New member really needing some fluid drive transmission help!

[ledfootslim]

Hey everybody, first off, I have really dug being part of this group, but now I need some help from all you knowledgeable ninjas of mopar- I recently finished thge engine work on my 1948 Desoto S-11. Shaved the warped head ninety thousands, forty thousands overbore, split the manifold, etc, just pretty much hopped it up like they would have in the early days of hot-rodding. It runs pretty swell, but I just had it out driving around the dirt roads where I live, and when I made it to some blacktop, it started getting funny. I could get it up to about forty or so maybe, but then it would start sounding like the engine was revving way too high, like I was going about ninety. Lifting my foot off the gas wouldnb't shift it, using the clutch didn't do anything, I don't know if it is still something wrong with my engine, or if the transmission just isn't shifting. I stick it into first for getting started up the hill in front of my shop, then clut h and shift into high when it levels out. Presumably, it should shift at about 23 miles and hour from most accounts, by just lifting your foot off the gas,and with a resounding clunk, from what I've heard. Mine does not:-) . I pulled back the carpet, and found there were two ways to access the tranny from above, via two ports on the right side of the hump. One gives access to the three solenoids, and a plug,and the upper one gave access to a large rubber plug, which I popped out, bumped the starter until the plug lined up, and found that that hole was full of the proper light oil. Could any give any help here!?! What else should I check? Should I be driving it differently? What does the plug beside the three soylenoids access? It consists of a cap, a spring underneath that which sets on a little stem, and no fluid at all that I can see. Sorry for the lengthy spiel, but I was wanting to show this girl by the fourth of July. I've searched everything the web has to offer, so I hope you guys can give me something fresh. Thanks!

[Don Coatney]

What does your service manual say?

[_shel_ny]

Some possible areas to check.

 

 

Edit: note- item 18 b. is referring to the transmission itself, and not the fluid coupling accessed through the floor.

 

Edit 2: The info shown is for the M6 transmission. Your M5 may follow the same basic principals.

Edited June 30, 2014 by shel_ny

[_shel_ny]

This may help.

 

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

[ledfootslim]

None of this really sounds like my problem- I really thought it might be the governor not letting me shift to fourth, but I don't think it would go 45 mph or so without shifting. I know this isn't a race car, but shouldn't it have more get-up-and-go than that? Has anyone else had a problem similar to this? Also, I had all the throttle linkage and everything off for the rebuild; is there something I could have done that prevents it from shifting whenever I lift my foot?

[Don Coatney]

Once again what does your service manual say?

[ledfootslim]

It didn't have a service manual. And my 1935- 1949 MoTors manual said that you check the fluid by prying off a screen and then turning the engine over till you can see the plug. The only screens I could find were two on the bottom and side and you really couldn't put liquid in them, but I think there may be another on top. Surely they wouldn't make it so you'd have to take the floorboard out to check the fluid!?!

[_shel_ny]

Two fluids.

 

Fluid drive coupling:

 

Seems you already checked that as described in your first post.

 

Transmission itself:

 

should have square head plugs on the right side.

Serviced from under the vehicle.

[_shel_ny]

I have seen posts stating that all the shop manual information is available free on line, and that there is no reason to buy a shop manual, but I do not know how to access that information, and found the purchase of the manuals (less than $30-  prices vary) to be valuable for the operation and maintenance of both my 1951, and 1948 Dodges.

[ledfootslim]

Hey thanks shel! I'll check that tomorrow! Is that the one that takes 90w oil?

[ledfootslim]

Okay guys, shes dry as a bone! I got under there amd took off the middle plug from the diagram Shel posted, and there was no juice at all that I could feel. Is this the one that takes 90W oil?

[ledfootslim]

Okay, I lied. I took out the drain plug after my last post, and there was maybe a little under a quart of oil in it. I am gonna pick up a few quarts of 85-130 tonight when I go get tires on my Pontiac. Keep your fingers crossed that this will solve

my problem, and that I didn't screw something up! :-)

[DJ194950]

Did I miss something about using 10wt. that was in the pic. posted by shel_ny on where the plugs where?

 

DJ

[ledfootslim]

Did I miss something about using 10wt. that was in the pic. posted by shel_ny on where the plugs where?

 

DJ

Totally.......I have always heard to use 90 weight for the actual tranny and 10 for the fluid drive coupling.....right guys?

[_shel_ny]

Totally.......I have always heard to use 90 weight for the actual tranny and 10 for the fluid drive coupling.....right guys?

Wrong    the M5 and M6 transmissions take 10wt oil as indicated in the diagram Probably 2 3/4 pints

 

Plain old 3 speed manual used the heavier gear lube in the 48. Later manuals recommend a lighter oil.

 

Edit: fluid coupling uses an ISO 32 hydraulic oil that has a viscosity around 10W if my memory does not fail. There have been many posts about the ISO 32. And thoughts about leaving it alone if the level is OK.

Edited July 2, 2014 by shel_ny

[Plymouthy Adams]

he was just on chat and stated it is fluid coupler with standard three speed..

[_shel_ny]

he was just on chat and stated it is fluid coupler with standard three speed..

With a solenoid, governor, and interrupt sw. ???(referred to as 3 solenoids in the 1st post)  and may not be shifting into 4th?

Edited July 2, 2014 by shel_ny

[Plymouthy Adams]

just sated what he said on chat...I have never had an actual visual of his car....we can only advise on the fact given at the time...it is their responsibility to provide accurate details..else we all just guessing

Edited July 2, 2014 by Plymouthy Adams

[_shel_ny]

just sated what he said on chat...I have never had an actual visual of his car....we can only advise on the fact given at the time...it is their responsibility to provide accurate details..else we all just guessing

Correct

[Plymouthy Adams]

If for some reason he stated the wrong information on chat then I will say that my advise is not what it would have been if he stated he had a M5/M6......it is very important that one knows the names of the various components in their car...I will also state that I never read this thread till after the chat....and while the hint that someone posted that the manuals are online I also have not seen a courtesy link posted nor have I come across them in my searches...those links would be a real valuable source of information to our readers here...the lubrication section of the manual is very clear on the lubes needed throughout the many service points on each car...and their suggested interval period

 

by reading the above...seems he is owner of a M series.....as for the location of the oil check for the coupler..yes it is by way of the floorboard...

Edited July 2, 2014 by Plymouthy Adams

[ledfootslim]

OK, now I'm confused again. I have a 1948 Desoto S-11 with a fluid drive transmission. It seems that Mopar slapped fluiddrive on just about anything that sat still, so there are a million different sources saying a million different things. It isn't a three speed, but the "regular" low and high range that you read about. I don't know the differences between the M5 or the M6. I just know there are only three positions in the tree: reverse, low or power range as they call it, and high or driving range. In my MoTors manual it says to fill the fluid drive coupling with 10 weight oil, and the transmission with 90 weight. The oil that I drained out of the tranny didn't look very thick though. Please bear in mind guys, I'm eighteen and this is my first project of my own. My grandad doesn't have any experience with Mopar transmissions, so I would love a definite answer from one of you guys!

[ledfootslim]

Here are just a few of the sources I found. Hoope you guys can view them and see which ones ring try, and which ones seem full of manure!

[Don Coatney]

First off there is no such thing as a Fluid Drive transmission. Fluid Drive is a hydraulic coupling and many different transmission can be bolted on behind it. The Fluid Drive hydraulic coupling uses ISO 32 fluid available at most tractor supply stores. Ten weight oil is not recommended for the fluid drive coupling.

 

There are many variations of transmissions that the factory used with fluid drive. I do not know what one you have. I do suggest you Google the "allpar" website and read everything you find there about transmissions.

[ledfootslim]

Thanks Don. Yes, I know there is no such thing as a Fluid Drive transmission, just a slip of the keyboard. From what I have read, it seems that I have either an M-5 or 6. The fluid I drained from it was definitely lighter than ninety weight, so I gonna grab some ten and return the 90 weight I bought.

[greg g]

Check out the Imperial Club website especially the repair section they have a lot of good stuff regarding the care and feeding of the Semi Auto trans, including trouble shooting guides for the mechanics of the time.