Need help with rear "bounce" problem please

Stroghty · Feb 13, 2015

I have 2011 f250. I am running 35 X 12.50 Nitto Mt tires that were balance by offroad shop who said they "balanced to zero". They are new.. The truck is stock height. I am not a mechanic but from the looks of the shocks they appear to be rancho 9000xl shocks and have the adjustment knob on them. The problem I have also was there with the previous tires I just changed.

My problem.. While driving down the road at around 55 to 60 miles per hour I get a hint of a "bounce/dribble" wanting to start, it is not constant and comes and goes. If I mash my breaks moderately it noticeable starts bouncing in the rear if I am in that speed range and smoothes once I hit 45 mph or so. If I am over 45mph and hit a bump in the road it feels like (my best description) my rear tires (more towards the right side) start dribbling. Not uncontrollable but noticeable. It smoothes out within a second or two.. Does not sway left or right... My brother said my right rear shock may have a little fluid on it..

Would/could this be a shock issue? What other issues could it be? When I called the local shop they said it was the death wobble. Doesn't feel anything like a wobble though. Another shop said it is something I have to put up with for having the oversized tires on the truck..

If I wanted to change the rear shocks which rancho shock model do I need. I have a 2 1/2" level kit and 3.75" rear block I am wanting to put on the truck.

Any help/advice is greatly appreciated...

Cheap6.7 · Feb 13, 2015

What's the tire pressure at?

Platinum250Scorpion · Feb 13, 2015

Cheap6.7 said:
What's the tire pressure at?

^ Yes & is it possible the shocks are just due to be replaced? Also, it sounds like you have new tires. But, is the tread worn evenly or cupping (if not new). Cupping, or every other tread knob higher than the one next in line around the tire &/or the knobs worn other than flat in relation to the tire's circumference, can be a sign of worn shocks &/or overdue tire rotation. My '03 250 (4" all-spring BDS lift on 35"s) had its own vibration/resonance around 65-70 I think. My '11 450 did it around 50-55 (stock everything) once in a while, dependant on selected gear & throttle position. And, my '14 250 (again with the 4" all-spring BDS lift on 35"s) is the same; with both 6.7s being very slight & intermittent with it. I think each rig has its own resonance where it'll have an ever so slight vibration; depending on tire pressure, size, & wear & shock life. The whole when you brake bit makes me lean towards shock(s) more likely than tires; while not ruling out the tire(s). But, that's just my garage gear head thoughts.

- A vet' that's gone from a 7.3 to a 6.7, tryin to gather info & help out when I can. New to the 6.7 & PSA. Please excuse my potential FNG ways.

sootie · Feb 13, 2015

this is a common ford issue due to frame flex. it is not death wobble becasue it is in the rear. a good set of shocks like Fox or something will help but the only solution i have found so far is to put 500 lbs in the bed.

Platinum250Scorpion · Feb 13, 2015

Interesting, and see I have a bunch of stuff in mine... tools, fluids, cables, straps, n such.

- A vet' that's gone from a 7.3 to a 6.7, tryin to gather info & help out when I can. New to the 6.7 & PSA. Please excuse my potential FNG ways.

Platinum250Scorpion · Feb 13, 2015

sootie said:
this is a common ford issue due to frame flex. it is not death wobble becasue it is in the rear. a good set of shocks like Fox or something will help but the only solution i have found so far is to put 500 lbs in the bed.

So, maybe that's why it's smoother on the 6.7s, coupled with being newer trucks, different suspension, & tires still wearing well.

- A vet' that's gone from a 7.3 to a 6.7, tryin to gather info & help out when I can. New to the 6.7 & PSA. Please excuse my potential FNG ways.

Spatel23 · Feb 13, 2015

I have this issue also.

I cant remember if it was also happening when the suspension was stock, but I think it was.
IMO.....its nothing to do with the shocks....they may help very little but not much. I have the Icon CDC adjustables and have tried almost every setting to no avail.

I think its in the angle of the rear blocks or driveline.
We have a really good driveline shop here that I plan to take it to and have them see if they can find anything. Just havent been bored enough to go yet.

TrickTruck · Feb 13, 2015

shocks

factory shocks are right next to junk

TripleE44 · Feb 13, 2015

sootie said:
this is a common ford issue due to frame flex. it is not death wobble becasue it is in the rear. a good set of shocks like Fox or something will help but the only solution i have found so far is to put 500 lbs in the bed.

This. It isn't the shocks.

sootie · Feb 13, 2015

traction bars make it worse and i have tried many combinations of carrier bearing mount, block taper block height etc. no change.

Stroghty · Feb 14, 2015

The tires are brand new... Less than 200 miles... Whivh rancho shock for 2.5" level kit... Front and rear... What are the best shocks

jcain · Feb 14, 2015

Traction bars really help my ccsb stop the bed shake. 600lbs of tube sand all but eliminates it. You can watch the bed shaking in the side mirror. Frame deflection.

WHY NOT · Feb 14, 2015

I have had this issue since the day bought the it bone stock and have pretty much changed everything in the suspension now and the thing will still bounce, but not as bad as factory. Everything seems to help a little bit with each thing added but I haven't found anything to completely solve the problem yet. Although I haven't driven the truck w/o the trailer behind it down a road that makes it bounce since I added the ALA's and went to 3.5" instead of 2.5". I really think the frame is just flexing enough to cause it to bounce. I need to get my go pro under it on one of the sections of road that make it bounce and see if the frame flex is visible

sootie said:
traction bars make it worse and i have tried many combinations of carrier bearing mount, block taper block height etc. no change.

My traction bars actually took a little bit of the hop out of my truck

TrickTruck said:
shocks

factory shocks are right next to junk

This is true the factory shocks are complete junk

Spatel23 said:
I have this issue also.

I cant remember if it was also happening when the suspension was stock, but I think it was.
IMO.....its nothing to do with the shocks....they may help very little but not much. I have the Icon CDC adjustables and have tried almost every setting to no avail.

I think its in the angle of the rear blocks or driveline.
We have a really good driveline shop here that I plan to take it to and have them see if they can find anything. Just havent been bored enough to go yet.

Out of all the things I have added to the suspension of the truck putting my 2.5 Icon resi shocks have helped the most. The problem isn't eliminated but it really cut down the constant bounce on some sections of road.

strokinpower · Feb 15, 2015

There was a good thread about this on the org and a guy made a frame brace and basically tied the bottom of the frame rails together mid way I believe and it helped tremendously. I had 9000xl's on my 6.4 and the back ones froze up and made the truck ride like hell so you might un bolt the bottom and see if they are frozen.

dseitler · Feb 15, 2015

You need to borrow a GoPro and see exactly what's going on. Could be wheel bounce, brake Rotor or 100 other things. Center of your rims not cleaned when they were installed or a animal with a air gun forcing the wheel on and shaving the aluminum off. I have seen it all with a fleet of over 100 super duties. Tires are far from perfect.
Go back to basics. Pull your wheels off and have them Road Force Balanced. Clean everything! Put the wheels back on and use a torque wrench only. Use the GoPro and see if the tires are leaving the surface of the road when you are having a problem. Most of the problems I have encountered have all been tire, wheel and brake rotor related. If you have ever towed and had a panic stop you rotor could be out of balance. Just my .02 before you start replacing everything on your truck.

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