Will You Fix That Humming Transmission?


– Gearbox bearings: the components of a gearbox

– The constitution of a gearbox bearing

– Price of replacing a gearbox bearing

A more and more critical humming invades the passenger compartment of your car during deceleration or acceleration phases; the gears shift with more and more difficulty… Everything indicates that a gearbox bearing is giving up the ghost. But what exactly is a transmission bearing? We tell you more about it in this post!

Gearbox bearing: the components of a gearbox

The gearbox is made up of five elements:

– the casing, a metal envelope containing the gearbox mechanisms and the lubricating oil;

– the shafts are two in number, arranged longitudinally side by side:

◦ the primary shaft is a shaft in connection with the engine that imparts motion to it;

◦ the secondary shaft, meanwhile, is in connection with the wheels to transmit its movement to them.

– Pinions are arranged on the primary and secondary shafts. There is a primary shaft pinion opposite a secondary shaft pinion for each gear selected: the first drives the second. The difference in diameter between these two gears (gear ratio) allows the engine speed to be changed at the gearbox output. Each gear (from first to fifth) has a different gear ratio.

– The selection system allows engaging the gear ratio corresponding to the desired speed.

– There are 4 main bearings in a gearbox, located at the end of the primary and secondary shafts, whose role is to guide them in rotation. If one of the bearings is destroyed, the shaft takes up axial play, and you may ruin the gears in motion with each other.

Note: As the operating range of an internal combustion engine is very small (from 1000 to 3000 rpm), the gearbox reduces or overdrives the engine speed to achieve a high vehicle speed, or on the contrary, to increase the engine’s force when starting or to drive uphill.

The constitution of the bearings of a gearbox


General description

A bearing is schematically composed of 3 main parts:

– The outer circular cage is integral with the gearbox housing and therefore fixed.

– The circular inner cage is fixed to the gearbox shaft and therefore rotates.

– The balls or rollers are positioned between the fixed outer cage and the inner cage. They allow the rotation of the inner cage and the shaft.

The designation of a bearing is defined by:

– its inside diameter;

– its outside diameter;

– its thickness.

The different types of gearbox bearings

There is a wide variety of bearings depending on the type of gearbox. Here we give you the most common ones:

– Straight ball bearings are the standard bearings described above. They can be single or double-row ball bearings.

– Tapered bearings. The outer cage is in the form of a female cone into which a male cone of the external enclosure is inserted. This arrangement counteracts the lateral forces that can be applied to the shafts. They can be made up of single or double rows of balls or rollers.

Price of replacing a gearbox bearing

Deterioration or destruction of a bearing can cause irreversible damage to the transmission. Even in damage, the replacement of a gearbox bearing is a technical operation mastered by few professionals today. The standard gearbox replacement is thus very often systematically proposed.

– For an average vehicle, a standard exchange gearbox costs between $1,000 and $1,500, not counting labor and materials (approximately $300 to $500 or more).

– Some gearbox reconditioning companies propose a price according to the work to be done on your gearbox, the difficulty being to evaluate the quality of the work done and the inherent risks (malfunctions, random guarantees…). It can go from $1 000 to more than $2000 when replacing the standard gearbox.

– The technician in your garage who reconditions gearboxes, replacing only the worn parts, will work based on an estimate: the replacement of a bearing can cost from $600 to $800.

After reading this post, it is up to you to choose whether you want to go for the gearbox replacement or sell the vehicle as-is. Remember to share your experience in the comment section below.

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