fstcrr54321

and why does it blow people's diff?

Please educate me....

'06 Quicksilver Z06

Car alternates between obtaining and losing traction.

The sensation the driver feels is similar to driving over a series of railroad ties spaced about 6 inches to a foot apart. A bumpy, sometimes violently bumpy sensation. Can happen during burnouts, hard launches, or on 1-2, 2-3 shifts.

Some say that parts of the driveline actually twist somewhat due to the torsional forces, because keep in mind we are talking about two rear wheels when this is happening.

The up/down twisting force is enough to break driveline parts, usually manifest with a cracked differential case and since the diff is bolted to the tranny in our cars, sometimes the tranmission case and output shaft along with the differential output shafts are destroyed.

It may only take one or two "hops" to destroy one's differential. It is generally felt, that once the car starts to hop, it is best to get out of the throttle.

A cracked differential case is among the things which can and will happen if it gets bad enough. And sometimes when this sort of thing happens, the transmission case gets it too and the tranny output shaft resulting in a very expensive repair.







One C5 owner blames wheel hop with subsequent destruction of his differential, for a loss of control of the car leading to an accident.

One company, and there is another, has developed a brace to limit the damage



But even it cannot totally eliminate the carnage resulting from wheel hop.









These pics came from this thread http://forums.corvetteforum.com/show....php?t=1076513





Don't know if it was wheel hop or a dead hook that got him, but they both result in lots of damage.

shurite44

DSOMZ51 good post.

SpinMonster

Very well put together response there. A tear came to my eye.

'06 Quicksilver Z06

Thanks guys.

I have aborted a few 1/4 mile passes in my C6 running on stock runflats after experiencing wheel hop and having mental images of those photos.

Wheel hop is no joke and can easily result in you leaving the track or the road on a flatbed.

CessnaDriver

Didnt the 06's have an improved design?

valdeztke

Why would GM allow for a diff that couldnt handle the torq from the stock system? I wouldnt consider the aggresive driving that may give you wheel hop "Abuse" on a corvette. Hmmm GM I think needs to step it up in that category.....

RossN

So what your saying is, If we plan on doing a fast crawl, we need to have a Diff Diaper on?

Sorry couldn't resist.

Or how about Diff Depends?

ZO6Gal

Is this what is happening when I hear the wheels chirp going mainly from 1-2 and 2-3? I don't go to the drag strip but I do enjoy experiencing the torque of the car. Thanks for your help.

TrackNoob

Thanks, DSOMZ51, I appreciate the pics although those are enough to make a grown man cry.

'06 Quicksilver Z06

Usually you can feel wheel hop. I don't think that what you are describing is wheel hop but rather the car losing traction between shifts. Usually when people talk about wheel hop they are describing events on a drag strip or from a dead stop. It is usually not described as happening from a highway or even a 30 mph roll. But make no mistake, wheel hop can and does happen on the street.

You are probably used to hearing the tires screech and then hook and hook for good the rest of the way through 1st. That is until you make the next shift, hear the screech/chirp, and then the tires hook for good in second, then the shift to third, the chirp and again they hook for good.

Thats not wheel hop. Wheel hop is different.

Imagine wheel hop this way, I already described the running over the railroad ties sensation.

Imagine that you had alternating wet and dry spots about six inches apart and around the entire circumference of each of rear tires. Lets say you then gave the car full throttle, either from a dead stop or after you were in the throttle and on a shift. The car would struggle to get traction and would "alternate" between getting traction and losing it. This is sort of what happens in wheel hop. The car catches/hops/catches/hops. It happens quick, and a lot of force is generated, and its bumpy.

Each time the tires rotated to a wet spot on the tire it would slip, each time on a dry spot it would catch. This would cause the car to tend oscillate in the rear, slight to severe bounce, slight to severe hop in the rear end. Thats the sensation of wheel hop. You don't get the screech and then the hook as described above. You get oscillation. Hop.

And it can get more violent the longer you stay in the throttle. And it might only take 1, 2, or a few hops/twists to do your differential (and transmission) in.

Usually one hop or just a few hops won't do it, unless it is a hell of a hop. When mine starts to hop it may last for about 2-3 seconds before I can get off the throttle and stop the hopping. There are some spectators who claim to be able to see it from outside the car, though I never have.

You can also hear it. Sometimes loud and clear. A bumping type sound as though you just ran over a long washboard.

TrackNoob

No.


Not all slip, or loss of traction is going to lead to wheel hop.

I guess I was fortunate as a kid to have a '67 Camaro with a hotted up 327, but single leaf rear springs, so wheel hop and I are old friends! Only experienced it once on my new 'vette, and immediately got off the throttle.

Even though the old Camaro is sprung differently, just picture a single leaf car. Now, if you load a lot of torque into the driveline, it is going to 'wind up' the spring by loading the springs as it also pushes the car forward. If you lose traction, you not only spin and therefore lose the use of the torque the motor is putting out for your car's forward progress, BUT, you are adding to that the stored energy the spring had as it 'unwinds', too! More energy changing places for that moment than even the motor is putting out. See? No big deal, except... guess what? The inertia of all the movement of spring, third member, etc, is going to carry it in the same new direction, and as this occurs the wheels will eventually begin to grip (they have less torque on them now). And when they do, wham -- the stored energy plus engine energy goes back into the system, tries to accelerate instantly, cannot, looses traction again...

you now have an oscillator, and that is a good way to tear things up as it pitches back and forth, expending it's energy in flailing around, and putting out peak torque pulses that are GREATER than the max instantaneous capability of the engine.

That is why a tranny 'rated' for 450 HP might get damaged by a 415 RWHP car with wheel hop.



[As an aside, when I first bought the coupe pictured in my avitar, after I began working on it -- rebuilding carb, recurving distributor, new plugs/wires, etc, and there came a point in time where I got wheel hop horribly. I just could not go anywhere without a terrible banging and shaking on hard acceleration, even when it seemed I launched with minimum tire slip. I checked out the suspension (late model Camaro rear, plus Mustang II front), and put in a pinion snubber and a makeshift traction bar to evaluate response... long story short, real issue was the engine physically picking up, that cut out the throttle (linkage), engine would lay back down and that put the throttle back on.. it would bang aroung like crazy until I sorted out the broken motor mount - another form of oscillator:]



One quick call to Jegs straightened me right out:

"...first and only polyurethane motor mount available with a safety interlock to effectively control high horsepower and torque. They're virtually indestructible..."

ZO6Gal

Thanks guys, I understand now what you are saying. I haven't experienced it and hope not to but at least I will know what is going on if it happens.