Gear oil coming out the frame rail 01 XJ/Dana 35

Hey All,

My factory Dana 35 is putting gear oil out the vent tube and into he frame rail where it drips. It's probably been doing it for years. I've been parking it on gravel for years and didn't realize what was happening until I started parking it in the garage. The axle does not make noise and gear oil is not coming out the axle shaft seals or pinion. I've been using Mobil SHC 80w-140 for years because the manual says to use 75w-140 synthetic for heavy use, towing, etc. The 80w-140 is thicker than 75w-140 but its also cheaper and readily available in a pail which is easier to pump from. I pump away until it starts running out the fill hole and put the plug back in.

Is this a common problem with the Dana 35? Should I try to fill to within 1/2" of the fill plug? Could it be the 80w-140? I've filled axles until it runs out the fill hole the same way on many vehicles for many years with the same gear oil and not noticed this before.

What cover are you running on the D35? An aftermarket one? Many aftermarket ones have the fill hole above the shafts. You might be overfilling the diff. The vent is there because as the housing heats up, the fluid and air inside expands. If it is too full, it will blow it out the vent. Think positive, at least the frame rail won't rust out :looney:

Its the factory cover. Yep, for sure that side won't rust, but it does leave a nice mark on the garage floor. I'm pretty pleased overall. 330,000 miles and the only thing I've done in the past 10 years is change the fluid every 30,000.

put a larger diameter hose on there. that will help the heavier oil not clog the hose and cause pressure buildup.

I cant find the thread right now but you could also take the hollow bolt out of the axle and cut the part that is not threaded to help keep fluid from entering the vent.