April 27, 2017

Engine & Gearbox

If your engine is starting to fail, you may need an engine overhaul. When an engine is overhauled, it is disassembled, cleaned, inspected, and repaired as necessary. Depending on what the issue is with your engine, sometimes an overhaul is better than if you would fully replace it. This can also save you money and you will not need a brand new engine for your vehicle.

What is an Engine overhaul?

When an engine is overhauled, a few basic things are done to restore it to a good working condition. The lower half of the engine is removed and is disassembled and cleaned so that it can be properly evaluated. Depending on the condition of the internal parts of the engine, bearings, and piston rings, they may need to be replaced. The internal surfaces of the cylinders are also reconditioned to make sure the piston rings can form a proper seal with the cylinder walls. The engine is then reassembled and installed back into your vehicle. If only a small part of your engine is having the issue, this may be the recommended choice for you.

Reasons you would need an engine overhaul?

Having your engine overhauled does not have to be a major expense or inconvenience. There are two main reasons why you would choose an overhaul over any other option. If there is any sign of wear to the engine bearings, it is usually best to have an overhaul done. This is also recommended if you have piston rings that are poorly seated. The moving parts of an engine are mounted on bearings, which allow them to move freely as they are lubricated by engine oil. The bearings are built to last over thousands of miles, but eventually they will start to wear down. The wear is accelerated when a vehicle is poorly maintained and running low on oil levels. Worn bearings will start to produce a loud knocking noise and will eventually cause the engine to fail. Piston rings can also cause issues to your engine if they are not properly maintained. They seal in the expanding cases that are created when the gasoline burns within the engine. As they wear, they no longer can seal the cylinders properly. When this occurs, the crankcase oil escapes past the worn rings and is burned with the fuel mixture that is in the cylinder. This is typically why older engines have an excessive amount of smoke in the vehicle’s exhaust. With all the issues that can happen with your engine, it is wise to always make sure to go to scheduled maintenance tune-ups so your vehicle is running as good as possible.

Signs you will need an engine overhaul

If you are wondering if your engine may need an overhaul, you can look for a few signs from your vehicle. One common sign is excessive oil consumption and white smoke in the exhaust, especially when the engine is cold. More extreme signs that your engine needs attention are metal shavings in the engine’s oil, or if you hear a knocking noise while the engine is running. If your vehicle makes any unusually noises, especially if it is becoming more common, you should bring it and have it evaluated for proper service and repair.


Gearbox System

The gearbox provides a selection of gears for different driving conditions: standing start, climbing a hill, or cruising on level surfaces. The lower the gear, the slower the road wheels turn in relation to the engine speed.

The gearbox is the second stage in the transmission system, after the clutch. It is usually bolted to the rear of the engine, with the clutch between them. Modern cars with manual transmissions have four or five forward speeds and one reverse, as well as a neutral position.

The gear lever, operated by the driver, is connected to a series of selector rods in the top or side of the gearbox. The selector rods lie parallel with shafts carrying the gears. The most popular design is the constant-mesh gearbox. It has three shafts: the input shaft, the layshaft and the mainshaft, which run in bearings in the gearbox casing.

There is also a shaft on which the reverse-gear idler pinion rotates. The engine drives the input shaft, which drives the layshaft. The layshaft rotates the gears on the mainshaft, but these rotate freely until they are locked by means of the synchromesh device, which is splined to the shaft.

It is the synchromesh device which is actually operated by the driver, through a selector rod with a fork on it which moves the synchromesh to engage the gear. The baulk ring, a delaying device in the synchromesh, is the final refinement in the modern gearbox. It prevents engagement of a gear until the shaft speeds are synchronized.

On some cars an additional gear, called overdrive, is fitted. It is higher than top gear and so gives economic driving at cruising speeds.

Ssynchronizing the Gears

The synchromesh device is a ring with teeth on the inside that is mounted on a toothed hub which is splined to the shaft. When the driver selects a gear, matching cone-shaped friction surfaces on the hub and the gear transmit drive, from the turning gear through the hub to the shaft, synchronising the speeds of the two shafts.

With further movement of the gear lever, the ring moves along the hub for a short distance, until its teeth mesh with bevelled dog teeth on the side of the gear, so that splined hub and gear are locked together. Modern designs also include a baulk ring, interposed between the friction surfaces. The baulk ring also has dog teeth; it is made of softer metal and is a looser fit on the shaft than the hub.

The baulk ring must be located precisely on the side of the hub, by means of lugs or ‘fingers’, before its teeth will line up with those on the ring. In the time it takes to locate itself, the speeds of the shafts have been synchronised, so that the driver cannot make any teeth clash, and the synchromesh is said to be ‘unbeatable’. Most modern cars have synchromesh on all forward gears, but on earlier cars it is not provided on first gear.


Call us today to make an appointment to have your Car Service at Legacy Tecnica Motorsports.
“WE KNOW YOUR CAR BEST”

LEGACY TECNICA MOTORSPORTS
39, Woodlands Close, #01-08
MEGA@WOODLANDS
Singapore 737 856
Tel: +(65) 8858 8851
Email: inquiry@legacytecnica.com