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Topic: Transmission seems to be hunting, 2003 U320, need help (Read 1562 times) previous topic - next topic

Re: Transmission seems to be hunting, 2003 U320, need help

Reply #25 –
Quote from: Pamela & Mike –
The throttle sensor is easy to find & get to it.  It is on the bottom of your throttle pedal and is held on with a couple of screws. If you lift the throttle petal and look on the right hand side you should see the 2 little screws.

Thanks - checked and good.

Quote
The engine position sensor is located behind your air conditioner compressor & in front of your air compressor.

Here is the best pic. I could get. The first is of the plug looking through the belts. The second is the sensor & plug.

Great - thank you!
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Transmission seems to be hunting, 2003 U320, need help

Reply #26 –
Michelle,  No idea how the interconnect between the ABS & the Allison, but it makes perfect sense why the hunting/searching due to the lock/unlock of torque converter as described.
Would guess FOT & James T would be on my list.
Might be a fuse to pull to eliminate it temporary.
I am lost beyond that.
Good luck

Re: Transmission seems to be hunting, 2003 U320, need help

Reply #27 –
Problems like this often won't throw a code, because the system is operating as it is designed for a given set of input variables. I'm not sure if all the module communication on your coach is via CAN bus or if it is like mine with mostly discreet inputs. If the latter, you can probably find the communication between the ABS module and the Allison computer and disconnect it and see if the problem goes away. On my diagram, there is a communication between ABS and ATAC computer--most likely to disable the retarder (just a hunch).

A torque converter lock-up clutch kicking in and out will feel like a gear change/hunt.
1998 U270 34'

Re: Transmission seems to be hunting, 2003 U320, need help

Reply #28 –
Received the ABS sensor test procedure from James T. today (attached below).

Thanks to Barry B. we have the tag sensor P/N and have ordered one from FindItParts (it's cheap enough at $47 and this particular sensor has acted up in the past, although not the same extreme symptoms).

We'll know in about 2 weeks if our efforts have solved the problem as that's when we leave this campground.  I'll report back, and in the meantime thank everyone for their ideas, photos, and support.
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Transmission seems to be hunting, 2003 U320, need help

Reply #29 –
Reporting after 2 drive days, roughly 8 hours total.  No "hunting" since replacing the tag ABS sensor, the transmission output speed sensor, checking and cleaning/securing all other obvious connections and suggestions from Pamela and Mike.

A couple of times over a fairly "assertive" expansion joint or pavement void we did have the torque converter drop out of lock-up, but only when on cruise control in 6th/OD.  It didn't happen when speed limits kept us in 5th and it was only 2 or 3 times yesterday and once today.  Of course now we're hyper-sensitive to shift/tc behavior so this may be perfectly normal.

Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Transmission seems to be hunting, 2003 U320, need help

Reply #30 –
How about some photos of replacing ABS sensor.  I have a bad one that needs replacing so was wondering how hard it might be.

Jim
Jim McNeece
2003 U320 40'
2017 Chevy Colorado Tow
 

Re: Transmission seems to be hunting, 2003 U320, need help

Reply #31 –
Quote from: Jim McNeece –
How about some photos of replacing ABS sensor.  I have a bad one that needs replacing so was wondering how hard it might be.

Jim, if it's the tag it is pretty easy.  I'll scan the instructions and post them soon. 

If it's the drive axle, according to James Triana the coach has to go into a shop (I suspect you have to remove wheels). 

I didn't ask about the steer axle since the VMSpc code said "3rd axle left", meaning driver tag.  We bought the part at the local Freightliner shop, $43.xx.  Meritor R955335 is the part for a 2003, per one of Barry B's posts (and what we bought).
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320