does the P4 transmission have synchronized gears? It shifts better than my Model A Ford, but still requires a double clutch at times or a very slow gear change.
What weight gear oil should be used in this transmission?
What should be used in the differential?
Thanks in advance,
Phred
Second and High are synchronized. Low is helically cut and it should be possible , after a bit of practice to get back into low without double clutching. It was so in my 37.
80-90 gear oil is what is used. Some say to avoid Hypoid oil if you can, it is for the differential and may be a bit to slippery for good synchro action, however, I have used it without any problems.
the model A trans, while typical for its era was pretty crude compared to the 37 Plymouth.
You might want to check that your clutch is releasing all the way. I had a situtatio where to get into reverse of first, Ihad to shift into 2nd, this apparently stops any movement of the input shaft. then it would select low and revers with no trouble, I went under and lengthened the rod to the throwout fork and it made things much easier.
First and reverse are not synchronized so you need to come to a complete stop to get into those two gears. Second and third are synchronized but you still have to shift somewhat slowly. If you try to slam the shifter from one gear to the next, it will grind.
Phred,
All the DPCD 3-speed passenger car gearboxes of '35 and later vintage have synchronising cones on second and top gears.
The low and reverse gears are 'helical', as opposed to 'straight-cut', which reduces gear noise.
Its obvious that you must be at a dead stop to engage reverse.
When backing the car just after it has been started from 'dead cold', i.e., it hasn't run for a few hours time, put the gearbox in second or top gear momentarily (just a second or so, long enough to engage the gear), which uses the synchro cone to surely stop the first motion shaft. (this is the effective equivalent of a 'clutch brake' which is used on heavier equipment, but not on cars)
Always nipping into second or top for a second to surely stop the first motion shaft before engaging reverse is actually a good habit to form, every time you engage reverse, as it saves wear on the reverse gears. The reason for this is that even tho you've disengaged the clutch, the first motion shaft, with the weight of the clutch disc, will have some momentum, and take a small amount of time to come to a stop.
As for low gear, you can double-clutch into low at any reasonable forward speed, just as you would with a non-synchronised 'crash box'. This is purely a matter of understanding, and 'making friends with' your gearbox. Another option is to 'single-clutch', meaning that you let off on the throttle until the gearbox goes into 'float', at which time your gearset will slide gently into neutral with the clutch still engaged. Then, you open throttle as needed to bring the engine up to a suitable speed, disengage the clutch, and shift into low.
With practice, you'll find that you can usually just shift 'in float', without having to use the clutch at all, once you are moving. This saves fatigue on your left leg, but it does take a serious amount of practice until you can 'feel' your engine speed relative to road speed, and 'feel' when the gearbox is 'in float'. 'In float' simply means that you have brought the engine speed exactly to that which corresponds to the road speed, so that the gearbox is neither 'driving' nor 'decelerating', but 'floating' between those two conditions. When in float, the gearset can easily be slipped into neutral, then the engine speeded up or slowed down as may be needed to have the engine speed match the road speed in the gear you intend to select. As a generality, its still safer to 'double clutch' or 'single-clutch' when down-shifting into low, as on a really steep grade.
cheers
Carla