frustrated over bounce

[SoCalRefuge]

Seven years later....I'd love to know how this story ended...

[Kurt Combs]

My bounce started when I removed Dodge 16" rims and 225x16 tires and install later model Ford 16 steel rims and 265x16 tires. I thought they were out of balance, but I still have a bounce and it will never be resolved, tired of throwing $$$ at it. Things I have done or changed:

Replaced 360 with 460 and a different transmission
upgraded to second set of tires, these are Michellin, which are worse
tire rod
all front end bushings
u-joints
rear spring bushings
front shocks
tires rebalanced with proper lug centric adapter
new engine and tranny mounts
new Red Head steering box
There are other things I replaced that I have forgotten in the list, but you get the idea

My guess is there are multiple issues that can be attributed to old age causing my problem.

[ultraranger]

You mentioned having a '69 2WD but, I didn't catch if it's an F100 or other (?).

IF it's an F100, I would presume you have a Ford 9-inch rear under your truck. Has the 3rd member ever been rebuilt while you've had the truck?

If not, the bearings, particularly the driving pinion bearings/races could have some wear and some added degree of slack in them. The drive shaft is coupled directly to the input of the driving pinion on the 3rd member. Engine off or engine on while traveling at 43/44 MPH, the drive shaft will still be rotating. Worn driving pinion bearings could induce vibration or wobbling through the drive shaft.

Another possibility is driveline angle could be a little off.

[blumule]

ive never tried to run that speed in 2nd gear. Ive got a 3.50 gear in the back. And yes ive swapped in two other center sections hopeing by chance that was the problem.Ive got 6 extra rear axles with new bearings that ive swapped back and forth.Driveline angle is fine. Ive got a 3 degree operating angle at each end.,swapped trannies, springs, mounts you name it ive tried it. I can rebuild this truck blindfolded but just cant track down the wobble. its a speed related wobble pure and simple ,but from where if it aint tires? ive rebuit frontend, had it aligned, numerous balanceing jobs. I feel like curt, maybe its just the age of the truck causeing some freaky harmonic imbalance from the frame somewhere.I wish the offending part would just wear out so I would know what it is.i really appreciate everyones input,but im sure I tried it all.

[iwhodat]

Get someone to ride on the side of you and look at your front wheels while you are experiencing the wobble. That's when my buddy saw my passenger side wheel hopping up and down. He told me he thought it was a bad shock. I thought it was a tire with a busted belt. I replaced the 2 front tires and found out $300 later it was a bad front shock. I should have listened to my friend and changed the shocks first.

[68RGR]

I'd like to suggest a slight modification to the last suggestion -

Have SOMEONE ELSE drive your truck and YOU ride along beside it!

If I were you, I'd want to see the problem firsthand with my own eyes. If this works, you might want to wear a diaper 'cause you'll probably wet your pants if you do see something that narrows it down!

Good luck!

[blumule]

ive tried both methods .trying to lock in at that direct frequency 'speed' , or getting her to watch while I drive while dodging traffic seemed fruitless.So yesterday, I mounted a video camera underneath. [ I wanted to mount myself but who would cut the grass if something happened ].I watched both tires in motion at said speed with no apparent wobble or bounce to either side . The trucks frontend still bounced. I could clearly feel and see left frontend going up and down.so if tires are round but my frontend bounces at a particular speed what does that tell me? Shocks? shocks are a year old. All steering and suspension bushings are new and tight. driveshaft was balanced professionally from a reputable driveline shop.I even purchased a balance ring from balance masters . both procedures did produce a smoother operation ,but didn't fix the shake.this is far fetched but I now want to throw this out there.i did replace the driver side cab mount , along with several other mods including disc swap about two years ago. I think , but not sure , this may be when my problem started.ive done so much refreshing this truck . anyway the new cab mounts bottom surface was about a 1/4 to 3/8 of an inch lower than the original mount. in effect raising the cab on that side when mounted.It isn't noticeable just looking at it but I now wonder if this is somehow someway playing into this bounce? The cab mount is a slip over design from flashback 100s. I riveted it in . what do yall think?

[Kurt Combs]

Here is a thought, you might try swapping your front disk brake rotors from one side to the other and see if it feels different. And I think you might be on to something, looking at mounts might be a good idea. Good luck!

[sargentrs]

Hate to state the obvious, and hoping I don't offend you with the suggestion, but with all the obvious swapping, removing and reinstalling you've done on the front end components, are you sure you got the LH parts on the LH side and the RH parts on the RH side? I'm only saying this because, when I swapped in my '74 disc brake spindles, I installed my I-beams backwards and had to RnR them, then started to put my disc brake spindles on the wrong sides. Fortunately I double checked before I put my radius arms and coil springs back on or I almost put those on the wrong sides too!

[blumule]

No offence taken.don't think I haven't Thought of that.its all good.

[sargentrs]

This is going to be a revelation to all of us if you figure out what's causing it.

[blumule]

ive gone over and over and over the driveline, wheels, tires ,suspension and steering.nothing stands out as being worn out or loose. Actually most everything is new. the feeling is an out of round tire even though it does it with other wheels and tires. im afraid im resigned to living with it like curt. my hope is the offending part will eventually wear out and show itself. my latest thought is a slip over cab mount I installed on driver side. the mount is riveted in and very secure. the bottom of new mount was 1/4 to 3/8 of an inch below factory mount, in effect raising cab on that side. its not noticeable with the eye but makes me wonder if this is somehow playing into my problem. idk. clutch and steering operate as normal. I also wonder if shocks or springs can be too stiff. after installing new coils and shocks up front the truck did have a very stiff ride afterward.I did the disc swap, coils, shocks and cab mount all at same time . I also yhink its around the time my shake started. Not sure as it has been several years ago and truck was not driven that much. I also remember buying the new tires thinking my old tires were my problem. so tires can be ruled out.

[Gramps Ridde]

Just to let you know you are not alone. Got my stock 77 short box 2WD in 95. Left front wheel hopped at 61-63mph. Since then I have lowered it with DMJ axles, new king pins and bushings,new mags and tires, stiffer springs and shocks, bearings, etc. Had it down to the frame and rebuilt the 302, C6 trans and 9", new drive line, etc. THE BOUNCE IS STILL THERE! I'm seriously considering a CV front end this winter. This will replace every moving part and mount in the front suspension.

[67 StylesLide]

borrow a pair of good decent tires/wheels and swap them out.
To me it sounds like a slipped or broken belt in a tire.