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Author Topic: HT740 Lockup Solenoid  (Read 2232 times)
TomC
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« on: March 22, 2009, 03:24:46 AM »

I'm having the HT740 installed now at Pedco in my Kenworth.  I remember reading about being able to add a dash switch operated manual lockup valve to the transmission that kept the transmission in continuous lockup until you shut it off again.  It is so effective that if you forget to turn it off, the engine will stall when you come to a stop-like forgetting to push in the clutch.  If any of you remember the thread, or have information on what is needed to add the solenoid, it would be appreciated.
I've learned that since 1983, the Allison HT740 and HT754CR mechanically shifted transmission have had a modification to the shifting pattern.  Pre 1983's shifted like- 1C-2C-2L-3L-4L with once the converter locked up, it stayed locked up continuously.  After 1983, Allison added a momentary fall out of converter lockup circuit to make the transmission shift smoother.  In another words, in the shift between 2-3, and 3-4 (in the HT 740), when the transmission makes the shift, the torque converter comes out of lockup mode momentarily to make the shift smoother, then locks up again.  This makes the lockup circuit work through the rear governor instead of the front governor-hence the problem we're having trying to figure out where and how to plumb in the manual lockup converter solenoid.  Any help will be appreciated.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
JackConrad
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« Reply #1 on: March 22, 2009, 04:51:46 AM »

Tom,
   Hopefully, someone else will chime in with a link to the article. I do remember that the solenoid was installed between the lock-up pressure test port and mainline pressure test port on the transmission.  Jack
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Paul
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« Reply #2 on: March 22, 2009, 05:11:18 AM »


Brian & Hilary Diehl


http://home.earthlink.net/~diehls0792/HT754TorqueConverterLockup.html


Paul
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luvrbus
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« Reply #3 on: March 22, 2009, 06:14:27 AM »

TomC the lockup is a fire truck application  the diagram is in a supplemental page you can get from it Allison, United Transmission will have the parts and diagram and they are close to you. I remember the valve has to be mounted in a certain postion   good luck http://www.utxchange.com
« Last Edit: March 22, 2009, 06:24:46 AM by luvrbus » Logged

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1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #4 on: March 22, 2009, 06:19:34 PM »

Hi Tom,

I think the thread was my Jakes install. Brien Deihl sold me the selonoid which I never installed because the jakes worked so well.
http://www.busconversions.com/bbs/index.php?topic=5045.15

If you want it, I can pass it on to you for the same dollars it cost me.

Let me know
Nick-
« Last Edit: March 22, 2009, 06:26:54 PM by Nick Badame Refrig. Co. » Logged

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