86’ 720 shaking(?)

[Ian ferguson]

Once i hit 40 mph i notice power loss and a vibration (not sure from where exactly) i have replaced the fuel pump, im thinking it way be my vacuum lines but im not 100% sure, any ideas? Thanks!

[IHaveNoIdeaWhatIAmDoing]

I am assuming you have already replaced the fuel filter? also it being an 86 is it a 720 with a carburetor or a D21 with fuel injection?

[Stoffregen Motorsports]

The vibration could be engine related, but we need more info. Did you change anything? Did something happen? Is this truck new to you? Has it been sitting for a long time?

[jagman]

When I first started driving my 720 I noticed a vibration  at about thirty MPH. It turned out to be a sticky u-joint and the drive shaft donut support.

[Ian ferguson]

On 6/9/2022 at 8:16 PM, IHaveNoIdeaWhatIAmDoing said:

I am assuming you have already replaced the fuel filter? also it being an 86 is it a 720 with a carburetor or a D21 with fuel injection?

I have replaced the filter, it is a 720 carbed

[Ian ferguson]

On 6/11/2022 at 10:37 AM, Stoffregen Motorsports said:

The vibration could be engine related, but we need more info. Did you change anything? Did something happen? Is this truck new to you? Has it been sitting for a long time?

All i have changed so far is the fuel pump and front suspension

[datzenmike]

On 6/6/2022 at 11:50 PM, Ian ferguson said:

Once i hit 40 mph i notice power loss and a vibration (not sure from where exactly) i have replaced the fuel pump, im thinking it way be my vacuum lines but im not 100% sure, any ideas? Thanks!

 

You say vibration which in my mind is much faster than shaking. Yes? To me this may be a bad U joint.

 

There is another fuel filter in the base of the stock fuel pump and a very fine screen inside the banjo fitting where the fuel enters the carburetor.

[Stoffregen Motorsports]

Shaking and loss of power can also be a tight brake drum. As it heats up (due to being tight), it overheats and becomes out of round and feels like a wheel is falling off, the vibrations can be that bad.

[IHaveNoIdeaWhatIAmDoing]

Has the truck been sitting for a few months? Maybe it could be some bad gas. Also is it just a vibration or is it Shaking? if it is shaking it sounds like what my truck did when I was having fuel delivery issues. Mine ended up being carburetor related and required a rebuild, but yours may be a different issue.