Four Speed Marks It’s Spot

Four Speed Mark’s It’s Spot


larry hutchison, wadesville, IN, 1964 plymouth fury 361

My tranny 833 appears to leak oil around the reverse idler shaft. Is it possible to replace the seal (assuming it has one) with out a total dismantle of the tranny.


Larry, there is no reverse idler shaft seal. The front end of the shaft is totally inside the transmission — immersed in oil. The rear end of the shaft is “trapped” by the extension housing, and is effectively sealed by the housing gasket. So there’s no way for the reverse idler shaft to leak. Your problem is elsewhere!

Most leakage is from one of four areas:

1. Main drive pinion seal (i.e., “input shaft”) — this causes a clutch housing drip
2. Output seal
3. Housing vent – especially on early models such as yours that had no baffle.
4. Backup lamp switch

Of course, the shift lever seals can leak, as well as the side cover and extension housing gasket, and the reverse dentent gasket, but these seldom leak except if damaged during assembly.

My guess, in your instance — based on proximity — is the backup switch. Get a newer one with the white plastic filler (instead of the OEM black coal tar seal).


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