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I noticed that I have what appears to be a leak of some sort around my pinion seal area. The passenger's side of my differential and that side axle tube is caked with built up oil deposits. The driver's side is perfectly dry. What alarms me is that it looks like the floor pan around the ebrake line and the exhaust pipe has been sprayed with oil. The torque arm mount is covered with residue as well. From what I can see, the driveshaft and the u-joint look dry as well. I suspect that the pinion seal is blowing out while I am driving and spraying the oil on the exhaust pipe area under pressure. Underneath the car there is one single drop of fluid under where it looks like the fluid dripped off the torque arm bolt. The day following when I drove it and noticed the leak, the fluid on the bolt and on the ground is very sticky and not very fluid at all, if that information helps. I will post pictures of the area if that will assist anybody in helping me.
OK. So I pulled the drive shaft and removed the pinion yoke and seal. The yoke slid off a lot easier than I thought it would and the seal popped out rather easily as well. I went ahead and ordered the Timken 8610 seal that came in today. Now I have a problem.
The diameter of my pinion yoke shaft is 1 5/8".
The dimensions of the seals are as follows:
Old seal
Inner diameter=1 5/8"
Outer flange diameter=3 1/4"
Outer Seal surface diameter=2 5/8"
New Timken seal
Inner diameter=1 1/2"
Outer flange diameter=2 7/8"
Outer Seal surface diameter=2 5/8"
Is the inner diameter intentionally smaller and it is supposed to stretch to fit over the pinion yoke shaft? Here is a picture of the two seals.
Last edited by blacksunshine'91; 10-06-2016 at 05:50 PM.
The inner diameter of the old seal may be stretched, and is probably why it was leaking. Put a little grease on the new seal and see if the yoke slides in snug. If it does then it's fine. As for the outer part, the only thing that matters is that the part that is a press fit in the housing is correct. The flange doesn't matter.
What concerns me is that my pinion yoke is not original. I replaced my original one was leaking because of a gouge in the yoke itself. When I got the replacement one from the dealership, I remember it being noticeably beefier than the original one. In the pictures above, does my yoke look familiar to experienced people? Or is that not a GM piece from what you can tell? Do you feel I am safe to just lube the new seal and make the yoke fit?
GM updated the 7.6 yoke around 2000, so you might have the later style. If you do then you will also need the later seal. You didn't post a picture of the part of the yoke that goes into the seal, so I can't tell which one you have. I doubt that you have the later one, but it's possible. Try putting the new seal on the yoke and see how it fits.
I replaced my yoke in late 2002. I bought the replacement from the dealership so it is possible I might have the later style. I can get a picture today.
If you do have a revised 2000+ yoke then I believe you need national 710474. That is what comes up when I search 2002 camaro SS/ The one for my 86 was National 8610
Looks like the pinion nut/spline area was leaking as well.
It may have, but I don't think so. I didn't see any fluid on/around the nut before I removed it. There was some build up of gunk, but the whole area seemed to be coated in it. The u-joint on the drive shaft was dry without any gunk on it, so I wouldn't suspect that the nut/spline were leaking. When I popped the yoke out it came off easier than I anticipated and I dropped it into the pan collecting the fluid. If that is not what you are basing your opinion on, please elaborate.
I looked up that p/n on RockAuto, and it cross references with Timken 710474. The only visible difference is that flange that the national one has. I'd prefer to avoid National if I can, since that is what appears to be the one that came off the car.
Any thoughts or opinions on my preference for Timken?
It may have, but I don't think so. I didn't see any fluid on/around the nut before I removed it. There was some build up of gunk, but the whole area seemed to be coated in it. The u-joint on the drive shaft was dry without any gunk on it, so I wouldn't suspect that the nut/spline were leaking. When I popped the yoke out it came off easier than I anticipated and I dropped it into the pan collecting the fluid. If that is not what you are basing your opinion on, please elaborate.
In one of the pictures the threads/yoke looked a tad wet, the DS yoke had oil on it and the oil on the bottom of the car looked to be closer to the Ujoint area.
Since the yoke slid off easy, that tells me the splines were loose and leaking a bit too.
The driveshaft spins and slings the most of the oil off of the yolk and DS yoke onto the car so it doesn't leave much of a trace.
This is in addition to the seal leaking.
When putting it together, clean the splines and make sure you put a sealant of your choice on the splines so that doesn't leak out of the pinion washer and nut area.
I thought I read on another thread to put something like RTV or other sealant on the outer portion of the seal, but not to put anything on the splines. Did I read it wrong? Sorry for all the questions, just want to make sure I do this correctly. Thank you for your help.
You have the later updated yoke. You will need a pinion seal for a later 7.6 rear end. I'm not sure what year they changed it, but I think it was 2000. To be safe look for a seal for a 2002 or later. The S10 and Astro van also used the 7.6 rear end way past '02. Clean up your yoke and take it to the auto parts store with you so that you can test fit it before you leave. When you put the seal in you need to put a thin film of sealer around the outside of the seal before you drive it in to seal up any scratches in the housing. You also need to put some grease on the rubber lip of the seal before putting the yoke in.
This is very important. DO NOT put any sealer on the pinion shaft splines. You will ruin the outer pinion bearing if you do. You do need to put sealer in the splines of the yoke. If you don't then you will have a leak at the splines and it will come out around the pinion nut.
Get a new pinion nut while you are at the parts store. Put red Locktite on it and torque it to 150 foot pounds. That should have you fixed up and leak free.
I should have been more clear on the sealant placement and amount on the splines, thanks big gear head, I sometimes forget that some haven't ever done this.
This is very important. DO NOT put any sealer on the pinion shaft splines. You will ruin the outer pinion bearing if you do. You do need to put sealer in the splines of the yoke. If you don't then you will have a leak at the splines and it will come out around the pinion nut.
I am a little confused about the sealant placement. Do I put some inside the yoke before I put slide it back on the shaft?
This is very important. DO NOT put any sealer on the pinion shaft splines. You will ruin the outer pinion bearing if you do. You do need to put sealer in the splines of the yoke. If you don't then you will have a leak at the splines and it will come out around the pinion nut.
^^^ This. If you put the rtv on the pinion splines, the yoke will push the excess rtv into the rear end, where it doesn't need to be. By putting the sealant on the yoke splines, the excess rtv will be pushed harmlessly out the front of the yoke. The RTV I use is Permatex Ultra Black, which is a high temp RTV gasket sealant.
OK, so I got everything figured out now. Thank you all for the help. While I got it drained, I think I'm finally going to install the LPW cover that's been sitting in its box in the corner of the garage for the last three years.
One last question, its regarding the fluid:
I've read that synthetics are not the preferred fluid for the stock auburn diffs. However, the fluid I bought was Lucas synthetic with the friction modifiers already included. Is there anything wrong with using that fluid or should I take it back and get the standard fluid and buy the GM friction additive separately?
I've read that synthetics are not the preferred fluid for the stock auburn diffs. However, the fluid I bought was Lucas synthetic with the friction modifiers already included. Is there anything wrong with using that fluid or should I take it back and get the standard fluid and buy the GM friction additive separately?
Depends on the posi, Yukon told me it swells their clutches and caused them to bind. I just use the lucas conventional with some yukon additive. they also told me the GM additive is just fine.
So get the standard fluid and the additive from GM or use the synthetic Lucas with the additive already included?
I would probably just use what you have and if you have issues add a bottle of the GM stuff. You can visit a dealer and get the GM stuff and add it ahead oif time wont hurt anything.
People using the yoke GM upgraded to ~2000, the Timken 7457N and 8610 will not work. the inner seal is too small. The seal for that one from GM is 12471523. For what its worth, the seal comes pre-lubed. Thought that was a nice touch.
The pinion nut has been superseded by GM p/n: 88891763.
I was able to pick them up from the local dealer. The nut cost $6.22 and the seal cost $15.81. While you are there, you can grab the additive for $14.95 per bottle.
09-22-2016, 04:00 PM
