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Hey! There's no drain plug for the differential on my 48 DeSoto!


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I crawled under my DeSoto today and could find the fill plug that faces forward on the middle front part of the diff, but no drain plug.  I checked my DeSoto manual and it showed the drain plug on the lower right section of the diff housing.  The part that faces the rear, but no drain plug there.  Has anyone else had this problem?  

48 desoto underc.jpg

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How about just removing one of the third member bolts?

If studs used then double nut and tighten nuts together and remove the stud to drain?

 

Just a possibility?

 

Hope you all had  a safe and enjoyable Christmas!

 

DJ

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(Tongue in cheek)

See how advanced Chrysler engineering was!

It took the rest of the industry till the 1980s to omit drain plugs!

lol

Sometimes the pinion seal has leaked enough that dust and oil coat the axle so you need to clean it to find the plug.

Not the fun job you might expect. How do I know this? An axle I was going to drain looked like it didn't have a plug til I removed the 3rd member and found the plug location from the inside.

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If you are talking about #25 in the pic, that's awful high up for a drain plug.  While I have not drained the gear oil in my 51, yet, I have done so in several 8 3/4.  None had drain plugs so you had to pop the third member free to drain it. 

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Loren, I think you are right.  The diff is very greasy with caked on black grease.  Maybe the drain plug doesn't stick out as far as I thought.  The bottom of the diff feels wet with oil, but not enough to drip on the garage floor.  Replacing that pinion seal looks like a major disassembly job!  

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6 minutes ago, Sniper said:

If you are talking about #25 in the pic, that's awful high up for a drain plug.  While I have not drained the gear oil in my 51, yet, I have done so in several 8 3/4.  None had drain plugs so you had to pop the third member free to drain it. 

Good point!  Maybe #25 is the fill plug?  The plug I found on the front facing part was a square bolt.  If that's not the fill plug, i wonder what it is?  

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1 hour ago, DJ194950 said:

How about just removing one of the third member bolts?

If studs used then double nut and tighten nuts together and remove the stud to drain?

 

Just a possibility?

 

Hope you all had  a safe and enjoyable Christmas!

 

DJ

Yep. Somewhere, probably in one of my service manuals, I read the way to drain was to remove one of the lower bolts holding the pumpkin on to the axle housing.

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1 hour ago, MarcDeSoto said:

Loren, I think you are right.  The diff is very greasy with caked on black grease.  Maybe the drain plug doesn't stick out as far as I thought.  The bottom of the diff feels wet with oil, but not enough to drip on the garage floor.  Replacing that pinion seal looks like a major disassembly job!  

 

Sounds like a great time to swap out that 3.9 ratio 3rd member for 3.73 or a 3.54.

It's the old "All I wanted to do is drain the swap, now I am up to my butt in angry alligators!"

You just wanted to change the oil and now you're rebuilding the rear end! lol

What ever you do, do not use an original style pinion seal. The modern ones (like from NAPA) are so much easier to put in and cheaper besides.

 

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Loren,  No need to swap out the rear end.  Most 121" WB 46-48 DeSotos had a 3.73 diff ratio as standard.  3.73 is stamped right on the housing.  The 3.53 ratio was what my Parts List calls "special".  The 3.91 ratio was standard on the long wheelbase models.  I've been crawling around again under the rear end and found what I think in the drain plug.  It was not on the housing or cover on the back, but on the diff carrier part on the bottom.  I was not able to unscrew it because it was a concave square bolt.  I had some square end male wrenches, but they were too big, except for the small one that was tapered.  It slipped.  A 1/4" square wrench was too small and a 3/8 wrench was too big.  So maybe a 5/16" square male wrench would fit?  

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You're right 5/16ths, I said 7/16ths. I knew it was in 16ths. If memory serves it is off the bottom on the passenger side. (got a 50/50 chance there)

My "True Value" hardware store has Key stock in 5/16ths (or Tractor Supply). You can use a key with a Crescent wrench or they may have the tool.

3.73 is good ratio I am glad you don't have to go on a hunt for one. The 3.53 I have came out of a 1956 Plymouth with a V8 and automatic (I think).

 

The bits from amazon are too small. I looked at what they offered and found one but they don't tell you what size it fits and the others are all metric.

If you want a tool I think Tractor Supply would be my first choice.

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These work very well. I own one:

I have MV7201. Great for pressure feeding or vacuum removal of fluids. 

 

https://www.skf.com/mityvac/products/fluid-evacuation-and-dispensing-equipment-and-accessories/fluid-evacuators

Edited by keithb7
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I also purchased one of these. About $5 US Funds. I needed it or my engine oil gallery plug removal.

 

https://bcfasteners.com/shop/jet-h3700-21-3-8-drive-5-16-square-oil-drain-plug-socket/

 

 

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On fluid extractors:

My usual ride is a Mercedes GLK 250. I am not keen on the dealer and use them sparingly. The last time I couldn't reset a limp home situation and neither could they! Finally they had M-B USA call Germany for the "Super Secret Reset Procedure". Which fixed a lot of annoying characteristics I didn't tell them about.

Anyway, the fluid they use in the transmission HAS to be changed every 70,000 miles and the closer you get to that mark the more it SLIPS.

Both the dealers and the independents NEVER drain the torque converter, which means the transmission will slip at 50,000 miles and they charge $800!

There is no fill tube/dipstick in these cars. You have to use a "fluid extractor" to fill them from underneath. SO what I am getting to is if you're sucking lube oil out of something get a nice cheap one from Harbor Freight. If you're filling something, you won't want to have anything but clean fluid in it....So I guess you need two of them! I bought a really nice one for the GLK and still saved a ton of money on the next service...oh and I drained the torque converter. The bastards. Since diesels have fallen out of favor, I may have bought my last new car so I am keeping this one till the wheels fall off.

I started thinking about it and it made me wonder how many HyDrive Plymouth owners got screwed by lazy mechanics who didn't bother to drain the torque converter. Ugh!

 

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One could probably make a tool in less time that it takes to overthink the problem. 
 

I did it just now in 25 minutes from a 7/16 bolt. The shank diameter is the same as kitty corner on the 5/16 square. File one flat until it’s 5/16 across the flat, mark as your reference and use that surface to eyeball the other three sides for filing. Leave a bit of shank so the square end protrudes from the socket. 
 

I’m planning to drain and fill my diff next week and figured I’d get a head start making the tool today. Joke’s on me — turns out the ‘47 D25 doesn’t have a separate drain plug. 

6F4CA524-EA21-4C5A-AE21-F12C7153608D.jpeg

8C9DC567-FE40-4D3A-968F-24A5D9006D72.jpeg

08BAD73A-DC86-48DB-972C-6FC6F1D866B8.jpeg

30768493-492E-4D52-A180-403B424AFA6A.jpeg

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17 hours ago, Loren said:

 

Sounds like a great time to swap out that 3.9 ratio 3rd member for 3.73 or a 3.54.

It's the old "All I wanted to do is drain the swap, now I am up to my butt in angry alligators!"

You just wanted to change the oil and now you're rebuilding the rear end! lol

What ever you do, do not use an original style pinion seal. The modern ones (like from NAPA) are so much easier to put in and cheaper besides.

 

May want to plan on a speedi sleeve if replacing the pinion seal. I heartily agree with Loren on the modern seal as opposed to oem.

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21 hours ago, bamfordsgarage said:

One could probably make a tool in less time that it takes to overthink the problem. 
 

I did it just now in 25 minutes from a 7/16 bolt. The shank diameter is the same as kitty corner on the 5/16 square. File one flat until it’s 5/16 across the flat, mark as your reference and use that surface to eyeball the other three sides for filing. Leave a bit of shank so the square end protrudes from the socket. 
 

I’m planning to drain and fill my diff next week and figured I’d get a head start making the tool today. Joke’s on me — turns out the ‘47 D25 doesn’t have a separate drain plug. 

6F4CA524-EA21-4C5A-AE21-F12C7153608D.jpeg

8C9DC567-FE40-4D3A-968F-24A5D9006D72.jpeg

08BAD73A-DC86-48DB-972C-6FC6F1D866B8.jpeg

30768493-492E-4D52-A180-403B424AFA6A.jpeg

Home made tools are worth gold, hands down everytime. :)

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On 12/28/2020 at 2:45 PM, DJK said:

May want to plan on a speedi sleeve if replacing the pinion seal. I heartily agree with Loren on the modern seal as opposed to oem.

I wish I had seen that tip before replacing the pinion seal on my Chrysler this summer. I got it off ebay for a decent price but now it's started leaking again after I sucked out the who knows how old fluid and installed some new clean stuff. I pulled the vent off the axle tube and cleaned it out as it was pretty gunked up, but I still get a steady leak from the pinion even while just sitting in the garage. My only other guess is maybe it would need a speedy sleeve and/or the seal I installed is faulty.

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