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Farmhauler · Joined: 30 Oct 2005 Posts: 2

This may be a stupid question, but why don't we have syncromesh transmissions in our trucks? They have been used in automobiles for 40 years.

Splitshifter · Joined: 19 Jun 2006 Posts: 644 Location: Right here

To separate the real drivers from the wannabes.

MADLUX · Joined: 05 Jun 2005 Posts: 558 Location: Virginia Beach, VA

Farmhauler wrote: This may be a stupid question, but why don't we have syncromesh transmissions in our trucks? They have been used in automobiles for 40 years.

They cant take the power and torque of these engines.

Splitshifter · Joined: 19 Jun 2006 Posts: 644 Location: Right here

Now I'll give a serious answer.

I posted this on another site when someone asked basically the same question.

It's post #5 in the linked thread:

http://www.bigmacktrucks.com/index.php?showtopic=2873

Quote: An unsynchronized transmission is actually a safety feature. The transmission cannot accidentally be put in the wrong gear while going down the road.

Think of it this way: You could drive a manual transmission car down the road at 60 MPH in hi gear, and due to the fact that the transmission is synchronized, you could depress the clutch pedal and the synchronizers would make it possible to shift into first gear with no problem (keep in mind the car is going 60 MPH) So what do you think happens when you re engage the clutch?

Yup, massive overspeed of the engine, shock to the driveline and more than likely catastrophic damage.

Now picture that scenario in a 80,000 lb truck with a synchronized transmission.

I think that's one good reason why class 8 truck transmissions are not synchronized.

RockyMtnProDriver · Joined: 12 Jun 2005 Posts: 1558 Location: Cranbrook BC

Straight cut gear transmissions have more directional application of force allowing for less power loss and higher acceptable loads before they will fail than will a helical cut transmissions. It basically makes the transmission stronger and more efficient.

And we don't live in Europe.

By the way, some of the new auto shifts have helical cut gears. Which pretty much means the top part of what I wrote is crap.

Bottom line is that straight cut gears is old technology. There is no reason why we cannot have helical cut transmissions in the new trucks. We have them for the same reason we don't have disc brakes and Pete still sells trucks.

North American truckers don't like change.

And we don't live in Europe.

Farmhauler · Joined: 30 Oct 2005 Posts: 2

Hey there Mr. Splitshifter,

Your comment was kinda uncalled for. DUH! All kidding aside, I've been
hauling out of fields and tight places in Orchards for years, as well as down the road. Sooo, my question was rhetorical and for curiosity. Aside from your snide retort, I got some sensible responses. Keep enjoying truckin.
Best regards,
Farmhauler

Splitshifter · Joined: 19 Jun 2006 Posts: 644 Location: Right here

Farmhauler wrote: Hey there Mr. Splitshifter,

Your comment was kinda uncalled for. DUH! All kidding aside, I've been
hauling out of fields and tight places in Orchards for years, as well as down the road. Sooo, my question was rhetorical and for curiosity. Aside from your snide retort, I got some sensible responses. Keep enjoying truckin.
Best regards,
Farmhauler

And obviously you wouldn't recognize humor if it was staring you in the face. (Which it was, in this case).

Bandit102 · Joined: 22 Nov 2006 Posts: 242

Slipshifter, I enjoyed the humor.

durango360 · Joined: 16 Oct 2007 Posts: 4 Location: Ontario

I was told by several people that several transmission manufacturers played with the idea of adding synchronizers but the durability wasn't there. Sort of the same reason when automatics were first introduced. After 100 000miles after towing moderate to heavy loads the torque converter would burn up! Autos have improved a lot since then of course! The company I work for is ordering new Cascaida trucks with 10sp auto's. It should be interesting. The only HD autos I drove were Allison and ZF-Astronic in motor coaches.

bob h · Joined: 15 Oct 2006 Posts: 664 Location: Nb

durango360 wrote: I was told by several people that several transmission manufacturers played with the idea of adding synchronizers but the durability wasn't there. Sort of the same reason when automatics were first introduced. After 100 000miles after towing moderate to heavy loads the torque converter would burn up! Autos have improved a lot since then of course! The company I work for is ordering new Cascaida trucks with 10sp auto's. It should be interesting. The only HD autos I drove were Allison and ZF-Astronic in motor coaches.

The Freightliner MB transmissions are synchronized. The auxilliary section of Fuller multi-speed transmissions use synchronizers... so, I guess the durability is there.

The 10 sp autos that come in the Cascadias are auto-shifts, not hydraulic automatics; no torque converters.

Wild Bill Pete · Posted: Mon Feb 18, 2008 10:30 am Post subject:

I may be wrong, not being perfect, but it is my understanding that syncro boxes are damaged by the time honored and much used driving technique known as 'floating' - That fact, if true, is a very good argument against a syncro box.

special k · Joined: 10 Jul 2005 Posts: 247 Location: Ontario Canada

Volvo's have had synchronized trans available since the mid 90's. Usually the 14 spd model. I've never driven one but the gist I got is they shift a little slower and you have to use the clutch.

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