Suspension System: Overview Dodge Caravan IV

DESCRIPTION - FRONT SUSPENSION

This vehicle has a MacPherson Strut type front suspension. (Scheme 16)

Scheme 16

OPERATION - FRONT SUSPENSION

The front suspension allows each wheel on a vehicle to adapt to different road surfaces and conditions without greatly affecting the opposite wheel and the ability to control the vehicle. Each side of the front suspension is allowed to pivot so the vehicle can be steered in the direction preferred.

A strut assembly is used in place of the front suspension upper control arm and upper ball joint. When a vehicle strikes a bump, the force is transferred through the hub, bearing, and knuckle, into the strut assembly to absorb the force and dampen it. The top of the strut is mounted directly to the strut tower of the vehicle. During steering maneuvers, the strut assembly (through a pivot bearing in the upper strut mount) and steering knuckle (through the lower ball joint) turn as an assembly.

DESCRIPTION

The front wheel bearing and front wheel hub of this vehicle are a hub and bearing unit type assembly (Unit III). This unit combines the front wheel mounting hub (flange) and the front wheel bearing into a sealed one-piece unit. The hub and bearing is mounted to the center of the steering knuckle. (Scheme 16) It is retained by four mounting bolts accessible from the inboard side of the steering knuckle. The hub flange has five wheel mounting studs.

The wheel mounting studs used to mount the tire and wheel to the vehicle are the only replaceable components of the hub and bearing assembly. Otherwise, the hub and bearing is serviced only as a complete assembly.

OPERATION

The hub and bearing has internal bearings that allow the hub to rotate with the driveshaft, along with the tire and wheel. The five wheel mounting studs mount the tire and wheel, and brake rotor to the vehicle.

The steering knuckle is a single aluminum casting with legs machined for attachment of the strut assembly, steering linkage, disc brake caliper adapter, lower control arm ball joint and steering linkage. (Scheme 16) The hub and bearing assembly is mounted in the center of the steering knuckle using 4 bolts. The driveshaft's constant velocity (C/V) stub axle is splined through the center of the hub and bearing and is held in place using a nut, nut lock and cotter pin.

Service replacement of the front hub and bearing assembly can be done with the steering knuckle remaining on the vehicle.

The steering knuckle pivots with the strut assembly between the lower ball joint and the pivot bearing in the strut assembly. The steering gear outer tie rod end connects to the trailing end of each knuckle, allowing the vehicle to be steered.

The center of the knuckle supports the hub and bearing and axle shaft.

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

1. Raise vehicle. «(Refer to LUBRICATION & MAINTENANCE/HOISTING - STANDARD PROCEDURE)»(ref-248903-S02249938992007022700000)
2. Remove the wheel and tire assembly from the vehicle.
3. Remove the cotter pin, nut lock and spring washer from the end of the stub axle and hub nut. see scheme 14 1 - HUB NUT 2 - NUT LOCK 3 - COTTER PIN 4 - SPRING WASHER
4. Have a helper apply the vehicle's brakes to keep hub from turning, loosen and remove the hub nut. see scheme 14
5. Remove disc brake caliper and adapter as an assembly from knuckle as shown. see scheme 15 Hang assembly out of the way using a bungee cord or wire. (Scheme 17) Do not allow caliper to hang by brake hose. 1 - BRAKE ROTOR 2 - HUB AND BEARING 3 - STEERING KNUCKLE 4 - ADAPTER MOUNTING BOLTS 5 - BRAKE CALIPER 6 - ADAPTER 7 - CLIP 1 - HANGER SUSPENDING CALIPER 2 - HANGER SUSPENDING DRIVESHAFT 3 - DRIVESHAFT 4 - BRAKE CALIPER
6. Remove nut attaching outer tie rod end to steering knuckle by holding the tie rod end stud while loosening and removing nut with a wrench. (Scheme 18) 1 - TIE ROD END 2 - STEERING KNUCKLE 3 - WRENCH 4 - SOCKET 5 - TIE ROD END STUD
7. Remove tie rod end from steering knuckle using Remover, Special Tool C-3894-A. (Scheme 19) 1 - OUTER TIE ROD 2 - SPECIAL TOOL C-3894-A 3 - STEERING KNUCKLE
8. If equipped with antilock brakes, remove the front wheel speed sensor from the steering knuckle. (Scheme 20) 1 - MOUNTING BOLT 2 - WHEEL SPEED SENSOR 3 - STEERING KNUCKLE
9. Remove the two steering knuckle-to-strut clevis bracket attaching bolts.
10. Tip the knuckle outward and remove the driveshaft stub axle from the hub and bearing. Suspend driveshaft straight outward using a bungee cord or wire. (Scheme 17) Do not allow driveshaft to hang by inner joint.
11. Remove ball joint nut using a power impact wrench. Because the tapered stud is held sufficiently in the knuckle at this time, it is not necessary to hold the stud stationary to remove the nut.
12. Reinstall the ball joint nut until the top of the nut is even with the top of the ball joint stud. This will keep the stud from distorting while the stud is released from the knuckle in the following step. CAUTION: Do not remove ball joint stud from steering knuckle using a hammer. Damage to the Aluminum knuckle, ball joint or control arm will result.
13. Release ball joint stud from steering knuckle using Remover, Special Tool C-4150A, as shown. (Scheme 21) To ease Remover installation and use, it may help to rotate the knuckle around so the inside of the knuckle faces outward. 1 - ALUMINUM KNUCKLE 2 - SPECIAL TOOL C-4150A 3 - LOWER CONTROL ARM 4 - NUT INSTALLED ON BALL JOINT STEM
14. Remove the nut from the top of the ball joint stud.
15. Remove the steering knuckle from the vehicle.
16. If the hub and bearing needs to be transferred, remove the four bolts attaching the hub and bearing to the knuckle, then remove the hub and bearing.

The ball joint is an integral part of the lower control arm. (Scheme 16) The ball joint has a tapered stud that is pressed into the aluminum knuckle. The ball joint stud is threaded on the end for a retainer nut.

The ball joint has a non-vented seal boot. The seal boot has an integrated heat shield.

The ball joint used in the lower control arm of this vehicle is a sealed-for-life ball joint and requires no maintenance lubrication. The ball joint has been lubricated-for-life during the manufacturing process. A special fitting cap is installed on the fill port. This cap must not be removed and replaced with a common zirc fitting. The special cap is there to eliminate the possibility of lubrication latter during the ball joints life, thus damaging the non-vented seal boot.

Note. The ball joint does not require any type of additional lubrication for the life of the vehicle. No attempt should be made to ever add any lubrication to the lower ball joint.

The ball joint is a pivotal joint on the lower control arm that allows the knuckle to move up and down, and turn with ease.

DESCRIPTION - EXPORT

The lower ball joint seal boot is a two piece unit. It consists of the seal boot, plus a separate shield that is located in a groove at the top of the seal boot.

Note. The seal boot should only be replaced if damaged during vehicle service. The entire lower control arm should be replaced if the joint has been contaminated.

Scheme 22

1. Remove steering knuckle from vehicle. «(Refer to SUSPENSION/FRONT/KNUCKLE - REMOVAL)»(ref-248906-S36682432932007022700000)
2. Using a screwdriver or other suitable tool, pry seal boot off of ball joint. (Scheme 22) 1 - BALL JOINT STUD 2 - SCREWDRIVER 3 - SEAL BOOT
3. Inspect ball joint for evidence of dirt or water intrusion and wipe clean as necessary. If dirt or water intrusion is extreme and joint cannot be properly cleaned, lower control arm will need to be replaced. «(Refer to SUSPENSION/FRONT/LOWER CONTROL ARM - REMOVAL)»(ref-248906-S39422082912007022700000)

The lower control arm is mounted to the front suspension crossmember using a pivot bolt through the center of the front pivot bushing, and the front suspension cradle crossmember reinforcement traps the rear bushing in the crossmember. (Scheme 16)

The lower control arm is an iron casting with two rubber bushings and a ball joint. The lower control arm front bushing is the spool type and is pressed into the lower control arm. The standard (Low-line, High-line) lower control arm rear bushing is a push-on bushing that is pushed over a stem on the rear of the lower control arm. The lower control arm rear bushing used on all other models is a hydro-bushing that is pressed on. It has liquid filled voids that provide more effective dampening than the standard bushing. Vehicles with rear hydro-bushings utilize a different lower control arm than vehicles with standard bushings. They have a straight slightly tapered round stem where the hydro-bushing is mounted whereas the standard arm has a straight stem with a squared knob on the end to retain the bushing.

The lower control arm ball joint is pressed into the outer end of the arm. The ball joint has a tapered stud and retainer nut for fastening it to the steering knuckle.

The lower control arm supports the lower end of the steering knuckle and allows for the up and down movement of the suspension during the jounce and rebound travel. The lower control arm ball joint connects the arm to the steering knuckle.

Scheme 23

Scheme 24

1. Raise vehicle. «(Refer to LUBRICATION & MAINTENANCE/HOISTING - STANDARD PROCEDURE)»(ref-248903-S02249938992007022700000)
2. Remove wheel and tire assembly.
3. Remove the steering knuckle. «(Refer to SUSPENSION/FRONT/KNUCKLE - REMOVAL)»(ref-248906-S36682432932007022700000)
4. Remove the bolts fastening the power steering cooler to the front suspension cradle crossmember reinforcement. (Scheme 23) 1 - CRADLE CROSSMEMBER REINFORCEMENT 2 - POWER STEERING COOLER
5. Remove the lower control arm rear bushing retainer bolts located on each side of each lower control arm rear bushing. NOTE: The bolts fastening the cradle crossmember reinforcement are of three different thread sizes. Note the location of the various sizes.
6. Remove the bolts attaching the cradle crossmember reinforcement to the front suspension cradle crossmember. (Scheme 24) Remove the 2 bolts fastening the reinforcement and rear of cradle crossmember to the body of the vehicle. Remove the reinforcement. 1 - STEERING GEAR 2 - RIGHT LOWER CONTROL ARM 3 - LEFT LOWER CONTROL ARM 4 - CRADLE CROSSMEMBER REINFORCEMENT 5 - REAR CRADLE CROSSMEMBER ISOLATOR BUSHING 6 - STABILIZER BAR 7 - CRADLE CROSSMEMBER
7. Remove the pivot bolt attaching the front bushing of the lower control arm to the front suspension cradle crossmember.
8. Remove the lower control arm.

Scheme 25

1. Remove the lower control arm from the front suspension cradle. «(Refer to SUSPENSION/FRONT/LOWER CONTROL ARM - REMOVAL)»(ref-248906-S39422082912007022700000)
2. Mount the lower control arm in a vise without using excessive clamping force.
3. Using a sharp knife (such as a razor), slit the bushing lengthwise to allow its removal from the lower control arm. (Scheme 25) 1 - REAR BUSHING 2 - SLIT CUT IN BUSHING 3 - LOWER CONTROL ARM
4. Remove the bushing from the lower control arm.

Scheme 26

1. Remove the lower control arm from the front suspension cradle. «(Refer to SUSPENSION/FRONT/LOWER CONTROL ARM - REMOVAL)»(ref-248906-S39422082912007022700000)
2. Mount the lower control arm in a vise without using excessive clamping force.
3. Install Remover, Special Tool 8460, on hydro-bushing as shown. (Scheme 26) Removal Pin, Special Tool 8460-3, must extend though hole in center of bushing rear. 1 - REMOVAL PIN (8460-3) 2 - BRIDGE (8460-1) 3 - HYDRO-BUSHING 4 - LOWER CONTROL ARM
4. Tighten forcing screw of Bridge (Special Tool 8460-1), removing bushing from lower control arm.

The stabilizer bar interconnects both front struts of the vehicle and is attached to the front crossmember. (Scheme 16)

Attachment of the stabilizer bar to the front crossmember is through 2 rubber-isolator cushion bushings and retainers. A double ball jointed stabilizer bar link is used to attach each end of the stabilizer bar to the front strut assemblies. All parts of the stabilizer bar are replaceable as individual components.

The stabilizer bar to front crossmember cushion bushings are split for easy removal and installation. The split in the bushings should be positioned toward the rear of the vehicle, with the square corner facing down, when the stabilizer bar is installed.

Jounce and rebound movements affecting one wheel are partially transmitted to the opposite wheel of the vehicle through the stabilizer bar. This helps to minimize the body roll of the vehicle during suspension movement.

Connecting the stabilizer bar links to the strut assemblies helps reduce the fore-and-aft rate of the stabilizer bar from the rest of the front suspension.

Scheme 27

1. Raise vehicle. «(Refer to LUBRICATION & MAINTENANCE/HOISTING - STANDARD PROCEDURE)»(ref-248903-S02249938992007022700000)
2. Remove the bolts fastening the power steering cooler to the front suspension cradle crossmember reinforcement. see scheme 37 1 - CRADLE CROSSMEMBER REINFORCEMENT 2 - POWER STEERING COOLER
3. Remove the lower control arm rear bushing retainer bolts located on each side of each lower control arm rear bushing. NOTE: The bolts fastening the cradle crossmember reinforcement are of two different thread sizes. Note the location of the various sizes.
4. Remove the bolts attaching the cradle crossmember reinforcement to the front suspension cradle crossmember. see scheme 38 Remove the 2 bolts fastening the reinforcement and rear of cradle crossmember to the body of the vehicle. Remove the reinforcement. 1 - STEERING GEAR 2 - RIGHT LOWER CONTROL ARM 3 - LEFT LOWER CONTROL ARM 4 - CRADLE CROSSMEMBER REINFORCEMENT 5 - REAR CRADLE CROSSMEMBER ISOLATOR BUSHING 6 - STABILIZER BAR 7 - CRADLE CROSSMEMBER CAUTION: When removing the nut from the stud of the stabilizer bar link, do not allow the stud to rotate in it's socket. Hold the stud from rotating by placing an open-end wrench on the flat machined into the stud. (Scheme 27)
5. Remove the stabilizer bar links from each end of the stabilizer bar. (Scheme 27) To do so, place an open-end wrench on the flat machined into the link's mounting stud, then remove the nut while holding the wrench in place. Push each stud out of the hole in the stabilizer bar. 1 - RATCHET 2 - WRENCH 3 - STRUT 4 - STABILIZER BAR LINK 5 - NUT 6 - STABILIZER BAR
6. Remove the stabilizer bar bushing (cushion) retainers from the front suspension cradle crossmember. see scheme 40 1 - STEERING GEAR 2 - STABILIZER BAR 3 - RAISED BEAD 4 - FRONT CRADLE CROSSMEMBER 5 - RETAINERS
7. Remove the stabilizer bar and bushings (cushions) as an assembly from the front suspension cradle crossmember.

DESCRIPTION - STRUT ASSEMBLY

A Macpherson type strut assembly is used in place of a conventional front suspension's upper control arm and upper ball joint. The bottom of the strut mounts directly to the steering knuckle using two bolts and nuts going through the strut clevis bracket and steering knuckle. The top of the strut mounts directly to the strut tower of the vehicle using the threaded studs on the strut assemblies upper mount.

The strut assembly includes the components listed in the figure. (Scheme 28)

Scheme 28

Each component is serviced by removing the strut assembly from the vehicle and disassembling it.

The coil springs are side-oriented. Springs on the left side of the vehicle have a left-hand wind top-to-bottom while springs on the right side have a right-hand wind top-to-bottom. This helps provide better vehicle stability during jounce and rebound maneuvers of the front suspension. Left and right springs must not be interchanged. Coil springs are rated separately for each corner or side of the vehicle depending on optional equipment and type of vehicle service. If the coil springs require replacement, be sure that the springs are replaced with springs meeting the correct load rating and spring rate for the vehicle and its specific options.

OPERATION - STRUT ASSEMBLY

The strut assembly cushions the ride of the vehicle, controlling vibration, along with jounce and rebound of the suspension.

The coil spring controls ride quality and maintains proper ride height.

The spring isolators isolate the coil spring at the top and bottom from coming into metal-to-metal contact with the upper seat and strut.

The jounce bumper limits suspension travel and metal-to-metal contact under full jounce condition.

The strut dampens jounce and rebound motions of the coil spring and suspension.

During steering maneuvers, the strut assembly (through a pivot bearing in the upper strut mount) and steering knuckle (through the lower ball joint) turn as an assembly.

Scheme 29

1. Inspect for damaged or broken coil springs. (Scheme 28)
2. Inspect for torn or damaged strut assembly dust boots. (Scheme 28)
3. Inspect the coil spring isolator on the lower spring seat for any signs of damage or deterioration.
4. Lift dust boot and inspect strut assembly for evidence of fluid running from the upper end of fluid reservoir. (Actual leakage will be a stream of fluid running down the side and dripping off lower end of unit). A slight amount of seepage between the strut rod and strut shaft seal is not unusual and does not affect performance of the strut assembly. (Scheme 29) Also inspect jounce bumpers for signs of damage or deterioration. 1 - DUST BOOT 2 - STRUT SHAFT 3 - STRUT FLUID RESERVOIR 4 - INSPECT THIS AREA FOR EVIDENCE OF EXCESSIVE FLUID LEAKAGE

DESCRIPTION - REAR SUSPENSION

The rear suspension design on this vehicle uses leaf springs, and a tube and casting axle. (Scheme 30)and (Scheme 31). The leaf springs used on the rear suspension of this vehicle are of either a mono-leaf or multi-leaf design.

Scheme 30

Scheme 31

There are four different rear suspension designs available

1. Front-Wheel-Drive
2. Front-Wheel-Drive with Fold-in-Floor Seating
3. All-Wheel-Drive
4. Front-Wheel-Drive Commercial

The Front-Wheel-Drive (FWD) rear suspension uses an axle that is mounted to mono-leaf springs using isolator bushings at the axle mounting brackets. The stabilizer bar mounts behind the axle.

The Front-Wheel-Drive with Fold-in-Floor Seating rear suspension is very much like the FWD rear suspension except for the fact that the stabilizer bar mounts in from of the axle.

The All-Wheel-Drive (AWD) rear suspension uses a unique axle that is mounted to multi-leaf springs, and does not use isolator bushings between the rear axle and the leaf springs.

The Front-Wheel-Drive Cargo rear suspension uses multi-leaf springs and a different rear axle than either the standard FWD or AWD. It also does not utilize a stabilizer bar. It is very similarly to the AWD suspension.

The rear suspension consists of these major components

1. Leaf springs (One each side)
2. Jounce bumpers (One each side)
3. Shock absorbers (One each side)
4. Hub and bearings (One each side)
5. Track bar
6. Stabilizer bar

The rear wheel bearing and rear wheel hub of this vehicle are a one-piece sealed unit, or hub and bearing unit type assembly (Unit III). The hub and bearing is mounted to the center of the rear axle using 4 mounting bolts. It has five wheel mounting studs on the hub flange.

All-Wheel-Drive vehicles have a hub and bearing unit with a splined hole in the center of the hub for rear driveshaft stub axle acceptance.

Front-Wheel-Drive vehicles with antilock brakes have an internally mounted wheel speed sensor and tone wheel. This hub and bearing can be identified by the rounded cap and molded in connector on the rear of the assembly. (Scheme 32) The sensor and tone wheel cannot be serviced separately from the hub and bearing.

Scheme 32

The hub and bearing has internal bearings that allow the hub to rotate with the tire and wheel assembly (and driveshaft on All-Wheel-Drive vehicles). The five wheel mounting studs mount the tire and wheel assembly, and disc brake rotor or brake drum to the vehicle.

On All-Wheel-Drive vehicles, the splined mating of the driveshaft stub axle and hub allows the driveshaft to rotate with the hub and wheel.

Front-Wheel-Drive vehicles equipped with antilock brakes have a wheel speed sensor and tone wheel mounted to the rear of the hub and bearing. The tone wheel rotates with the hub which is sensed by the wheel speed sensor.

There are two jounce bumpers used in the rear suspension. One mounts to each frame rail above the rear axle.

The jounce bumper limits suspension travel and metal-to-metal contact of the rear axle with the frame under full jounce conditions.

There is one shock absorber on each side of the rear suspension. The top of each shock absorber is bolted to the frame rail. The bottom of each shock absorber is bolted to the rear axle.

This vehicle is available with either standard type or load-leveling shock absorbers. On the exterior, load-leveling shock absorbers are larger in diameter than standard shock absorbers. The load-leveling shock absorbers mount the same as the standard shock absorbers.

The shock absorber dampens jounce and rebound motions of the spring and suspension.

Each load-leveling shock absorber is a self-leveling, self-contained vehicle leveling system and shock absorber combined. It does not require an external compressor, hoses, or height leveling sensors. All the height leveling sensors, hydraulic pump, etc, are contained inside the shock absorber. It uses road inputs (bumps, stops, starts, turns, acceleration, deceleration, etc.) to activate pumping, which results in the extension and compression of the shock absorber.

Some front-wheel-drive models use a stabilizer bar. It is mounted behind the rear axle. All-wheel-drive models use a stabilizer bar that is mounted in front of the rear axle.

The stabilizer bar interconnects both sides of the rear axle and attaches to the rear frame rails using 2 rubber isolated link arms.

Both type stabilizer bars have the same basic components. Attachment to the rear axle tube, and rear frame rails is through rubber-isolated bushings.

The 2 rubber isolated links are connected to the rear frame rails by brackets. These brackets are bolted to the bottom of the frame rails.

Jounce and rebound movements affecting one wheel are partially transmitted to the opposite wheel to reduce body roll.

On front-wheel-drive applications of this vehicle that are equipped with single leaf rear springs, a track bar is used on the rear axle. (Scheme 30)

The track bar connects the rear axle to the frame/body of the vehicle. The track bar is isolated from the body of the vehicle by an isolator bushing located in each end of the track bar.

The track bar prevents excessive side-to-side movement of the rear axle. The track bar is used to keep the location of the axle in the correct position for optimum handling and control of the vehicle.

Scheme 33

1. Remove the nut and bolt mounting the track bar to the rear axle. (Scheme 33) 1 - MOUNTING BOLT 2 - NUT 3 - NUT 4 - MOUNTING BOLT 5 - TRACK BAR 6 - REAR AXLE 7 - FRAME MOUNTED BRACKET
2. Remove the nut and bolt attaching the track bar to the track bracket on the body of the vehicle. (Scheme 33) Remove the track bar.

DESCRIPTION - WHEEL ALIGNMENT

Vehicle wheel alignment is the positioning of all interrelated front and rear suspension angles. These angles affect the handling and steering of the vehicle when it is in motion. Proper wheel alignment is essential for efficient steering, good directional stability, and proper tire wear.

The method of checking a vehicle's front and rear wheel alignment varies depending on the manufacturer and type of equipment used. The manufacturer's instructions should always be followed to ensure accuracy of the alignment, except when DaimlerChrysler Corporation's wheel alignment specifications differ.

On this vehicle, the suspension angles that can be adjusted are as follows

1. Front Camber (with camber bolt package and standard procedure)
2. Front Toe

Check the wheel alignment and make all wheel alignment adjustments with the vehicle standing at its proper curb height specification. Curb height is the normal riding height of the vehicle. It is measured from a certain point on the vehicle to the ground or a designated area while the vehicle is sitting on a flat, level surface. Refer to STANDARD PROCEDURE - CURB HEIGHT MEASUREMENT for additional information.

Typical wheel alignment angles and measurements are described in the following paragraphs.