When pulling away from a stop I sometimes fill a slight secondary pull after the clutch is released, I only notice this when loaded and strating out in the lower gears, it does not always happen, I was wondering if there is ware on the trailer kingpin if this could be what I feel. Or maybe u-joints or other driveline problems. Thanks for any comments.

 

Set your trailer brakes and give it a good back and pull forward with somebody watching.

 

Pay attention for the feeling of the trailer lagging behind the trailer a little. You pull out, then a fraction of a moment later, you feel a whump. Let out of the fuel to coast between gears, whump, catch the next gear and accelerate, whump. That's what a 5th wheel that's slap worn out feels like. Kingpin problems are less likely, though I've heard of kingpins on tankers getting whittled down to nothing by all the surge action.

 

Check the 5th wheel bushings. Normally I would use a kingpin welded to a shaft. Then the pin in is locked in the 5th wheel, and then the shaft is used to lift the 5th wheel up to see if the bushings have any wear in them.

 

thanks for the info

 

The 5th wheel has teeth and can be adjusted a few times and tightened up. If there is no more room to tighten it, then it must be rebuilt.

I had this done once when I started and it's cheap.