Rear differential leak

Hey,

I've got an 88 Chevy C1500 2WD. I noticed some oil slinging around (exhaust pipes, gas tank, bottom of truck bed) where the differential meets the drive shaft. I naturally replaced the pinion seal which made perfect sense, then cleaned all of the oil around to see if the leak would continue, and sure enough it was. ( I installed the seal just like it was when I saw the old one, with the face of the seal tapped in evenly with the beginning of the opening; it wasn't pushed in any further) After I replaced the seal I noticed small amounts of oil in the same spots. Now I think my problem has to do with the torque of the pinion nut. When I took it off, it was very easy to take off (I did mark it before it was removed) with a large torque wrench. The flange came off easy without a puller aslo! I'm thinking maybe the pinion nut was too loose in the first place. The bearing was fine. I understand my design utilizes a crush sleeve, but I am unsure as to its effect on the bearing preload? So, if the nut was too loose to begin with, how could I tell. By the way, screwing the nut back on was a sinch also, which is weird because all of the sites I have seen say it was sooooo hard tightening the nut. In my Chilton book, there is a torque specification for the "pinion seal nut" and shows it to be 255 ft lbs. for GMC and 270 ft lbs for the DANA model? Should I re tighten the nut to this spec, because it was not that tight when i took it off. There was only 3 threads from the tip of the pinion shaft threads to the beginning of the nut. I understand if I over tighten it, I will ruin the crush sleeve and the bearing and have to replace both, so, I have the bolt on now at the same alignment marks as it was before the nut was off. Also, when I took out the seal, it actually didn't look bad at all.... oh and by the way, there was plenty of permanex no. 2 sealer in there! Please help...

Thanks,

Sounds as if someone was in there before. The nut should be a nyloc. Preload is adjusted by thrust washers that should not fall out by just removing the yoke, however, if the pinion nut is not to torque specs, the pinion will work in and out, however, I doubt that is happening here.

What does the seal race on the yoke look like? Are there grooves worn in it? If there are, you might need a speedy sleeve.

The permatex you saw may have only been to seal the outside of the seal.

And lastly, perhaps the pinion bearing is bad and causing the yoke to move laterally and wear the seal prematurely.

I would redo the job, remove the yoke and inspect for wear where the seal rides, if there are wear marks, get a speedy sleeve and install. Install the new seal, install the yoke and tighten to specs.

Hey,

I've got an 88 Chevy C1500 2WD. I noticed some oil slinging around (exhaust pipes, gas tank, bottom of truck bed) where the differential meets the drive shaft. I naturally replaced the pinion seal which made perfect sense, then cleaned all of the oil around to see if the leak would continue, and sure enough it was. ( I installed the seal just like it was when I saw the old one, with the face of the seal tapped in evenly with the beginning of the opening; it wasn't pushed in any further) After I replaced the seal I noticed small amounts of oil in the same spots. Now I think my problem has to do with the torque of the pinion nut. When I took it off, it was very easy to take off (I did mark it before it was removed) with a large torque wrench. The flange came off easy without a puller aslo! I'm thinking maybe the pinion nut was too loose in the first place. The bearing was fine. I understand my design utilizes a crush sleeve, but I am unsure as to its effect on the bearing preload? So, if the nut was too loose to begin with, how could I tell. By the way, screwing the nut back on was a sinch also, which is weird because all of the sites I have seen say it was sooooo hard tightening the nut. In my Chilton book, there is a torque specification for the "pinion seal nut" and shows it to be 255 ft lbs. for GMC and 270 ft lbs for the DANA model? Should I re tighten the nut to this spec, because it was not that tight when i took it off. There was only 3 threads from the tip of the pinion shaft threads to the beginning of the nut. I understand if I over tighten it, I will ruin the crush sleeve and the bearing and have to replace both, so, I have the bolt on now at the same alignment marks as it was before the nut was off. Also, when I took out the seal, it actually didn't look bad at all.... oh and by the way, there was plenty of permanex no. 2 sealer in there! Please help...




Matt, my rear diff seal is leaking as well, just as you described. can you describe the procedure you used to replace it? I know I have to take apart the u joint, will the drive shaft be able to move out of the way after that? at this point I'm not sure what would have to be done.

thnx

The 1 5/16 pinion nut should be very very tight! Mine is at 470 lbs. The crush sleeve is only for preload. Once you tighten to desired torque, do not back off nut at all or crush sleeve is useless.Torque the hell out of that nut and use 271 loctite. Once nut is torqued you should be able to turn yoke (with wheels off ground) with only 20 INCH! lbs. (not foot lbs.).

The 1 5/16 pinion nut should be very very tight! Mine is at 470 lbs. The crush sleeve is only for preload. Once you tighten to desired torque, do not back off nut at all or crush sleeve is useless.Torque the hell out of that nut and use 271 loctite. Once nut is torqued you should be able to turn yoke (with wheels off ground) with only 20 INCH! lbs. (not foot lbs.).

can you explain what the crush sleeve is. do I need to get a new one when I pull the pinion nut off? also, will the drive shaft drop down when I disassemble the u joint at the rear dif? or do I have to take more apart??

can you explain what the crush sleeve is. do I need to get a new one when I pull the pinion nut off? also, will the drive shaft drop down when I disassemble the u joint at the rear dif? or do I have to take more apart??

The crush sleeve is just a circular metal collar about 1 1/2 in. long that slips on the pinion shaft, in between the two bearings. As you tighten the nut the crush sleeve collapse's keeping pressure on the backside of bearings inner race (this is preload). You will not need a new one unless you tighten nut less than it was before, If you over tighten it's ok. The part itself cost probally $3. But to replace it, is no easy task. You have to pull the differential, press out the pinion gear.

just a friendly reminder... permatex is junk... i redid my valve covers. oil pan, and rear main /w the stuff when i went thru my 5.7, and all of it has leaked.... re sealed with black silicone RTV and not a leak yet...

just a friendly reminder... permatex is junk... i redid my valve covers. oil pan, and rear main /w the stuff when i went thru my 5.7, and all of it has leaked.... re sealed with black silicone RTV and not a leak yet...


Black RTV silicone is a Permatex product. You must be reffering to the permatex #1 & 2 gasket sealers (they suck). Ultra Black, Ultra Blue....etc. and the RTV silicones by permatex are very good products.