Hello all. Just a question from a novice here. Last week I was driving my father inlaws trucks around the farm helping him pick up hay bales, one truck was an International, the other was a Mack. Both of them had Eaton 10 spd transmissions. I had no problem at all upshifting either one of them, but when I went to downshift, I could not get them to engage without clashing, even when double clutching. I figured I must just not have the feel of the trucks, but when I did some research online I found out that some transmission have a clutch brake when you push the clutch to the floor. I am now wondering if this was my problem. When I tried to double-clutch downshift, I pushed the pedal to the floor before trying to engage the gears. The only other non-syncronized transmision I have ever driven was a WWII surplus aircraft tow vehicle with a 3 speed tranny. I could downshift that one quite nicely by double clutching. I am just wondering if either I should not have pushed the pedal to the floor, or do I just not have the feel for the tranny yet? Thanks in advance!

 

Yes they have a clutch brake.

In a big truck the only time you ever push the clutch pedal all the way to the floor is when you are at a complete stop. Other than that you only need to push the clutch in about 1/4 of an inch or so. Just kind of tap it.

 

Yep, your right on both :wink:

 

Why would you want to use the clutch brake for downshifting? (or upshifting, for that matter?)

To downshift you have to raise the engine RPM's to where they would be if the truck was already in the gear you're trying to shift into, then put the stick gently into gear.

To downshift:

Depress clutch, take stick out of gear.

Let up on clutch and raise engine RPM to the level it would be at in the gear you want to shift into.

Depress clutch and shift into gear.

This has to be done as one smooth flowing motion, if you depress the clutch and wait before shifting into the lower gear, the transmission gears will slow down and you won't get it in gear.

You can also "float" it into gear:

Take stick out of gear.

Raise engine RPM to the level it would be at if the truck was already in the gear you want to shift into.

Gently put the stick into the desired gear.

If you feel grinding, raise or lower RPM's slightly while keeping gentle pressure on the stick.

You'll feel the grinding either getting worse, or getting less.

Use the throttle to manipulate the engine RPM's so the grinding just about stops, then put the stick into gear.

Never "jam" it into gear.

 

To my understanding....all non-synchronized transmissions have a clutch brake. Other wise you would never be able to engage gears from neutral to a forward gear or reverse when stopped.

Upshifting without the clutch or downshifting without it is normal....you just have to learn the "sweet spots" for that particular truck and have the rpm's right when you shift.

 

The answer is: Your tranny probably doesn't have a clutch brake anymore, now that you've destroyed it by pressing the pedal all the way to the floor at any kind of road speed.

It's very easy to wreck a clutch brake. If you've wrecked it, you won't be able to get it in gear from a stop without the old

PRRRRRRRRRRRRRRRRRRRRRRrrrrrrrrrBLUNK! routine.

 

You really managed to capture that sound I know all too well from my early driving days. :lol: I actually became rather adept at replacing them before my boss found out. I think my record was 5 in one month.

 

all class 8 trucks have a clutch break,

the best thing to do to learn to clutch correctly is place your toes only on the clutch and when u need to clutch move your ancle and not your leg. once u get the hang of it, you dont need to think about it or expell extra energy.

here is the correct double shifting technique,

allow engine to slow down to approx 1000 rpm,
clutch in, shift to Neutral
quick shot of fuel (bring rpm up 500.... ) ..............Don't rush the rpm will stick there for 1/2 second
clutch in, and switch to next lower gear.

the only thing i can tell you as a newb is before u start to downshift, look at your RPM gauge, know what your rpm is, and add 500 so u know during your shift, if by chance u cant pop it into gear and the rpm drops or goes thru the roof , u know where the rpm has to be be to get it into the correct gear,

still if u miss a shift, start the entire process over.