Won't get over 60 in 5th gear

[Amy Holman]

Won't get over 60 in 5th gear I'm assuming clogged fuel filter or needs new fuel cap any suggestions thank you

 

[Road Dog]

I assume the truck doesn't have a fuel pressure gauge. It worth having one installed.

Loaded or empty? What RPM? 5-speed or 6-speed transmission? Automatics are 4-speed.

A clogged fuel filter will cause problems but usually it will stumble from a lack of fuel.

In 5th gear at 60 mph the engine RPM will be low and there won't be much turbo boost. That will limit any get up and go.

 

[BigPapa]

Run it with the fuel cap off to test that.

 

[AEdelheit]

Have you also checked the air filter and boot hoses? A clogged or restricted air inlet will cause similar issues and create a decent bit of smoke. Is there excessive black smoke?

 

[Matt42]

See post 37 in this thread: https://www.turbodieselregister.com/threads/12-valve-low-power.274390/