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Discussion Starter · #1 ·
Hello all... Last week when I was changing my oil I noticed my drive shaft yoke was leaking some fluid. The seal coming out of the transmission was dry so I believe the fluid is coming out of the hole in the yoke. I've talked to 2 mechanics, as well as a few transmission shops and getting mixed answers so now I'm pretty confused on which route to take. From what I understand the yoke gets slipped onto the drive shaft; the part of the drive shaft that connects to the yoke has splines on it, and there's an o-ring that goes onto those splines (please correct me if I'm wrong). I've been told that I can simply seal the hole on the yoke and the leak will stop. I've also been told that sealing the hole won't fix the problem and I need to replace the o-rings on the splines and inside the yoke to correctly fix the problem. Then from another shop I've been told that I just need a new yoke and it has nothing to do with the o-rings on the drive shaft splines (behind the inside of the yoke) going bad. I really don't know who or what to believe? I just want my problem fixed. The leak isn't bad, I don't even notice any drops on the floor or my transmission fluid going down. Nonetheless, what would you guys recommend to fix this? I'm reading more and more online forums stating people simply seal the hole and problem solved (only issue I have with that is if the o-ring on the drive shaft splines is bad and the yoke hole is sealed, won't it build up fluid inside the yoke?)???? I could be understanding this wrong but would love to know how I can fix this problem.
 

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Not familiar with much of what you have stated, but let us know what year car you are working on.

On the older Chevys, '55 to '76 anyway there is a Seal on the End of the Trans and the Driveshaft Yoke just slips into it. That Seal is what keeps the Fluid from leaking out.

If your car is a '77 or newer, I'm pretty much lost, lol.

Bill
 

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Replace the rear trans seal if its a older Impala with a powerglide , 350 or 400 trans.
 

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Discussion Starter · #4 ·
Not familiar with much of what you have stated, but let us know what year car you are working on.

On the older Chevys, '55 to '76 anyway there is a Seal on the End of the Trans and the Driveshaft Yoke just slips into it. That Seal is what keeps the Fluid from leaking out.

If your car is a '77 or newer, I'm pretty much lost, lol.

Bill
Hi Bill... I have a 1967 Impala. I have a seal at the end of my transmission, however the seal is completely dry so I'm guessing the culprit is the hole on the yoke (which is also what a few shops told me the leak is coming from). I read a lot of people just seal the hole and problem solved, however some shops told me I need to replace some o-ring on the drive shaft splines.
 

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Discussion Starter · #5 ·
Replace the rear trans seal if its a older Impala with a powerglide , 350 or 400 trans.
when i was restoring the car I had a transmission shop put in a new (rebuilt) transmission. i don't know what kind - however i have the following gears: park, neutral, reverse, drive, drive 1 (which i never shift into, however i believe it's used for up or down hill driving).
 

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Hi Bill... I have a 1967 Impala. I have a seal at the end of my transmission, however the seal is completely dry so I'm guessing the culprit is the hole on the yoke (which is also what a few shops told me the leak is coming from). I read a lot of people just seal the hole and problem solved, however some shops told me I need to replace some o-ring on the drive shaft splines.
Still sounds strange to me. If you have a "hole in the yoke", how did it get there?

Bill
 

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The hole in the yoke was to let air in and out of the yoke as the suspension traveled up and down. It is normal and is supposed to be there. There is no O-ring on a rear wheel drive car, that is a front wheel drive thing. If you have a newer (2000-0215 Impala we really can not help[ you as this board is of interest to only those who have a 1960's rear wheel drive Impala with a V8 engine.

If you open the hood and the motor is siting sideways you have a newer wrong wheel drive V6 Impala that has computer controlled everything. We can only provide good info on carburetored American V8 that have a belt driven fan and a radiator in front of the engine.


Big Dave
 

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Discussion Starter · #8 ·
The hole in the yoke was to let air in and out of the yoke as the suspension traveled up and down. It is normal and is supposed to be there. There is no O-ring on a rear wheel drive car, that is a front wheel drive thing. If you have a newer (2000-0215 Impala we really can not help[ you as this board is of interest to only those who have a 1960's rear wheel drive Impala with a V8 engine.

If you open the hood and the motor is siting sideways you have a newer wrong wheel drive V6 Impala that has computer controlled everything. We can only provide good info on carburetored American V8 that have a belt driven fan and a radiator in front of the engine.


Big Dave
Hi Dave... I have a 1967 Impala, rear wheel drive, carbureted American V8. Why would anyone even buy a new Impala :). I've read online that a lot of people simply patch the hole shut and the problem is solved. I also had 2 shops tell me I could do that. My question: 1) If I patch the hole shut won't it build up pressure inside the yoke and cause other problems? 2) If I patch the hole will it cause any other issues (i.e. it's leaking for a reason, are there any internal components that will continue to leak if I just patch the hole?)?

If I can simply just patch the hole and be done with it then obviously that's the cheapest and easiest way to do it. However, if there's any other issues that may arise from patching the hole what's the best way to fix the problem?

I believe the yoke only leaks out of the hole when you park on a hill with the head of the car facing up, right?
 

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The problem you are having with the leak is caused by the fact that there is tranny fluid inside the tail shaft. The seal is designed to stop leaks of a little bit of oil that may have worked it's way into the tail shaft but most of the oil that finds it's way back there is supposed to drain back into the pan.

If you are leaking out of the air vent then either you are parking your car on an incline at night so that oil drains into the tail shaft instead of out of it; or you have overfilled the tranny.

To check the fluid level you need to go for a 15-20 minute drive. Then on a flat surface with the engine running pull the dip stick; and wipe it off with a clean paper towel or shop rag. Reinsert the dip stick and pull to check where the fluid is. It should be in about the middle of the cross hatched area. There are three holes punched in the dip stick. The middle hole is where the fluid level should be when it is cold and fluid level is checked on level ground with the motor running. It expands that much (moving from the middle hole to about the middle of the cross hatched area when heated).

The motor has to be running to suck fluid into the front pump and fill the torque converter which drains down with the motor off (if you have an old cast iron case PowerGlide it has a rear pump as well as a front pump). It has to be on level ground to get a reading for what I hope is an obvious reason.

If your fluid levels are normal and you are parking it inside a garage with a level floor then you have excessive wear in your tranny in many of it's components beyond the bands and clutches. I would also examine the front yoke to verify the splines are straight and not bent from a hard launch. As worn splines can also create your symptoms of a leaking air vent.

Big Dave
 

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OK guys, I've been working on these old cars since 1968 and I can never remember any kind of Hole in the Driveshaft Yoke, and I've changed many a U-Joint through the years, but just to make sure, I wanted to wait till I checked on some. I just went down back and checked on a bunch of old Full Size Chevy Driveshafts, from about '58 to '68 and I didn't notice any Holes anywhere.

Where are these "Holes" supposed to be at ?

Bill
 

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In the middle of the steel cap pressed in the center of the front yoke like a welch plug, but it is a domed cap without sides that a Welch plug has. Tomorrow If I remember I will look around in the tool shed to see if I still have one hanging on the wall that I use as a plug to pull a tranny without dumping the fluid on the floor. I have only see them on the back of TH400 front yokes.

Big Dave
 

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I have several drive shafts from 60's era cars and a few what I call dummy splines to plug the back of a trans befor I pull it. None have holes in them. Maybe its a later model thing.
 

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Here you go!



The one on the left had a solid plug like the one below but I knocked it out trying to clean out the spiders.

Big Dave
 

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Interesting. I'm wondering if all the ones I've worked on through the years were just covered up with old grease and I just never noticed any.

I'll be keeping it in mind to check on them from here on.

Bill
 

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Sounds like it is leaking around the plug.

When we put a 700r4 in our 61 we had the front driveshaft shortened. After the first drive it was leaking transmission fluid, the drive shaft was just a tick too long and when the suspension compressed it knocked the plug loose and caused it to start leaking.
 
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