So I took my new to me truck for ~450 km trip yesterday doing everything I would normally do on a fishing trip, except towing a trailer. Highway speed climbing grade, winding roads, up hill gravel roads, backing up against a picniic table and pushing it around by mistake (okay, I don't normally do that, but I missed seeing the table) and downhill on gravel roads.


Truck performed great except for one thing I'm not sure is right. When coming downhill, even shifted into 1st, I had next to no engine braking. My tranny just sat at 700 rpm or so and I was forced to use my brakes more than I would have in my gas truck.


Is this a difference between the gas and diesel? Or is my tranny not working correctly? Both my trucks have a 4L80E so the difference is the motor.

There is a small clutch pack called the overrun clutch that applys when in 3,2 or1. It keeps the roller clutch from overruning on decelleration. There could be a problem with those clutches, the apply piston or fluid circuit to the piston.

So, this is not expected behavior and there is something wrong with my tranny.


Think it's going back to the shop.

IIRC, gas will give you much more engine braking than a diesel- thats why people but an exhaust brake on diesels, to get some braking when off the "gas". I think a gas motor provides the retarding force by sucking against the throttle plate, the diesel has no such thing but an exhaust brake works like a throttle plate by allowing the motor to "push" against something.


Those really in the know feel free to correcthttp://dieselplace.com/forum/smileys/Big%20Smile.gif

But, if I'm going downhill at about 20kmh, in first gear and the tranny is sitting at 700 rpm, this really has nothing to do with engine braking.

thats true, missed the first gear part of your original post. I definitely get a braking effect in first gear!