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Old 11-19-2010, 02:56 PM
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T-400 output shaft questions

I pulled the short tail shaft housing off my '75 Cadillac 400T, about 4" from the end of the output shaft is a small raised machined area with an O ring. There is nothing around it that I can see, just wondering what it is for.

Also the splined area on the output shaft measured exactly 3", is that the usual length on the 400? Thanks, Dave
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Old 11-19-2010, 03:29 PM
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The o-ring is a seal, the original Caddy shaft slip yoke would have had the first 1.25" or so of the inside diameter of the slip yoke machined smooth to fit over that O-ring and make a seal. A yoke with splines full length will crash into the raised groove that the o-ring is in, so be aware of what yoke you use.

The smooth bored yoke will also have a weep hole in the center of the plug at the u-joint end of the yoke, to prevent pressure build up. Also, this type of sealed yoke should have the splines lightly greased, since trans fluid is prevented from getting to the spline.
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Old 11-19-2010, 03:46 PM
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Ericnova72.....very very good, that makes perfect sence...and since I didn't get the orig. Cadillac slip yoke with the engine and trans. I would have never known that. Now my next question, I bought a standard 400 T slip yoke with the splines extending all the way to the opening. I'm setting up the driveshaft to give me the usual 3/4"-1" clearance when it's installed. Will this different yoke cause a possible leak because of it not covering the O ring?

Also as you know the Cadillac came with a L O N G tail shaft, is a short shaft yoke available with the first 1.25" smooth section? What to do huh??

P.S. I can't even spell "output" correctly in the title!!

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Old 11-19-2010, 03:57 PM
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As long as the slip yoke you intend to use is short enough that it doesn't come into contact with the o-ring boss on the shaft when fully bottomed out in the trans it will be fine. If it is long enough to hit the boss, the only solution is to bore the end of the yoke to remove the splines, or hunt for the correct yoke.

The non o-ring yokes don't have a air pressure/weep hole, so they don't have a way to leak. Problem happens when someone uses a o-ring type yoke on a trans with no o-ring(or leaves the o-ring out using this yoke), there will be a pesky tiny drip leak out of the back of the yoke that can be maddening if you don't realize there is a hole there.

There were some short tail o-ring shaft trannys but I can't tell you what they were in exactly. It is mostly a middle 1970's thing. Pontiac, Olds, Buick all had them at one time or another.

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Old 11-19-2010, 04:29 PM
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Ok, thanks for all the info...HATE LEAKS you know. Like I said I will have about 3/4" to 1" in/out play when the yoke is installed. Not much suspension travel on the rear end of a '32 Ford.....thanks again, Dave
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