Foretravel Owners' Forum

   Our coach is headed to the shop today. The Allison torque converter doesn't seem to be locking up in 3rd gear or any higher gears either.  Coach isn't heating up yet but in the higher gears the tachometer and the speedometer are no longer in sink. Said another way. If I give it more fuel and the tachometer responds, the speed ,  not so much.  Or at least the way it did before.    All fluid levels seem normal and we never realy had an overheat situation.    We are now in Sedona and did just make the 7,000 ft clime into Flagstaff but the temp never went over say 190.  And on the downward side I never let the retarder get over about 220.

  Any ideas about things to check ??

  I'm driving it to a shop about 20 miles away and hope I don't do any further damage ??

Did you check for diagnostic codes using the shift pad?  That is where I would start.

If you need help with this, PM me.

I don't know when they changed the shift pad to have the ability to read the codes but if it does not, use the switch and light bulb under the flip up dash top. I have all the codes if needed. The two switches, engine and transmission are forward against the plywood bulkhead on our '93 U300 with a HT746 Allison.

Doubt if driving will hurt it. Lock up does drop the temp but not a big deal especially in fall temps.

Pierce

Electronic diagnosis from shift pad came in with the introduction of the Allison 3000 and 4000 transmissions.

I had this happen a couple of times and I shut down the coach and restarted letting the transmission computer reset.  The pad did not show any error just normal shift.  After reset transmission shifted and locked up correctly.

Tom,

Did you go through the check procedure for diagnostic codes when this happened?

Brett,  I didn't see any error codes displayed when the lock up failed.  Is there another way to read codes stored on the transmission computer that are not displayed ?  Tom

Tom,

As I asked in the PM, did you use the shift pad to enter diagnostic mode and check for codes?

No codes were shown for our tranny.        Drove the 86 miles to Phoenix and the W.W.Williams service facility. Checked the coach in and the Allison person will check it out first thing in the morning.  Three fire trucks sitting and waiting for service so I'm thinking I've found the right repair shop for our precious coach.  More to follow.....

Brett,  No I didn't do that.  Not familiar with how to do that.  Searching for write up on how to enter diagnostic mode.  Tom

In the Media section here on the forum (starts on p. 29 of the second item - the full manual)  ;)

So the coach spent entire morning ( had to get up at 7 am, been a while on that one) at W.W.Williams. They are the only authorized repair and replace shop for Allison trans in Phoenix. They found nothing    Other than maybe change out the synthetic trans fluid sometime soon.  It wasn't shifting into 4th very well so they reset the ECU for the trans allowing it to re learn my driving habits.  After driving it about 20 miles, the jury is still out on whether that worked.  All I can say is it's shifting best if I have my foot in it, I just normally don't drive that way.  22 year old coach and all. 

  The remaining problem is the trans retarder isn't working and they said it might take 4 to 6 hours of trouble shooting ( at 150 per hr) the wiring and components. I'm ok with the price but they didn't sound too confident about solving the problem.  My take was that they aren't familiar with Foretravel.  He did say that voltage to the toggle switch was at 11 1/2.  That seems low to me.

  So,  good news is trans is fine but bad news is no retarder and I need it for the mountains.  I hope the answers for what to check lie within this forum or I may need to go the 1000 miles to Nac for answers.

The pleasure of a state of the art motor coach is a small bit offset by the blank look on repair people faces when you cannot tell them who made your chassis. Blank looks.

Had that happen in Idaho falls before the eclipse  when I lost a disk brake rotor. 

Capped the air line after inspecting every thing then drove it home to be fixed correctly.

Still worth it

Sounds like you may need to seek out a more qualified Allison dealer.

Actually, I would start by verifying that you are getting 12.5+ VDC to the Allison ECM.  Start checking at the IGNITION SOLENOID, then both fuses/breakers for the Allison (one if for "memory", the other, larger one for ECM operation).

Low voltage will cause all kinds of issues.

Thanks Michelle for the Allison Manual information.  More to learn.  On the transmission retarder issue, the term or voltage comes from the ABS system to activate the retarder.  I would have to check the schematics for pin out. Tom

Interesting bit of information there. 

A few years ago we had an issue with the transmission dropping out of lock-up. 

Thanks to the forum search (and particularly Art and Polly for sharing Torque converter locking up and then unlocking at highway speeds. (http://www.foreforums.com/index.php?topic=13997.0) ), we identified it as an ABS wheel sensor telling the transmission to do so.  Fortunately, it was a tag axle sensor so easy to replace and solve the problem.  Transmission seems to be hunting, 2003 U320, need help (http://www.foreforums.com/index.php?topic=22487.msg173307#msg173307)