Cat 3406 B RPMS / shifting

Below 1200 mine sounds like it is starting to lug the motor. On normal driving I run 65 at around 1500 rpms. I shift up at 1700 and down at 1400. Jakes work better that way. Now on hard pulls I will downshift at 1700. It seems to pull the best without losing road speed in the 1900 rpm range so shifting at 1700 when pulling a grade will keep it in the 1900 range. This also serves another purpose, it moves that fan faster and keeps the coolant and egt temps cooler.

 

As for downshifting with the splitter, you do not want to ever let off then snap the throttle. You will feel the truck doing bad things to your rears and drivelines... This is the reason most are driving 10 speeds. The 13 and 18 is a nicer transmission for the driver but it is also easier to screw up the drivetrain.

Most of the time you do not even need to let off the throttle when splitting a gear on the downshift. If you have enough room in the RPM range and you are not lugging the motor and you have to to is put the splitter in the low range and slowly increase the rpms and at about 300 rpm increase it will shift into the lower gear.

 

Had a boss years ago that said don't idle your truck when cold. Bring up rpm till it's warm. Fuel washes cylinders,ect.

 

Describe the issues. Is it changing gears with a hard "clunk"?

 

I did that once by accident and it scared the bejesus outta me! First though, "that's broke", I was afraid to touch the throttle for a sec dreading the idea that I just scrapped the tranny.

 

Behind a B its apt to be an RTO instead of RTLO which means aux gear is splined to the main shaft. Splits completely different than the RTLO. You can't preselect the RTO. If the last 3 digits are 613 thats what you have

 

I don't even take my e models below 1300. Lotta folks commenting have never ran a 3406.

 

+1 to replies from @wore out, @cnsper and @ramblingman. I have a 15 over so my steps are bigger than a 13, but it doesn't really like me to upshift below 1700 with a jag on

 

Check splitter for air leaks. Let truck build air. Then shut off truck. Place shifter in high range, you should hear a click. Then move splitter forward. Should hear click. Should work .