Shifting A 13 Speed and Peterbilt 385 Brake Pedal Adjustment

[StraightTimeStirrups]

What are the best techniques to shifting one of these? Upshifting seems to be no big deal as I got that figured out very quickly but downshifting seems to be my downfall! I know about matching the RPM's etc but I am more interested in figuring out how/when to shift from Hi back to Lo. I know it upshifting you just release the throttle and it shifts from Lo to Hi but going the other way what/how do you do it?

The brake pedal on my truck is near the floor and doesnt seem to have much modulation to it. You can get full pressures on the brakes but I was expecting the pedal would be higher up and allow you to modulate the brake pressures through more travel of the pedal. Any help?

Thanks

 

[Racer X 69]

Downshifting is just the reverse of up shifting, only with the blipping of the throttle to keep things matched for speed as you mentioned. The tachometer should be marked for the engine operating range, upshift when you reach the upper limit and downshift when you are at or just under the the lower limit. On downshifts you need to blip the throttle just a bit to keep the revs matched with the gear train speed. Everyone has a little difficulty with it at first but you can only get better with practice. Just don't force the shifter or grind the gears excessively.

As for the brake pedal, they usually do not have any adjustment, what you get is what you get. The pedal is only opening (on depression) an air valve or closing (on release) the same valve. I would think as long as the operation of the brakes is as it should be and the application gauge shows pressure increase in proportion the the amount of pedal pressure you are applying you should be good to go.

Hope this helps.

 

[StraightTimeStirrups]

The only way I can see of making a Pedal height/angle adjustment is to put a larger diameter roller in the pedal assembly.

As for the downshifting when going from say 6th Hi to Lo do you just move the switch on the lever from Hi to Lo and then blip and release the throttle to make the shift? That sequencing is what has me baffled.

Thanks

 

[StraightTimeStirrups]

For some clarification:

Lets say I want to shift from 6th Hi to 6th Lo what sequence of events do I need to do to make this happen correctly?

Now I want to go from 6th Lo to 5th Hi what sequence do I need to follow to make that work?

Joe

 

[Racer X 69]

For some clarification:

Lets say I want to shift from 6th Hi to 6th Lo what sequence of events do I need to do to make this happen correctly?
Joe

Going from 6 hi to 6 lo flip the hi/lo lever, lift then blip the throttle and it should drop down a half a gear.

Now I want to go from 6th Lo to 5th Hi what sequence do I need to follow to make that work?

Joe

Going from 6 lo to 5 hi you can pre select the hi then move shifter and as it is passing through neutral gate lift throttle, then blip and move to 5. This should be all in one fluid movement and for some takes practice.

Also remember to turn off the engine (or jake) brake or as it attempts to operate it will interfere with the shifting. I just barely touch the clutch pedal enough with my left foot to disengage the engine brake (you might be able to hear the microswitch click) but not enough to disengage the clutch even the slightest so as not to cause premature wear on the clutch disk.

 

[Racer X 69]

The only way I can see of making a Pedal height/angle adjustment is to put a larger diameter roller in the pedal assembly.

Thanks

Like I said, what you get is all you get as long as the brake function is normal. I worked on these things for 30 years and have never seen any way to adjust the brake pedal. Even the medium duty GMC 7000 series trucks that had the pedal suspended like the automotive hydraulic types did not have any real adjustment except the clevis that attached the pushrod to the air valve and pedal arm. Replacing the roller with one of different diameter will change the leverage the pedal has on the plunger in the air valve and thereby will change the way the brakes respond to application of braking. Changing anything in a braking system away from the original design is asking for problems and foolish as well. Manufacturers spend huge amounts of time and money making trucks ergonomic and safe. For drivers who are used to hydraulic brakes in cars and pickups the layout and function of air brake systems can seem a bit foreign.

 

[2xR]

I drive a 13... If I'm heavy, I'll use all the gears going up... But, coming down, I get lazy and never flip the hi-lo but once, usually while in top gear. I just let her wind down a little further, then, shift down like it was a 9 or 10 speed. If I'm light, I just use the stick, skipping all of the hi-lo shifts while accelerating. Perfect ratios to git 'r pumped up, real quick.

Leaving the jake on is good if you're trying to get it rolling on a steep grade and need to shift real fast before your momentum is lost. That jake will make the RPMs fall a lot faster and you can catch the next gear quicker, but, it is a little tricky, and, requires some practice. No time for hesitation when doing this.

As far as the brake pedal is concerned, it is suppose to be low. It should be the same height, or lower, than the foot throttle, so, you only have to move your foot over, not up and over. The up part takes a millisecond longer, and, when you're trying to put the whoa-hah on a 40 ton machine, every millisecond counts.

You're gonna' learn to love that 13 speed. If I ever have to drive a 9 or 10 again, you'll hear me cryin'.

 

[StraightTimeStirrups]

I agree that the pedal should be near level with the Throttle but it is at least 2-3 inches lower. I will have to take a photo tomorrow and try to post it here to show you.

Joe

 

[Sinister]

18 speed is the best transmission there is, and to be able to split the low gears, and a smooth takeoff (which admittedly requires a BUNCH of shifting)...I'm surprised more tanker companies don't use them to help ease the slosh...

 

[2xR]

18 speed is the best transmission there is, and to be able to split the low gears, and a smooth takeoff (which admittedly requires a BUNCH of shifting)...I'm surprised more tanker companies don't use them to help ease the slosh...

I've never touch an 18 speed... Howzit work? Is it just like a 9 speed, except you split every gear?

My product never sloshes during acceleration. I keep it pinned to the rear bulkhead.

The slosh gets me after I've been cruisin' fast and low for a few hours, then something happens that causes me to lift, just slightly, then ease back into the throttle. Suddenly, for no apparent reason, it feels as though I was just rear-ended by a Buick. No shit, it'll make me check the mirrors to see who just died.

 

[Sinister]

Picture a 13 speed, except before you get to the high side, all those lower gears can be split.

It makes more A LOT more shitfting, but for heavy loads that need smooth acceleration, I think it'd be a pretty good deal. Also, when you need lots of torque at low speed in mud and stuff it helps to keep momentum up. Coming to a stop in soft crap off pavement = getting pulled, and buying rounds later on. It sucks.

As far as downshifitng a 13 all the way to the low side...

..that just happens on the sticker on the dash. Or the visor. Or wherever it is. I don't know anyone who actually does that with normal loads in order to slow down. Drop about 3 - 4 gears, jake, foot brake once or twice, and most of us who are honest about it won't fault you.

 

[StraightTimeStirrups]

• As downshifitng a 13 all the way to the low side.....that just happens on the sticker on the dash. Or the visor. Or wherever it is. I don't know anyone who actually does that with normal loads in order to slow down. Drop about 3 - 4 gears, jake, foot brake once or twice, and most of us who are honest about it won't fault you.

So what do you do? Just shift from 8th Hi to 8th Lo and then just work your way down to 7th Lo, 6th Lo and 5th Lo and accelerate from there. What gears to you use to say roll around a right hand intersection turn? Is 5th Lo sufficient to keep from stalling around a slow corner such as that or do you downshift into 4th, 3rd or 2nd gear?

Thanks,

 

[Sinister]

Actually, right now, I just spend a lot of time bitching at a 9 speed, and wishing I hd my 18 back. I haven't seen a 13 speed since 2001.

I know...I'm a huge help aint I....

 

[terrylamar]

Depending on how sharp the corner is, if it is 90 degrees or maybe sharper and depending on what my load is I down shift to at least 5th, which is a little hot, preferably to 4th and maybe third if it is a heavy load and 90 degrees. If I need to ease around because of traffic all the way to second.

On light loads or empty I always drove my 13 speed as a nine speed then shifting into 8 high, which, I guess, would be a 10 speed, but since I don't use low it would be a 9 speed. Maybe that is why I don't drive 18 speeds, I get confused enough as it is.

 

[freedhardwoods]

I rarely split any gears on my 13 speed up or downshifting except 12/13 for low rpm cruising. I will If I am starting out going up a fair sized hill or if I am at speed and splitting will carry me over a smaller hill. If I am going to have to move the stick when pulling a big hill, I usually don't split it. The rpm's stay in the pulling range so I don't see any reason to do it.

 

[Rigjockey]

I drive a 13... If I'm heavy, I'll use all the gears going up... But, coming down, I get lazy and never flip the hi-lo but once, usually while in top gear. I just let her wind down a little further, then, shift down like it was a 9 or 10 speed. If I'm light, I just use the stick, skipping all of the hi-lo shifts while accelerating. Perfect ratios to git 'r pumped up, real quick.

Leaving the jake on is good if you're trying to get it rolling on a steep grade and need to shift real fast before your momentum is lost. That jake will make the RPMs fall a lot faster and you can catch the next gear quicker, but, it is a little tricky, and, requires some practice. No time for hesitation when doing this.

As far as the brake pedal is concerned, it is suppose to be low. It should be the same height, or lower, than the foot throttle, so, you only have to move your foot over, not up and over. The up part takes a millisecond longer, and, when you're trying to put the whoa-hah on a 40 ton machine, every millisecond counts.

You're gonna' learn to love that 13 speed. If I ever have to drive a 9 or 10 again, you'll hear me cryin'.

thank you for for explaining that i have been driving 13 s and 18s i just did what felt right no one explained it to me and i was emberassed to ask turns out i do it the way you do. it s good to hear it from the old school drivers like i said i was too afraid to ask thanks

 

[misterbreeze]

Flip the switch, rev the engine and it should down shift as long as you are at the correct road speed. You will feel it catch and the R's should stay at about 1500 til you slow down more and reach the next shift point. Same concept as a ten but with different shift points. Usually if it isnt supposed to shift, the switch wont move. Dont force it. The splitter only works in the high range gears as I recall.