I have a f250 with a 460 c6 trans. A while back I was on about a 3hr road trip and during that point my engine shut down with a bang so I put it in neutral and coasted to a stop on the side of the road. I saw tranny fluid overflowing out of the top of the dipstick fill port. I thought that it was from something that broke in the tranny when I heard the bang. Well it wasn't, I still don't know what the bang was, but my starter relay fried and I had to change the distributer to get it running. So that was fixed, but I still don't know why my tranny fluid was overflowing. Any ideas? I'm guessing it got too hot? Anyways I haven't done anything to the trans since, just made sure it had fluid. Once I got the truck back running everything has been working fine since. Now I haven't used the truck more than an hour at a time to and from somewhere since getting the engine running again. The reason why I ask is because I'm moving the truck from Alabama to Texas. So any ideas from you guys on what could have been the problem with trans fluid over flowing from top of dipstick tube would help. Oh and also I drove the truck from tampa Fl to mobile Alabama which is and 8 hour drive in itself. the truck did fine no problems and I was towing a 16 ft trailer full just weeks before that 3 hr trip I just described. Also the truck had a new radiator installed with a built in trans cooling system when i first bought the truck. So I know it not that because I cracked the lines to make sure fluid was pumping through the cooler. Unless its just not cooling enough. Thanks for any help.

 

It sounds like you have at least two things going on. The "bang" was probably an electrical short which is what shut the truck down. Hopefully you have found and fixed cause of that problem.

The fluid overflow is another problem. The C6 is completely mechanical/hydraulic in its function so the electrical issue wouldn't change anything to cause fluid to overflow. In the spirit easy things first, overfill of fluid could cause the overflow. Excess temps maybe... however with a working cooler and moderate to light load (no towing I assume) temps should be OK unless there is a problem inside the transmission. Does the fluid smell burnt or look brown from overheating? Also possible is a plugged vent on the trans. I'm not a C6 expert so hopefully others will post.

 

That is screwy. If you are towing you should add an external cooler in front of the radiator. Maybe your vent cap on the transmission is plugged up with dirt and grease.

You should flow test that cooler in the radiator also. I can't remember the rule of thumb but I believe it should flow about a quart in 90 seconds from the outlet side of the cooler. It is possible to have a restricted new cooler.

 

Did your in radiator cooler fail, pushing coolant into the tranny??

 

Co425: I checked and there is no coolant in tranny neither tranny fluid in radiator.
blue and white: the fluid isnt brown nor does it smell burnt.
I think maybe I was just overfilled. But this vent cap you guys are talking about where might that be at on the trans? Thanks again everybody for the info.

 

I don't think there is a vent on a c6. There are vents on manuals for sure.

 

The vent is a little cap dohicky on the top side of the trans. It's about the size of a nickel

 

I had that happen to a customers vehicle. The filter got clogged, so instead of cycling the fluid through the trans, fluid returning from the cooler just filled up the pan until it came out the dipstick. The problem was intermittent. It wouldn't do it all the time, just when enough garbage got slung through the filter. I bet if you do a service and new fluid, it'll be ok. The bang and shut off could've been fluid being crammed in a clutch assembly in the trans, temporarily locking it up. Once the engine and pump weren't running, the fluid settled back down and everything was good again. Sometimes big problems have simple solutions.