaped teeth on the low/reverse slider and on the low and reverse gears on the cluster. The idler gear is different also. The spiral gears on the tail shaft are different pitch and the shaft is not interchangeable with earlier trans. The `51-`53 trans are easy to tell by looking at the shape of the teeth on the low/reverse slider and the low gear on the cluster. Overdrives starting in `51 also use the different trans main shaft. If you`re converting to an OD in a `49-`50 convertible or station wagon, be sure to get the solenoid with the OD. They are VERY UNIQUE, RARE, AND SUPER EXPENSIVE (try $500 and up for a used solenoid!). You can do some torch work on the mounting member to come up with solenoid clearances, but don`t recommend it without reinforcing it afterwards. I`ve heard a `51 passenger car OD will work in a `49-`50 convertible since the solenoid mounts lower and differently, but I`ve never tried it. Use 90w or 140w grease in these gear boxes. I know Borg-Warner says to use 30wt oil but there`s no way I`ll use this in any of these early transmissions. And I`ve got over 380,000 miles on one! I use straight 140w in my Lincoln geared `39 box, but don`t drive it a lot in cold weather. If I did, I`d go to 90w in the winter. I don`t use synthetic oil since it seems to leak out of places I`ve never seen before and I can`t stand leaks. The end finally.... rumble seat

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