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
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
Brian & Hilary Diehl
http://home.earthlink.net/~diehls0792/HT754TorqueConverterLockup.html
Paul
Incredibus .com
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
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-