What Is the Difference between Constant and Sliding Mesh in a Manual Transmission?

By Mister Transmission

Driving a stick? Get to know more about the gearbox that powers your car or truck

The history of manual transmissions and their evolution is fascinating. For instance, at one time, your car’s manual transmission included either a sliding-mesh gearbox or a constant-mesh gearbox.

A manual transmission sliding mesh is typically found in older vehicles. It is, in fact, one of oldest types of gearbox. To shift between different speeds using a sliding-mesh gearbox, the gears on the main shaft are shifted right or left for meshing them with the appropriate gears on the counter shaft (this is where the phrase ‘shifting gears’ comes from).

The problem with a sliding-mesh gearbox is when changing gears, the speeds of the input and output shafts must be matched first. Otherwise, the sliding dog teeth of the meshing gearwheels do not align, and they “crash” into one another. That is why this type of gearbox is alternatively referred to as a ‘crash box’.

A manual transmission constant mesh, meanwhile, is commonplace in newer manual transmissions – notably those in large trucks and farm vehicles. All of the gears mesh together simultaneously and at all times. In other words, the gears rotate freely on the main shaft, and the gear ratios are selected by clutches that connect them to shafts to power your vehicle.

Why a Constant-Mesh Gearbox Is Your Better Option

A sliding-mesh gearbox may be mechanically efficient, but the noise it generates when changing gears, and the difficulty that was involved when changing gears left much to be desired.

In comparison, the advantages of a constant-mesh gearbox include:

  • The gears used in a manual transmission constant mesh are helical and double helical and are quieter during operation
  • Because the gears in a constant-mesh gearbox are in constantly meshing, it’s less likely to damage the gear teeth, and there’s typically less wear on the gears
  • If a driver makes a “bad” change in gears, any damage that may occur will be limited to the dog clutch

The Synchro-Mesh Gearbox Comes to the Fore

For stick-shift enthusiasts, though a manual transmission constant mesh was an improvement over the sliding-mesh gearbox, drivers still required tremendous skill to operate them. That gave way to the synchro-mesh gearbox, a unit that has many similarities to its constant-mesh predecessor since the gears are always engaged. The exception is the inclusion of a cone clutch that sits between the dog clutch and gears. That means motorists no longer have to trouble themselves with the necessity of double declutching as they would using a constant-mesh gearbox.

 

Are you experiencing transmission troubles or have questions about your vehicle’s transmission? Visit the Mister Transmission location nearest you and get the expert help you need.

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Ted Wilson
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I brought my car there this morning. I spoke to a gentleman named Steve who was very polite and professional. I didn’t end up needing work done but Steve was very pleasant and gave helpful suggestions. I was impressed
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Call Mel for any transmission...
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Bethany Corner
I am a petite, doe eyed, 20-something, female and I was amazed by their professionalism and integrity. I had a mechanic from another shop tell me he thought the problem I was having with my car was with my transmission. I took my car to Mister transmission to get a second opinion and they did a free diagnosis and told me my transmission was fine. They didn't make a penny off me, but I know for sure I will recommend them to anyone who asks because of their integrity.
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I went into Mister Transmission...
Paul Roy
I went into Mister Transmission to have what I thought was a Transmission problem. It wasn't but they found the issue in no time being a transfer case and right front axel. Only the work required was performed. Could't be happier.
Date: September 23, 2020
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Very helpful owner and staff. Also very knowledgeable. Thanks
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Dan Savage
Great place
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Went off-roading and had my Jeep fall into a giant mud hole that ruined the engine. Decided to take my Jeep to Off-road addiction in St Thomas who were going to do an engine swap. After 2+ months, they weren't able to complete the work nor figure out the issue. They said to take it into a dealership. Dealership quoted me $10k for a new transmission. Was recommended to checkout Mister Transmission and I wish I knew about them sooner.Pete was awesome to work with, he explained everything that was wrong, documented it and took pictures. Previously the engine and transmission weren't seated properly and had cracked the transmission pump. These guys were able to rebuild my transmission, put in a new transmission pump, seat the engine and transmission properly, and have the whole thing running properly with the quoted estimate in both cost and time. I was completely amazed by how quickly they were able to fix my issues.This is the only shop I'll take my Jeep in for any work done in the future. Last year I had my gear and pinion swapped from 3.23 to 4.56, again with flawless work and 0 issues.100/10 recommend you take your vehicle here for any servicing needs. These guys know their stuff and I'm happy to throw money at them any time I need work done.
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Good service, decent prices.
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