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-   -   transmission sometime kicks when engaging reverse and drive (https://www.cumminsforum.com/forum/4th-gen-powertrain/1261385-transmission-sometime-kicks-when-engaging-reverse-drive.html)

jsapp2013 08-11-2014 12:46 PM

transmission sometime kicks when engaging reverse and drive
 
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When u put my truck in reverse or drive sometimes it will kick hard before going in gear. It's really annoying. It doesn't do it all the time so I know it's not suppose to do it I just don't what could be causing the problem. It feel like something may be sticking in my valve body but I do t know alot about transmission. I have also read about u joint. I just need some guidance in the right direction. It did it bone stock, before I did any modifications.

jsapp2013 08-11-2014 04:34 PM

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Help please

lvramcummins 08-11-2014 06:12 PM

Mine does it too. I don't worry too much about it. I thought I had read somewhere on here it had to do with the torque converter.

jsapp2013 08-11-2014 06:36 PM

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Yea it acts funny when on lock up too. I love thinking about getting a new converter. It kinda jerk when I throttle up or release throttle in lock up

lvramcummins 08-11-2014 06:58 PM

mine acts funny on the lockup in 5th. Like it hesitates then locks fast. The shift strategy is a lot different than it is on my gf's 3rd gen 6.7.

Mine downshifts like crap too. I'm not too fond of it.

djbatt 08-11-2014 11:13 PM

What does it mean when you guys use the term "lock up"? My trans tends to allow the rpm of engine to rev up between shifts. Is that "lock up"?

CumminsPwr89 08-11-2014 11:19 PM

Mine does the same exact thing. I believe the transmission filter sump pump may be the issue.

It could also be high line pressure in the transmission.

Any input from anyone would be great..

6.7laramiebrown 08-12-2014 01:53 AM

I had this issue and now gone. I will try to explain shortly. I Came to the dealer 3 times. For First they relearned the tranny it helps but not diseappear and finally the issue came back. Second time same thing. Third time I was in a week of vacations and the relearned works fine for all. But I work with my truck and I have 250 gallons water tank in the box. The second week after the relearned the issue start slower to came back another time. And when i work i have to stop for 5 minutes maybe 60 times a day. And I noticed the issue came back when the tank was at the3/4 level and I have a big wave when I stop the truck but just for 5 minutes I did not put my parking brake but I did for the long stop. When I started to put my parking brake at every stop the issue completly diseppear and not came back for now 8 000km. The last guy I talked to the dealer said to me if the relearned help for the issue i had to check my way to drive my truck because it's an auto adaptative and it seems that the tranny try to compensate for something. Maybe if you try put always your hand brake it will helps if it's not cause by a mechanical problem. Wih it helps.

TransEngineer 08-12-2014 08:16 AM

Quote:

Originally Posted by djbatt (Post 14118673)
What does it mean when you guys use the term "lock up"? My trans tends to allow the rpm of engine to rev up between shifts. Is that "lock up"?

"Lockup" refers to the Torque Converter Clutch (TCC), which is a clutch inside the torque converter, between the impeller shell (the part that is bolted to the engine via the flexplate) and the turbine (which is the input to the transmission). The torque converter is a fluid coupling, so normally there is slippage between the engine and trans input. For example, when you're sitting at a stop light (in Drive), the engine is at idle speed (700 RPM maybe) but the trans input is at zero speed (since the wheels are stopped). So there is 700 RPM slip within the converter. This slippage decreases as you bring the vehicle up to speed, but cruising down the highway you might still have 200-300 RPM of slippage.

The TCC is designed to increase fuel economy by reducing (or eliminating) the slippage within the converter. It's often called a "lockup" clutch because it locks the two halves of the converter together. You can normally notice this as a slight dip in engine speed, which sometimes feels like another shift in the transmission.

TransEngineer 08-12-2014 08:47 AM

Quote:

Originally Posted by jsapp2013 (Post 14107049)
When u put my truck in reverse or drive sometimes it will kick hard before going in gear. It's really annoying. It doesn't do it all the time so I know it's not suppose to do it I just don't what could be causing the problem. It feel like something may be sticking in my valve body but I do t know alot about transmission. I have also read about u joint. I just need some guidance in the right direction. It did it bone stock, before I did any modifications.

Harsh engagements into Drive (or Reverse) are annoying, but typically they are not a durability concern (the engine torque at idle isn't high enough to do any significant damage). Clunky / banging engagements may be due to worn U-joints, or high engine idle speed.

Another factor may be the length of time the engine was shut down before startup, or whether (or how long) Reverse was engaged (before shifting into Drive). On a Drive engagement, the UD clutch is the applying clutch, so it controls the smoothness of the shift. The primary adaptive (learned) value for UD clutch engagements is the UD Clutch Volume Index (CVI). Actually, there are several UD CVIs, including one for "normal" Drive engagements, and one for "1st" Drive engagements (1st engagement after startup, or after shifting out of or past Reverse). When the engine is off, fluid can slowly drain out of the UD clutch, so the volume of air in the clutch (that the CVI value has to compensate for) may vary depending on how long the engine was shut down. Let's assume that the "1st" N-D UD CVI is set to compensate for a fully drained clutch. If you make a quick stop at a gas station or store (just a few minutes), maybe the UD clutch doesn't drain down all the way, so when you restart and shift into Drive, the CVI is too high (it assumes you need more fluid to apply the UD clutch than you actually do, since the clutch is still part-way full). That could give you a clunky / harsh engagement.

So pay attention to the circumstances immediately before your harsh engagements. Do they happen when the engine is cold, or hot? After a short shutdown, or a longer one? After you've engaged Reverse, or after you've simply shifted from Park (right past Reverse) into Drive?

I probably can't tell you how to "fix" an intermittent harsh engagement, but maybe you can at least better understand what circumstances tend to produce those harsh engagements.

jsapp2013 08-12-2014 09:39 AM

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Will a transmission relearn mess up my mcc on my mini max. Or can I so it with all my mods in tact.

TransEngineer 08-12-2014 10:00 AM

What's an MCC?

The quicklearn procedure is programmed into the PCM. All the scan tool does is send a command (to the PCM) telling it to run the quicklearn routine. But the routine is all within the PCM, so I'd expect you could run it without affecting anything else.


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