I changed my seals, why do my axles leak!?

[RMP&O]

I am sure some of you have experienced this.

Here is the deal. The actual seal is only one part of the sealing process. Every seal is going to sit or ride on the sealing surface. Take your average 50yr old 4wd that has seen use off pavement. Often mud, silt, or even just dust gets in the sealing surface. Most seals when the truck is being used, the sealing surface is spinning on the actual seal. Over the years groves can and will be worn into the sealing surface. The other issue will be rust. Rust from water will pit the sealing surface. If you just slap a seal in and don't inspect and then if required deal with the sealing surface you are very likely to experience leaks after installing a new seal.

This can be every thing from trans seals, to t-case seals to axle seals and more. Front and rear axle seals plus the t-case output seals and pinion seals on diffs are often the most prone seals to leak. Say you just rebuilt the e-brake and while at it put in a new rear t-case seal. You sure don't want to foul that fresh e-brake rebuild when the rear seal starts leaking again. The output flange is your sealing surface. Inspect it when you change the seal. Very minor groves or surface rust you can try to polish out. Start with some 200-300 grit sand paper, sand very light and quickly work your way up to 400 & 600. Get to at least 800 with a wet sand, you want a really high polish, take it to 1200. This will remove the very minor flaws in a sealing surface and polish it up. If you have deeper grooves or pits try to replace the parts with something better. If you can't find the parts, take the sealing surface part and the seal to a local machinist. The machinist will know right off the bat what needs to happen. They can likely fix it for you by turning down the sealing surface just a few hundredths of an inch.

Hand sanding and working up to a polish also works on knuckle balls. Knuckle balls are also a common place to find grooves and pits. Without a smooth surface here you are going to get some gunk in the closed knuckle. Grit, sand, mud and water reek havoc on a closed knuckle, it is very bad for the tracta joints or the later CVs.

Nissan knew all this, parts like the output flanges on the t-case and diffs are meant to only last so many years. once worn badly they are meant to be replaced. Only problem is nowadays you can't get these parts from Nissan. Front axles are particularly prone to pollution in off-road use. This is why Nissan put a collar on the front axle spindle. The collar is your sealing surface and it is removable and meant to be changed out when it gets grooves or pits. You can still get this collar in OEM form from Nissan. Knuckle ball seals also wear quickly in mud, silt, sand and so forth. This is why the original knuckle ball seals can be changed without removing the knuckle. It is a high wear item so Nissan designed it to be changed without a complete tear down of the outer front axle.

Nobody likes to buy and install new seals and have leaks all over again.

Cheers