Transmission growls

[BobDeSoto]

I have a 1951 DeSoto Custom, fluid drive.

 

A couple of things:

I have to use the clutch to shift from 3rd to 4th.  Car downshifts at a stop sign normally.

If I don't use the clutch when it is supposed to shift by lifting on the gas pedal it makes a tremendous grinding noise as if the transmission would

just fall out the bottom of the car.  Once in 4th it will occasionally slip out of gear so if I Iet up on the gas it goes back in gear and is fine.

Also,

At times it is very difficult to back up.  I have to really give it the gas in order to move.  I don't think this problem is the emergency brake but

it could be I suppose.

I've owner the car for 30 years and nothing has changed.

 

 

[keithb7]

Bob the transmission noise could be caused by a couple of things. A good start to troubleshooting the repair is understanding how it works.

The transmission needs signals from various sources to work properly. Your problem could be related to electrical, mechanical or hydraulic problems.

Have you checked your tranny oil level? It's important. Low could mean the piston is not able to fully engage a shift. A partial shift could lead to gear clashing and the awful noise you are hearing.

 

If you are inclined here is some great reading that will help you.

 

http://www.imperialclub.com/Repair/Lit/Master/023/Cover.htm

 

http://www.imperialclub.com/Repair/Lit/Master/012B/cover.htm

 

http://www.imperialclub.com/Repair/Lit/Master/024/cover.htm

 

My initial thoughts are the tranny is trying to shift so the hydraulic pump, valve, and cylinder should be ok. 

 

Lastly, I put this video together to help people understand how the tranny works. Perhaps this will help a little in understanding things: 

 

Edited March 19, 2020 by keithb7

[BobDeSoto]

Thanks, I'll read it all.

 

 

[Tom Skinner]

There is also a Transmission Selenoid with a fuse in it. Check the Fuse, if Burnt Replace.

Check all wiring for breaks and good connections. Check Tranny Fluid Level, Fill if necessary.

It is probably one of these three issues as Fluid Drive Transmissions are usually bullet proof.

Tom

[Dodgeb4ya]

Probably the blocker ring and sleeve are worn severely... 

Oil pump design changed in 1951 are can be pone to wear..

Causing too low of oil pressure behind the piston...popping out of direct high range gear.

Popping out of gear. (big bang kicking back to low) tears the teeth off the direct speed blocker ring, sleeve and input shaft.

Not a good thing.

Also as mentioned if oil level is low same problem can occur...no oil to push shift piston forward all the way for a complete upshift.

 

Edited March 20, 2020 by Dodgeb4ya

[Tom Skinner]

Bob,

There is also a Transmission Screen that can be cleaned while refilling the Tranny.

Tom

[Dodgeb4ya]

Filter screen access plate at rear of trans....the round tubular screen will typically have some brass and metal in it....should not be a lot though.

 

Edited March 23, 2020 by Dodgeb4ya

[MarcDeSoto]

In addition to the Master Tech booklets, there are also the MTSC filmstrips that went with the booklets.   MyMopar.com  has a whole library of these booklets and filmstrips online.  Here is the one for Troubleshooting the semi-automatic transmission from 1949.  They also have the filmstrips for the M-5 transmission from 1948 if you own a 46-48 Chrysler or DeSoto.  

 

http://www.mymopar.com/index.php?pid=382