Arizona Classic Bronco - Tech Time Article #10

The Arizona Classic Bronco trip to Charaleau Gap last fall was memorable for a variety of reasons; beautiful scenery, comfortable temperatures, record amounts of water in the creeks, and the sight of at least three of the trucks on the trip puking transmission fluid during their attempts at climbing the "Waterfall" obstacle midway through the trip.

Located on the adapter between the C4 automatic transmission and the Dana 20 transfer case is a small, capped vent that allows the transmission to breathe and relieve pressure a bit when needed. As several of us found out on the steep angles of the Waterfall, when the transmission is tilted at a steep angle, fluid likes to flow out of this orifice. This causes several problems. First, it can make a nice smoke screen or even a fire if the fluid happens to flow onto the hot exhaust system. Second, it's messy. And third, the fluid drips onto the trail and rocks below your Bronco, making the rocks slippery in an already tough climb. Transmission fluid on the trail also does not adhere to the premise of "Treading Lightly" to which we as a club adhere to. So what can you do to solve this problem?

After you make it through the obstacles on the trail that caused your truck to expunge fluid, clean up the mess on the trail and then check the transmission fluid level to make sure no additional fluid is needed. It's unlikely enough fluid was lost to make a difference on the dipstick.

When you get home, crawl under your truck and reach up on top of the tranny-to-t-case adapter and feel around for a small metal cap about the diameter of a dime. This cap should be fairly loose-it's held onto the adapter by a couple of ears.

If for some reason you have access panels in your floorboard like the Bronco shown in the photos, simply remove the access panels and you'll see the breather. Using a pair of locking pliers or large screwdriver, pry the breather cap off the fitting in the t-case adapter. You'll see a hole and fitting as in the first photo.

hose adapter

This hole is ¼" diameter. Your goal is to find a fitting that can be inserted in the hole that you can attach a piece of hose to. The second photo shows a suitable candidate. This particular fitting has a ¼" o.d. piece on one end and a barbed fitting on the opposite end to accept a 3/8" i.d. hose-perfect! I found this particular fitting at a Napa store in Prescott in their miscellaneous bin-gotta love those small town auto parts stores! I'm sure it's a Weatherhead fitting but unfortunately I don't have a part number for it.

adapter JB Welded in place

I mixed up some J-B Weld and inserted the fitting into the hole in the adapter. After letting the adhesive cure overnight, I attached a piece of 3/8" i.d. transmission vent hose with a hose clamp as shown in the photo.

hose routed to firewall

The other breather shown in the photo is for the front axle vent. The K&N breathers are expensive but they're hard to beat from both a functionality standpoint and they're aesthetically pleasing.

This is an inexpensive, easy modification that can make a difference in keeping your transmission fluid in the truck when you're out four wheeling on steep, rough inclines. Here's to keeping our babies from burping!