[Graymist]

Most of the companies that I've checked out on the net, seem to have 10-speed transmissions. What could be the possible reason for that ? I've driven a 10 & 15 speed ( same shift pattern, except that the latter has a splitter ), as well as a 13 & 18 speed ( same shift pattern, except that the latter has a splitter in low range too ), and find that the 13/18 speed shift pattern is more user friendly & ergonomic. Could someone please throw some light on this for me ? Thanks.

[obiedon]

The reason I always hear, 10 speeds are cheaper to fix when a driver busts one up, and supposedly the 10 speed will take more driver abuse. Don't know if it's true just what I have heard.

[Uturn2001]

Less expensive, lighter weight, and easier to learn to drive.

[allan5oh]

There are some 10 speeds that are direct drive too, they're more efficient.

[Drew10]

Just FYI: Werner uses 9 speed Eatons, they used to mix them up with Super 10s....but as far as I know all their trucks are now only 9's. Simple to teach and use, and when it comes time to put the truck into fleet sales, its very easy to convert the 9 speed into a 13 speed, making easier to sell the truck.

[silvan]

Originally Posted by allan5oh

There are some 10 speeds that are direct drive too, they're more efficient.

Why is a 10-speed where the top gear is a direct gear more efficient than a 10-speed where the top gear is an overdrive? Overdrive transmissions have to have that little flipper thing in the shift works in order to maintain the normal shift pattern, and I don't think I've seen a 10-speed "up against the dash" configuration, but that little flipper doesn't look substantial enough to make a large difference in overdrive vs. non-overdrive 10-speeds. It makes me wonder if this isn't supposed to be comparing a normal straight 10 to a Super-10, with the funky back box that splits gears and changes ranges all in one.

Not that I know anything about transmissions or gear ratios and stuff, mind you. I just got curious how these things work, and started digging around until I found shop manuals online, to get some idea how the thing I use every day works inside. Pretty fascinating, but not fascinating enough for me to become a mechanic I'm afraid.

[Graymist]

Originally Posted by silvan

Why is a 10-speed where the top gear is a direct gear more efficient than a 10-speed where the top gear is an overdrive?

Silvan, you've lost me completely, buddy !! :? What is a "direct gear" and what is an "overdrive" ?

[jorlee]

Originally Posted by Graymist

Silvan, you've lost me completely, buddy !! :? What is a "direct gear" and what is an "overdrive" ?

Direct is when in top gear the input shaft is connected straight to the output shaft, also known as a 1:1 ratio. Overdrive is a gear that turns the output shaft faster than the input shaft. ie. .71:1 Overdrive allows the engine to turn slower, in getting the same output shaft speed.

Direct---> Input shaft][main shaft][output shaft--->
Overdrive-->Input shaft][gearset][countershaft][gearset][output shaft--->

[married to the road]

Are the extra gears and overdrive and all that any better? I have drove a 8,9, str 10 and super10 before. I like what I have right now, a str 10 w/ a 435 hp Cat. A driver said the tansmissions w/ more gears were needed with higher hp engines. I think he said it had like 600 hp and an 18 speed was the only one that could handle that big of an engine. Is that really the case, or was he just talking big?

[Graymist]

Originally Posted by jorlee

Direct is when in top gear the input shaft is connected straight to the output shaft, also known as a 1:1 ratio. Overdrive is a gear that turns the output shaft faster than the input shaft. ie. .71:1 Overdrive allows the engine to turn slower, in getting the same output shaft speed.

So then, is there any difference in the actual shifting action to be employed by a driver ?