MCI-DL345 high speed idle, shift pad dead

[plyonsMC9]

Thanks very much Bob,

Will indeed check that wiring - i have the DDEC II.  Also see a fuse below the shift pad. 
And well, I found the big red breaker button on the Vanner this evening. How could I miss it?  In the IN position, not tripped.  But I figure let's pop it out.  Well, not a good idea when wife is cooking things - and the lights go dark & pitch black inside. 

And again thanks to Fred for noticing this thread:

https://www.busconversionmagazine.com/forum/index.php?topic=31850.15

Talked w/ Kevin briefly - he did not have the software but we may talk again tomorrow. 

No time to clean the plug that goes into the transmission today - will take a day off troubleshooting tomorrow as my real-job needs me to catch up.

Kind Regards, Phil

[luvrbus]

That transmission doesn't have a neutral switch but does have a neutral relay someplace in the start circuit ,I am still trying to find a shift pad I think that is your problem,the check transmission light should come on if it is throwing a code,the 700 series electronic transmission are like eating a elephant sorry to say
   

[Van]

Phil if the need arrises here is a link to a place up North that my buddy used that rebuilt his ecu .and key pad.
https://jultech.com/
Good luck.

[robertglines1]

FWIW they make a harness to go from ddec II to ddec III..

[plyonsMC9]

Not much time for troubleshooting today;
But did snap a picture of the Allison Serial number plate / driver side to verify identification.  Plate was covered in grease. If you need to find it, right above the oil pan - it's not real large.

Also setup a visit w/an Allison Trans specialist from Williams DD tomorrow morning.  It's been almost a week of troubleshooting and we're still here.  Will post updates as I receive them.  Suspicion being the shift pad and the TCM, though testing tomorrow should be helpful.

Van, thank you - that may indeed be helpful.  Parts are 'not plentiful' for this task to be sure. 

Bob, I had no idea, and I will ask about that.

Kind regards, Phil

[niles500]

Phil I don't believe that's the vanner I was referencing, the one 1 (or more) I  am talking about should be located near your 24v master switch about the size of a small USPS priority box - HTH

[plyonsMC9]

thanks Niles!, I have located it.

More updates, while the Allison tech was here troubleshooting, he pulled out, pushed back in the ATEC fuse in the front junction box near driver, then we heard a click in the front j-box and the 1st bay j-box.   Then we had 26volts on that circuit.   

This is an exact repeat of what happened last time when the mechanics replaced the fuse in the 1st bay/ATEC - suddenly the system came to life.  So they replaced the fuse holders, fuses and thought all was happy until the ATEC stuff went dead. 

So, right now, it's again, not failing - so more difficult to troubleshoot.  Going over schematics, more testing. 

[freds]

Today, went over a number of the circuits, especially atec circuits, took apart connections, cleaned, put back together, no good.  Thanks to Fred who's here working on his Prevost for helping. 

Ideas, suggestions welcome!,  Kind Regards, Phil

Your very welcome, nothing worse than an intermittent problem that fixes it self when you stare at it hard enough!!!

[DoubleEagle]

Not much time for troubleshooting today;
But did snap a picture of the Allison Serial number plate / driver side to verify identification.  Plate was covered in grease. If you need to find it, right above the oil pan - it's not real large.

Well surprise, surprise, it's a HT741! See what happens when someone assumes what it is. From the outside appearance the 741 and 748 look very much alike, but if you had a HT746, it would look a lot different even if the internals are very close.

[luvrbus]

Walter the transmissions are the same the models changes you posted a picture of a 746 with the retarder with a few parts missing they bolt to the rear of a 741 to 748 they will have 2 numbers in front of the 7XX and 2 or 3 numbers after the 7XX to identified the application,the Allison parts manual cover all 700 series electronic transmission and you will not find a foldout on the 741 or 746 it has only the updated 748,they are the same transmission as the 740 with 8 electronic updates and valve body     

[DoubleEagle]

Not counting the retarder, what about the difference in the oil pan? The HT746 seems to be distinctive.

[luvrbus]

Phils 741 has the updated oil same as the 746 and 748,if you look close you will see that is a adapter that bolts to the standard 740 housing Walter forgot to tell you that part   

[plyonsMC9]

Well this is a fine kettle of fish.  We made it from Quartzsite to Phoenix in heavy rains, stop n go traffic, 65-70 on the freeway.  Allison guy from Williams followed us almost the entire way - no issues.   Started it up 2 -3 times this morning, no issues.  Going in for a trans service and have them diag the trans fluid if they do that.  Filters looking a tad aged / bit of rust on the porcelain.  Suggested a service.  We'll do that plus a couple of other items.  No firm diagnosis of what the issue was since it hasn't failed again to be diagnosed.  I will swap out all the atec fuses soon back to the original holders.  And it turns out that actually voltage was supposed to be approx 26+v on the 3rd fuse position (attached picture).  Original information I had received on those values was incorrect from MCI.  Correct from the schematic.  Still don't really know the exact cause.

Allison guy says they don't much work on these models any more. Harder for them to get the parts.  Test equipment older, etc.,    Only because I was curious about what he was seeing out in the field - so I asked.

If all goes well the next week, will attempt the long grade up to the Prescott Valley area from Phoenix. Though, there's no snow down here!! 

Thank you all have have assisted.  Such a tremendous group of helpful folks jumped in.  My wife & I really appreciate it!!

Kind Regards, Phil