Guys,

I have this weird bounce after installing my Fabtech 6" lift. I can't really describe exactly how it feels, but its an up and down OR back and forth motion. NO real steering wheel shake at all. It happens at various speeds, then goes away ater accelerating or decelerating.
I have had my wheels and tires balanced THREE times and it hasn't fixed this. Shocks are good to go.......brand new RS9000X's.
Could my driveshaft be the culprit? There was absolutely no bounce before the lift.There was no torsion crank so thats not it............im lost and wishing this would just go away

Thanks,
Mark

 

Welcome to the world of lifted trucks . I had it pretty bad on my old '97. Change the setting on the shocks. I think it usually has to do with the road conditions and the stiff suspension.

 

I'm not talking about a ride with a "lifted truck"...i've been there and done that.

This is sick. Driving home on the freeway from Phoenix it got so bad at 65-70mph that I thought I was going to wreck. The passenger side head rest looked like it was being used as a punching bag. It was bad, and still is.....

Any words of wisdom?

Mark

 

What tires do you have?

 

Goodyear MTR's 315/75R/16 (35")

I dont think its tires or wheels at all. I've had it balanced 3x now and even had the front 2 tires REPLACED because the first set was said to be "slightly" out of round.
The allignment after lift seems to be dead on also.....no pull left or right at all.

The truck came out awesome! I just wish I could cure the bounce.....heres a pic.
<img src="http://www.gladesteen.com/lifted%20(4).JPG"/img>

Mark

 

anything that has mass will vibrate. If that piece vibrates near its natural frequency (function of several things), you'll achieve resonance, or a real bad vibration. That's what could be happening here, especially if you feel you've eliminated the tires. Unfortunately, I don't have any idea how you can go about finding out if this is the cause. Just something else to chew on...

By the way, I like the way your truck turned out - looks real sharp. I'm looking to go 6" also (combo of Rancho 4" and PA 2") and like how the 35s and 6" lift work.

Good luck with the vibration problem -

Mike

 

It seems the problem may be tranny related. I am now leaning towards the Torque Converter acting up. This weekend I am going to drain and refill the converter with fresh fluid.
Hopefully that will solve my bouncy ride. I have noticed a shudder from a dead stop and other F-150 owners have described this EXACT problem which related back to the TC.
I'm hoping a flush and fill will solve it !!!!!!!!!!

Mark

mike-
If you want a 6" lift, get the Fabtech! Its very well built. Only downside are the shocks, but I put RS9000X's on mine and they are great! The Rancho lift is also nice, but why bodylift and suspension lift when you can get it all at once! My .02

 

Mark,

Hopefully the tranny flush and fill cures the vibration problem. I hope it wasn't the lift that caused it, so keep us posted on what fixes it!

On the lift...I never really looked into the Fabtech lift because 1) never heard of them until recently, and 2) read where another member complained of the 6" lift. I don't know if Fabtech has transmission/t-case drop brackets or something to keep the driveshaft angles near stock? I kind of have this rule (no real "scientific" backing to it) that I don't want to lift the suspension more than 4". Honestly, I should look into it some more. Plus, I'd like to lose the body lift cause, well, truck frames just aren't pretty things.

Anyway, thanks for the advice, and good luck -

Mike

 

Does it do it all the time? The shudder from the stop could be axle wrap.

If you were on I-17 when it happened, I would expect it. That highway sucks ***. It makes any truck bounce. Especially the lifted ones.

 

Probably not it, but just an easy thing to check: U-joints. If they go bad, it can throw you drive shaft off, and then you have something that vibrates like crazy at highway speeds. Just an idea.

 

I will get the tranny flushed this weekend. Hopefully its something that simple. The shudder doesnt happen all the time, only at certain speeds. Its definitately not caused by road conditions either.
The driveshaft, U-joints and pinion angles have all been checked and are all good.

I will keep you posted!

Mark

 

Just one thing, how is your alignment? I know that won't really make the truck bounce, but it will cause it to shudder at certain speeds.

 

I see you've had it checked but I would have bet on the drive shaft angle and the u-joints binding.

 

There is a way to start eliminating things but it can be dangerous if not done properly. I am going to skip the safety warnings and just give you the methods needed to track down the possible source(s) of your bounce.

Raise the rear tires into the air (at least 3" inches above the ground) and carefully run the vehicle up to the speed that you noticed the bounce. If it bounces really bad this could knock the vehicle off the stands and cause injury, damage, or death. If you feel the bounce try taking the tires off and doing it again. If it still bounces you now know it's NOT the wheels or tires. Next to go is the driveshaft. If the driveshaft is removed and you still get the bounce you know it has something to do with the transmission.

This method of testing is hazardous but is sometimes the only way to track down the offending problem. In your case it might be a bad pinion angle and a pair of inexpensive shims can fix it. If you had a shop install this kit I'd ask them to do the investigative work and then go from there. If you installed it yourself (or had a friend do it) I recommend the test procedure outlined above.

Jeff @ PLC

 

How was the lift in the rear achieved Stacking blocks or Add a Leaf? It really sounds like a rear spring condition to me you may want to take it back to the place you had it installed and have them double check all the bolts to make sure everything is tight. Also tell them the problem and take on the the installers for a drive to show him what it is. My stock 4x4 bucks pretty terrible on certain freeways.

Richard D.

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