Ker-Thunk in my F-150


#1

My 2005 Ford F150 with 65k miles has developed a habit of modest backlash when stopping and starting off. At a traffic light for instance, I apply the brakes to come to a full stop, and immediately after the moment of complete stop, it will settle back in place as if the body is not fully connected to the frame. The same thing happens when I start out. I lift my foot off the brake pedal, the truck inches forward at idle with the automatic transmission until I apply the gas at which time it acts as if it takes up slack in the drive train.


#2

When if feels as if it’s “taking up slack,” is there a noise accompanying that?
If so, I’d look at worn universal joints in the driveshaft.
Other issues to check would be the condition of the brakes.


#3

The brakes have a groaning sound down at my feet with I apply pressure to the pedal. If I push down hard, the pedal keeps going although it never goes all the way to the floor.


#4

So where/when is the ker-thunking?


#5

The ker-thunking doesn’t seem to relate to the groaning. The groaning is when I am running at speed in traffic. The ker-thunking is only when I stop or start. I’ll look at both the brakes and the universal joints. Thanks.


#6

I would look at the drive shaft and rear differential. Too much play in either one could case this.


#7

Rear Drive Shaft Slip yoke binding on the splines… Fairly typical for this vintage truck. This can be verified by removing the rear shaft (drive shaft) and driving the vehicle using the front drive shaft in 4x4 (If equipped)… If the stop bump is gone, you can lube the slip yoke with the appropriate Teflon grease and put the rear shaft back in. There are some cases where the slip yoke spline surface finish is too course/rough, in this case the grease repair will only be temporary and replacement of the yoke will be required.


#8

Forgot to make note, you must index the driveshaft using a paint marker or some other method… The driveshaft MUST go back in in the same orientation as it came out. This means that the driveshaft must be orientated/clocked in the same location of the rear companion flange and the Transfer case output shaft as how it was originally installed. There is the potential for creating 1st order prop shaft vibrations if shaft is installed out of time. (This is even more critical on 2wd) Make your paint marks on the comp flange and shaft so that they will be side by side… (Typically at the 6 o’clock position) Make another make at the 6 o’clock position at the slip yoke. When you slide the shaft out of the t-case, make a small mark on the output shaft (6 o’clock pos) this will ensure proper shaft clocking/alignment when you put her back together. If driving with the rear shaft out, a rubber glove and a zip tie will reduce the oil leakage from the t case. (Glove can be put over the extension housing. Top off the t-case as needed.


#9

Bakes will make that noise, ujoint inspection is my reccomendation.