Rear vent tube leak/bumb when start/stop Help!

JamesSandberg · #1 (**permalink**) 07-01-2008, 12:17 AM

So ive had my new truck for a few weeks now and I have noticed a couple of things that I hope you guys can help me resolve.

First-
My rear axle vent tube appears to be leaking an abnormal amount of gear oil. I searched the forums and it sounds like this is kinda normal when you have been through deep water recently, which I have. The problem is that I have only done this once and there is quite the buildup of oil under the truck which means it was probably leaking before I went through the water. On two different occasions I have come out in the morning and found a wet spot on the ground from oil. Also, the oil is leaking onto my brakes causing them to squeak. What causes this leak and is it really normal? Should I be concerned? Can I stop it?

Second-
I have noticed that every time I accelerate and stop I feel and hear a slight bump. It is not immediately when I hit the gas, its about a second later. It also happens a split second before I come to a stop. I also searched the forums on this topic and found something about a slip yoke needed greased. Could this be my problem? How exactly would I go about fixing it? Any other ideas

I am not the most knowledgeable person when it comes to trucks, but I can do just about anything with a little instruction. Any help you guys can offer is greatly appreciated.

kameronth · #2 (**permalink**) 07-01-2008, 11:48 AM

As for the rear axle, I would pull the plate and drain or else you are going to have some serious rust issues. It sounds like your axle seals are toast if they are leaking into the brakes and sand in the water can cause them to go bad. Although, since you have water in the differential it could also be the reason for the leaking into the brakes because water is a lot thinner then gear oil. As for the slip yoke, I am not sure but there are others here that have done it and will give ya some help.

JamesSandberg · #3 (**permalink**) 07-01-2008, 04:56 PM

Im not sure if the seals are bad because it looks like the oil is coming from the vent tube. I can see the path of oil from the tube down to the brakes. I was just concerned that so much was coming out of the tube. How would I go about changing the oil? What would I need?

alxsnmr · #4 (**permalink**) 07-01-2008, 05:55 PM

Drain pan, wrench to open up the diff cover, 3/8" extension to remove the oil fill plug on the front of the diff, 2 quarts of 80W-90 gear oil (if I remember right), friction modifier if it is limited slip, and Black RTV sealer for new gasket of the cover. Depending on the mileage, 100,000+, you may want to pull the drums off the the sides and inspect the oil seal on the outside of the axle. The 8.8" has a tendency to wear at the oil seal area causing a leak. There is a different axle bearing/seal available to change the position of the axle seal so it has a fresh area to seal on the axle shaft.

JamesSandberg · #5 (**permalink**) 07-01-2008, 06:22 PM

Thank you for your help! I know what a limited slip is, but how do I quickly tell if I have one. As I have just bought this truck I am still trying to figure out all of the modifications that have been done to it!

twisted limb · #6 (**permalink**) 07-01-2008, 06:39 PM

Are you sure it is not your rear diff. making the thump?I just had mine in the shop for a loud thump last Dec. when backing out and pulling out.Needed all new bearings in rear end.To grease slip yoke take one end of drive shaft off(I unbolted the front )take rubber boot loose and slide slip joint apart and grease it well.This took away thumping I had at the time a few years ago.

JamesSandberg · #7 (**permalink**) 07-01-2008, 07:15 PM

I cant be sure, but what did each of your thumps sound/feel like? Maybe you can help me narrow down the cause...

twisted limb · #8 (**permalink**) 07-02-2008, 08:08 PM

Well-A few years ago when I was coming to a stop I would hear and feel a slight thump thump, thump.Nothing major mind you.That is when I greased the slip joint and solved that problem.Now, last december I got fluid coming out of the rear breather and when I would pull out or back up I would get a very loud and hard thunk in rear end(also, the rear end whined pretty loud at hwy speed).I drove it about a week or less and called the shop and he said to bring it in right away and found the rear bearings bad.I am still getting a tiny bit of fluid seeping out.I may take it back and talk to the shop about it.Hope that helps.

JamesSandberg · #9 (**permalink**) 07-02-2008, 08:13 PM

The bump I am feeling is very slight and when I accelerate and when I stop almost as if something is rocking back and forth... I don't know what it could be

alxsnmr · #10 (**permalink**) 07-03-2008, 10:47 AM

The door id tag can tell but I dont remember the code, the tag on the diff cover can tell as well with LS somewhere near the ratio id, or you can lift the rear end up and spin the wheel on one side while watching the other. May have to take the trans out of gear to do this, but if the spin the same direction, mostlikely limited slip, if they spin in oppisite directions it is open diff.

You will have to open the diff up for the fluid change but you will be able to look at the carrier bearings to tell. I think if the pin holding the axles out comes loose it will also cause a bump sound, but I dont know for sure. Look for damage and loose bearings/pieces inside the diff while changing fluid to determine anything.

JamesSandberg · #11 (**permalink**) 07-09-2008, 07:59 PM

Yet another bump has been solved by greasing the slip yoke! I finally had a chance to do it today and the bump is gone! As for the rear diff I drained 4 quarts of oil out and the thing has been leaking for a while! So that means that there was even more in there at one point! no wonder it was venting! I will keep you infromed if the venting continues.