Bronco Shakes at 65ish MPH!!!

[broncoitis]

Ok, this is kinda weird I think. Been putting more and more miles on the Bronco lately. Nothing crazy but just driving it more often. This is something that is not new just haven't mentioned it on here and it is a bit strange I think! I will say that my suspension has improved as I have driven it more and more. I guess it is breaking in and it only has like 3000 miles on it maybe. That is a Good thing but I still think it could be a little better in the front. The rear is decent but I think that is more attributed to a lack of weight back there and a bumper and spare tire should greatly help that weight issue.

Ok, enough rambling. No matter what, whenever I hit around 65ish maybe more or less, my trucks starts to shake! I notice it mostly from the Tach Mounted on my rollcage starting to move left to right rapidly. Now if I go a little slower or faster it is non existent and pretty smooth. However, go in the 65ish range and boom it starts to shake. Driving home from shore last night and enjoyed the HELL out of it and it has me motivated to get STUFF done to make it even better. However, the shakes have to go if you know what I mean! Heck, I was literally hauling butt at one point like 95+ MPH and truck was tracking like a RockStar to me. I only mention this because you would think that the shaking would only get worse and not just stop completely. It literally stops at a couple MPH over or under 65! Having said that, 65ish is where I am 95% of my driving and the shakes at that speed cause me to drive faster than I would like.

Any Ideas for this oddity? I have checked underneath and all seems tight and the angles are all pretty close. I will take some pics to post but I am lost with this. Next step is a go pro or something similar attached to bumper to see what happens! %)

As always, maybe someone has an idea of the cause or has had something similar and figured it out.

 

[badmuttstang]

Could have thrown a wheel weight I'd have them checked to see if there out of balance common thing when i worked for les schwab only other thing I could think of is driveline.

 

[broncoitis]

Wheel weights aren't it I don't think! Recently I installed these balancing disks which have actually made a big difference with the tire noise and overall smoothness of ride but did the same thing prior to them being installed. They run them on the Big Rigs and all the guys give them glowing reviews so I thought what the hell can't hurt and they weren't that expensive and extend the tire life by up to 20 - 30 %. Because your tires and wheel assembly are continuously balanced. I honestly think that these things flat out work and the noise from the tires was easily cut in Half maybe more as a result. In fact you don't even have to balance you wheel and tires with these disks on there according to Centramatic. Mount up the tires and that is it. The media in the disks does it for you while driving constantly adjusting to balance things. I think they are called Centramatic check them out and see what you think! Great product it think!

 

[okie4570]

Not on my bronco, but EVERY time I've started to loose a u joint on my f250 or excursion, it would do the same. Usually at 35mph or 55mph.

 

[bronconut73]

Mine does the same thing.

Everything is new.

It has had the same 60 to 70 shake through all the suspension work, steering linkage, leaf spring shims, WH Wrap Trap, New leaf packs, all new rear end, all new front end, New drive shafts, New shocks, etc....

I figured that with how extensively I planned to go through it I would eventually find the problem.
But no such luck.

Please keep us informed. Like you I typically drive below or above the 60 to 70 range which is inconvenient.

 

[Flhtrdr]

My 2011 f150 developed a shake and after checking the tires for balance I crawled under it and noticed a weight had fallen off the driveshaft. Had the driveshaft rebalanced and no further problems.

 

[broncoitis]

Do you think that a drive shaft imbalance could appear to be the front end actually be coming from the back? As much as I don't really wanna pull the driveshaft maybe I will have it checked. Just think it is weird how it only happens in that sweet spot. Literally 1-2 mph over or under and smooths right back out!

 

[badmuttstang]

Yes and the 1-2 mph over or under is the common sign pointing to a imbalance from either the tires or driveshaft and you have pretty much ruled out tires so check driveshaft won't hurt.

 

[Rustytruck]

You could pull the rear driveshaft and drive it on the front. Never driven one on the front only that fast. But I would remove the rear shaft and check the the driveline angles between the faces of the shaft mounts. I would also check the output shaft on the transfer case for a wiggly yolk. When I got my Bronco back in 1977 it had 10,000 miles on it and the rear yolk was wiggly. I had to re-shim the output bearing to get it into proper spec. Ford screwed that up from the factory. I would also check the mounts for the transfer case and make sure it isn't wiggling about.
I have also seen wear on the yolks that allowed the u-Joints to move sideways in the yolks.

Tires can be balanced but not mounted correctly so try swapping the front tires to the back and see if the vibration moves.

 

[sykanr0ng]

Check your tires for tread separation.

I had a car tire that did that, 50 it was fine -55 it shook like crazy - 60 it was fine.
It was a smaller tire so it was turning faster.

 

[broncoitis]

Ok! Gonna start with the Driveshaft angles and see where they are at and check the output on the tcase and mounts. From there see where I get. I will do my best to figure this out. LOL! Gotta be something fairly simple I would think! Only problem with that is I don't think all the time!

 

[70Sport]

I just went through the same thing. It would shake at 65 mph and smooth out if I slowed down to 60 or speed up to 70+. New tires mounted and balanced fixed it for me. My tires were old and unevenly worn so I needed them anyways.

Good luck!

 

[Mark]

I'd also make sure the driveshaft is phased properly (ujoints on the same plane).

 

[dave67fd]

If it shakes at one speed point and "not" below or above it is usually always a tire/wheel issue as mentioned. Driveshaft imbalance may be more pronounced at a certain speed but is generally still there at lower or higher speeds.

 

[broncoitis]

Don't want this to archive but still working on the issue! Hopefully will figure it out and let yall know what the solution was.

To be honest, I kinda opened up a pretty big can of worms by pulling my rear main seal. Seems like it is gonna be a real PITA to get back in without loosening in the caps a bit. However that is another issue and not related to this shakin.

 

[DirtDonk]

After you do the driveshaft test, I would rotate the tires. Even if it's a balance issue and not a bad tire, rotating them should at least change the circumstances for the shake.

Paul

 

[67RT]

Slow down! You are driving an old truck... Sorry, not helpful. I hate working on Fridays!
I agree with the tires as the cause.

 

[Crush]

I think tires also. There are problems that arise with tires that balancing can not take out. Busted belts, cupping issues etc. all of which would only resonate at a certain rpm

I have been wondering anout those balancing discs too. The quoted me $200 for discs to fit the bronco. Im heavily keaning towards doing this. How have they worked out so far

 

[70_Steve]

Just saw this thread, and will admit I didn't read each posts, but...

I just went through this. Bought new KM2s a few years ago. They drove great at all speeds when new, but developed that same, almost violent, shake around 65 MPH that was gone over 70 MPH. Went back to Discount Tire several times to try to resolve the problem and each time they would re-balance the tires. The vibration would lessen for a while, then come back as violent as ever.

My last trip to Discount Tire, I was determined to have the problem solved. I talked them into doing a Force Balance on the tires. The found two tires that, even though they balanced fine, showed way off when force balanced. They warranted two tires and now I'm back to smooth driving at all speeds.

 

[markw]

Steve, what's force balancing?