My recent cross country trip with the new Breakaway 5.9, 190hp, has proved to me that I don't know how to drive a diesel pusher, at least not that one. Even with my foot to the floor, shaking and all, I couldn't get that thing much beyond 60mph. It did climb all the hills, but the rpm's would drop to 2200 with the pedal to the metal. Should I have dropped into 3rd and run at higher rpm? Or is 60mph about all that the 5.9 can produce? Due to the shaking of the coach, I couldn't get much of a running start on the hills. Any driving advice would be welcome.
Jim

Jim
On my breakaway with 160 HP 66 mph on a level
road is about all it has. The fastest speed I saw
Was 74 going downhill
That was on the GPS. (Speedometer said 82) cruise control
Not needed just put a Brick on the pedal

You shouldn't have expected much more in the speed department.

But shaking?
badly out of balance tires?
flat spots from sitting a long time?
bad shocks?
One of my steering tires was out of round and shook the front of the coach. put it in the rear, where the married-up dual diminished the tramping.

Will attack the shakin' tomorrow. In the meantime, is it best to downshift manually into 3rd, or just keep the accelerator all the way to the floor and let it downshift automatically? Or will it even do that? My experience is with the GM 3speed and when you floor that on a hill, it will down shift by itself. With the Gear Vendors, I do the downshifting from third overdrive to third, to second overdrive to second and so forth. My thinking is with the Breakaway and the limits of the 5.9/190hp, you have to some of the shifting yourself or is that not so? What is the peak torque RPM? Do you want to keep the RPM at a certain point for torque and shift to do so? I'm talking about going up hills of course.

Yes, downshift manually.

I recently purchased six new tires to replace the ones that came on the coach when I purchased it. The rear tires were seven years old and the front were eleven years old. I was pleasantly surprised to find out that all of the vibrations I had been experiencing had gone away with the old tires. Before the new tires I hated to travel between 35 and 40 mph because the vibration just about shook my teeth out, seriously. After new tires, no vibration at all.

If your RPM only goes down to 2200 up a hill in 4th, down shifting to 3rd is not going to help, you will be way over the upper RPM of the engine and it will slow until you hit 2800 RPM or so.

Do this to get better feeling what gear you should be in.

Find an open road and start out in 1st, go all the way to the top of the governor, should be about 2800 +/- RPM. Note the speed. Repeat in 2nd, 3rd and if you can 4th. That will tell you where you can shift down to while going up a hill or keeping the engine in a more suitable RPM range so that you don't "lug it" down.

You can also find what "top of the governor" RPM is by standing on the peddle stopped in neutral. The engine upper RPM is limited by the governor and will not exceed this RPM unless going down a hill forced to go higher in a lower gear.

Also going down hill you should not go over 3000 RPM as both the engine and trans have upper RPM limits.

Torque converter loss is another factor in this equation. With no lock up torque converter, engine RPM will always be higher than the RPM delivered to the transmission gears.

From a calculation based on rear end ratio and trans ratios the following speeds are what is calculated without factoring in the torque converter loss and 2800 RPM max. 8R19.5 tires/628 Revs/mile 3.73:1 rear end ratio,

1st, 20.8 MPH
2nd, 31.9
3rd, 51.0
4th, 71.7

If you were to use 225R70 19.5 tires on the back the speeds would be 2.5% lower due to the smaller rolling radius. (644 Revs/mile)

Throwing in converter loss speeds will be lower, you will find out what that is if you do the test I mentioned previously.

quote:

Find an open road and start out in 1st, go all the way to the top of the governor, should be about 2800 +/- RPM. Note the speed. Repeat in 2nd, 3rd and if you can 4th. That will tell you where you can shift down to while going up a hill or keeping the engine in a more suitable RPM range so that you don't "lug it" down.

Should I do this manually or in the automatic mode? My guess is manually.
Also, what about torque? Would I have more torque in 3rd@2800RPM or 4th@2200RPM? What I should have mentioned is that when I started up these hills, and they weren't real steep hills, I was turning about 2300/2400RPMs. It dropped to 2200RPMs but that's all until I crested the hill. Since the speedometer was not working, I don't know what my speed was. PO said speedometer stopped working on way to Denver. I guess the other question is 'at what RPM should you drop to a lower gear?

If you have a GPS unit use that for speed measurement.

Manually shift, you need to do that so that it doesn't upshift and will stay in that gear selected.

As far at what speed or RPM to shift lower, can't tell you until yo do the test or someone else with a 542 trans and knows what the maximum speed is in each gear.

No magic, just that you need to know what the maximum speed is in each gear so that if you are slowing you should only shift down when the engine can support that speed in a lower gear.

On a LONG hill climb, as I approach the lower speeds, I manually shift down as soon as I know shifting down will not exceed 2400 RPM. I do that for two reasons.

It will pull better in a lower gear at that point

The engine at 2400 RPM will have a lot more air thru the radiator to help cooling.

This is my example with a 6 speed and lock up torque converter but 4 speed operation would be similar. Ratios are slightly different and the slop in the TC needs to e considered.

As far as more torque? I can't say, my 230 HP "defuels" above 2400 RPM and power actually drops off a bit to keep the EGT within reason. On the flat it will still accelerate but the rate is noticeably slower after 2400 RPM

Under full throttle, my 6 speed will shift up thru all gears at 2400 RPM unless I manually select and hold in each gear longer.

I have mentioned before, I use my shift pads a lot. I don't like the pre-programmed shift points. Under light throttle it will shift way to soon into higher gears.

Again this is for reference, yours is very different than mine.

In our recently completed 7,500 mile trip out west, we had ample opportunity to study the characteristics of the 6-speed Allison coupled to our 230hp Cummins.

Most of the time we cruised in 5th gear. Only hit 6th a couple of times in the rare instances where we were in no-headwind conditions, were straight and level and able to sustain speeds in excess of 73mph. At 73mph we were showing 1650rpm in 6th gear and that's when we got our best mileage (12.9mpg).

As for manually downshifting, I found it quite necessary, for the lugging was bothering me each time. Lugging seemed to start around 1500rpm, with no chance of speed or rpm increases with more pedal.

I used the manual pad a lot. Some hills were easily crested in 4th gear, but there were times I had to downshift to 3rd and even 2nd a couple of times. The key was that since I could see rises ahead that the tranny couldn't possibly anticipate I was able to get ready to downshift as soon as the rpm started downward. I would shift one gear down knowing I wouldn't cause excessive engine rpm and that produced the combination I needed to "walk-up" most hills.

Engine heating was a factor on the bigger hills. Twice in northern California I pulled over into the truck lane and used the 4-ways so I could downshift and ease up on the pedal in order to keep the temps under control.

Shaking: I had an unusual set of circumstances on the right front wheel. Just before we set out on our trip I had the front bearings greased and the mech got some grease on the right brake rotor. I reasoned that that caused some inconsistent grabbing and figured it would "burn off" soon enough. It had caused some pronounced shaking in the steering wheel (I had some mild shaking in the past). The more-pronounced shaking seemed to hang on too long however, and it wasn't until we serviced the front brakes in L.A. that I noticed a good-sized slug of old grease stuck to the inside of the front right rim. Removing it solved the problem, for all the way back to Michigan we didn't have any shaking at all; not even the mild shaking I had been getting used-to.

Hey Lou, what size tires do you have? 19.5 or 22.5?

I know you had an issue with the throttle position linkage. I had the same problem and had to fix and re-fix issue a couple of times. It still isn't right. Throttle position calibration will definitely have an effect on shifting automatically.

Some of my shifting (or lack of shifting automatically) is caused by not having the throttle position sensor calibrated correctly. The early Spartan chassis with first use of the 3060 had a real kluge setup to connect the throttle position to the throttle linkage at the injection pump.

Hi Ed,

Good to hear from you. Tires are r22.5.

Here's an excerpt from the workorder/invoice when I had the linkage serviced in Rapid City, SD:

"CEl AND DOWN SHIFTS WITH NO TORQ
hooked up trans diag. got the computer to hook up found the tps failed low got back to throttle linkage and found the tps linkage was loose, took off then filled old hole with weld and drilled new 1/4 hole for bolt then got it back in rv set the linkage the tpr counts was with in spec the fault went inactive and I recalibrated tps and reset fast adaptive shift points test drove down shifted good."

The queen is beside herself re: the use of the English language, but I think this all means that after the fix they did indeed put it back on the computer and found the shift-points to be within spec.

Some of the slow shifting could be me and a lack of discipline. It takes a lot of pressure to get the pedal all the way down to where it needs to be in order for the trans. to properly detect the true shift points. I don't always "floor it" so the readings could very well be inconsistent. It's just easier sometimes to push the button when you know it's going to have to downshift anyway.

Lou

Ok, I think you have one of the 6 speeds that will not shift into 6th until 70 +/- MPH. That is because you have a 4.1:1 diff ratio, same as mine but I have 19.5 tires. That is why you stay in 5th. With that diff and tires it will be a bit slow off the line also.

If you have a similar linkage that mine had, It can be set within TPS counts but the range from low to high is going to be off. This will not show up on their diagnostic readings but will effect the shift points a bit. I have the same issue, in order to get it to shift down, I have to completely floor the peddle. Even when I am on cruise control, I have to assist the peddle or shift down manually going up a grade to get it to shift down.

Programming the shift points is one thing but that will not change the reaction to the throttle, only the set points where it will shift. If the TPS is not sending the correct range of signal (voltage)from zero to full throttle,it could be off at the high end.

The ECU is much more sensitive to idle position ("O" throttle) than it is to full throttle. IMHO the range of the TPS value to the ECU is very broad

I have been playing with mine and have gotten it better but I have to change the linkage again to get the full range TPS voltage to track the full range of the throttle.