'741 pinion seal problems...
#967668
04/06/11 12:33 PM
04/06/11 12:33 PM
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Joined: Jan 2003
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Windsor, ON, Canada
Diplomat360
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I have a rebuilt '657 housing (657 and 741 seems to be often lumped together though). I installed a CR 18708 pinion seal in the housing and used an OK looking yoke. Shaft had some wear marks, but I really didn't think it was that bad. Anyways, as I fired up the car and got the drivetrain moving I discovered that the seal was leaking, and leaking real bad, as in the gear lube was dripping out and getting slung around the floor pan, exhaust pipes, etc....in other words: major leak & mess.  I now pulled it all apart and suspect that the yoke shaft scoring is simply too deep. However, the brand new replacement billet yoke I have also appears to have some clearance between the shaft and the seal itself once I install the yoke. I had expected that the seal would fit around the shaft with some amount of 'interference', meaning that it would tightly wrap around the shaft. So...I'm a little stumped here. I hate to button it all up only to have the leak again...am I missing something here?
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Re: '741 pinion seal problems...
[Re: Diplomat360]
#967669
04/06/11 12:48 PM
04/06/11 12:48 PM
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Joined: Feb 2003
Posts: 12,675
Columbia, CT
moper
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Is it coming out of the seal area or in front of it? When I do the final assembly I use a little rtv on the splines of the yoke. Not much, but a little. I've had drips from oil that found it's way through the space between the splines before. Not usually a fast leak. But a leak. I've also seen the seal leak between the case and steel jacket of the seal when the case was damaged (scratched) removing the old seal. A little rtv on a new seal can stop that too.
Oh yeah, one other thing... make sure the vent for the axle is not plugged...
Last edited by moper; 04/06/11 12:48 PM.
Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
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Re: '741 pinion seal problems...
[Re: moper]
#967671
04/06/11 02:19 PM
04/06/11 02:19 PM
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Joined: Jan 2003
Posts: 1,753
Windsor, ON, Canada
Diplomat360
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Quote:
Is it coming out of the seal area or in front of it? ...Oh yeah, one other thing... make sure the vent for the axle is not plugged...
With the old yoke in place the gear lube was coming out from the pinion seal...basically the lube would leak out and get tossed out from behind the yoke dust-shield. Nothing was leaking through pinion nut-washer area.
Seeing the responses so far I'm thinking the old yoke was just too worn out...I'll try to measure the wear tonight and compare to the seal shaft specs.
Thanks guys!
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Re: '741 pinion seal problems...
[Re: bigsbigelow]
#967673
04/06/11 05:38 PM
04/06/11 05:38 PM
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Windsor, ON, Canada
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Quote:
Is the axle assembly properly vented? If not, after the oil heats up the pressure will push it past the seal. My father just went through this. Not saying this is exactly your issue but it is free to check and an axle vent is super cheap. 
Ah, I forgot to mention this in my previous post...yes, the axle housing has a brand new vent on it. I will double check today that it's open and vents freely though.
In my limited drivetrain testing I really wasn't able to heat it up...the seal starting leaking basically as soon as I brought up the RPM fast enough so start spinning the shaft at a higher speed. Hard to explain....but with the wheels up in the air (car on axle stands) and the rear end geared 3.91 I was getting about 2700 RPM...so maybe 40 MPH?
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Re: '741 pinion seal problems...
[Re: Diplomat360]
#967674
04/06/11 06:17 PM
04/06/11 06:17 PM
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Joined: May 2004
Posts: 679
N.E Indiana
repad
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Quote:
leaking real bad, as in the gear lube was dripping out, the brand new replacement billet yoke I have also appears to have some clearance between the shaft and the seal itself once I install the yoke. I had expected that the seal would fit around the shaft with some amount of 'interference', meaning that it would tightly wrap around the shaft.
Sounds to me like you have an incorrect size seal, it should have a snug fit around the yoke shaft.
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Re: '741 pinion seal problems...
[Re: repad]
#967675
04/06/11 06:22 PM
04/06/11 06:22 PM
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Joined: Jul 2008
Posts: 30,424
Florida STAYcation
dOc !
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Quote:
Sounds to me like you have an incorrect size seal, it should have a snug fit around the yoke shaft.
x 2 .... I have seen some high-mileage-stuff ...HECK .. the 8 3/4 pig in my car now is a 1974 741 2.76 SG pig out of a Monaco that had 100kPLUS miles on it.... 100% leak-free.
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Re: '741 pinion seal problems...
[Re: Diplomat360]
#967676
04/07/11 11:27 PM
04/07/11 11:27 PM
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Joined: Jan 2003
Posts: 1,753
Windsor, ON, Canada
Diplomat360
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Well you guys...I pulled the CR 18708 seal out...measured it, the outer lip is 1.877, inner is 1.835 (about, as much as one can measure a seal lip with a vanier caliper...LOL). Tossing this over the yokes' shaft seals it up tight, both the old and new yoke have a decent interference fit. Sooo....what gives? I have no idea why the gear lube would have been slinging out...however, looking at the pinion end, I can clearly see the bearing, should there be some kind of a washer on top if it. Directly beneath it in the housing is the passage that feeds the lube...I'm assuming somehow this was maybe overloading the seal??? Yeah...I know...makes no sense. Here are a couple of pics:   I'm open to all ideas here...the benefit of putting the billet yoke will be that it has no dust-shield on it, so if the leak comes back I'll be able to tell exactly where it's coming from.
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Re: '741 pinion seal problems...
[Re: Mopar_Country]
#967679
04/08/11 12:07 AM
04/08/11 12:07 AM
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Joined: Jan 2003
Posts: 1,753
Windsor, ON, Canada
Diplomat360
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Quote:
Did you replace the seal when you went to the new yoke? If not that old seal might be chewed up from the old yoke.
I haven't had the chance to try the new yoke yet. The leak occurred with the old yoke, the seal lip surface looks pretty darn good though, new actually. I didn't put any miles on this yet, maybe 3 miles total with the wheels up in front of my garage.
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Re: '741 pinion seal problems...
[Re: Diplomat360]
#967680
04/08/11 12:55 PM
04/08/11 12:55 PM
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Joined: Feb 2003
Posts: 12,675
Columbia, CT
moper
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I can't see the pics but there is not usually anything behind the yoke. Just shims behind the narrow end of the front pinion bearing on the pinion gear. Make sure the seal housing (the case) is not scratched where the seal goes. If a seal puller is used and no care taken it can put a decent gauge in the housing that needs to be removed or smoothed.
Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
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Re: '741 pinion seal problems...
[Re: bb74swngr]
#967682
04/09/11 10:33 AM
04/09/11 10:33 AM
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Joined: Jan 2003
Posts: 74,942
U.S.S.A.
JohnRR
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Quote:
Quote:
Well you guys...I pulled the CR 18708 seal out...measured it, the outer lip is 1.877, inner is 1.835 (about, as much as one can measure a seal lip with a vanier caliper...LOL).
Tossing this over the yokes' shaft seals it up tight, both the old and new yoke have a decent interference fit.
Sooo....what gives? I have no idea why the gear lube would have been slinging out...however, looking at the pinion end, I can clearly see the bearing, should there be some kind of a washer on top if it. Directly beneath it in the housing is the passage that feeds the lube...I'm assuming somehow this was maybe overloading the seal??? Yeah...I know...makes no sense.
Here are a couple of pics:
I'm open to all ideas here...the benefit of putting the billet yoke will be that it has no dust-shield on it, so if the leak comes back I'll be able to tell exactly where it's coming from.
I just did two 741's and a 742. With the seals installed I could not see the bearing as shown in your picture. I don't know what that means.
Russ
He has the seal removed in those pictures ... 
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