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Author Topic: MCI-9 Transmission won't engage  (Read 34819 times)
NJT5047
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« Reply #135 on: January 14, 2008, 08:26:19 PM »

Sammy can verify, but I believe most of the electronics inside the trans can be replaced once the pan is off. 
All in, or on the valve body.
I've been looking at ATEC manuals...can you imagine that!   Coachinfo has a manual for the HT748...but not sure it has the diagnostics.  Have to call or email to see exactly what they are offering. 
After watching what you're going thru, I'm definitly going to get a diagnostic manual for my 748.  I think it's the same as yours...but it's connected to a DDEC engine. 
It would be nice to find out the ECM is the problem, and it sounds like it may be.  Both seem to have issues.
Could be the EEPROM.  A DDEC EEPROM isn't expensive at all.  I bought one of the bastard DDEC 1 EEPROMs for about $125 bucks.  Made a huge difference in highway performance...enable my cruise control which is really nice on flat roads.
It would be cool to have a working relationship with an ATEC repair facility too.   At least an electronic repair facility.
Where does Sammy hang his hat?   He would be invaluable on site.   
Oh well, reckon we'll have to wait for word from Randy.  Suppose he'll let you know what he finds once he runs diagnostics.
Do they have a test-bench for ATEC/DDEC ECMS?   Or some sort of emulator?
Good luck, JR

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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

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NJT 5573
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« Reply #136 on: January 14, 2008, 08:58:23 PM »

Bill, at this point why don't you just tell Randy that you know he gave a free manual to the last conversion bus guy he helped out and you think he should give you one too!

I think General D&E and Sammy will get you sorted out at this point, manual or no manual. I don't trust you with mine anymore!

I wonder if Randy can pull all your history codes from the parts you sent him?

« Last Edit: January 14, 2008, 09:10:03 PM by NJT 5573 » Logged

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Kristinsgrandpa
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« Reply #137 on: January 14, 2008, 09:58:59 PM »

Gents, 

I bought a manual from Allison, the cover says "Service Manual HT, HTB 700 Electronic Controls Series Transmissions".  SM2004EN    Dated 1 May, 1990

It covers the HT, HTB 741
                   HT, HTB 748
                   HT, HTB 755 CR
                   HT, HTB 755 DR
It only shows wire harnesses and solenoids, it shows the shift pad and wire harness and that is all.

It appears to be quite comprehensive in the hydraulics and mechanical sections but is lacking in the electrical section for troubleshooting.  No schematics at all.

I does show the temperature sensor and all the solenoids in the valve body. They appear to be accesible with the pan removed.

I'll be looking for a trouble shooting guide, something with schematics etc.

I do have a DDEC II Diagnostic Troubleshooting Guide, appears to be quite comprehensive.  Dated May 1988. It has some updated info sheets in the front.

Ed.
« Last Edit: January 14, 2008, 10:03:04 PM by Kristinsgrandpa » Logged

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« Reply #138 on: January 14, 2008, 10:25:41 PM »

Ed,

My heart bleeds for you....really.  I am a trouble shooter from the early 60 on up till present.  Radar and other large systems.  The old style rule in trouble shooting is to use the "split half" method.  Today they trouble shoot by replacing "modules".  They get to having so much faith with this method because the same problem is almost always in "that module".  My generation did split half and then hand over hand to the failed component.  I think you need "old school" but I am not bus savvy.

You have a number of major components in the system.  I would go to the component/module that is at the closest point to the trans.  Guess that would be the Trans Control Module.  It only has so many inputs that control it.  Dummy out each....ground what should be a ground in normal ops....open what should be open....a resistor for what is normal....+12 for what that is.  When you are done it will work or not and you can concentrate on what is before of after the TCU.  It it works, start reconnecting circuits till you get the failure back.  You have to get as close to the ecu circuit as possible and inside the can and on the tcu side of the connector.

Another problem I see is with the circuit conditions being specified for a connected TCU and you disconnect the plug to get at the wire to measure.  There are often loops that require that the connector be connected for you to see that ground or voltage.   Unless it is a spec for the connector being off.  Goes both ways. 

You are in a bad way with this and you need to rule out some of this stuff.  We trouble shoot to eliminate things as possible failures.  I probably should not even open my mouth because you have gotten very smart people involved in your problem and I certainly can't hold a candle to their expertise.  Sincerely!  I have been following your adventure like a soap opera and the whole thing upsets me.  So many good minds, so many years of experience, so many hours of labour and still NO JOY IN THE COCKPITT.  We always win in the end, never forget that.

For morale support,

John
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« Reply #139 on: January 15, 2008, 04:27:42 AM »

Bill,

I'm kind of with John Ed here on this, although I think at this point we may want to look at the transmission itself and start the split half there. I never did hear any of the transmission solenoids click, except when we had first gear.

Now, if we have first gear, does that mean we have 2,3 and 4 also? Is it possible the reverse solenoid is FUBAR and that is giving the donot shift light?

As much time and effort as you have into this transmission, I still lean toward a strictly electrical problem.

If you need help, holler, we're still close by and have extra hydraulic jacks!

Dallas
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JackConrad
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« Reply #140 on: January 15, 2008, 05:21:37 AM »

Bill,
   I don't know if this is relative or not, but on our F350 Ford diesel dually pickup, we fought erratic shifting for several years in a Ford rebuilt transmission we had installed (OD light would flash on shift lever=fault). Had it back to the Ford dealer many times. They kept telling us it had to be something else because the computer said the trans was working properly. We then took the truck a privately operated transmission shop. He had the truck for about 1 1/2 weeks and he did a lot a head scratching and talking to several tech service companies. Final diagnosis was that everything was working electrically, BUT the 4th gear solenoid was not working MECHANICALLY!   I wanted to take the bad solenoid back to Ford and throw it at their "transmission service tech" but Paula said NO, just call them and tell them.  Jack
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Kwajdiver
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« Reply #141 on: January 15, 2008, 11:38:10 AM »

I've just spoke with Randy.  He say's my ECU is bad.  The chip (s) in the TPS circurt, have a problem.  The cost of repair, that and any other problem is $800.00   I said fix it.  He will try and have it out of his shop by Thursday.  He will waive the $150.00 to check it out.

Bill
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Auburndale, Florida
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Kwajalein Atoll, RMI
NJT5047
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« Reply #142 on: January 15, 2008, 06:10:38 PM »

Next question (which you may have already axed) is what could cause a TPS related failure in the ECM?  One thing that comes to mind is getting 12V...or 24V on the sense circuit due to wiring problems...or during dx. 
Does Randy believe this sort of failure to be spontaneous?
Stuff happens.
Hope that sucker has about 5 years warranty! 
Glad to hear that something's proven to have failed.  Is that your ECM, or the 'other' ECM that was sent to Hibbing?
Spending $800 bucks should allow you to pick Randy's brain for a bit. 
Waiting again!   JR

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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

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« Reply #143 on: January 15, 2008, 06:13:11 PM »

Gosh Bill,

I sure hope you found the problem. Sounds like this Randy fellow might know a thing or two. Good Luck and always be safe.

Paul
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Kwajdiver
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« Reply #144 on: January 16, 2008, 09:12:03 AM »

Randy called,,,,,,  My ECU is  fixed.  It was the TPI input chip.  Should have it back Friday Grin.  Before installing I'm going to go through the CODE 33 (Shift Pad) Fault Trouble shooting guide.  Just to make sure I don't have a wire or something I missed.  Randy said the chip was shorted to ground.  Which caused my ECU to not flash a code.

I'm praying to the bus gods that this corrects the problem, and I can roll on my merry merry way.

Bill
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Auburndale, Florida
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buddydawg
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« Reply #145 on: January 16, 2008, 09:15:30 AM »

Great! Look like things are finally looking up.  I hope whatever caused the problem was just a one time fluke of sorts.  I would hate for it to short out again.  (I know you would)
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Brandon Stewart - Martinez, GA
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« Reply #146 on: January 16, 2008, 11:09:03 AM »

Bill,

The absolute worst problems to find are the ones where "two" malfunctions occur simultaneously.  When I bought pubs for the Navy I verified every step of any troubleshooting guide/procedure.  Those books were encyclopedic.  I was once told that to include a guide that addressed the symptoms for dual failures would cost in the multi trillions of dollars.  Now, the bright side of this is that if you still have a failure....it will be far,far more simple to find.  I think this is the fix you were looking for based on my HUNCH, though.  Love it when a plan comes together for a guy that richly deserves it.  Good Luck.

John
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« Reply #147 on: January 16, 2008, 02:07:14 PM »

Good that the ECM is diagnosed and repaired...but first, the obvious.   Verify that the none of theTPS circuit leads (power, sense, and ground) have continuity to the chassis.    I suppose that would include the trans temp sensor too.
TPS may have been your problem after all.
Checking all the wires in an ATEC system is a mind boggeling exercise.   Once the new unit is in plugged into the circuit, probably be a good idea to disconnect the ECM before testing of dinking with the wiring.
Hope you don't have the cold weather that they're calling for us this weekend.  Working on a bus in 25* would be a negative!
My thought of the day.  Now my brain's all tired out.  Wink  JR

   
 
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

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« Reply #148 on: January 17, 2008, 02:45:41 PM »

Did you get your ECM back today?  I'm hoping that it gets you back on the road especially since you have been down for 2 months now. 
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1972 GMC T6H-5308A #024

Brandon Stewart - Martinez, GA
Dallas
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« Reply #149 on: January 17, 2008, 02:54:35 PM »

I tol' ya we could stick a MT 545 in there!

Just kiddin' Bill, I hope the repaired ECM does the job.

Dallas
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