Tag Archives: Clutch Adjustment

Manual Transmission Basics Trouble Shooting

 

 

manual-transmission repair

 

As you drive your car, you become used to noises, vibrations and the feel of the car in different gears. Any changes in these sensations may indicate the beginning of a problem. It’s important to note what gear you are in, at what speeds the problem occurs, noise level and whether it disappears from one gear to another. Most problems in the clutch and transmission are a job for a mechanic, and usually require removal and service.

 


The Problem Is Caused By

Excessive clutch noise Throwout bearing noises are more audible at the lower end of pedal travel.

The usual causes are:

  • Riding the clutch
  • Too little pedal free-play
  • Lack of bearing lubrication

throw-out-bearing-failure manual transmission clutch

A bad clutch shaft pilot bearing will make a high pitched squeal when the clutch is disengaged and the transmission is in gear or within the first 2″ of pedal travel. The bearing must be replaced.

 

Noise from the clutch linkage is a clicking or snapping that can be heard or felt as the pedal is moved completely up or down. This usually requires lubrication.

Transmitted engine noises are amplified by the clutch housing and heard in the passenger compartment. They are usually the result of insufficient pedal free-play and can be changed by manipulating the clutch pedal.

 


Clutch slips (the car does not move as it should when the clutch is engaged) This is usually most noticeable when pulling away from a standing start. A severe test is to start the engine, apply the brakes, shift into high gear and SLOWLY release the clutch pedal. A healthy clutch will stall the engine.

Clutch Pressure Plate

If it slips it may be due to:

  • A worn pressure plate or clutch plate
  • Oil soaked clutch plate
  • Insufficient pedal free-play
  • Bad waste or slave cylinder
  • Low fluid

Clutch drags or fails to release The clutch disc and some transmission gears spin briefly after clutch disengagement. Under normal conditions in average temperatures, 3 seconds is maximum spin-time. Failure to release properly can be caused by:

  • Too light transmission lubricant or low lubricant level
  • Improperly adjusted clutch linkage
  • Bad cylinder
  • Low fluid
  • Air in line

Low clutch life Low clutch life is usually a result of poor driving habits or heavy-duty use. Riding the clutch, pulling heavy loads, holding the car on a grade with the clutch instead of the brakes and rapid clutch engagement all contribute to low clutch life.

 


Transmission shifts hard Common causes of hard shifting are:

  • Improper lubricant viscosity or lubricant level
  • Clutch linkage needs adjustment/ lubrication.

Transmission leaks lubricant The general location of a leak can be found by putting a clean newspaper under the transmission overnight.

  • Lubricant level too high
  • Cracks in the transmission case
  • Loose or missing bolts
  • Drain or fill plug loose or missing
  • Vent hole plugged

Transmission is noisy in gear Most problems such as this require the services of a mechanic. Causes include:

  • Insufficient lubricant
  • Worn gears (excessive end-play)
  • Worn bearings
  • Damaged synchronizers
  • Chipped gear teeth

Transmission is noisy in Neutral Noises in Neutral are usually caused by:

  • Insufficient/ incorrect lubricant
  • Worn reverse idler gear
  • Worn bearings or gear teeth

 

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Differential Issues and Other Noises

The automotive differential is designed to drive a pair of wheels while allowing them to rotate at different speeds.

 

Your Vehicles differential service place - The Shop in Alvin Tx

Driveline, Axle, Ring and Pinion Gear and Differential Noise

 

Noises, vibrations and other irregular driving characteristics can often help diagnose a differential or driveline problem. Here are a few typical symptoms and their possible cause:

 

  • Whirring noise only while decelerating at any or all speeds is most likely caused by bad pinion bearings or loose pinion bearing preload, and almost never by bad ring and pinion gears.
  • A howl or whine during acceleration over a small or large speed range is usually caused by worn ring and pinion gears or improper gear set up.
  • Rumbling or whirring at speeds over about 20 mph can be caused by worn carrier bearings. The noise may change while turning.
  • Regular clunking every few feet may indicate broken ring or pinion gears.
  • Banging or clunking only on corners can be caused by broken spider gears, lack of sufficient positraction lubrication, or worn positraction clutches.
  • Rumble while turning may indicate bad wheel bearings.
  • A steady vibration that increases with the vehicle’s speed can be caused by worn u-joints or an out of balance driveshaft.
  • Clunking only when starting to move or getting on and off the gas might be loose yokes, bad u-joints or worn transfer case or transmission parts.

 

How the Rear Differential Works

 

One of the most important things about a rear differential is how it operates around corners. It uses side gears or spider gears for cornering.

When a vehicle turns into a curve or goes around even a slight bend the wheels on the outside have to travel a greater distance than the wheels that are tracking on the inside.

If it wasn’t for this situation the two axles could just be linked together and everybody would have a positraction rear end. The operation of the spider gears allows for the rear wheels to turn at different speeds when cornering. This also provides beneficial handling characteristics.

 

Noise from Rear Differentials

 

Where this knowledge comes in handy is for noise diagnosis. If your vehicle only makes noise or has a problem when cornering then the inspection of the spider gears or often called side gears should be performed.

If there is no noise when the vehicle is traveling straight-ahead the ring and pinion gears and their associated bearings are probably not having a problem. In the case of an automatic positive traction type differential such as the one on a 2004 Chevrolet blazer, noise diagnosis can be further complicated.

These types of rear ends have a clutch pack that transfers power to the wheel with the most traction. When the wheels are not slipping this clutch should be released and allow the vehicle to corner normally.

Problems with the clutch pack can be mistaken for problems with the side gears or spider gears. Also in the lubrication fluid the General Motors positraction unit has a special additive to prevent sticking operation of the clutches.

If regular gear oil is installed in a positraction unit with no special additive, grabbing, jerking and noise can occur around corners. Check the auto repair manual for your specific vehicle to make sure you have the correct fluid installed in the rear differential.

 

Positractions & Limited Slips:

 

Limited Slip - Differential Repair in Brazoria county - Alvin Tx The Shop
Posis and limited slips transmit equal torque to both wheels when driving straight. However, when one wheel spins due to loss of traction, a patch of ice, mud, too much throttle, etc., the unit automatically provides more torque to the wheel that has traction. Recommended for daily driving, works well in ice, rain, mud and snow. However, in situations where absolute lockup is needed, a limited slip is not the best choice due to the fact that limited slips do slip in some situations.

Positraction is a type of limited slip. The name “positraction” was used by General Motors for their limited slip differential and the name has been associated with limited slips for many years.

 

Limited Slip - Differential Repair in Brazoria county - Alvin Tx The Shop

 

Automatic Lockers:

Lockers Differential Repair in Brazoria county - Alvin Tx The Shop
Lockers (mechanical locking differentials) provide 100% transfer of power to both drive wheels. This power can be lost if both wheels spin, but a locking differential will never let one wheel spin free by itself while the other one sits still (unless the unit is broken). Automatic locking differentials are engineered to keep both wheels in a constant drive mode, yet have the ability to unlock to permit a difference in wheel speed while negotiating turns.

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