The truck is a 1957 3100 with a 4 speed floor shift Muncie SM420 transmission. The previous owner had transmission issues and installed a rebuilt transmission which I believe came from a '59. (59 printed in yellow paint on the case) Lots of issues repaired on the truck with the help of the forum. Lots of short round-the-block trips taken. Yesterday was the first day for a 20 mile trip to see how the truck was doing. According to the rebuilt speedometer we hit about 50 mph. All seemed good. Pulled into the driveway and a small puddle of transmission 90w appeared. Then pulled it into the garage with my intent to check it out today. Large puddle (12" x 8") under the transmission. It was not engine oil. Smelled like 90w and was clear. Coming from the front of the transmission. So off I went looking for availability of a front seal. From what I read, the 420 does not have a front seal. Correct? But I also saw a note that later ones might have had a neoprene front seal. So, does anyone know at which casting number, or even year, that a neoprene seal was used? Also, if this transmission is not supposed to have a seal, what has worn, and what is the remedy? I hope there is some good news out there. Thanks in advance!
I used Novak as they specialize in the Muncie SM 420. You can get everything you need there including the upgraded front seal that does require machining to your input shaft housing and all seals plus advice!
So, are you suggesting the transmission was overfilled or that if I keep the oil level below the bottom of the seal, then there is no real problem. BTW, I went through Novak documentation and it appears that the '59 should have the neoprene seal, it is just a major hassle to install it, i.e. pull the transmission.
Sounds to me that it was overfilled. Now being 1/2" below the fill plug, I'd just keep and eye on it.
Craig
My '50 Chevy 3100 5 window, '62-235cu, 3:55 rear My truck ....... Respect The Rust If I'm not working on my truck, '65 m00stang or VW camper, I'm fishing with the wife or smoking Salmon.
If the front seal was leaking, fluid would have to travel to the end / front of the input shaft main bearing retainer to leak out and it would drip down and exit out of the hole in the bottom of the dust pan and onto the ground. The 59 front bearing retainer did not have a weep hole.
I think I would bring the oil level back up to the bottom of the fill plug hole and then recheck the level the next time you drive it and see a "puddle". Unless the rebuilder failed to reinstall the oil slinger on the main bearing (input clutch housing) input shaft, there is no reason for transmission oil to be leaking out of the front of the transmission.
Earlier models 1948 -55 did not have the oil seal , but did have a weep hole at 6 o'clock in the bearing retainer housing to prevent fluid from getting near the clutch plate . What I've read is that the seal was added to address problems with fluid leaking in extreme cases where the truck was being operated in steep downhill grades or truck parked on a downhill grade.
Here's some photo's / illustrations that may be helpful. Feel free to private message me if you wish.
Ron - - Dusty53 1954 Chevy 3604 In the Gallery Forum "You can't dance with the Devil and then wonder why you're still in Hell." "They will forget what you've said, and they will forget what you have done but they will never forget the way you made them feel."
Guessing the problem got resolved. Always like hearing what was found and what was the solution.
Ron - - Dusty53 1954 Chevy 3604 In the Gallery Forum "You can't dance with the Devil and then wonder why you're still in Hell." "They will forget what you've said, and they will forget what you have done but they will never forget the way you made them feel."
