At 50,000 miles I found that my rear factory shocks were leaking. So I replaced all my factory shocks with Trail Masters. These shocks were definitely better than the factory shocks and gave a nicer ride. But I now have 100,000 miles on my truck and the rear shocks feel like they are getting worn out. The rear end of the truck seems to bounce around too much when traveling on the interstate. Does anyone know what the expected life of the Trail Master shocks are? I’ve heard numbers from anywhere from 30,000 miles to 75,000 miles. I now have about 50,000 miles on my Trail Masters. I’m sure it really depends on what kind of driving you do, but I was wondering if anyone had a similar situation.

-2001 F-150 4x4 XLT

 

Hit the nail on the head. If you find that your handling and ride is fading. Truck is bouncing more than it should etc, chances are you are about due for a new set.

To answer your exact question I do NOT know the average lifespan of Trailmaster shocks.

 

I suspect that only the rear shocks need to be replaced, but should I replace all 4 shocks?

 

I would. The fronts get just as much use as the rear, they are just not as noticeable when going bad due to the extra weight on the front.
As to when to replace, if you feel that it is bouncing more and not giving you the ride they should, then it is time.

 

50,000 miles is the general rule for replacing shocks. That or when you feel a ifference in ride qaulity. You have hit the 50,000 mile mark with your current shocks AND feel a difference in ride qaulitly.

Time for new shocks.