Drivetrain & Power Delivery Upgrades for Traction and Control
You installed coilovers, set the ride height, dialed the damping and had the alignment done right. Then you roll hard onto the throttle out of a corner and something feels off. Wheel hop. Mushy response under load. The coilover kit may not be the problem. Drivetrain upgrades could be the missing link.
A good performance suspension setup controls how weight moves. It cannot control a drivetrain that moves on its own. Soft mounts let the engine, transmission and differential shift around under load. Here is how that shows up, and what to do about it.
THE FLOATING ENGINE PROBLEM
Factory mounts use soft rubber to keep vibration out of the cabin. That rubber lets the engine and transmission rock and shift under hard cornering, braking and throttle. How far depends on the car and the mount design.
When that mass shifts mid-corner, it arrives at the chassis a beat late. The car takes a set, then gets a second small nudge as the engine catches up. The coilovers have to manage that extra input on top of the normal weight transfer. Stiffer mounts hold the mass closer to the chassis and let the coilovers do their job.
The same idea applies to the transmission. A transmission mount that deflects on hard acceleration changes the driveshaft angle for a moment. That shows up as a lag between throttle and grip. Firming up the mount closes the gap.
On many transverse-engine cars, a torque mount, often called a dogbone, controls the fore-aft rocking. Upgrading that one mount can deliver much of the gain. It also adds less vibration than replacing every mount at once.
This is why a car on fresh coilovers can still feel inconsistent on corner exit. Once the engine stops floating, your coilovers stop reacting to a second, delayed load. Response becomes more predictable.
CHOOSING THE RIGHT DUROMETER
Durometer is the hardness of the mount material, measured on the Shore A scale. Higher numbers are harder. Mount makers usually sell a street insert and a track insert, and the right one depends on how you use the car. Our guide to suspension bushings covers the same trade-off at the arms.
A softer street or sport mount cuts engine movement without harsh vibration. It suits a daily driven performance build. The car responds faster on throttle, and the cabin stays livable.
A harder track mount holds the engine and transmission firmly under load. Shifts can feel more direct. Daily driving is still possible, but road texture and engine vibration come through the shifter, seat and pedals.
Solid mounts are for race use. Zero compliance means the drivetrain stays put, at the cost of severe noise, vibration and harshness. Trailered race cars can live with that. Street cars usually cannot.
Give It a Break-In
New polyurethane mounts can feel stiffer at first. Some owners report that vibration feels less noticeable after a break-in period. Do not judge a fresh poly mount install in the first week.
LSD: The Differential Side of the Equation
A limited slip differential (LSD) sends drive to the wheel that can use it. For grip-focused driving, a 1.5-way LSD is a common choice. It locks firmly under acceleration for corner-exit traction. Under deceleration it locks only partly, so the car still turns in.
A tight LSD needs a firm drivetrain to work as intended. Pair one with worn differential and subframe mounts, and the casing can twist on its mounts when the diff locks. That windup can feed wheel hop.
Wheel hop is a cycle. The tire grips, the driveline winds up, the tire lets go and the driveline springs back. Then it repeats, fast. Soft mounts and loose damping both make that cycle easier to start.
Matching your LSD with firmer differential and subframe bushings gives a more direct mechanical link. The diff locks and drive reaches the tires sooner. Your coilovers then manage the weight shift cleanly, and the car exits the corner the way you expected when you bought the coilover kit.
ECU TUNING AND MECHANICAL HARMONY
Every driveline has some lash, or slack, between the engine and the wheels. An aggressive throttle remap on soft mounts makes that slack worse to live with. Power arrives suddenly, the engine rocks, and the rear suspension gets a sharp hit. The dampers end up handling a jolt instead of a smooth load.
The right order is to stiffen the mounts first, then tune the throttle ramp. Remove the slack mechanically. A smooth throttle ramp can then match power delivery to the grip available at the tire. The chassis stays settled from apex through corner exit.
A sensible order for drivetrain upgrades looks like this. Coilovers and an alignment come first, so the body is under control. See our guide to suspension geometry and alignment. Mounts come next, starting with the ones that move most. Then the LSD, if the car needs one. The throttle tune comes last, written for a drivetrain that no longer flexes.
Drivetrain Upgrades: Differential and Subframe Mounts
On rear-drive cars, the differential and subframe mounts are a common source of wheel hop. Factory rubber lets the diff and subframe rotate under torque. When an LSD locks and that load arrives suddenly, soft mounts let the rear end move before the tires grip.
Polyurethane differential and subframe mounts cut that movement. The rear geometry stays closer to where your alignment put it. Toe and camber change less under power, so the tires stay planted.
One thing mount upgrades do not touch is unsprung weight. The mounts bolt to the body, so they are sprung mass. Unsprung weight lives at the wheel: wheel, tire, hub, brakes, knuckle, and part of the arms, springs and dampers.
A well-damped coilover kit makes drivetrain slack easier to feel. Once the body is controlled, a loose mount stands out. That is true whether you run BC Racing, KW, Fortune Auto, Öhlins or Feal.
SPRING RATE, DAMPING, AND DRIVETRAIN
Wheel hop has two common contributors at the axle. One is too little damping control on the driven axle. The other is drivetrain windup from loose mounts. If firming the damping does not cure it, look hard at the mounts.
On many solid-axle cars, a stiffer rear spring rate cuts squat under acceleration. Less squat means less change in pinion and driveshaft angle. That eases stress on the U-joints and smooths power delivery. Pair it with clean mounts before you reach for more damping.
Ride height plays in too. On full-length kits like BC Racing and Fortune Auto, you set height at the lower mount and lock it with the locking collar. Lowering the car changes the angles of CV joints, half shafts and driveshafts. Check those angles after a big drop, and see how to set ride height on coilovers without overdoing it. A joint running at a steep angle wears faster and can add vibration under load.
Putting the Power Down
Power delivery is a traction problem, and traction lives at the contact patch. The coilover kit controls how weight transfers under acceleration. The spring rate at the driven axle decides how much the chassis squats. Too little control and the tire scrabbles. Too much and the suspension cannot load the tire.
Matching the Coilover Kit to the Drivetrain
Front-drive, rear-drive and all-wheel-drive cars each ask different things of the suspension. A front-drive car wants the rear to rotate without snapping, which rear spring rate and damping control directly. A rear-drive car needs the driven axle to squat just enough to load the tires. The front should not go light.
Front-drive cars have their own drivetrain quirk. Soft mounts and worn bushings let the front geometry shift under power, which can add to torque steer. Firmer mounts and a good alignment help keep the steering straight when you get on the throttle.
All-wheel drive blends the two and rewards a balanced setup front to rear. Front and rear differential mounts both matter on these cars. There is no universal answer. There is only the answer that suits how your drivetrain puts power down.
Adjustable damping helps here, so check the adjusters on any coilover kit you consider. The BC Racing BR Series gives you 30-click simultaneous compression and rebound. KW V3 and the Fortune Auto 510 Series let you set compression and rebound independently. On BC Racing kits, Swift Springs SPEC-R springs are an upgrade option on most fitments.
Frequently Asked Questions
Will stiffer engine mounts ruin my daily driver?
Not with a street-grade insert. Expect a little more vibration at idle. Many owners find the sharper throttle response worth that trade. Track or solid mounts are a different story on the street.
Should I upgrade suspension or drivetrain first?
Coilovers first. Once the suspension is dialed, drivetrain slack becomes obvious. You then know which mounts to address and in what order.
I am getting wheel hop during launches. Is my suspension too soft?
Often it is drivetrain movement. Check differential and subframe mounts first. If wheel hop continues, look at damping on the driven axle. Spring rate changes come after that.
What is drivetrain lash?
Slack in the driveline between the engine and the wheels. Soft mounts let the engine rock before force reaches the tires. Stiffer mounts take up the slack and spare the suspension from sharp hits.
Is a 1.5-way LSD a good fit for street and track?
For most combined use, yes. A 1.5-way locks under acceleration and only partly on deceleration, so the car still rotates. A 2-way locks both ways, which tends to resist turn-in.
Can I run an aggressive throttle tune without upgrading mounts?
You can, but it will not feel right. Stiffen the mounts first to remove mechanical slack. Then tune the throttle ramp. In that order the changes work together, not against each other.
How do differential mounts affect coilover performance?
Soft differential mounts let the rear subframe and diff move under torque. That movement shifts the rear toe and camber when you are on the power. The coilovers then work against a moving target. Firmer mounts keep the geometry where you set it.
Keep reading: Our guide to drivetrain and fitment.
Get the Full Picture on Traction and Control
We carry BC Racing, KW, Fortune Auto, Öhlins, Feal and TEIN, and we know how drivetrain parts interact with each coilover kit. Call 1-800-460-9106 for guidance on your build.
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