Shop Transfer Case Chains → Browse at CoreTransmissionParts →
Crow hop is the shudder, skip, or hop you feel when a 4x4 makes a tight turn on pavement. The front tires scrub, the steering wheel fights you, and the truck may lurch as the tires break loose and grab again. Sometimes there is a bang as the driveline unloads. People call it binding, wind-up, or crow hop, and the first question is always the same: is something broken?
The answer depends entirely on what kind of 4WD system you have and what mode it is in.
When Binding Is Normal
A part-time 4WD system locks the front and rear driveshafts together inside the transfer case. In a turn the front axle travels a longer path than the rear, so the front driveshaft wants to turn a little faster. On dirt, gravel, snow, or mud the tires slip a bit and the difference goes away. On dry pavement there is nowhere for it to go, so the driveline winds up like a spring until a tire skips.
That is normal. If your truck is in 4HI or 4LO on a part-time case — an NP231, NP241, NP208, BW1356, NP205, and many others — and it binds in a tight parking lot turn on dry pavement, the system is doing what it was built to do. The fix is to stay out of 4WD on high-traction surfaces. Repeated wind-up on pavement is hard on u-joints, CV joints, axle shafts, and the transfer case chain, so do not make it a habit.
When Binding Means a Problem
It Binds in 2WD
If the truck binds with the selector in 2HI, something is still engaged. Check in this order:
- The 4WD indicator and the scan tool. Does the module think it is in 2HI? On electric-shift cases, a failed encoder motor or shift motor can leave the case in 4WD while the dash says 2WD.
- The front driveshaft. With the truck safely supported and in neutral, see whether the front driveshaft turns with the rear. If it does in 2HI, the transfer case did not release.
- Hubs and front axle disconnect. If the front driveshaft is free but the front wheels still drive, look at locking hubs, vacuum hubs, or the axle actuator.
A case that will not leave 4WD is often a mechanical problem: a worn shift fork, a damaged shift collar, or a shift rail that is gummed up from sitting in 2WD for years.
It Binds in a Full-Time or Auto Mode
Full-time and automatic modes are not supposed to bind on pavement. Systems like the NP242 in Full Time, the NP249 Quadra-Trac, and GM Auto 4WD cases such as the NP246 use a center differential, a viscous coupling, or a clutch pack to let the front and rear turn at different speeds. If one of those binds in a turn, something inside is not slipping like it should.
- Viscous coupling hardening: the fluid in an old viscous coupling stiffens and the unit behaves like a locked case. Common on aging Quadra-Trac cases.
- Clutch pack sticking: clutch-type auto 4WD cases need the specified fluid. The wrong fluid makes the clutches grab and chatter in turns.
- Center differential failure: a damaged or seized center differential can lock the case solid.
Mismatched Tires
This is the most overlooked cause. Two different tire sizes front to rear, a new pair on one axle and worn tires on the other, or one low tire is enough to make a full-time or AWD system work constantly and a part-time system bind even on loose surfaces. Measure the rolling circumference of all four tires before you spend money on parts. On full-time cases, differences that seem small can overheat a viscous coupling or clutch pack over time.
Mismatched Axle Ratios
After an axle swap or a regear, make sure the front and rear ratios match. Even a small difference will bind every time you engage 4WD, on any surface.
Do Not Confuse It With These
- Rear limited-slip chatter: a clutch-type limited-slip rear differential that needs friction modifier will chatter in tight turns in 2WD too. That is an axle fluid issue, not the transfer case.
- Bad front CV or u-joint: clicking or popping in turns that changes with steering angle is a joint, not binding.
- Stretched transfer case chain: a long chain clunks on engagement and on throttle changes, but it does not cause wind-up by itself. See our chain stretch guide.
Quick Diagnosis Table
| Situation | Likely Cause | What To Do |
|---|---|---|
| Part-time 4WD, dry pavement | Normal wind-up | Shift to 2WD on pavement |
| Binds in 2HI | Case stuck in 4WD, hubs, actuator | Check front driveshaft, shift motor, fork |
| Binds in Full Time or Auto | Viscous, clutch pack, center diff, wrong fluid | Check fluid type, then internals |
| Binds on dirt and snow too | Tire size mismatch or axle ratio | Measure tires, verify ratios |
| Chatter in 2WD turns | Rear limited-slip | Axle fluid and friction modifier |
Parts That Usually Come Out of This Diagnosis
If the case is stuck in 4WD on a GM truck with push-button 4WD, the encoder motor is the usual suspect — we stock the GM encoder motor 600-899 for 2007-2018 trucks and the NP246 encoder shift motor for 2003-2007 trucks. On Ford F-150s, see the F-150 transfer case shift motor.
If years of pavement wind-up have stretched the chain, the NP242 drive chain, the NP241C drive chain, and the NP231/NP233 chain cover the most common chain cases. For a full bearing job on a GM Auto 4WD case, the NP246 bearing and seal kit is the place to start.
And whatever you find, put the correct fluid back in. Clutch-type cases are fussy about it. Our transfer case fluid guide lists the common specs.
Transfer Case Parts Ship Same-Day
Chains, bearing kits, and shift and encoder motors for the most common 4x4 transfer cases. Same-day ship before 2pm Eastern. CoreTransmissionParts carries the broader catalog if you need something we don't stock direct.
Shop Transfer Case Parts → Shop CoreTransmissionParts →FAQ
Is it bad if my truck crow hops in 4WD on pavement?
On a part-time 4WD system it is normal behavior, because the front and rear driveshafts are locked together and can not make up the speed difference in a turn. It is still hard on driveline parts, so shift back to 2WD on dry pavement.
Why does my truck bind in turns in 2WD?
Something is still engaged. The transfer case may not have released because of a failed shift motor, encoder, or worn shift fork, or the front hubs or axle actuator may still be locked. Check whether the front driveshaft turns with the rear in 2HI.
Can different size tires cause 4WD binding?
Yes. Different rolling diameters front to rear make the driveline wind up even on loose surfaces, and on full-time or AWD systems they make the center coupling slip constantly, which wears it out.
Why does my full-time 4WD bind in Auto mode?
Full-time and auto modes should not bind. Common causes are a hardened viscous coupling, a sticking clutch pack from the wrong fluid, a failed center differential, or mismatched tires.