I'm wondering if there's a possibility that gear oil from before the '50s might have been tackier than today's oil. Here's why.
I have two antique vehicles built without transmission input shaft seals. One is a 36 Plymouth and the other is a '57 Chevrolet truck. After operating the vehicles for a period of time with oil that had been in the gearbox for years, I replaced the oil. In both cases the gearbox which did not leak while filled with "old" oil started leaking after being refilled with new oil. Both vehicles had been parked for many years prior to me getting them and the "old" oil was indeed old.
I have been working on resolving this issue for many years with the '57. I have tried multi grade oil and single grade oil. I have used recommended weight oil and higher viscosity oil up to SAE 140W I have opened up the return passage in the transmission case, switched to a sealed front bearing, and installed a NOS oil slinger. I have tried adding viscosity improver, too. Currently I leave the transmission oil level about 1" low. No matter what I've tried, the clutch and inside of the bell housing gets oil soaked. I thought the issue was with this particular transmission until I changed the "vintage" oil in the Plymouth. About two weeks after the service that transmission began leaking, too.
While pouring bar and chain oil into my saw yesterday the thought came to me that maybe some aspect of old gear oil made it tackier, and that's why the engineers could get away without installing a front seal.
Thoughts?
I have two antique vehicles built without transmission input shaft seals. One is a 36 Plymouth and the other is a '57 Chevrolet truck. After operating the vehicles for a period of time with oil that had been in the gearbox for years, I replaced the oil. In both cases the gearbox which did not leak while filled with "old" oil started leaking after being refilled with new oil. Both vehicles had been parked for many years prior to me getting them and the "old" oil was indeed old.
I have been working on resolving this issue for many years with the '57. I have tried multi grade oil and single grade oil. I have used recommended weight oil and higher viscosity oil up to SAE 140W I have opened up the return passage in the transmission case, switched to a sealed front bearing, and installed a NOS oil slinger. I have tried adding viscosity improver, too. Currently I leave the transmission oil level about 1" low. No matter what I've tried, the clutch and inside of the bell housing gets oil soaked. I thought the issue was with this particular transmission until I changed the "vintage" oil in the Plymouth. About two weeks after the service that transmission began leaking, too.
While pouring bar and chain oil into my saw yesterday the thought came to me that maybe some aspect of old gear oil made it tackier, and that's why the engineers could get away without installing a front seal.
Thoughts?
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