Reverse to Drive Thump

[wptski]

I think that I've mentioned this someplace else, maybe!

Backing down a driveway, probably is the longest time most people drive in reverse.

It don't happen all the time but when I stop, shift into Drive, press the throttle, vehicle moves a few feet and I get a thump which is sometimes louder than other times. I don't know where it's coming from either. The vehicle isn't straight, so your pivoting on one side or the other. Could be the brakes, maybe the discs in front and drums in the back aren't releasing together. Since it's a 4WD and Ford's choice to engage the rearend from every stop, it might be something to do with that too. I'll have to closely monitor the rearwheel torque on my Scanguage-II at the same time to see if anything odd is going on there.

This is the only time I normally back up that far, engine is cold, transmission is cold, etc. Maybe I hit the throttle harder sometimes?

We've had some humid day with patchy morning fog. I know on my '97 Ranger the front disc brakes would make a moaning sound backing up on damp days.

Anybody else get a thump also? It's one of these odd things that's a waste of time trying to explain to your dealer's service department.

BTW>> The 4WD Escapes may make a "hooting" sound while leaving a dead stop which they claim does no damage. There is a TSB #09-12-11 that's supposed to "only reduce" that sound. I'm planning to have that done in the near future. It invovles reprograming the 4WD module.

[JFUSION21]

I've seen that on many vehicles where the brake pads flex from the change in direction and you get a clunk as you change directions, usually happens on the first cold start as you get "stuff" accumulate on the pads/disc overnight.

My other guess would be the cold idle messing with the tranny or drivetrain as the engine puts more force on the tranny on cold start due to higher rpms in neutral.

[wptski]

Originally Posted by JFUSION21

I've seen that on many vehicles where the brake pads flex from the change in direction and you get a clunk as you change directions, usually happens on the first cold start as you get "stuff" accumulate on the pads/disc overnight.

My other guess would be the cold idle messing with the tranny or drivetrain as the engine puts more force on the tranny on cold start due to higher rpms in neutral.

It doesn't happen as I shift from reverse to drive but after it's in drive and have actually moved forward a small amount.

There are TSBs about thumping sounds but none are same situation as mine.