The History of Synchronized Transmissions

[Damon]

So im not to mechanical savy but i know when i drive my 1994 Ford L9000 with 18 speed Eaton Fuller i have to double clutch in order to match the gears, and when i drive my 1994 Ford F-350 with 5 speed manual this is not the case, much easier to drive. I asked my mechanic what the difference was and he said that the F-350 has a synchronized transmissions and the L9000 has a non-synchronized transmissions. After some research i get the idea. I am now looking at buying a new truck and i was looking at a truck with a 2013 Eaton Fuller 18 speed manual and the owner said that it was a synchronized transmissions, bonus! So i assume that sometime between 1994 and 2013 there was a general transition between non synchronized to synchronized. My question is when exactly did this happen, not just for Eaton but for all brands. Any info on the topic would be much appreciated. P.S. This is my first post on the forum so be nice to the newby!

 

[RonG]

Take the time to double clutch and make it a habit,your equipment will thank you for it.It is much easier on the drive line and you will look better for it.Pretend that you are driving a non synchronized all the time.If you have an engine brake learn to use it to help draw the engine down while upshifting.That will help the shock on the drive line too.Generally speaking the smaller "passenger"type vehicles tend to have the synchronized standard transmissions to be more friendly to the drivers who do not have truck driving experience,it is good for the manufacturer and the owner.Ron G

 

[Damon]

Hi Ron. So you mean that even if the transmission is synchronized you should still double clutch because it's easier on the transmission? Is this so because when you engage the clutch without double clutching there is more torque getting transferred through everything as it is being brought up to speed? I suppose double clutching would make the synchronizers last longer too. When you talk about using the engine brake you mean when you are upshifting (building up speed?) you turn the engine brake on so that when you disengage the clutch, take it out of gear, engage the clutch, allow the engine brake to slow down the shaft, disengage the clutch, and then go to the next higher gear, the engine will slow down faster allowing you to engage the next gear sooner? I think i get the idea but this is something new to me. Very interesting, thanks for the info. Damon

 

[RonG]

You basically have the idea but when shifting the object is to match the engine speed with the road speed in the gear that you are shifting tnce you get the "habit"of shifting as you would a nonsyncro transmission it will be second nature and the timing will more or less fall into place for you no matter what you are driving,you won't even think about it.Wait until you get into a Mack with the quadruplex transmission and learn to split both sticks smoothly and make it sound so you cannot tell the difference between a shift of the compound transmission or a split of both sticks then you can appreciate the art of shifting.Ron G

 

[Steve Frazier]

This is news to me. It's been quite some time since I've been in a big truck and I've never driven one with a synchronized transmission. I'd love for someone to comment on this further!

 

[Goodysnap]

I think the OP was misinformed about the 18speed trans being synchronized. Eaton's website is great to learn anything and everything about proper shifting and which trans you have.

Double clutch or not it's all about timing to prevent wear and failed components.

The market is becoming flooded with fully automated mechanical transmissions to rid driver error. Even CDL licenses now have restrictions for automated only.

 

[Oxbow]

Damon, your F 350 should not be shifted without the clutch because the synchronization cannot work with the clutch engaged. All one is doing by shifting it without the clutch is wearing the synchros.

I know that Eaton now has some auto-shift 18s out, but I know nothing about them.

On our 18 speeds that are older, I double clutch sometimes, depending on the circumstances, but float the gears in the majority of the time. This is on an older mechanical Cat that the throttle can be adjusted slightly with ease as opposed to many of the newer engines that have much snappier throttle response, in which case shifting without the clutch becomes primarily timing, and misses are harder on the drivetrain.

I second Ron G regarding double clutching. It is the best way to get familiar with the trucks attributes without casing damage. Eventually you will find yourself just barely touching the clutch when entering a new gear, but until then it is best to double clutch for the sake of the equipment.

In case you do not understand the purpose of double clutching, it allows one to take the transmission out of the gear that it was in and into neutral on the first clutch, then you match the rpm of the next gear that you are going to with the clutch engaged (in neutral), then you put the transmission into the next gear with the clutch disengaged to remove shock and allow for minor adjustments of the trans/engine rpm match the next gear requirements. The reason that you need to engage the clutch in neutral is that you cannot slow down the trans (or speed up if downshifting) with the clutch disengaged.

Also, do NOT depress the clutch clear to the floor when shifting as this will activate the clutch brake and wear it prematurely. The clutch brake should, with few exceptions, be used only when stopped and wanting to stop the spinning of the clutch in order to place it in gear. In addition, never use the clutch brake to hold the truck on an incline while waiting for a light to turn green as it is not designed for this.

I hope that this makes sense, but feel free to ask for clarification. Others may be able to describe the functions better than I have.

 

[Goodysnap]

I know that Eaton now has some auto-shift 18s out, but I know nothing about them.



QUOTE]

The internals are virtually identical to a manual shift as far as I know, no matter the speeds.

Differences include, added trans speed sensors, clutch, clutch actuator, and X-Y electronic shifter and TECU, depending on the model. Range and splitter shifts have switched from air to electric control.

 

[pushbroom]

Any large eaton that is current is non syncro. That is including eaton auto trans. The only synco shift is the high/low range

 

[Damon]

Oxbow, first off, i never said that I don't use the clutch on my F-350. What i meant was that i dont have to double cluch, i only have to "single clutch" if you will. Secondly, clutch brake? Iv never heard of such a thing. I push the clutch all the way to the floor and always have and there isn't anything wrong with the it. Whats the point of a clutch break?

 

[RonG]

A clutch brake is used to stop the transmission shaft from turning so that you can engage (select) any speed from neutral at idle because when you disengage the clutch it sometimes takes some time for the transmission shafts to stop rotating to allow a smooth gear selection.Sometimes a clutch that is over adjusted can contribute to that.Ron G

 

[Steve Frazier]

Damon, Oxbow is only offering you advice to improve the longevity of your clutch and transmissions in both trucks, and it would appear that's why you came to our forum. The clutch brake is only on the L9000, not the F-350. It will wear out prematurely if you hold the clutch to the floor for extended periods of time. When you are idling the L9000 in neutral, there's a whole lot of metal spinning in the transmission which carries quite a bit of momentum. When you push the clutch in to the floor, the clutch brake helps to stop the shafts from spinning so you can put the truck in gear without grinding or gear clash. If it wears out you'll have to wait for everything to stop spinning on its own which can take some time.

 

[Oxbow]

Thanks Steve!

 

[Damon]

Thanks everyone for the info. I have a lot to learn about trucks. So just to be clear, when im juat doing a normal shift like from 5th to 6th or whatever im only supposed to push the clutch in maybe half way?

 

[RonG]

As was said before Damon,timing is everything.Generally at the road speed you would be going for that shift you might only have time to depress the clutch halfway before the engine RPM dropped off enough to make smooth upshift,again,it is timing and you will find that out as you "practice".Theoretically you could make that shift not using the clutch at all but you will find that the shift lever has a tendency to "hang" in the gear that you are shifting out of unless you catch it just about right and the clutch being disengaged takes the curse off and is just good practice.You will see all this if you persue it and you will look back on this and think that all our comments make sense now.Ron G

 

[Oxbow]

Thanks everyone for the info. I have a lot to learn about trucks. So just to be clear, when im juat doing a normal shift like from 5th to 6th or whatever im only supposed to push the clutch in maybe half way?

It depends on how your clutch is adjusted, and may be a little more than half, you just do not want to feel additional pressure towards the bottom unless you are stopped.

As RonG said, sometimes just touching the clutch pedal a bit is all it takes to let the trans shift into neutral, and then it will just about fall into the next gear. You just need a bit of practice, and just don't try to force things.

 

[Truck Shop]

I know this thread is slightly old but ------------ The Fuller and Eaton RTLO's were designed to shift without a clutch, one of my forte's is 9,10,13,15 and 18 speed
transmissions. The sliding clutch's and engagement teeth in the corresponding gears on the main shaft are cut at an angle for smooth engagement without the clutch.

 

[Goodysnap]

While I agree with you and also do not use the clutch except to start and stop. Eatons recommended shifting method is to double clutch all shifts on their HD transmissions.

 

[Truck Shop]

While I agree with you and also do not use the clutch except to start and stop. Eatons recommended shifting method is to double clutch all shifts on their HD transmissions.

A lot of things change over the years. Around 79 or 80 I went to a Fuller transmission clinic, the rep running the show stated at that time It was ok to float the gears when shifting.
I think the reason for Eaton to state that using a clutch is required is because DOT standards have changed. You will fail a driving test if you don't use the clutch, Eaton does not
want the liability or be in contest with DOT saying it's ok to not use a clutch. Plus Eaton wants you to wear out those clutch's so they can sell more.

 

[BoxCarKidd]

Steve: Volvo FE7's were at least class 7 and had fully synchronized transmissions. On others when the pedal is pushed to the floor with the truck moving the clutch brake is trying to stop the truck and can break the center out of it. Then if one continues to milk it the input shaft will be ruined by the brake spinning on the shaft.