Hey everyone. My front axle has been leaking for a long time from the bottom of the plastic cable housing. Just dripping a dime to quarter size spot on the ground per night. Where is it actually leaking from is a very good question. It seems to be leaking from where the plastic cable attachment connects to the rest of the axle (the triangular shaped part with 3 bolts), but I can't find exactly where. For some reason, I try to keep topping up the fluid little by little (doesn't seem like it is leaking that much), but for the past few weeks, I would go to pull the fill plug and it would come pouring out for some reason because it is overfilled. But before that, I would have to add a little bit of fluid. There are two separate spots on the ground: the dark engine oil with little scent and the light colored gear oil that has the smell. Here is what I tried to find or stop the leak:

1. The 4x4 shop diagnosed a leaking seal on the left side of the axle and replaced it. Didn't solve this leak. For some reason, I don't think it was leaking at all. If it really was leaking and I never added fluid before that, wouldn't it be destroyed by now? The shift fork was broken when we got the car 11/2007 and between then and 1/2011, it wasn't touched except for the CV axle on that side (all fluid came out at the shop that did it and they replaced it) and one fluid change.

2. I pulled the plastic cable housing and instantly I saw fluid pouring out the bottom bolt hole. I tried RTV sealant on the bolt itself, thread sealer, and even a small amount of epoxy putty on the end of the bolt (That one didn't work. All it did was reveal hairline cracks on the bottom of the differential right below it. No leak at all from the cracks and I think it resealed itself.). No more fluid out that hole, even though anything I put in there was rendered useless by the gear oil.

3. Different type of thread sealer on all 3 bolts and make sure they were tight. Didn't work.

4. Epoxy putty applied around the bottom half of the outside of the differential case (where there is a space where the cable assembly connects to the differential) where I suspected it was coming from. Didn't work, but it seems that fluid is building up under it and dripping on the bottom where it always was leaking.

5. I was going to try RTV between the plastic cable housing and the metal where the cable connects, but the space is too tight to get to and there doesn't seem to be gear oil leaking from between there anyway.

Personally, both me and the mechanics are at a loss to explain why this axle is leaking. Where else are common leak sites for the front axles on these trucks?

Now for the second problem:

I had my pinion seal replaced 1/2011 because it was seeping. By the looks of it, it looked like it was doing it again, but when comparing the oily residue scent to a drop of gear oil from the front axle, the oil from the rear axle had almost no scent (could barely tell). Could this be oil from the engine hitting the axle? It is much darker and both axles had the fluid changed at 98-99k and I am at 106k now. I know I have an engine oil leak and I can see a drop accumulating on the drain plug (which is why I have a set of two spots on the driveway). Is it possible that engine oil could be posing as a repeat pinion seal leak because it is hitting the flat surface of the differential under the driveshaft? I tried topping off the rear axle, but it only took a few pumps before it was pouring out (I use a marine gear oil pump from Walmart and it pumps little by little). What else could this be?

 

Little elves must be filling the diff for you over night! Damn elves.

Putting anything on the outside of a leak won't really do anything. You need to pull the surfaces apart, clean them thoroughly, and apply a small bead of RTV.

It is unlikely that a leak at the engine would cause drops of oil from the rear axle. Oil that blows back while driving rarely collects in the same spot enough to cause it to drip to the floor at the back of the truck while not dripping from up front. You need a serious leak to cause it to collect at the back.

 

It would seem that might be the case. LOL.

Ok. Where are the other seals that would cause this type of leak?

The rear isn't dripping. It is only the front one. The reason why I suspected the engine was that there were traces of oil on both crossmembers along the centerline of the car. The oil pan and the transmission pan have engine oil all over them, but yet I rarely have to top off the oil for some reason.

 

Sorry, somehow I thought the rear axle was dripping. If it's the front axle that is dripping what you think is engine oil, that is definitely a possibility. With the propensity for oil cooler line leaks in these trucks, there is a good chance that is what is doing it. Could be what is causing the drips all over the diff. You could put a fluorescent dye into the engine oil and continue driving it. After a few days, take a black light under the truck and see if the leaking oil glows.

 

The front axle is definitely dripping gear oil. I can smell it and it is light colored. The engine oil is darker and the oil on the pan that is dripping is dark (the oil pan gasket is bad. At least it kept the frame free of rust for all these years since there was a layer of oil on it that I had to scrape off to paint it last year.). Besides, the leak doesn't seem to be coming from above the axle. The shop thought it was the power steering, but it isn't going down on the dipstick and the smell is different (same color).

The cooler lines are only a couple years old and these aren't leaking. Sorry, I should have mentioned that.

I will have to do the UV dye. But since I suspect the differential for this leak because of the site of it, smell and color, wouldn't I put it in the axle? I bet the whole undercarriage would glow if I put it in the engine oil. If I wanted it to glow, I would put in neon or LEDs! LOL

 

You can put it where ever you want to. It's a good diagnostic tool to use. I would suggest you degrease EVERYTHING under the truck first though.

 

The rear axle is wet again with an oily residue, but once again it is a dark, thin type of oil and in a small quantity, not that bad and doesn't smell like gear oil. In fact, I think I matched the scent (almost none) and color to the engine oil that was coming from the oil pan, with a drop forming at the drain plug (but I do not notice a leak on the dipstick). It wasn't even close to the gear oil dripping from the front axle, which I could smell very easily. I compared the oily residue to one drop of the oil from the oil pan and one drop from the front diff and the differences were clear. The oily residue is not nearly as thick as the gear oil and is closer to the oil leaking from the engine (Yes, I know where it is coming from and I don't believe it is worth fixing. Oil pan gasket.). I think that the drops are coming from the oil pan after all since it looks like oil from the pan has a straight shot to the rear axle where it is hitting (especially since it would clear the exhaust and the gear oil from the axle would not).

I am having alot of stuff done this week (new rear brake rotor that is running warmer than all 3 of the others (new caliper and pad installed) that is scoring and scratched, inspect and/or replace trans cooler hose that was rubbing against plastic and metal parts, NY State inspection, grease front end since I can't do that myself right now and moving the Posi-Lok cable because it is touching a brake line) before I go back to school since I use this truck to get to class several times a day and also in feet of snow during the winter. Inspecting the front diff is one priority of that appointment and if the leak is easily fixed, it will be done. However, if it is leaking where I think it is (between the cable housing and the rest of the differential), how hard is that to fix? Do they have to drop the axle or tear it apart all the way?

 

Sounds like you just need to park on the stones and quit looking under your truck. It makes your OCD kick in too much.

If it doesn't look/smell like gear oil, but more like engine oil, then why are you looking to open up the diff? Sounds like you have an engine oil leak... Have you put any tracer dye into one or the other? If you aren't going to use the advice given, you may find that people will stop giving it... Why spend time to tell you something if you aren't going to listen? Just sayin'.