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Discussion Starter #1
When not in Tow/Haul, if I lighten up on the throttle my D/A will shift to overdrive at about 40 mph. I then get torque converter lockup at about 50 mph.


I was under the impression the Allison TCM always locked the torque converter in 4th and 5th (not in Tow/Haul). Is torque converter lockup at 50 mph in 5th typical of the D/A?
 

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The Allision will go into lockup in fourth or fifth gear depending on the conditions your in at the time. With the Tow/Haul on it will go into lockup just after shifting into second gear.
 

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If in normal mode (not tow/haul) and WOT, will the torque convertor still lock up in 5th?
 

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Discussion Starter #5
I will re-phrase my question:


When not in Tow/Haul and when not accelerating hard, will the torque converter lock up IMMEDIATELY upon shifting to overdrive or will torque converter lockup be delayed until AFTER a speed of about 50 mph has been achieved?


On my D/A, I do not believe it is locking up in overdrive until 50 mph.
 

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I think that if your cruising at say 65 MPH and above and slap the accel pedal it will try to remain locked. With setings above 4 and 4 on my TST comp. box I will sometimes get a bad shudder that I attribute to my Tq. converter slipping. It's eally bad if the 5 to 4 downshift is inhibited with the cruise control.


On edit, I believe what is happening at 50 mph is overdrive, when the cold weather gets here you will notice that shift will not happen until the tranny or eng., I don't know which warms up a little.Edited by: a64pilot
 

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The lockup clutch or TCC is applied as follows:
1st gear - TCC does not apply
2nd gear - TCC will apply at 31 mph at Wide Open Throttle (100%)
3rd gear - TCC will apply at 41 mph at 75% throttle and above
4th gear - TCC will apply at 50 mph between 66% and 80% throttle and 56 mph at 88% throttle and above.
5th gear - TCC will apply at 50 mph between 0% and 45% throttle, 52 mph between 50% and 75% throttle, and 56 mph at 85% throttle and above.
The TCC will release as follows:
2nd, 3rd, and 4th gear - TCC will release at 26 mph
5th gear - TCC will release at 48 mph at 0% throttle
- TCC will release at 46 mph from 0.1 - 75% throttle
- TCC will release at 53 mph from 80% throttle and above


The reason the TCC is not engaged before 50 mph is to avoid driveline growl which is present on vehicles under 48 mph when the engine is at power (i.e. not at zero throttle).
 

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Discussion Starter #8
Thank you all for your posts. I have learned a lot.


Wow, Mic_!!!! Now I will probably have a wreck tooling down the highway while I am busy confirming these different lockup and release points. Great info.
 
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