2013 Jolt

S

smooth9883

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Hi Guys,

I have a new 2500HD Duramax and I've been noticing when I stop there is a big jolt coming from the back of the truck after the truck has stopped. I'm not sure what it is. I'm guessing here, but is it the gas in the fuel tank shifting from the back to the front. It seems to happen more on harder stopping than light stopping.

What are your thoughts?
 
smooth9883 said:
Hi Guys,

I have a new 2500HD Duramax and I've been noticing when I stop there is a big jolt coming from the back of the truck after the truck has stopped. I'm not sure what it is. I'm guessing here, but is it the gas in the fuel tank shifting from the back to the front. It seems to happen more on harder stopping than light stopping.

What are your thoughts?
Click to expand...

Nature of the Allison transmissions when coming to a quick stop. Transmission downshifts smoother if you come to a smoother stop and let the transmission downshift to slow you down.

The harder downshift is more noticed when your H/T mode is turned on and your on the brakes. A weak rear wheel speed sensor will also cause this. They start to drop signal at low speeds first then go out completely. The check engine light won't come on until it's a major problem.

Symptoms are what you described before the speed sensor starts going out and replacing it under warranty just to eliminate that possibility if the dealer finds it going bad. The part is just under $30 and it's on the back of the transfer case. Another symptom is a sluggish speedo needle from a stop, though yours may still be fine. I have the same issues with the Allison transmission on my tour bus when the sensor starts going bad.:eek:

Keep us posted but sounds like your transmission is running normal.

Molson02536
 
Wow that's some great info. I took it to the dealer today so they could look at some paint issues. I mentioned the symptom and they are going to check it out once they take care of the paint problem.

Ill keep you posted.
 
Looking forward to hearing more about what your dealership found today, smooth9883.
Sarah (Assisting Stacy), GMC Customer Service
 
Tell them to slap a butt ton of grease on the drive shaft yoke (can't remember the exact name, but near the back where it connects to the diff. I've had two trucks do this before, a Tundra and a Frontier. Fixed both. Others have called this "axle wrap"..... not sure what that means ....
 
spline in tranny locking up! inheritant characteristic of that set up.
 
HI Guys,

So it's been a month now and I thought i would touch base and give you an update. I took the truck in to have the paint worked on and they looked at the issue I was having. Unfortunately they couldn't replicate the issue. Go figure :)

Luckily I can replicate it at will and I'll ride with the service manager to show him what's going on. I'm not 100% sure but I'm really thinking it's a wheel speed sensor. I can be going 1 mph and when I stop the truck I'll get a jolt from the back a second later. Also, I've noticed that the torque converter isn't locking up all the time. I'm not sure if this is normal Allison operation, bu you can definitely tell when the torque converter locks up and when it doesn't lock up. I've read somewhere that these issues are related.

I'm going to take it in this week to have it fixed. I'll let you know. Before I go in though, does it sound like these could be related problems?
 
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