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Dave Nova
Dave Nova, GMC Technician
Category: GM
Satisfied Customers: 19451
Experience:  ASE Master Certification. GM World Class Certification
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2003 chevy Trailblazer: 4X4..the transfer case..hose..leaking oil

Customer Question

I have a 2003 chevy Trailblazer 4X4. over the transfer case a open 5/16 hose thats leaking oil. Its not the transfer case breather. The oil is some what in color of red. I check the oil levels and good. Any help would be greatful. Thank You
Submitted: 5 years ago.
Category: GM
Expert:  Dave Nova replied 5 years ago.
Hello and thank you for using JustAnswer. My name is XXXXX XXXXX I will do my best to help you with your GMC problem.

The transmission and transfer case vent hoses are interconnected. The transmission fluid is red. If there is red fluid, the transmission could be overfilled, or the transmission may be overheating and pushing fluid out of the vent.
Customer: replied 5 years ago.
Hi and Thanks. The transmission and the transfer case is not over filled. If the two vent lines are interconnected where is the "T". and why would chevy leave a open line. The transfer case vent line goes up to the back of the engine head with a vent cap. I had no work done to this car.
Expert:  Dave Nova replied 5 years ago.
The vent hose travels up to the back of the cylinder head and the transmission vent hose tees in on the passenger side of the transmission.
Customer: replied 5 years ago.
The vent hose for the transfer case and this open hose that is leaking oil run side by side along the top of the transmission. The fuel line are next to them on the driver side. It's hard to follow this line over the transmission. This line thats leaking has all factory hold downs and ends next to the vent steel line thatcomes out of the transfer case. Any ideas what this line is?? Thanks
Expert:  Dave Nova replied 5 years ago.
Picture shows aXXXXXmodel, but this is the transmission vent tube. #2 and #3 are the retainers for the vent tube. Bottom end by #3 is open.

Customer: replied 5 years ago.
If the transmission and the transfer case vent line are interconnected and the line goes to the back of the engine head with a vent cap on it. Why have a line going to the end of the transfer case that is open??
Expert:  Dave Nova replied 5 years ago.
The lower end of the line is open so fluid can drip out. If the lower end is submerged as when driving through high water, the transmission and transfer case will still vent through the upper portion of the hose. (it is much easier for the vapor to pull through the line, so water will never get sucked up into the transmission or transfer case.
Customer: replied 5 years ago.
OK. so what could be the reason why I have a oil leak out of this hose. the transmission and the transfer case is not over filled. I'm the only own of this car and no work has been done. Only servicing of oils. Transmission at 25,000 miles and transfer case and front & rear diffs. at 50,000. I was going to service the trans. when I saw the leak. The car has 56,000 now. Do you this this is something I should take note on. Transmission R&R?? I hope not .
Expert:  Dave Nova replied 5 years ago.
Is there fluid pouring or dripping out of the vent hose onto the ground, or is there just a little residue around the end of the hose?
Customer: replied 5 years ago.
Sorry I didn't say that. It's covering the back of the transfer case down to the crossmember and the forward side of the fuel tank. When the car is parked over night a spot about 4 inches round on the ground. When the car is running I haven't looked to if its leaking or pouring out. I plan on washing the case and the I would move that hose to a lower spot. Just to see thats the only leak.
Expert:  Dave Nova replied 5 years ago.
Verifying that the fluid is only coming from the vent will be the first step. Then double check the transmisison fluid level with the engine running. A common mistake is to have the transmission filled all the way to the HOT mark on the dipstick. This is actually overfilling the transmission. Have the fluid level down at the COLD mark. If the transmission is hot enough for the fluid to be at the HOT mark, the dipstick will be too hot to hold.

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