diff --git a/frc971/control_loops/drivetrain/BUILD b/frc971/control_loops/drivetrain/BUILD
index 9fef8f9..30abc87 100644
--- a/frc971/control_loops/drivetrain/BUILD
+++ b/frc971/control_loops/drivetrain/BUILD
@@ -691,6 +691,7 @@
         "improved_down_estimator.h",
     ],
     deps = [
+        ":drivetrain_config",
         ":drivetrain_status_fbs",
         "//aos/events:event_loop",
         "//frc971/control_loops:control_loops_fbs",
@@ -707,6 +708,7 @@
         "improved_down_estimator_test.cc",
     ],
     deps = [
+        ":drivetrain_test_lib",
         "//aos/testing:googletest",
         "//aos/testing:random_seed",
         "//frc971/control_loops/drivetrain:improved_down_estimator",
diff --git a/frc971/control_loops/drivetrain/drivetrain.cc b/frc971/control_loops/drivetrain/drivetrain.cc
index 77c52c4..1c0ac4f 100644
--- a/frc971/control_loops/drivetrain/drivetrain.cc
+++ b/frc971/control_loops/drivetrain/drivetrain.cc
@@ -41,6 +41,7 @@
       gyro_reading_fetcher_(
           event_loop->MakeFetcher<::frc971::sensors::GyroReading>(
               "/drivetrain")),
+      down_estimator_(dt_config),
       localizer_(localizer),
       kf_(dt_config_.make_kf_drivetrain_loop()),
       dt_openloop_(dt_config_, &kf_),
@@ -177,6 +178,9 @@
       case IMUType::IMU_Y:
         last_accel_ = -imu_values_fetcher_->accelerometer_y();
         break;
+      case IMUType::IMU_Z:
+        last_accel_ = imu_values_fetcher_->accelerometer_z();
+        break;
     }
   }
 
diff --git a/frc971/control_loops/drivetrain/drivetrain_config.h b/frc971/control_loops/drivetrain/drivetrain_config.h
index 5a29008..a33ff22 100644
--- a/frc971/control_loops/drivetrain/drivetrain_config.h
+++ b/frc971/control_loops/drivetrain/drivetrain_config.h
@@ -37,6 +37,7 @@
   IMU_X = 0,          // Use the x-axis of the IMU.
   IMU_Y = 1,          // Use the y-axis of the IMU.
   IMU_FLIPPED_X = 2,  // Use the flipped x-axis of the IMU.
+  IMU_Z = 3,          // Use the z-axis of the IMU.
 };
 
 template <typename Scalar = double>
diff --git a/frc971/control_loops/drivetrain/drivetrain_test_lib.cc b/frc971/control_loops/drivetrain/drivetrain_test_lib.cc
index 336025a..6a90122 100644
--- a/frc971/control_loops/drivetrain/drivetrain_test_lib.cc
+++ b/frc971/control_loops/drivetrain/drivetrain_test_lib.cc
@@ -190,16 +190,23 @@
   auto builder = imu_sender_.MakeBuilder();
   frc971::IMUValues::Builder imu_builder =
       builder.MakeBuilder<frc971::IMUValues>();
-  imu_builder.add_gyro_x(0.0);
-  imu_builder.add_gyro_y(0.0);
-  imu_builder.add_gyro_z(
-      (drivetrain_plant_.X(3, 0) - drivetrain_plant_.X(1, 0)) /
-      (dt_config_.robot_radius * 2.0));
+  const Eigen::Vector3d gyro =
+      dt_config_.imu_transform.inverse() *
+      Eigen::Vector3d(0.0, 0.0,
+                      (drivetrain_plant_.X(3, 0) - drivetrain_plant_.X(1, 0)) /
+                          (dt_config_.robot_radius * 2.0));
+  imu_builder.add_gyro_x(gyro.x());
+  imu_builder.add_gyro_y(gyro.y());
+  imu_builder.add_gyro_z(gyro.z());
   // Acceleration due to gravity, in m/s/s.
   constexpr double kG = 9.807;
-  imu_builder.add_accelerometer_x(last_acceleration_.x() / kG);
-  imu_builder.add_accelerometer_y(last_acceleration_.y() / kG);
-  imu_builder.add_accelerometer_z(1.0);
+  const Eigen::Vector3d accel =
+      dt_config_.imu_transform.inverse() *
+      Eigen::Vector3d(last_acceleration_.x() / kG, last_acceleration_.y() / kG,
+                      1.0);
+  imu_builder.add_accelerometer_x(accel.x());
+  imu_builder.add_accelerometer_y(accel.y());
+  imu_builder.add_accelerometer_z(accel.z());
   imu_builder.add_monotonic_timestamp_ns(
       std::chrono::duration_cast<std::chrono::nanoseconds>(
           event_loop_->monotonic_now().time_since_epoch())
diff --git a/frc971/control_loops/drivetrain/improved_down_estimator.h b/frc971/control_loops/drivetrain/improved_down_estimator.h
index 27de867..c1c8e1b 100644
--- a/frc971/control_loops/drivetrain/improved_down_estimator.h
+++ b/frc971/control_loops/drivetrain/improved_down_estimator.h
@@ -6,6 +6,7 @@
 
 #include "aos/events/event_loop.h"
 #include "aos/time/time.h"
+#include "frc971/control_loops/drivetrain/drivetrain_config.h"
 #include "frc971/control_loops/drivetrain/drivetrain_status_generated.h"
 #include "frc971/control_loops/runge_kutta.h"
 #include "glog/logging.h"
@@ -276,6 +277,8 @@
 // accelerometer calibration).
 class DrivetrainUkf : public QuaternionUkf {
  public:
+  DrivetrainUkf(const DrivetrainConfig<double> &dt_config)
+      : QuaternionUkf(dt_config.imu_transform) {}
   // UKF for http://kodlab.seas.upenn.edu/uploads/Arun/UKFpaper.pdf
   // Reference in case the link is dead:
   // Kraft, Edgar. "A quaternion-based unscented Kalman filter for orientation
diff --git a/frc971/control_loops/drivetrain/improved_down_estimator_test.cc b/frc971/control_loops/drivetrain/improved_down_estimator_test.cc
index 86ef5e9..2edce5a 100644
--- a/frc971/control_loops/drivetrain/improved_down_estimator_test.cc
+++ b/frc971/control_loops/drivetrain/improved_down_estimator_test.cc
@@ -4,6 +4,7 @@
 #include <random>
 
 #include "aos/testing/random_seed.h"
+#include "frc971/control_loops/drivetrain/drivetrain_test_lib.h"
 #include "frc971/control_loops/drivetrain/improved_down_estimator.h"
 #include "glog/logging.h"
 #include "gtest/gtest.h"
@@ -91,7 +92,8 @@
 }
 
 TEST(DownEstimatorTest, UkfConstantRotation) {
-  drivetrain::DrivetrainUkf dtukf;
+  drivetrain::DrivetrainUkf dtukf(
+      drivetrain::testing::GetTestDrivetrainConfig());
   const Eigen::Vector3d ux = Eigen::Vector3d::UnitX();
   EXPECT_EQ(0.0,
             (Eigen::Vector3d(0.0, 0.0, 1.0) - dtukf.H(dtukf.X_hat().coeffs()))
@@ -112,7 +114,8 @@
 
 // Tests that the euler angles in the status message are correct.
 TEST(DownEstimatorTest, UkfEulerStatus) {
-  drivetrain::DrivetrainUkf dtukf;
+  drivetrain::DrivetrainUkf dtukf(
+      drivetrain::testing::GetTestDrivetrainConfig());
   const Eigen::Vector3d ux = Eigen::Vector3d::UnitX();
   const Eigen::Vector3d uy = Eigen::Vector3d::UnitY();
   const Eigen::Vector3d uz = Eigen::Vector3d::UnitZ();
@@ -167,7 +170,8 @@
 // that we are slightly rotated, that we eventually adjust our estimate to be
 // correct.
 TEST(DownEstimatorTest, UkfAccelCorrectsBias) {
-  drivetrain::DrivetrainUkf dtukf;
+  drivetrain::DrivetrainUkf dtukf(
+      drivetrain::testing::GetTestDrivetrainConfig());
   const Eigen::Vector3d ux = Eigen::Vector3d::UnitX();
   Eigen::Matrix<double, 3, 1> measurement;
   // Supply the accelerometer with a slightly off reading to ensure that we
@@ -192,7 +196,8 @@
 // that we are slightly rotated, that we eventually adjust our estimate to be
 // correct.
 TEST(DownEstimatorTest, UkfIgnoreBadAccel) {
-  drivetrain::DrivetrainUkf dtukf;
+  drivetrain::DrivetrainUkf dtukf(
+      drivetrain::testing::GetTestDrivetrainConfig());
   const Eigen::Vector3d uy = Eigen::Vector3d::UnitY();
   Eigen::Matrix<double, 3, 1> measurement;
   // Set up a scenario where, if we naively took the accelerometer readings, we