Gunfreak25
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There seems to be a lot of confusion on axle seals and what each seals intended purpose is. I thought i'd clear this up for those who are new to these trucks or are currently covered in axle grease at the moment.
-The inner axle shaft seal is designed to keep the oil out of the steering knuckle and universal joints. GO is for the differential only but sometimes it works it's way into the axle shafts where it is hopefully stopped by the axle shaft seal. If the seal is worn, GO will run into the steering knuckle, universal joint and out of the steering knuckle seals. This is what's happening when you see GO leaks on your wheels. If the differential is overfilled (must be 1/2" below filler plug when cold) then it will also leak past the axle shaft seal even if it's still good. The seal is NOT designed to hold back that much gear oil and for good reason. Too much GO in your differential can cause foaming and overheating of your differential gears. Bottom line.....if your seal leaks...replace it.
-The hub seals. This is where most of the confusion starts. The hub seals are designed to keep the bearing grease in and water out. Period. They are NOT designed to keep GO out of the bearings. That's the job of the axle shaft seal.
One may ask how the hub seals keep can keep water out but let GO in like crazy....the hub seals are designed as "one way" seals and as such they will keep things like water and other contaminants out but since GO comes from the "inside", they usually don't stop much of it if any at all.
-Spindle keyways. You will notice keyways or "slots" on all of your axle spindles.
On the rear tandems these keyways MUST MUST MUST have a seal in them to keep the GO out of the wheel bearings. The rear tandems do not have inner axle shaft seals....no reason too.....there are no universal joints or steering knuckles to keep the GO out of. The only thing that keeps the GO in the shaft and out of the bearings is this keyway seal. Usually made of cork, but they eventually break down and let GO into the bearings. You usually do not notice this until you unbolt the axle flanges and pull the axle shafts out. So if you haven't already, have a bucket handy and pull those rear shafts. Replace the keyways seals with new cork or most people seem to be using good quality RTV silicone. Degrease the little slot well so the RTV can adhere.
So...In a nutshell....
If you have GO leaking onto your front wheels, your inner axle shaft seal has failed and must be replaced.
If you have GO in your rear wheel bearings the keyway seals have deteriorated and must be replaced. Just because you don't see any GO on your rear wheels, doesn't mean the keyway seal is still good. Pull em' and check! All 4 take less than a few hours to do. I just use RTV on the flanges instead of making up new flange gaskets. It was all pretty confusing to me at first but then you see each seal was designed a certain way and for a good reason.
Later I'd like to make a tutorial showing how to clean and replace the outer steering knuckle seals.
-The inner axle shaft seal is designed to keep the oil out of the steering knuckle and universal joints. GO is for the differential only but sometimes it works it's way into the axle shafts where it is hopefully stopped by the axle shaft seal. If the seal is worn, GO will run into the steering knuckle, universal joint and out of the steering knuckle seals. This is what's happening when you see GO leaks on your wheels. If the differential is overfilled (must be 1/2" below filler plug when cold) then it will also leak past the axle shaft seal even if it's still good. The seal is NOT designed to hold back that much gear oil and for good reason. Too much GO in your differential can cause foaming and overheating of your differential gears. Bottom line.....if your seal leaks...replace it.
-The hub seals. This is where most of the confusion starts. The hub seals are designed to keep the bearing grease in and water out. Period. They are NOT designed to keep GO out of the bearings. That's the job of the axle shaft seal.
One may ask how the hub seals keep can keep water out but let GO in like crazy....the hub seals are designed as "one way" seals and as such they will keep things like water and other contaminants out but since GO comes from the "inside", they usually don't stop much of it if any at all.
-Spindle keyways. You will notice keyways or "slots" on all of your axle spindles.
On the rear tandems these keyways MUST MUST MUST have a seal in them to keep the GO out of the wheel bearings. The rear tandems do not have inner axle shaft seals....no reason too.....there are no universal joints or steering knuckles to keep the GO out of. The only thing that keeps the GO in the shaft and out of the bearings is this keyway seal. Usually made of cork, but they eventually break down and let GO into the bearings. You usually do not notice this until you unbolt the axle flanges and pull the axle shafts out. So if you haven't already, have a bucket handy and pull those rear shafts. Replace the keyways seals with new cork or most people seem to be using good quality RTV silicone. Degrease the little slot well so the RTV can adhere.
So...In a nutshell....
If you have GO leaking onto your front wheels, your inner axle shaft seal has failed and must be replaced.
If you have GO in your rear wheel bearings the keyway seals have deteriorated and must be replaced. Just because you don't see any GO on your rear wheels, doesn't mean the keyway seal is still good. Pull em' and check! All 4 take less than a few hours to do. I just use RTV on the flanges instead of making up new flange gaskets. It was all pretty confusing to me at first but then you see each seal was designed a certain way and for a good reason.
Later I'd like to make a tutorial showing how to clean and replace the outer steering knuckle seals.
