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Spline shaft replacement advice needed.


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Hello:
My 50 Buick Super has the familiar Dynaflow leak that fills up the rear end with tranny fluid.  I’m about to tear into the torque tube to replace the spline shaft seal.  Not disassembled yet, but viewing from the outside, the torque ball itself seems dry and to be in good shape.  

 

My question is this: will replacing the spline seal eliminate the source of leak down the torque tube to the rear end, or should I be searching for another leak “further up the line” that may be “feeding” the leak at the spline shaft seal?  I'm trying to determine why fluid is being pushed past the spline shaft with enough force to make the seal fail.

 

I really only want to do this once….  Any recommendations about sourcing the best quality parts to use?  Steele vs Bob’s Automobilia Vs ???.

Thank you.

David in Santa Cruz, CA

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On our ‘56, the shaft seal was the real problem, not the torque ball itself. It looked like someone had installed the wrong seal decades ago. 
 

When we bought our tq ball kit, it had the wrong seal too, so we acquired one locally. 

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Yes. That is all you need to do for that problem. You will need to re-seal the torque ball retainer upon reassembly. 
Why? Because while I have installed several spline shaft seals without removing the rear end, you can’t pull back the rear without at least loosening the retainer. 

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When you perform the work, use guide bolts(as shown in the manual) to  assure the two assemblies mate without buggering up the newly installed  seal.   I get bolts from the hardware store and cut the heads off.   

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Just curious here. How did you first notice the rear was filling up with tranny fluid ? Leakage around the differential cover, fluid oozing out rear axles onto drums ? Or just low reading on the dip stick.

 

I was thinking of tapping in a short 3/8" pipe in the end of the torque tube to intermittently check for fluid passing the spline shaft as other owners here have suggested.

 Thank you !

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Thanks all for your info re: the spline shat seal.  Any additional info is welcomed.

 

Kestral: the big (and expensive) clue to the leaking spline shaft seal is tranny fluid saturating your rear brakes.  Eventually the fluid gets pushed past the rear axle seals and drips into the brakes, ruining the linings. 

Usually you'll see (from under the car w/o taking the wheel off)  wetness on the backing plate and tire.  This happened on my 57 wagon as well as the 50 Super.  Once the shoes are soaked, you've got to toss 'em....I even tried boiling them in a pot of water....but the fluid keeps seeping out....linings absorb like a sponge.

 

Regarding the 3/8" pipe, I've done exactly that, drilled and tapped a small hole in the torque tube, then fitted a shortened brake line to it,  just ahead of the differential so the fluid could drain out, before forcing its way into the diff.  Not a complete solution....... but a fluid soaked driveway is easier/cheaper to deal with than a brake job.   Hope that helps.

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Thanks Roadmaster_56. I replaced both rear wheel bearings , inside and out last year. The brakes were wet but I suspected it was from escaping differential gear oil caused by worn axle seals. Didn't know about the spline shaft seal, but all is dry now, no issues after a few hundred miles.

 

Question: If the spline seal was leaking as well , wouldn't ATF fluid or a mix thereof, come pouring out  the differential fill plug when removed ? I haven't checked it since the replacing the gear oil last year. 

 

Also, at what position did you install your " inspection tube" ? Bottom, or side of tube ? Thanks again !

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Posted (edited)
24 minutes ago, Kestrel said:

Question: If the spline seal was leaking as well , wouldn't ATF fluid or a mix thereof, come pouring out  the differential fill plug when removed ? I haven't checked it since the replacing the gear oil last year. 

 

Yes, absolutely, the diff fluid will become diluted w/tranny fluid and if not replaced will ruin same.  I installed the drain tube straight down....6 o'clock position, figuring to drain from the lowest spot within the torque tube.  Was considering running a line from the fitting to some kind of container to spare my driveway, but decided to resolve the issue at the source. 

 

Been putting off replacing the spline seal for 3 years.....but with covid.....might as well go for it....what else is there to do?

Edited by roadmaster_56
grammer (see edit history)
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Don’t put a pipe in your torque tube. Use a small screw that can be removed whenever you change your oil. That way it doesn’t ruin your driveway. Not enough trans fluid drains down there (even in a year) to warrant a tube. 

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