Prime Inc Is Disabling Manual Mode On Their Trucks With The D12 Manual Automatic Transmission !

I trained at Prime Inc on a 10-speed manual transmission and drove about 6 months solo on one until they put me in a new truck with the D12 transmission. I hated it at first but I ended up driving 519 K miles in it and I got pretty used to it. I got to the point where I could take steep downgrades fully loaded without touching the service brakes by downshifting to lower gears in manual mode and engaging the Jake brake, including in the winter. Well now, they’ve put me in a new used truck and the first thing I noticed was the manual mode didn’t work. I took it to the shop to get repaired and was told that Prime is purposely disabling the manual mode ! This makes no sense to me and in fact I think it’s dangerous. The D12 is called a Manual Automatic Transmission. The manual mode was put there by the manufacturer for a reason. By not having it available, it discourages the use of the Jake Brake because whenever you do use it, the truck wants to immediately downshift by 2 gears and there you are over RPMing. In manual mode, you simply put it in the gear you want and you work the Jakes all the way down the mountain and you maintain a steady speed and RPM. I can’t imagine what it’s going to be like out in Wyoming going over Elk Mountain next winter. Has anyone else heard of a company tinkering with the basic controls of the truck like Prime Inc is doing ?

Is it possible that your other truck was a former "lease truck?"

It is my understanding that all Prime company trucks have the manual option disengaged on their automated transmissions. They have been doing that for a long time. I don't know the reason, but maybe some of our Prime drivers will chime in on this with an explanation. You can figure out how to drive that thing down a mountain. Everyone else does it.

GRS is upset:

The manual mode "switch" was put there by the manufacturer for a reason. By not having it available, it discourages the use of the Jake Brake because whenever you do use it, the truck wants to immediately downshift by 2 gears and there you are over RPMing. In manual mode, you simply put it in the gear you want and you work the Jakes all the way down the mountain and you maintain a steady speed and RPM. I can’t imagine what it’s going to be like out in Wyoming going over Elk Mountain next winter.

The manual mode switch was put there, and the buyer (Prime, Inc.) ordered it and set it that way. That's the real reason. Why? Manual shift is better on MPG and maintenance. You do like the MPG bonus, don't you?

The engine retarders and the transmission work together and are linked in the computer system. "Over RPMing"? Maybe you should have set the Jakes sooner. The answer to the over-revving is to use the foot brakes to get to the slower speed. Then just as you like to, let the engine do the slowing.

"over Elk Mountain next winter" Do you use Jake brakes going down a grade covered in ice and snow? We'll see your action on Bonehead!

Don't be such a stranger! (3 posts in 5 years)

GRS is upset:

The manual mode "switch" was put there by the manufacturer for a reason. By not having it available, it discourages the use of the Jake Brake because whenever you do use it, the truck wants to immediately downshift by 2 gears and there you are over RPMing. In manual mode, you simply put it in the gear you want and you work the Jakes all the way down the mountain and you maintain a steady speed and RPM. I can’t imagine what it’s going to be like out in Wyoming going over Elk Mountain next winter.

The manual mode switch was put there, and the buyer (Prime, Inc.) ordered it and set it that way. That's the real reason. Why? Manual shift is better on MPG and maintenance. You do like the MPG bonus, don't you?

The engine retarders and the transmission work together and are linked in the computer system. "Over RPMing"? Maybe you should have set the Jakes sooner. The answer to the over-revving is to use the foot brakes to get to the slower speed. Then just as you like to, let the engine do the slowing.

"over Elk Mountain next winter" Do you use Jake brakes going down a grade covered in ice and snow? We'll see your action on Bonehead!

Don't be such a stranger! (3 posts in 5 years)

Can't say I'd be real happy about not having it either. While it hasn't 'over rpmd' yet, there's been a couple times where even turning the Jakes on at the top of the hill it drops gears and takes it right up to the redline, close enough to make me nervous. Doesn't do it all the time so it's not really something you can anticipate.

As for the winter thing, I wouldn't use the Jakes but manual mode is nice to get the damn thing to stay in gear. Assuming it's the same setup as Wilson's it'll go into E, which is freightliners fancy term for 'rocketing down the hill in neutral'. Not ideal in good conditions, let alone winter. You're left with the option of using the jakes or riding the brake the entire time to keep it in a gear.

GRS is upset:

The manual mode "switch" was put there by the manufacturer for a reason. By not having it available, it discourages the use of the Jake Brake because whenever you do use it, the truck wants to immediately downshift by 2 gears and there you are over RPMing. In manual mode, you simply put it in the gear you want and you work the Jakes all the way down the mountain and you maintain a steady speed and RPM. I can’t imagine what it’s going to be like out in Wyoming going over Elk Mountain next winter.

The manual mode switch was put there, and the buyer (Prime, Inc.) ordered it and set it that way. That's the real reason. Why? Manual shift is better on MPG and maintenance. You do like the MPG bonus, don't you?

The engine retarders and the transmission work together and are linked in the computer system. "Over RPMing"? Maybe you should have set the Jakes sooner. The answer to the over-revving is to use the foot brakes to get to the slower speed. Then just as you like to, let the engine do the slowing.

"over Elk Mountain next winter" Do you use Jake brakes going down a grade covered in ice and snow? We'll see your action on Bonehead!

Don't be such a stranger! (3 posts in 5 years)

I use my engine brakes all the time during the winter. Granted, it won’t be on the highest setting and I’ll make sure it’s in the proper gear but it still helps control the speed and as long as you’re paying attention, won’t get you into trouble. I agree with the complaint of disabling the manual mode because using it properly helps maintain downhill speeds and in conjunction with the engine brake, will allow for a controlled descent at reasonable rpm with very little to no use of the service brakes. White bird summit in Idaho is a much bigger challenge than Elk and I’ve taken it in a manual at 147,000# barely using the brakes and at 79,800 in the Volvo I’m now driving without using the service brakes. It’s all about learning to use the equipment but if a company takes away an important aspect, it puts drivers at a disadvantage.

Like Errol said, you have to reduce speed and then set the engine break. I've found that with a heavy load and a steep grade, the Jake's aren't able to maintain speed over 60mph (with descent control engaged too). There is too much momentum. But, when you use the service break and go below 60, the engine automatically shifts into a lower gear and the RPMs shoot up to the 2300-2400 range.

For me the "sweet spot" is between 50 and 53mph, engine break level 3, and descent control engaged. This works to keep you at a steady speed without hitting the service break at all on most grades 6% or less. Moreover, the RPMs will stay under 2,000.

I'm sure most drivers know that it is important to use the service break initially in order to reduce momentum before applying the Jakes on steep grades. After that, with the cruise set (descent control) you should be able to cruise down a hill at a consistent speed without touching anything.

I never had the manual selector in my truck at Prime, and I managed to safely get around wherever I needed through speed control, descent control, and just heads up driving.

I wonder if the manual selector is available to lease ops? If not, my guess is Prime disabled it for the same reason they don't have Johnson bars in the trucks: L/Os will use these tools 24/7 instead of their service brakes, reducing their own maintenance costs while causing undue wear and tear to the vehicles. Just a guess.

Reply to Turtle: So my understanding of descent control from reading the trucks owners manual and watching some videos from Freightliner is that you slow down, engage the engine brake and set the cruise control. How do you use cruise on snow and ice ?

This is from the CMV CDL manual:

Caution. When your drive wheels have poor traction, the retarder may cause them to skid. Therefore, you should turn the retarder off whenever the road is wet, icy, or snow covered

2.3.4- Retarders

Trying to control your downhill speed using the drive axles only, leaves a traction imbalance between the steers, drives and tandems since the steers & tandems are more or less coasting while the drives try to slow things down. This is jackknife territory.

You guys do know that you can turn off E-Coast on Freightliners??? Settings menu buried in there. Have to manually turn it off every time you start the truck other wise it defaults on.