Wheel Hop?

[OLDROCK&ROLLER]

Anybody else on here have/had this problem? How can I prevent it? This is what I got. Rear Trailing arms suspension with air bags,lowering blocks and a posi. Thanks for any help,Kenneth

[neonlarry]

What shape are your shocks in? what pressure are you running in your bags? Trailing arm suspensions usually hook up quite well.

[OLDROCK&ROLLER]

Originally Posted by neonlarry

What shape are your shocks in? what pressure are you running in your bags? Trailing arm suspensions usually hook up quite well.

Thanks for the reply. I have new gas shocks and have tried different air pressure setting. It will spin about 3 or 4 trucks lengths and soon as I think it might be near the end of spinning it will start to wheel hop. Could it be the rubber bushings in the trailing arms?

[68LSS1]

Wheel hop is a direct result of the pinion angle changing (as the tires "catch" traction). You need to do some measuring and go from there. Might just need a few shims from Stock Car Products. Keep in mind in a trailing arm truck the pinion is forced down instead of up like on leaf springs vehicles. Basically your forcing the pinion angle down far enough that instead of the rear joint making a circle it's in such a bind that the path is a eclipse. Where it's binding on this elliptical path is were your wheel hop is coming from. I would assume your running a adjustable panhard rod. Set your suspension were this is parallel with the ground as this is were it's most effective and make sure the rear end is centered. Your blocks could be contributing to this also. May want to try and remove them and see if it's any better.

[bagged72blaz]

I have trailing arms and bags no wheel hop at any hieght. I also use Early classics extended pan hard, and shock relocator, but no blocks. It wheel hops bad when in reverse though!

[OLDROCK&ROLLER]

Thanks for the replies. 68LSS1 pinion angle could be the problem cause I raised the back of my transmisson 1 1/2" to level up the motor. Do you have the correct angle settings? Thanks,Kenneth

[68LSS1]

Here is a list of links. This one is probably one of the more in depth as has good pictures. This is another good one. They will tell you how to measure your angles and talk a lot about drivetrain vibrations. I would imagine since you didn't say you have any other problems, i.e. vibrations, that it is just the pinion angle remaining relatively constant on acceleration (as they slip during loss of traction) and as the tires do start "grabbing" the angle is increased as the pinion is pushed down which in turn creates the bind in the rear joint producing the wheel hop. This is of course my opinion as I plan on running about 750rwhp/tq so I have done a lot of reading on the subject. That's what I'm hoping the Hot Rods to Hell kit that I'm using will be able to control.

[Bagd72Chevy]

I have bags, 2 inch blocks, an lt1, and a posi. It'll light 'em up good, but never any wheel hop. I also have a custom tranny crossmember, but can't remeber what angle i put it at.

[LONGHAIR]

Wheel Hop has nothing to do with pinion angle at all, especially any kind of binding. It comes from "movement" in the suspension/drivetrain at the critical point where horsepower and traction meet.
When horsepower is greater than traction.......you get wheel spin.
When traction is greater than horsepower.......you get a bog.
Basically you are fighting between the two and once it starts the harmonics exagerate it.
As you accelerate and the vehicle speed begins to match the wheel speed you get wheel hop if there is enough movement in anything to cause the suspension to "un-load". This can be springs/bushings, engine/trans mounts, tire pressure, etc.

The coil spring and control arm suspension of these trucks (in like new condition) will generally handle this. If however there is wear on the bushings, rust (causing flex) in the arms, loose motor mounts or even too tight of a torque convertor....you can run into this. Leaf spring cars/trucks also have spring wrap to cause hop, and although the pinion angle does change as the springs wind-up, that is the effect....not the cause.

Look at it like this...It happens to Top Fuel dragsters/Funny Cars too. They have totally solid mounted engine and rear axles, but if the clutch comes in too quickly (more traction than horsepower) the tires (being the soft point) will un-load and shake like crazy...........there is only one way to stop it, let off of the throttle

[68LSS1]

Sorry but your wrong. The effect of the tires gaining and loosing traction is wheel hop (worst cases). The cause is that the suspension has "wound" itself up to the extent that it can't go any further. The tires then at some point start gaining traction so this "wind up" is released. When then axle housing is wound up is WHEN/WHERE the wheel hop occurs. Why? Because we have our pinion angles way out of whack. Causes of this can be worn bushings, bad shocks, etc. I agree. But it sounds like everything is tight on his truck. What do you think adjustable suspension are for (i.e. 4 link)? Adjusting pinion angle perhaps? What due traction bars do (i.e. Cal-Tracs, Slide-a-Links, etc.)? They try and prevent the winding off the suspension/axle housing (which maintains the pinion angle). As far as your Top Fuel example (not that it's a great one for our purposes here) do you have any idea of how much additional angle they have dialed in on their 4 links? There are many sites that I can show you that say this but I'll just give you one for now: Competition Engineering. When your done reading that let me know and I can give you a list of good books on the subject.

Edit: I do agree tha normally the trailing arm suspensions work great but I think we have found the problem. By moving the tranny up you changed the pinion angle. It's not enough that it shows up in every day driving meaning it's ok. But it enough that it shows up under hard acceleration. I would not recommend putting the tapered shims in with the lowering blocks. I would get a spare set of blocks, measure the angles like from one of the above posts and then taper the blocks to correct. I am guessing that you would need taper the blocks more towards the rear meaning to angle the axle housing(pinion) up. I wouldn't do much maybe a degree or two (unless you can get some good measurements. Install them and give it a try. May take a couple times to get it right. good luck.

[LONGHAIR]

Well, this is going to go nowhere......

The spring wind-up you are talking about is what causes the hop as does flex in the trailing arm suspension. The trailing arms CANNOT flex far enough to cause the problems that you are stating. If the U-Joint bound up it would spit the driveshaft out, not make the tires jump. It is all about loading and unloading of the suspension.

Adjusting the arms of a 4 link (in terms of raising or lowering the pivots) change the instant center of where the axle is pushing from. While it does affect the launch this is not the pinion angle interference you are speaking about. The whole point of them being adjustable is so that you can change with track conditions.....adding or taking away traction. Raising the front mount of the upper bars makes the vehicle think that the pivot point is further foreward, giving more traction/lift to the front. But too much can be bad too...lift is not moving foreward. Pro Stock cars run 4 links and I will guarantee you that they have no axle wrap problems, but they will get wheel hop if they are down on power, cluch comes in too fast, ect...

Top Fuel dragsters DO NOT have links/bars of any kind. They are solidly mounted to the frame. If the clutch comes too fast and the traction too good...shake. The tires wind up and (wheel turning faster than the tire) the car moves, if this comes in too slowly the tires spin...to quickly and the when the tire catches up to the wheel it jumps/bounces oscallating ...again fighting between traction and horsepower.......NO u-joint to bind. The u-joiunt thing it total BS.

The tire/ground is the weakest link. Everything else can be stiffened/improved, but the sidewall of the tire will still wind-up...

BTW........I just looked at the CE link you posted...Looks like you need to read it yourself. There is nothing about U-joint bind...'cause that is NOT the problem.

[crazy longhorn]

Guys, the reason for hop is spring wrapup, & u joint bind (leaf sprung). leafs are the worst for this hop problem! you wouldnt think the coil trucks would have a problem......but if the angles are a long way off , due to suspension mods, or line angle mods(back of trans raised 1 1/2")...that could do it i would also suggest to check all the easy stuff 1 st ( bad bushings, stand the shocks up, ect). If the line angles are off far enough to get you to bind under hard throttle, you will see hop.....if you see it long enough, you will break some parts.....crazyL

[LONGHAIR]

It has NOTHING to do with U-joint bind
If it did there could be no possible way for a coil spring car (3 link, 4 link, or even ladder bar car/truck to do it. Let alone a Top Fueler....they don't even have u-joints. It is a direct coupler between the drive line and the pinion.......with everything solidly mounted.

Now, u-joint bind (of a leaf spring car) may be the upper rotational limit .....but it is NOT the cause. It may be the effect, but it is more likely that the spring tension causes the un-load. It would take very long and soft leaves to allow that much twist, hardly a pick-up truck. Lift/lowering blocks can add leverage and increase the tendancy.

But this all started about a coil sprung truck with (what 3 foot long?) control arms.......NO WAY can they allow that much rotation. It is all about loading and unloading of the suspension......The meeting of horespower and traction limits.

[crazy longhorn]

Originally Posted by LONGHAIR

It has NOTHING to do with U-joint bind
If it did there could be no possible way for a coil spring car (3 link, 4 link, or even ladder bar car/truck to do it. Let alone a Top Fueler....they don't even have u-joints. It is a direct coupler between the drive line and the pinion.......with everything solidly mounted.

Now, u-joint bind (of a leaf spring car) may be the upper rotational limit .....but it is NOT the cause. It may be the effect, but it is more likely that the spring tension causes the un-load. It would take very long and soft leaves to allow that much twist, hardly a pick-up truck. Lift/lowering blocks can add leverage and increase the tendancy.

But this all started about a coil sprung truck with (what 3 foot long?) control arms.......NO WAY can they allow that much rotation. It is all about loading and unloading of the suspension......The meeting of horespower and traction limits.

LONGHAIR.....never, & always, are 2 words that "ALWAYS" get my @ss into trouble I dont think anyone is totally right/ wrong in this, there is a lot of good advice goin on. i have seen what wrap up, & bad angles do to your driveline........I dont have any sites to back me, just past experience! dont tallk to me about strip stuff.....I am street bound... its a bit different than the 1/8, or 1/4 mi run trust me (that could be "scarey")......I DO NOT admiss any thing you have printed, but do have a slightly different point of veiw after 47yrs, I think I am entitled to that..... most of what I have learned, has been in the "school of hard knocks".....I D@mn sure dont "know it all", but.....all has been learned the hard way! we are all here for trucks, & all opinions count(yours, mine , the next guys)......let us try to play this truck game , with "no fight"......too d@mn many things arent about who is right/wrong........but many different opinions, sure do leave a different point of veiw(,maybe im not wrong, i could just be different ) . I know that you have seen what I have learned over the last 30 yrs......I WILL BET YOU DAMN GOOD MONEY.......there arent one of us that can "trouble shoot " over the phone , or internet"......crazyL, rowin 6 in that old Chev

[grnddwn]

What kind of shape are your trailing arms in?

[68LSS1]

OLDROCK&ROLLER, to get things back on track you let us know what you do. You can't change engines, tranny's, go to a one piece shaft, air ride suspensions, lower a vehicle and expect traction if u-joint angles are not a consideration. For the most part you will never have a issue until you have enough hp/tq to really stress the suspension and frame. I really feel that raising the tranny to level the engine has put the operating angles on the ragged edge of being acceptable. And it looks like you have enough torque to find this out. Good luck getting it figured out and let us know what/how you do.

Longhair, I guess we'll just agree to disagree. I don't think you're comparing apples to apples here. I agree that the loading and unloading of the suspension is wheel hop but what is setting (secondary) this in motion is the operating angles become the limit of the axle housing travel, the pinion snubber if you will. If the u-joint could still turn freely you wouldn't have the unloading until you had full traction or got out of it. As I previously stated and agreed to, these trailing arm (which are a lot longer than 3' by the way) trucks usually have no issues with these problems. If his engine mounts, tranny mount, trailing arm bushings, shocks (including operating angles) are all good you still could have enough of a deflection in operating (u-joint) angles especially since the tranny was raised to level the engine. As far as the adjustability of a 3/4 link for moving the instant center, I'm aware of this and how this works. It's also called anti-squat and believe me it's built into the chassis. But apples to apples. As far the the CE link, "This causes the springs to distort, resulting in severe driveshaft/U-joint misalignment." One last thing. I can't believe that with you being the lead mechanic in a 4X4 shop for ten years that you never experienced wheel hop after installing a suspension lift. The kits are a lot better now a days but years ago they were terrible about screwing up operating angles. But in your theory it shouldn't be possible to induce wheel hop by changing this. I know a bunch of BS right?

I've said what I said and I won't say another word in this thread. If either of you wish to respond here great. If either of you would like a response from me you'll have to email/PM as I would prefer this to get back to the topic at hand and that's getting OLDROCK&ROLLER some help because I know it sucks when you can't get your power to the ground.

[LONGHAIR]

Ok, you have forced me to draw pictures to disprove that garbage.

While I stated that u-joint bind may and I stress may be the limit that causes to suspension, it is not likely and certainly not the only thing. The most likely is the spring wrap itself. It can physically only go so far ...and as it does it is lifting the wheels (in relation to the ground) which reduces traction anyway. Then the wheels begin to spin, which releases the tension on the springs.....allowing them to relax. When they relax, the traction comes back...which wraps the spring back up........vicious cycle started.
But even if the upper limit of u-joint travel were to cause the initial un-load, then the other senarios you sited would reslove the problem...not make it worse.
1) If you raised the transmission: You have given the driveshaft a greater angle in relation to the ground. This would give you that many more degrees of rotation before the u-joint could bind.

2) Same with the lift blocks in the rear: The greater driveshaft angle gives you more rotation before you ever hit a bind from up-ward rotation of the pinion.

Now we all know that blocks in the rear cause greater spring wrap because of the additional leverage. But your u-joint bind theory doesn't enter into it at all.


The main thing in all of this is that this (incorrect) theory of yours could only ever apply to leaf springs.......and some of the most violent shake (wheel hop) I ever saw was on a Top Fuel car that has totally rigid suspension and Pro Stock cars that are coil-over 4 links. (Just because the Horsepower and Traction are greater)....... Which is what I said causes this in the first place.
It happens for the same reason in every vehicle....it just "looks" different based upon were the "soft spot" is, whether it is springs, bushings, tire sidewalls...whatever.

Pinion snubbers are a totally different ball of wax.(that was not mentioned before) They can cause the un-load too...if there is too much rotation before the housing strikes it.......just like the old slapper bars.

I'm done now........If you don't get it from here, you never will.

[roj2323]

well personaly from being new to this suspention system, i would check everything and experiment. checking bushings and shocks doesn't cost anything but time and if you think pinion angle has something to do with it the shims from scp are extreemly cheap. if all else fails i have an open rear end i'll trade ya j/k.

ondrew

[N2TRUX]

Hey guys, here's an idea. Since it obvious that you guys have some great knowledge on this subject why not share it rather than turn it in to a pissin contest?

I'm not going to get in the middle of this, just suggest you guys put it in a positive perspective so everyone can share the vast amount of knowledge you guys have before you get the thread locked.....

[OLDROCK&ROLLER]

Wow that's a lot of info. Thanks to every one for your replies. Didn't mean for this tread to be controversial. I knew I good get some good info on here. There was couple of modifications that I forgot to list (old fart thing)
I have a one piece drive shaft,adjustable track bar and shock mounts have been relocated also the trans has the long tailshaft so the drive shaft is pretty short (swb). I think I will start with changing out the rubber trailing arm bushing with some urethane bushing and check the drive shaft,pinon and trans for alignment. I will post the results when I get all this done.
Thanks again, Kenneth

[crazy longhorn]

Best of luck crazyL