4L70 blowing fluid after 3 hrs on highway

[berno56]

The tranny in my truck is aggravating me over this issue. It seems to happen after a couple hours of high speed driving between 70-80 MPH. Then you smell the sweet smell of tranny fluid and their is a cloud behind the truck from the fluid on the exhaust. The truck has a 2500 stall converter and has been rebuilt with new everything. I have about 7500 miles on the eng/tranny.

Any hints or similar experiences/remedies would be appreciated.

 

[Charlie]

 

[74 Shortbed]

Welcome to the site..

What is your RPM at 75-80mph???..

 

[berno56]

about 2700-2800. It has 3,73 posi gears

 

[74 Shortbed]

Converter is causing the heat, you need a big cooler with that converter..

 

[smoothandlow84]

Possibly over filled

 

[berno56]

OK, I get it. Having a new Summit store less than 5 miles from home is going to marital stress. Picked up a C&R cooler, temp bulb and fluids. Ordered a Dakota Digital tranny temp gauge to match my other gauges. I will see what the pan looks like when I change the filter. I hope I have not caused any damage by getting the fluid too hot. Live and learn.

Thanks for the input.

 

[74 Shortbed]

Color of the fluid will give an indication, could have been overfilled too, if the fluid gets up into the rotating mass it will get aerated and blow out the vent/tube.

 

[smoothandlow84]

My Chevy Duramax transmission (Allison)....was overfilled by the dealership and it spewed trans fluid out of the upper vent of the transmission when I was pulling my fifth wheel on the highway. Pissed me off because all of the fluid was not only under my truck, but all over the front and side of the new fifth wheel. Make sure to check the fluid level of any transmission when the truck has been warmed up to normal operation temp.

 

[yevgenievich]

As mentioned verify that it is not a heat problem. But it is very easy to overfill by filling to the hot mark when it is not warmed up. And it can take a good amount of driving to fully warm up the transmission.