1949 Desoto Gear changing problems

[Desoto1949]

@Dodgeb4ya Hello Bob H ? , I need help on my gear changes for a 1949 Desoto custom. I was sent here from a buddy named Rocky aka ( Flat Six Fix)from the h.a.m.b saying you can help out!

[casper50]

What's your problem?

 

[Desoto1949]

If any one else can help I'll gladly appreciate it thanks ! 

[Desoto1949]

1 minute ago, casper50 said:

What's your problem?

 

I'm trying to figure out why my vehicle stalls when I'm on the road . if it's because of the gear changes that doing wrong or something with the transmission .  I know that this desoto has a different transmission so when I put it in high range I'm good to go but I'm not sure if it shifts from 3rd to 4th 

[Desoto1949]

And a little while after it ends up slowing down and it turns off

[normanpitkin]

sounds like my problem! car shifts from 1st to 2nd fine but then when it tries to change from 3rd to 4 th it just dies  ,as if the interrupter switch is going on? Have check all the wiring and the relay HRE 4001 may be faulty ,have you checked your  relay ,its on the firewall?

[dpollo]

Try disconnecting the wire that goes from the  transmission control circuit to the points side of the  ignition coil . This will prevent the ignition from being interrupted. If that prevents stalling then try to find a shop manual  which gives the diagnosis and testing for the Simplimatic .  My 49-52 manual WM 4247 is quite thorough in this regard but too detailed to get into here.   

[Desoto1949]

@dpollo @normanpitkin will do... here's a clip of my vehicle https://www.youtube.com/watch?v=FIQs9LU8vAo 

[casper50]

Desoto1949 very nice car.  Imo the under hood wiring lets it down.  If it was cleaned up a bit and straightened out your engine bay would look much nicer.

[Dodgeb4ya]

The car has been converted to 12 volts. All bets are off regarding as to why the car dies or won't possibly upshift . 

That M-6 trans must be wired 100% as designed for the car to shift right and have the no more than 6 volts.

Yes as mentioned.... disconnect all the wiring at the 3" square resistor/ circuit wire box ( it's supposed to be on the air cleaner support bracket).

If it's not factory I'm of little help!

[James_Douglas]

Unless you want endless problems with the M6 transmission, convert the car back to 6 volt positive ground.  I have run my 1947 Desoto for 15 years here in San Francisco (proper not the burbs) and 6 volt works just fine.  As long as it is maintained correctly.

 

My 1949 Desoto is also 6 volt positive ground.

Use a lithium 12 volt emergency starter battery with a radio, cell, or other in the car if need be. No need these days to convert unless you are changing the car over to a modern engine.