I have an issue of my 2003 F250 7.3l PSD slamming into 4x4 when using the electronic shift on the fly switch. This has happened both times that I have used the 4x4 recently (recently bought truck). I stop the vehicle and switch the ESOF into 4-HI. When I start to move there is a loud bang about 30 sec (+/- 10 sec) after first start to depress the accelerator. The 4WD is engaged after that and works fine. Any help is greatly appreciated.

 

Welcome to FTE.

Have you tried turning on the 4x4 while moving? No reason to stop to put it in 4x4 high, only when you put it in 4x4 low do you need to be stopped with trans in neutral and foot on brake.

If you are get that much of a delay in the vacuum response, you might have a bad solenoid.

 

I get that every now and then, usually in the winter when everything is cold.

Keep exercising the 4wd system. If the previous owner never used 4wd, it's going to stick a little. The ESOF seems to like being used often.

 

Thanks for the quick responses. I will give that a try this evening. I definitely have been educated on the 4WD Lo, I had know idea that the trans had to be in neutral and foot on the brake. I wonder why Ford engineered it like this?

 

So you don't accidentally put the thing in low at the wrong time. It would play hell on the transfer case if it would go in low while moving.