Vibration and noise when driving at 100kph or faster

Looking for some ideas from anyone here on excessive vibration/noise at highway speeds.  About a month ago I started noticing significant vibration when going at 100kph or faster.  It seems to occur only when I have my foot on the gas pedal and I "think" it's coming from the front end but it is hard to tell.  I searched through the posts here and it sounds like it has been a problem for some.  The usual culprits seem to be:

• Wheel/bearing issues:  The issue occurred with my old tires and now with my new tires mounted and balanced recently and have verified my front bearings have no play.
  

• U-joints:  I've jacked up the van on four jack stands and could only find the tiniest of play where the drive shaft connects to the front differential.  I may just order and replace all four U-joint spiders as a troubleshooting step.
  

• Front differential:  From searching here it could be one of the bearings in the front differential but I am hesitant going to that path right away as it is more intense mechanical work for myself.
  

• Does lifting the Hiace cause an accelerated inner CV bearing to wear out like on other lifted Toyota trucks?:  While researching the front differential and U-joint spider work I noticed that fellow Toyota truck owners have encountered an issue where the lifted angle can cause and accelerated wearing of the inner CV bearing and some have replaced the needle bearing with an East Coast Gear Supply (ECGS) bushing instead.
  

I'd appreciate any troubleshooting advice before I start the whack-o-mole approach of replacing parts. Much appreciated.

Hello Brewera. Sorry to hear of your woes.

Your suggestions seem sound but are not exhaustive. I’d also be interested to know how you experience the vibration and noise. Do you feel it though the floor or through the steering? It is up and down or side to side?

As a start, if you think it’s in the front, I’d look for play or slop in the whole of the front suspension setup. All the bushing and mountings (top and bottom points) plus the front anti-roll bar and steering arms. The front diff also has lots of rubber mounting points. How are the rubbers for the shocks?

How did this start? Gradually got worse or sudden onset? Has a weight dropped off a wheel? Is it worth swapping the wheels front to back? Is the steering wheel still the same or might you have knocked the tracking in a pothole or sim? Are there any locknuts that might have come loose? Are the steering rack mount bolts tight?

This is about as much as I can think off. Hope it’s some use.

Appreciate the insights. To me, it doesn't feel like anything related to steering, suspension, or wheels as it is directly related to pressing on the accelerator pedal. If I get up to 100kph and then let off the pedal it substantially goes away. I have ordered four new U-joint spiders and will swap them out and let you all know what I find.

Sounds like worn engine mounts allowing to much movement.

Hello brewera.

If it is the engine mount then don’t neglect the rear one, which is on top of the transmission. This was very noisy on mine on overrun but fine when on power so it could be the problem, the other way round? I’ve just written a fairly comprehensive post on my show us yours page so take a look?

Previously there, there was quite a discussion on the main engine mounts, but more on comparisons between types and not covering the rubber parts as I’ve not had to tamper with these. I thought it might be helpful to round this off with the rear engine mount; complete the set sort of thing. Take a look (it’s on p2 of my show us yours page)!

HTH!

LH119V's post about the rear engine mount is very thorough, but just to add to that, here's a video of someone replacing the rear engine mount with the engine and transmission in situ: https://www.youtube.com/watch?v=ds4FIjixPC4&t=61s&ab_channel=nathansharma87

Thanks all for the feedback. I have replaced my rear engine mount already and have the two front ones on-hand but haven't actually gotten around to them yet. If anyone has done the front ones it would be great to know what needs to be disconnected/moved in order to use the engine hoist my buddy has at his house. Much appreciated.

UPDATE: I took off both my drive shafts yesterday and replaced all the U-joints. The first one took the longest and then I had a system. I then went and did a test drive on the highway and the vibration/noise is gone. I replaced with non-Toyota U-joints (from Rock Auto here in the US) but they have grease fittings.