CCLB rear end bucking

[kampy]

I have a 96 CCLB that the rear end hops or bucks about 95% of the time when operating in the 39 – 42 mph area when the truck is unloaded or lightly loaded, problem is I seem to spend an enormous amount of time in that speed range with the speed limits in our town.

Doesn't matter if I'm accelerating or decelerating lightly, it still does it.

It doesn't do it if it has a significant load in the bed, say 800 lb or more.

It feels just like a case of axle wrap but axle wrap doesn't really make sense because it does it even when there's no or very little load applied to the drivetrain.

Here's a list of things that have been changed over the years for various reasons that had no impact on the hop/bucking.
3 different sets of brake shoes
3 different sets of brake drums
Changed to SD springs (part of an RSK swap) did it before and after
3 different sets of shocks
3 different sets of tires, all the tires have been force balanced at different times

It's done it the whole 4 years I've had the truck and it really bugs me, I'd really like to get it fixed if someone has any ideas.

I've been contemplating switching to a F250 block from the F350 block to see if its a leverage thing working against the springs. If anyone has a set of the shorter 250 rear blocks they want to give away let me know!

Does anyone else have this issue? I drive an '06 450 at work and it does the same thing at approximately the same speeds and I've read on other forums other people with new trucks under warranty having the same described problem, is it possibly just a normal thing for some ford trucks?

I'm open to suggestions.
Thanks

 

[WHY NOT]

It seems to be a cc/lb problem. My truck will even buck on concrete highways. The only solution I have read is to put really nice shocks on the truck to help. Like icon 2.5 piggy backs with the cdc valve. I'll buy some one of these days I guess. I know what you mean though. It's not axle wrap for sure as I have traction bars and still have the issue although they may have helped a little.


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[kampy]

Yeah, mine jumps around bad on the cut lines/expansion joints in a concrete highway, I think all trucks do that to some degree, this is a little different, what I'm talking about here is perfectly smooth asphalt and between 39 and 42 it acts just like a tire is out of balance or out of round, goes away as soon as you get over 42 mph.
What kind of traction bars do you have?
I appreciate the input.

 

[WHY NOT]

I have ouo traction blocks on my truck. I can get mine to hop on smooth roads too sometimes when I have my gn behind my truck. My trailer is really well balanced and it seems to amplify the hop going down the road.


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[mandkole]

Right after TC lock?

 

[Chvyrkr]

It's tires...

Driven these trucks since I bought my first SCSB 97, and the only thing that stops that buck is new tires.

 

[kampy]

Not necessarily right after T/C lock...if the converter just locked then sure, but if the converter isn't locked it still does it, does it in second, does it in third, pretty damned sure it would do it in od if it would shift in that low.


I hope your not right Chvyrkr but I'm afraid you might be, I'll keep chasing this for a while and hope someone pipes up that has experienced and cured it. short of a new set of tires every 10K.
Thanks guys.

 

[florida 6.0]

Did not realize the OBS trucks did this to . My 99 cclb and my 05 cclb do the same thing . Must be a Ford thing .

 

[Powerstroke Cowboy]

I can run my tire all the way to bold and i have never had this trouble. Have you tried jacking it up and spinning the tires by hand?? Makes me wonder if it in the differential. Do you have limited slip or just the one tire burner?

 

[Chvyrkr]

There's this neat thing called rotation and balance... On all three trucks, when it starts bucking, rotate, balance as required...

Problem solved.

 

[WHY NOT]

There's this neat thing called rotation and balance... On all three trucks, when it starts bucking, rotate, balance as required...

Problem solved.

My tires were balanced 7k miles ago rotated 2k ago. I rotate every 5k. It did it with brand new stock tires and my atzs. all were properly maintained. Balanced and rotated. Tuck still bounces. Pretty neat still though.


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[Chvyrkr]

AAAAAAnd you're running 35x13's...

Those balance like a dream, after all.

 

[Powerstroke Cowboy]

My tires were balanced 7k miles ago rotated 2k ago. I rotate every 5k. It did it with brand new stock tires and my atzs. all were properly maintained. Balanced and rotated. Tuck still bounces. Pretty neat still though.


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AAAAAAnd you're running 35x13's...

Those balance like a dream, after all.

Take a look at the post above yours in red.

I still would like to know what everyone has for a differential that has this problem.

 

[WHY NOT]

E locker with 3.55s in my 11


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[Chvyrkr]

3:73 in my 02.

My wifes 06 is 3:55

My 97 is 4:10

My 74 does it too, with 4:10's...

Had an 81 in high school, 3:73...

And I'm sorry I'm not letting go of this one, it pissed me off for a long time.

Until one day... I had a set of 35x15's goin on the 74, and the dude mounting them asked me if I wanted the powder in the tires instead of wheel weights.

Driving home, and driving that truck over the next however long those tires were on it, it didn't bounce at 40-45. When those tires wore out and I put 35" buckshots on it, they balance it with wheel weights. And the hop was back.

Knowing what little I do about tires, an E load range tire is a b1tch to balance. It's even worse the bigger the tire gets.

And it's hardly an issue patented by pickups. Plenty of Jeep guys I know have their tires balanced AND shaved so that their jeep won't get the buck/hop/bounce at 40-45.

 

[Powerstroke Cowboy]

I here you there. We had powder in ours and it would vibrate @ 40-45 next set we went back to weight and it would no longer do it. We have (had) 4 OBS pickups and to SD ones (just sold one) Not a one of them had this problem you all are talking about. We have stock tires up to 34" tires with 3.73 4.10 and 3.55 gear, Limited slip and lockers and one wheel burners. Never had that problem. That is very interesting.

I wish I could help you there. What brand of tire do you run? I have wrangler goodyears, cooper, General, and toyo. Never had that problem yet. WE even have a set of cheap junky tires (some chines company) Still no problems. The only time we did have that was with the powder or beads in the tires.

This is a problem I have never heard of til now. I though maybe we could trace it to something.

Chvyrkr....But like you stated tires and the balance job can play a BIG part in that.

 

[Chvyrkr]

That's precisely the opposite of the experience I described.

The powder balance method, doesn't have a weight limit.

Wheel weights do have a limit, as per DOT.

E range tires are heavy. They get heavier the taller and wider and more aggressive they get.

I know for a fact I've had several sets of tires (BFG - Dunlop - Toyo - Nitto) that weren't "optimally" balanced with max wheel weight.

And they hopped.

Those nasty super swampers I put on the 74 wouldn't have come close to balancing with weight, so the guy asked if I wanted powder. And that beat up old farm truck rode better with those tires at 40-45 than anything else I have.

Jeep guys shave their aggressive tires, because like I said, weight alone doesn't get a big heavy tire where it needs to be for comfort.

They can only balance it for certain speeds, not every speed.

 

[Powerstroke Cowboy]

For the most part I run all stock sizes. and I get the lightest tire i can find for what I want.

Not sure if that would make the difference. Where the beads and powder did help for me was if i was in mud a lot. When i would have dry mud built up it still would even out good with the beads or powder. The wheel weights could not keep it even.

I wonder if there are more that can post up what they have seen. Funny thing is most time they really do not put much weights on to get them balanced. Sometimes they are just little ones that are about 3/4 of a inch long. Maybe I am just lucky? The only set of Toyos I ran were 315/75/R16 I hated them and they did bounce a little. I just ruled that as the fact that they were almost bold and were big.

 

[WHY NOT]

I'll agree with you beads/ powder will balance a tire better but I know my tires are in balance. You can feel an out of balance tire at speed no problem and I know what that is like. The cc/lb trucks seem to get this hop more often than the sb trucks. I think it just has something to do with the wheel base especially when hitting joints on concrete highways is where I get it worse.


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[kampy]

Thanks for the info everybody, to answer the questions for my particular case...I have a 3.55 with limited slip, and while I haven't added friction modifier, the 85w140 I use in the diffs has it in the specs. Is it enough? I don't know. That said, the circumference of the tires are all within about a half inch so the speed differential between the 2 sides shouldn't be enough to cause clutch pack chatter. Clutch pack chatter normally gets worse as the speed differential grows bigger so in theory if it was causing this it should be worse at 70 than at 40 instead of just going away. I have run the truck on jackstands and didn't notice the wheels or tires tracking funny or causing a shake.

I'm running stock sized (235/85R16E) BFG all terrains, they get rotated and balanced every 5k, the wear is fine, the bounce is there both before and after the rotate/balance, also like I said in the beginning, they've been run on the force balancer also. I had Hankook ATM's before and I liked them better but I had the same issues with them at the same speed, just not quite as noticeable.

CHVY, I also have an 03 TJ running 35 BFG muds on beadlocks mounted by me with no weights, beads or powder and its as smooth as butter at speeds up to 75.

This "seems" to be more related to a specific speed, the speed is the only thing that remains a constant, most everything else has been changed at one point or another. I'm gonna have a friend follow me to see if we can try to pinpoint exactly what/where this bounce is originating from.

Thanks again guys.