Shifting A Mack Ch-600

[Student1]

I am a student in training to get my CDL-A. Right now I,m having a little trouble with down-shifting smoothly. My instructor says to use the sound of the engine and so far I'm doing a fair job but not good enough job to pass the final skills test. I am hoping someone out there might have some idea of what the shift operating RPM or MPH range is for the gears on a 9-speed Mack CH-600. I'm not sure what the year is but I think it is a 1995 model. Thanks

Edited January 15, 2011 by Student1

[Rob]

I am a student in training to get my CDL-A. Right now I,m having a little trouble with down-shifting smoothly. My instructor says to use the sound of the engine and so far I'm doing a fair job but not good enough job to pass the final skills test. I am hoping someone out there might have some idea of what the shift operating RPM or MPH range is for a Mack CH-600. It is a 9-speed. I'm not sure what the year is but I think it is a 1995 model. Thanks

Every truck is different. If you use the double clutch method, (which always works) you will become accustomed to the sounds of the truck on short order as familiarity is gained. Soon you will not be using the clutch except to start, stop, and the occasional downshift. If is all practice to become perfect. Watch that tach needle as you pull it into, and out of gear. Pretty soon you will know that rpm by sound and feel.

Rob

[hatcity]

RPM range is in the area of 1900-2100 on the hi side. 1200-1300 low side.

Like Rob said, practice, practice. Even now I find myself double clutching alot. Old habit. That is if i use the clutch

[Bobby Covert]

Since you are trying to get your CDL and everything you do is being supervised try and shift around 1500+-50 rpm 1450-1550 rpm. You will eventually be able to shift without touching the clutch( except when starting out).Get the double clutching down, get the CDL and then move ahead. Remember if you try and shift with the rpm too high it is not going to come out of gear for you.It goes into gear best as the rpm is falling so you will have to run it up some.If you can't get it into gear run the rpm up again and try again. Make a note of when it went in and notice the enjine sound too. Hope this helps!

[Lmackattack]

as you instructor noted you should listen to the engine. Under stand that when the truck is in motion the trans and rear ends are always spinning in sync with each other. So apon a shift change the revs will need to match each other when you shift to a diffrent gear. If you are up shifting the engine will need to drop a few hundreed RPM to catch the trans in the next higher gear. Down shifting your doing the same thing but have to rase engine RPMs. When learning its best to have a slight load on the truck/trailer so that it maintains its speed thru the gear change. This way you dont louse road speed and further complacate the shifting. also learn on flat roadway as hills will allow the truck to change speeds also. I learned to shift with no clutch and find using the clutch for shifting is harder.

Upshifting

RPMs should be no more than 1500RPM so that when you find the next lower gear, your RPMS wont exceed Max engine RPM. Lower the RPM the smoother the shift. try down shiftin at 1200RPM and see how that goes. the process......lift up on the throttel to put slack in the trans, lightly pull on the stick and it will come out of gear as soon as you have slack place stick to next lower gear, as you are moving the stick to the next lower gear you will need to raise about 300RPM to catch the lower gear. For starts, slowly raise the RPM to get a feel of the grind just before it falls into the lower gear. you may need to "float" the RPM untill you find the correct RPM for the gear. as you get better you will be able to stab the throttel quickly to get the fast raise of the RPMs and find the gear. with everthing start slow and understand what all is going on to make the shift. When you get a feel for things it starts to become smoothe

For smooth up shifting and trying to impress the instructor I suggest you rev up to around 1600RPM and as you are about to lift off the throttle,slightly pull on the stick so it comes out of gear smoothly. move stick to the next higher gear, press on that gear lightly and feel the "grind". as you reduce pedal on the throttel the RPMs will drop, as they drop the stick will fall softly into the next gear. When ever you have light presser on the stick waiting to find the next gear you will feel a slight grind in the wrist, but thats ok, as long as you cant hear it.Go slow and get a feel for the gears and how the revs make the stick feel right before it goes in. after you understand what it feels like when the revs are to high or to low you can focus on timing the shifts so that there is no grind at all. you simply will be timing the gear changes with the sound of the engine and will start to get good at it. when learning I think that slight soft grinds (only felt in the wrist) is perfectly fine because you get a feel for what the trans is doing and what too hi or too low of a RPM feels like. however you never want to pull hard on the stick because when it does get close to the right RPM it will jam it into gear and can damage things. Mack transmissions are diffrent than others. I drive both and have a hard time jumping back and forth. been doing this for a while and I still make mistakes so dont feel bad. just that you are asking for helps shows you want to learn correctly and that says alot about you. Hope this helps and good luck!

Trent

[bgloss]

I can drive an 8speed eaton fuller transmission without a clutch, but not a Mack. I have only driven Macks with 13 speeds in then and I always pretty much double clutch