Fitting 35’s with minimal trimming NOW ADDING LONG TRAVEL AND 934 CV’s

Hard to say because any change right outside of 40mph makes it stop. I haven’t been able to coast without dropping speed long enough to see. I’ll play around with it some more. Rear diff from ECGS was put in about 8k miles ago. Changed gear oil this weekend. Bout as much on the magnet as the 500 mile break in.

 

Is it accompanied by any noise? I would get it up to the speed it vibes at and see if you can make it come and go depending on what you do with the pedal. Another thing to think about is axle bearings. They will vibrate pretty good as well. However, they usually don’t stop. What oil are you running in the rear? After my first change I’ve never seen any metal on the magnet.

 

Have you checked your transmission mount on the cross member ? I've definitely read of multiple folks discovering a completely clapped out bushing on the mount.

 

I’ll give that a shot. Just had the rear axle bearings done thinking that was it. After doing the JD LT kit I hear a slight whine up until 45 and it stops. I thought maybe it was the CVs breaking in or something. Not sure that’s a thing, but just the thought that popped in my mind. Might be related to this. Hasn’t gotten worse, hasn’t gotten better. I also swapped front wheel bearings too. Running 85w140 per ECGS recommendation.

 

I have not. What’s a good way to test it or will it be obvious?

 

the images that I have seen were very obvious wear / crushed bushing w/ slop

 

I would expect to hear a little more rear noise with how the JD shackles are uniball. It’s naturally going to transfer more noise and vibration to the chassis. But the vibe that comes and goes would make me a little nervous. ECGS is stellar with warranty. So if it is the diff, they won’t even ask questions. They have been awesome to work with.

 

I’ll give it a look. Something is pooping itself under there at 40mph. And it’s worse when it’s cold. I wish I had a GoPro to stick under there.

 

I’ve got the Archive set up in the rear. Still had this rear weird stuff before doing that though. Thought it was tires at first and still not totally ruling that out since it gets better the warmer it is…I should find a friendly Tacoma and swap…

too many variables for my feeble mind. Will probably end up waiting for something to catastrophically fail and saying oh yeah, that was it!

 

I will say, my current tires flat spot pretty good when it sits in the cold over night. Takes a little driving to make them run smooth again. But mine is more of a bounce than a vibration.

 

I would definitely classify mine as a bounce too. Like damn near coming out of the seat. E rated 35’s at 28psi parked on gravel overnight. Maybe it’s that simple…

 

Very well could be. MT’s are notorious for it. Mine will rattle your teeth out for a hot minute when it’s below freezing. I run 26/24psi so it’s definitely on the low side.

 

That seems to be the easiest place to start if I can find someone to swap with. These suckers are wearing on my nerves but damn they do so well offroad…

 

@Dayman Karate I had some gnarly vibes as well for a while fairly recently. There were two pretty distinct ones. The first vibe was solved by a new driveshaft with double cardan joint. The second vibe was solved by a new transmission.

This is what I would do to try and diagnose:
- swap wheels/tires.
- put the truck on jack stands or a hoist and get somebody to accelerate the truck to the speed it starts shaking at while you are underneath listening and looking.
- pull rear driveshaft off and drive around in fwd. If the shaking stops you know it's something behind the t-case.

 

That sounds like a good game plan. What speed/s did you have your vibes and was it bad enough to shake the bed?

 

So I drove around at lunch and it’s 40ish mph no matter what. Foot on the pedal, off the pedal, 4wd, neutral, fourth gear etc. less noticeable than this morning but still bad. Starting to think it’s the tires. Would a road force balance do any good?

 

Itll show high spots and low spots in the tires. Only way it'll work is if they match the tire to the wheel and if that gets them within spec.

 

One of them was a deep and extremely violent rumble sort of thing, and that seemed to happen when it shifted to second and third, and was solved with the new tranny.

The other one happened at around 40-50km/h and was pretty rough as well. That was mostly poor driveline angles, but I think I may have had a small amount of play in the carrier bearing as well. I tried lots of different shims etc, but could never get it to work right. This was solved by the double cardan and a new CB

 

I guess the next logical step is to find a taco friend with tires to swap out with and try to rule that out.

 

Didn't you say your wife has an FJ cruiser?