| J-rim
| A groove around the outer edge of a wheel rim to provide a lock for the tire bead. |
| J/B
| Junction block |
| Jack the Bear
| A top-performing driver. |
| jacketed gasket
| A gasket having metal grommets around bolt and water holes. |
| jacking
| Modifying the suspension to raise or lower one corner of an oval-track race car in order to provide better handling characteristics. |
| jackrabbit start
| The sudden acceleration from a standing start. |
| jackshaft
| A shaft found in most overhead cam engines that is used to drive the distributor, fuel pump, and oil pump. |
| Jacob's ladder
| A triangular control linkage to center the rear axle assembly found on some rear-wheel-drive race cars. |
| Jacobs brake
| A device more commonly known as Jake brake. |
| jalopy
| 1. A low-budget, dirt-track racing car rebuilt from an older vehicle. 2. An old automobile. |
| jam nut
| A second nut tightened against a primary nut to prevent it from working loose; used on inner and outer tie-rod adjustment nuts and on may pinion-bearing adjustment nuts. |
| JAMA
| An acronym for Japan Automobile Manufacturers Association. |
| Japan Automobile Manufacturers Association (JAMA)
| An international trade association of Japanese car, truck, motorcycle, and bus manufacturers. |
| Japanese Industrial Standards (JIS)
| Japan's equivalent of the DIN in Germany or the SAE in the United States. |
| jeep trail
| A road or trail suitable only for a 4WD vehicle. |
| jeeping
| Driving a 4WD vehicle, generally off the road. |
| Jendham
| An Automotive training company |
| jet
| A calibrated passage in the carburetor used to meter fuel flow. |
| jet car
| A race car powered by a jet aircraft engine for open course competition. |
| jet valve
| An intake valve, located in a precombustion chamber, that admits a highly concentrated air/fuel mixture into a stratified charge engine. |
| JFET
| (Junction Feld effect transistor) A field effect transistor formed by combining layers of semiconductor material. The JFET has an input impedance equil to the reverse bias impedance of a p-n junction. This imperance is approximately 20,000 Meg. oms. |
| jig
| 1. A fixture for holding work. 2. A device used as an aid to straighten the frame of a vehicle. |
| JIS
| An acronym for Japanese Industrial Standard. |
| JMS
| Jet mixture solenoid |
| Johnson rod
| A mythical automotive component that is blamed for any problem that cannot otherwise be explained. |
| joint
| A junction of members that are to be joined or have been joined. |
| joint penetration
| The depth a filler metal extends from its face into a joint, exclusive of weld reinforcement. |
| joule(J)
| A unit of energy, measured in newtons per meter. The rate of using joules per second is watts. |
| jounce
| The inward reaction of the spring and shock absorber when a wheel hits an obstruction. |
| journal
| The part of a rotating shaft that turns in a bearing. |
| journal size
| The finished diameter of a crankshaft journal. |
| Jubilee Clip
| English term for Hose Clamp |
| judder
| A low-frequency vibration of the clutch or brakes. |
| jug
| A carburetor. |
| juice
| 1. The current in an electrical system. 2. A special racing-fuel formula. 3. Any fluid, such as brake fluid. |
| jump
| 1. To begin early rapid acceleration in a rolling-start race before the green flag. 2. To make an early, sudden start off the line in drag racing before the green light. 3. To bypass the ignition switch to start a vehicle. 4. To jump start a vehicle. 5. An obstacle that causes an off-road vehicle to become airborne. |
| jump out
| A condition when a fully engaged gear and sliding clutch are forced out of engagement. |
| jump start
| Using battery jumper cables to connect an able battery to a disabled battery to start the vehicle. |
| jumper cable
| Two heavy-duty cables used to connect two batteries, as for starting a vehicle. |
| jumper wire
| A wire used to bypass electrical circuits or components for testing purposes. |
| jumpers
| A term used for jumper cable or jumper wire. |
| junction
| 1. A contact point between two or more conductors in a circuit, also called a node. 2. The region separating two layers in a semiconductor material, e.g. a p-n junction. |
| junction block
| A device on which two or more junctions may be found. |
| junction transistor
| A PNP or NPN transistor formed from three alternate regions of p or n type material. Also called a bi-polar transistor. |
| Junior fueler
| An old drag-racing term for a lower-class fuel dragster. |
| Junior stocker
| An old drag-racing term for a lower-class fuel stocker. |
| junk
| Anything that is so badly worn or deteriorated that it is of no further use. |
| junker
| A vehicle that is ready for the junk box. |
| junky
| Anyone in the vehicle salvage business. |
| junkyard
| A vehicle salvage business that sells used parts. |
Auto & Car Glossary
