68RFE slipping in 1st gear pulling a trailer - Dodge Cummins Diesel Forum
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post #1 of 7 (permalink) Old 09-11-2017, 01:44 PM Thread Starter
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68RFE slipping in 1st gear pulling a trailer

2012 3500 SRW 68RFE

From at take off from a dead stop, tow/haul mode engaged, pulling a 7K lb trailer. The transmission feels like it's slipping/shuddering in 1st gear only. Doesn't do it if I ease out of the stop. Doesn't do it when I jam on the throttle in any other gear, even going up a grade.

Is this normal? I took it to the dealer with the trailer and took a tech on a drive to show him what it was doing. Tech said it could be a clutch or something in the torque convertor, he also said it could be normal. They submitted a STAR case and we're waiting to hear back from the engineers. Anyone else experience anything like this?

Warranty expires this month and I'd like to get this addressed if it is a problem.

Thanks.

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post #2 of 7 (permalink) Old 09-11-2017, 03:15 PM
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Is your RPMs surging? Do you have a code? What makes you think you're slipping?


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post #3 of 7 (permalink) Old 09-12-2017, 05:57 AM
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You're probably getting "launch shudder," which is not a transmission issue but rather caused by movement of the driveshaft center bearing. I presume you have a 2-piece driveshaft? If you mount a GoPro camera under the truck and video the center bearing, you can see what's going on.

Although some such shudder is apparently normal (unavoidable) with a center bearing, you can sometimes reduce the shudder by shimming the center bearing support, to slightly change the driveshaft angle at the center joint.
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post #4 of 7 (permalink) Old 09-12-2017, 01:09 PM
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The torque converter doesn't lock in first gear, so it would not be the lockup clutch. Does it do it if you put it in manual low?
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post #5 of 7 (permalink) Old 09-13-2017, 12:41 PM Thread Starter
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Quote:
Originally Posted by cumminthanstrockin View Post
Is your RPMs surging? Do you have a code? What makes you think you're slipping?
RPM is not surging, no codes, not sure if it's slipping, just feel a significant amount of shudder on take-off.

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Originally Posted by TransEngineer View Post
You're probably getting "launch shudder," which is not a transmission issue but rather caused by movement of the driveshaft center bearing. I presume you have a 2-piece driveshaft? If you mount a GoPro camera under the truck and video the center bearing, you can see what's going on.

Although some such shudder is apparently normal (unavoidable) with a center bearing, you can sometimes reduce the shudder by shimming the center bearing support, to slightly change the driveshaft angle at the center joint.
Thanks TransEngineer! I'll have to try the gopro then next time I hook up the trailer.

Do I shim the support to make the angle flatter? Any recommendations how I would go about it? Could the bearing be going bad?

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The torque converter doesn't lock in first gear, so it would not be the lockup clutch. Does it do it if you put it in manual low?
I haven't tried. Thanks for the info, that was my main concern. It's for sure only happening in 1st gear.

Thanks for all the responses guys and sorry it took me a few days to get back, I just got a Aussie pup and she has been soaking up all of my free moments.
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post #6 of 7 (permalink) Old 09-14-2017, 06:04 AM
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Do I shim the support to make the angle flatter? Any recommendations how I would go about it? Could the bearing be going bad?
I'm not a driveline expert, but I believe that yes, you would add shims between the center bearing and the crossmember to move the bearing down slightly (reducing the driveline angle).
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post #7 of 7 (permalink) Old 09-14-2017, 11:49 AM Thread Starter
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I'm not a driveline expert, but I believe that yes, you would add shims between the center bearing and the crossmember to move the bearing down slightly (reducing the driveline angle).
Ok, as always thanks very much for the info.

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