Johnathin Posted May 2, 2020 Report Share Posted May 2, 2020 I have a 1949 Desoto custom. She's got transmission problems. As in it won't stay in 2nd gear. It has the fluid drive tip toe trans. It starts out fine . shifts into second and go's for a while then pops out of gear with a loud clunk. I have taken it into a shop and it looks like the pump is bad and the housing and syncros also the speed blocking ring. Thats what they're telling me. I don't know that much about transmissions. Anyway We are not finding any parts for this trans. Can anyone steer me in a good direction where I might find parts?. Or someone who can machine the extention housing?. Or possibly buy one in good condition? Thanks Quote Link to comment Share on other sites More sharing options...
greg g Posted May 3, 2020 Report Share Posted May 3, 2020 Is this happening in low range??? The transmission was actually designed to use the high range for normal driving. Low range was intended to be used in low traction situations or to use engine compression braking on long steep down grades. The system was meant to provide clutch less driving on the road or street once high range was selected. What happens in high range? Quote Link to comment Share on other sites More sharing options...
greg g Posted May 3, 2020 Report Share Posted May 3, 2020 (edited) A friend had a 50 DeSoto in highschool. If I remember 2nd gear in low range was a only good for 18 mph. Think of it as a dual range power glide.The Imperial Club website has a lot of semi auto trans info in its repair section. Edited May 3, 2020 by greg g Quote Link to comment Share on other sites More sharing options...
Dodgeb4ya Posted May 3, 2020 Report Share Posted May 3, 2020 If Jonathin is being advised correctly.. Yes it is true there could be a case of too low of oil pressure caused by a worn oil pump..pump pressure needs to be at least 40 lbs. Low oil pressure will cause banging or popping out of automatic upshift into high gear ........in either low or high range If this happens a few too many times the direct speed blocker ring, sleeve and input shaft teeth get rounded off. Once that happens the M6 trans will not stay locked in direct high gear..2nd or 4th gear. If the trans 10W oil level is low it can also bang out of gear on auto upshifts too. ****Transmission oil level must be checked first to be sure it's full before a fatal diagnosis! If the rotor oil pump gears are worn and also the pump housing (part of the extension housing) it might be best to find another transmission. Any of these parts can be very hard to find new and will be very costly if found. Shown are the direct speed blocker ring, clutch sleeve and input shaft. 1 Quote Link to comment Share on other sites More sharing options...
James_Douglas Posted May 3, 2020 Report Share Posted May 3, 2020 11 hours ago, Dodgeb4ya said: If Jonathin is being advised correctly.. Yes it is true there could be a case of too low of oil pressure caused by a worn oil pump..pump pressure needs to be at least 40 lbs. Low oil pressure will cause banging or popping out of automatic upshift into high gear ........in either low or high range If this happens a few too many times the direct speed blocker ring, sleeve and input shaft teeth get rounded off. Once that happens the M6 trans will not stay locked in direct high gear..2nd or 4th gear. If the trans 10W oil level is low it can also bang out of gear on auto upshifts too. ****Transmission oil level must be checked first to be sure it's full before a fatal diagnosis! If the rotor oil pump gears are worn and also the pump housing (part of the extension housing) it might be best to find another transmission. Any of these parts can be very hard to find new and will be very costly if found. Shown are the direct speed blocker ring, clutch sleeve and input shaft. I agree. As someone who has rebuilt several of these transmissions... I have found that the oil pumps tend to get worn but still produce enough pressure. I have seen in a couple of instances that the problem being described is not the oil pump but a bad shuttle valve. The spring is bad for the valve or bore had issues so it does not slide properly. The Direct speed blocker ring, the clutch it goes into and the input shaft are well documented. If they get messed up, the thing will never work correct. One thing to add. The clearances listed in the repair books ARE CRITICAL to having a very good functioning transmission versus just and OK functioning one. If something calls for a particular clearance, try to get it right in the middle of the specification range and not on either edge of it. Contact me directly and I can email you a bunch of items that may help. James. Quote Link to comment Share on other sites More sharing options...
Johnathin Posted May 5, 2020 Author Report Share Posted May 5, 2020 On 5/2/2020 at 9:36 PM, greg g said: Is this happening in low range??? The transmission was actually designed to use the high range for normal driving. Low range was intended to be used in low traction situations or to use engine compression braking on long steep down grades. The system was meant to provide clutch less driving on the road or street once high range was selected. What happens in high range? On 5/2/2020 at 9:44 PM, greg g said: A friend had a 50 DeSoto in highschool. If I remember 2nd gear in low range was a only good for 18 mph. Think of it as a dual range power glide.The Imperial Club website has a lot of semi auto trans info in its repair section. Thanks for your input. I'm trying to learn how to work this forum, sorry I didn't respond sooner. I will see if I can find the Imperial website. My trans works fine in high range. pops out of 2nd gear in the low range. makes a scarry clunk noise and is free wheeling then. Quote Link to comment Share on other sites More sharing options...
Johnathin Posted May 5, 2020 Author Report Share Posted May 5, 2020 On 5/2/2020 at 10:44 PM, Dodgeb4ya said: If Jonathin is being advised correctly.. Yes it is true there could be a case of too low of oil pressure caused by a worn oil pump..pump pressure needs to be at least 40 lbs. Low oil pressure will cause banging or popping out of automatic upshift into high gear ........in either low or high range If this happens a few too many times the direct speed blocker ring, sleeve and input shaft teeth get rounded off. Once that happens the M6 trans will not stay locked in direct high gear..2nd or 4th gear. If the trans 10W oil level is low it can also bang out of gear on auto upshifts too. ****Transmission oil level must be checked first to be sure it's full before a fatal diagnosis! If the rotor oil pump gears are worn and also the pump housing (part of the extension housing) it might be best to find another transmission. Any of these parts can be very hard to find new and will be very costly if found. Shown are the direct speed blocker ring, clutch sleeve and input shaft. Thanks for your info. I did check the oil level and had to put about a pint in. but that didn't help much. I will forward this info to the shop that is working on my car. So far no luck in finding parts. Thanks again. 1 Quote Link to comment Share on other sites More sharing options...
Johnathin Posted May 5, 2020 Author Report Share Posted May 5, 2020 On 5/3/2020 at 10:37 AM, James_Douglas said: I agree. As someone who has rebuilt several of these transmissions... I have found that the oil pumps tend to get worn but still produce enough pressure. I have seen in a couple of instances that the problem being described is not the oil pump but a bad shuttle valve. The spring is bad for the valve or bore had issues so it does not slide properly. The Direct speed blocker ring, the clutch it goes into and the input shaft are well documented. If they get messed up, the thing will never work correct. One thing to add. The clearances listed in the repair books ARE CRITICAL to having a very good functioning transmission versus just and OK functioning one. If something calls for a particular clearance, try to get it right in the middle of the specification range and not on either edge of it. Contact me directly and I can email you a bunch of items that may help. James. THANK YOU James. I am trying to learn how to work this forum. Sorry I didn't get right back to you. I will send this info to the shop as it will help. Still no luck in finding parts. We will be contacting you. Thanks again. Quote Link to comment Share on other sites More sharing options...
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