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Topic: Oh boy, more vibrations. (Read 414 times) previous topic - next topic

Oh boy, more vibrations.

Hey, I'm back.  :o

Last year, we had this strange problem with vibration throughout the coach when the engine/trans was in a very specific configuration.  You all had a bunch of ideas of what it could be, and then, some 3000 miles later...  it just went away completely.

We've done several shorter trips since then, including a weekend one a few weeks ago that had 400 miles of perfect driving.  Although, we did start out with a dead engine start battery that I revived with a tender and then had working for the drive.

Interestingly, during that trip though, I had this weird retarder problem:  the retarder works if I have the switch ON and I press the brake pedal.  But if I just let off the gas, the retarder didn't engage.  Super annoying, but still safe and comfortable on the downhills, as long as I remembered to at minimum feather the brake pedal.  Allison reported a service code
Code: [Select]
SERIAL COMMUNICATION INTERFACE FAULT

Well, that was our shakedown trip for this summer's long one, which we started today.  Well, tried to!  My engine batteries were this time super struggling, enough that I gave up and went and bought two replacements and swapped them out.  Before that, I did manage to get the engine...  partially cranked?  It was really weird, like it was lugging or something, the whole time.  I let it turn itself over for 30 seconds (I let off the key, engine was turning on its own without the starter) before giving up and shutting it down.

Anyway, got two new batteries, and everything spun up just fine.  And shortly thereafter, a little sweatier but otherwise none the worse for wear, we started out.

Along the way, shortly, I noticed a lot of voltage fluctuation on the meter I have up front.  Like, I was expecting stable 13.5V or more, but it was dropping down into the low 12s and kind of bouncing around.  I got out and put my clamp meter on the battery cable and saw strange fluctuation of current, sometimes just draw and then momentary current the other way like it was charging, and then back.  Oscillating, at times.

My theory was that we'd burned up the alternator asking it to try to charge this nearly-dead battery, and that I'd need to replace it or something.  I did some reading and decided that I would tackle this back at home and with the benefit of all of my tools and the shop, so we turned around and headed 20 miles back. 

Along that way, I noticed that the voltage had come back up to something reasonable, and then separately I felt some strange vibration throughout the coach coming from the rear.  It reminded me of those adventures last year, and not in a good way!

We got home, and I put more meters on the coach and the alt, and now...  it charges just fine, surprise surprise.  I took the coach back out for a 20-mile test spin around the "block" and the voltage stayed high the whole way, just like it always had before.  The battery seems fine, and the engine starts great.  Weird?

Anyway, we got back in to head out, again, and this time...  there is a Check Engine light that mostly stays lit but occasionally flickers.  AND the Allison no longer shows its SERVICE fault on screen.  AND the retarder now works the way it always did before, engaging whenever I let off the pedal! 

Except, for sure:  now, whenever I ask for more than a nominal amount of torque from the engine, at least in gears above 2, I get a vibration that builds throughout the coach.  Holding cruise at 62mph on the flat freeway, it's fine.  Ask it to accelerate, it'll vibrate.  Set cruise at 65mph, the vibration starts (needs more power because of wind resistance, I bet).  Even at 35mph in 4th gear, accelerating creates the shakes.  I don't seem to get the shaking in 2nd gear in parking lots, though.

This vibration is not the same as the one last year at all in terms of what seems to trigger it, but it is the same in terms of making the coach feel uncomfortable and like, if it continued, it'd be a tiring ride at minimum and maybe damage some interior parts if it kept going.

So...  I'm at a loss (and tired, ha).  I don't know if any of these things are related.  I'm sort of happy that my retarder is working again, and I like that the alternator looks like it's behaving nominally.  I haven't DONE anything, ha ha.  I'm not comfortable going on a long trip with the engine behaving like that, but I'm not sure what to do next. 

To clarify:  two weekends' ago, the trip was perfectly smooth.  I've changed essentially nothing in the coach...  we have the same the loadout, the same towed car, it's the same tank of diesel, etc.  Oil was fine right before we left.  With the exception of the fresh chassis batteries, I can't think of anything else that I can point to as a smoking gun.

Any ideas?  (First thing to do is find a scan tool to get the code from that check engine, I know.  I do have a Bluefire, but the app updated seems to have updated itself into a state where it is incompatible with the hardware, so apparently I have to mail the hardware in to get an update...  yeesh.)
1997 U295 36' WTBI

Re: Oh boy, more vibrations.

Reply #1 –
Sounds like you need to check the bearing play at the transmission,you can do this with a pry bar,you put the pry bar against the
balancer coming out of the trans,you can research the forum for the spec but think it may be 20 thousanths and you have too much play,if so you need to find a shop that is familiar with this problem.If that is the problem it will not go away by itself.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Oh boy, more vibrations.

Reply #2 –
Thanks, John.  Does it make sense to you that a bearing play problem would manifest only under high torque, but not cruising on flat road?

I've read a bunch of old threads about high speed vibration issues on my era (and length) coach, but I'm getting this at 25mph under load and not at 72mph when coasting.
1997 U295 36' WTBI

Re: Oh boy, more vibrations.

Reply #3 –
Have you changed the fuel filters? Sounds like maybe you have a plugged fuel filter. Have you kept an algicide in the fuel?
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: Oh boy, more vibrations.

Reply #4 –
Fuel filters were changed back in Jan or Feb, and no algicide was added to the tank.  However, the rig drove 400 miles on that same tank, just fine, for the 400 miles of our Memorial Day trip. 

I don't seem to have any problem producing plenty of power, at any speed.
1997 U295 36' WTBI

Re: Oh boy, more vibrations.

Reply #5 –
Code: [Select]
Cylinder #6 Injector Current Low

That's the code.  Closing in on it!
1997 U295 36' WTBI

Re: Oh boy, more vibrations.

Reply #6 –
So you have a code reader now? Good. Still guessing you have an electrical problem. They may hide and go away but will return. Having a load cell really helps to make those hiding problem show up.
Coach wont start trouble shooting (Battery)
Your vibration almost sounds like it could be a U-joint. Just backseat guessing on the U-joint.

Re: Oh boy, more vibrations.

Reply #7 –
Well, I *had* a Bluefire, but the darn thing now requires me to mail it end to upgrade its bluetooth radio, so I can't use it.  (I think it can show codes?)

But I found a mechanic with a reader, and separately I just ordered a Scangauge D to maybe give me a chance with the next one of these, LOL. 
1997 U295 36' WTBI

Re: Oh boy, more vibrations.

Reply #8 –
Quote from: nebster –
Well, I *had* a Bluefire, but the darn thing now requires me to mail it end to upgrade its bluetooth radio, so I can't use it.  (I think it can show codes?)

But I found a mechanic with a reader, and separately I just ordered a Scangauge D to maybe give me a chance with the next one of these, LOL.
Yes the Bluefire will read codes. I also have one sitting on the shelves needed the 10$ update.  :headwall:

Re: Oh boy, more vibrations.

Reply #9 –
Retarder sounds like it is working as designed if there is no joystick installed or joystick is in zero/off position.  Retarder only with progressive brake pedal pressure.
Retard is designed to come on when throttle is lifted AND joystick is in position 1-6.

Re: Oh boy, more vibrations.

Reply #10 –
Okay, problem solved, whoohoo!

Closing the loop:  on these CAT engines (ours is 3126), there's a pair of wires that bring electricity in to each injector solenoid.  Those wires land in a little plug with a clip that is supposed to hold it onto the solenoid's receptacle.  Apparently that clip is prone to getting bent out of shape, over time, and eventually letting the plug loosen up.

So basically we were driving either down one cylinder or with it only partially contributing.  Kind of amazing it worked at all, actually!

Steps to fix:

1.  detach CAC pipes and move them out of the way
2.  remove valve cover
3.  get some surgical tools and squeeze the wires/plug out from under the valve assembly
4.  bend the plug's metal clip back into shape
5.  do more surgery and plug it back in
6.  button everything up

That's about it.  And with the excellent engine access, only about a 90-minute job.  :)
1997 U295 36' WTBI

Re: Oh boy, more vibrations.

Reply #11 –
Quote
Retarder sounds like it is working as designed if there is no joystick installed or joystick is in zero/off position.  Retarder only with progressive brake pedal pressure.
Retard is designed to come on when throttle is lifted AND joystick is in position 1-6.

I should probably open another thread on this (now clearly, a separate) topic, but while we're here... interestingly, while the 3000 was showing the code and the retarder was not auto-engaging on throttle liftoff...  it was honoring the joystick's selection when pressing the brake pedal.

So a lot of it was working normally, just not the part where it detects no throttle pedal, for some reason.

Since it's back to working magically, I'm not going to think about it until it starts flaking out again.  Ha ha.
1997 U295 36' WTBI

Re: Oh boy, more vibrations.

Reply #12 –
Yes transmission bearing as John 44 mentioned, the repair upgrades the bearing. Use a pry bar to see if there is play where the driveshaft goes into the transmission.  Should be no up/down movement.
David & Emma Roche
Dino (Golden Doodle)
1999 U270 WTFE 36' Build # 5534
Xtreme "Lights, Stripes & Roof"
Motorcade# 18321
Dayton, Ohio
Towd: Jeep Grand Cherokee
Two Townie Electra Bikes

Life is made to enjoy, the Foretravel helps!

Re: Oh boy, more vibrations.

Reply #13 –
The injector solenoid connector was the problem this time; we are back to smooth sailing.  Whew!
1997 U295 36' WTBI