09 97x "bucking" "lurching" tcase problem

T

trandy45

Member
Jul 11, 2025
8
Wisconsin
Hey guys, first post, i usually find things by searching the forums but not this time

Im looking for some help/input
I have an 09 97x 5.3 with about 130k miles on it. When im accelerating light to mederate i get a "bucking" condition (like a jerking almost like a misfire) but it only happens for a second or less. This may happen several times a drive, its sporadic as far as i can tell there is no particular speed or rpm it happens. I just replaced the tcase due to it being stuck in awd and it banging and cracking and the problem is still there. I have no codes anywhere in the engine or trans, bucking is still there if im lightly on the brake and i dont see anything out of wack in the data. One thing i have noticed is that when the bucking happens the speedo jumps up a mile or two per hour example - if im accelerating it will buck once or twice at say 50 mph, the seedo stays at 50 until the bucking is gone (maybe a second) and then jumps to 51 or 52 and smoothly reads accurate again.

Tonight i pulled the 30 amp atc fuse and the bucking is gone, put it back in and its back but no tccm codes

Im lost, any help would be greatly appreciated
 
Welcome to GMT Nation...

This reads to me as being symptomatic of something like "Mouse or Rat Depredation of Automotive Wiring". However... I am also using Nomic's FREE AI Chat-Bot called *GPT4ALL* here to consider what you wrote in your First Post. THIS is what *IT* thinks might be involved:

Your First Post (as a Prompt)

TCCMTROUBLESHOOTING1.jpg

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TCCMTROUBLESHOOTING2.jpg

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Bonus: "How To Read TCCM Trouble Codes"

How To Guide: Reading TCCM Codes

Last year I spent a lot of time trying to pull TCCM codes from an 02 trailblazer. At the end I was able to access them manually via the command line. Below is the writeup on it. Hopefully this helps some folks diagnose their own 4WD issues :) There is a lot of info below, if you are looking...
gmtnation.com gmtnation.com
 
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Maybe i was trying to be to descriptive, essentially i have a jerking or bucking when accelerating, i believe it to be from the transfercase as when i pull the atc fuse the problem goes away
 
Of course... but the conditions under which these jerking events occur....can often describe a Broken Harness Wire occasionally separating and then making contact...so as a clue in this regard... examining ALL of the TCCM Wiring AND the Connector under the vehicle...might reveal a corroded green sign of the break... or a loosened connector.
 
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Just so I understand what you're experiencing, you're cruising along and when you lightly push on the pedal to accelerate just a little, you get that bucking/jerking? If that's the case, it's you're Torque Converter Clutch (TCC). When accelerating without disengaging the TCC, it loses its grip and slips until you press on the pedal a bit more to make it disengage.

I would change the tranny filter and fluid and see if that helps. I would also add one of these. If it still does it or has improved but not eliminated, add a second one.


Mine did that and one tube fixed it.
 
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Mooseman said:
Just so I understand what you're experiencing, you're cruising along and when you lightly push on the pedal to accelerate just a little, you get that bucking/jerking? If that's the case, it's you're Torque Converter Clutch (TCC). When accelerating without disengaging the TCC, it loses its grip and slips until you press on the pedal a bit more to make it disengage.

I would change the tranny filter and fluid and see if that helps. I would also add one of these. If it still does it or has improved but not eliminated, add a second one.


Mine did that and one tube fixed it.
Click to expand...
No its really any time at all when im accelerating, ive tried driving with my foot lightly on the brake and it still does it. With the atc fuse pulled it does not do it. Im leaning torwards tccm or wiring at this point unless im missing something
 
I wonder if there is a problem with one of the speed sensors on the transfer case. Or the front differential is not spinning the front driveshaft at the proper speed with the wheels. When you turn sharply on asphalt and move forward, does the truck crow hop?
 
Mooseman said:
I wonder if there is a problem with one of the speed sensors on the transfer case. Or the front differential is not spinning the front driveshaft at the proper speed with the wheels. When you turn sharply on asphalt and move forward, does the truck crow hop?
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No there is no hopping, all four wheel speed sensors are reading correctly. I notitced that the pwm slip adapt was all over the place last night from -16% to 70%, all while driving on smooth dry road. My tcase also seems to stay locked or engaged, im not sure if that is propper operation or not
 
There are two other speed sensors on the transfer case for the front and rear driveshafts which are used by the TCCM to know if it needs to engage the front wheels.

So at least the transfer case is not stuck locked since you're not getting the crow hopping while turning but maybe it's engaging the front wheels while driving. Since it stops when you pull the ATC fuse, I think the transfer case is engaging the front wheels. This could be possible if you have mismatched tires front and rear if there is a difference in diameter. It would think that the rear wheels are slipping and engage the fronts if the fronts are turning a little faster. If there is a difference in tire diameters, this would also create a sort of crow hopping driving straight ahead with the fronts engaged.
 
Mooseman said:
There are two other speed sensors on the transfer case for the front and rear driveshafts which are used by the TCCM to know if it needs to engage the front wheels.

So at least the transfer case is not stuck locked since you're not getting the crow hopping while turning but maybe it's engaging the front wheels while driving. Since it stops when you pull the ATC fuse, I think the transfer case is engaging the front wheels. This could be possible if you have mismatched tires front and rear if there is a difference in diameter. It would think that the rear wheels are slipping and engage the fronts if the fronts are turning a little faster. If there is a difference in tire diameters, this would also create a sort of crow hopping driving straight ahead with the fronts engaged.
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The tires are pretty evenly matched, the used tcase came with sensors and i just left those in and the problem remains. The tires are pretty closely matched but i suppose i could try to measure them. Im heading to the junk yard shortly to see if i can find a tccm and at the least rule it out.
 
It is also possible that the connectors for the two sensors were switched and that is throwing things off. Try unplugging the rear sensor. If the speedo stays at 0 and the transmission won't shift, then that is correct. If it still shifts normally, then it's picking up the speed from the front sensor. In that case, swap the connectors. It can happen, I've seen it before but not on an AWD like this one.
 
Mooseman said:
It is also possible that the connectors for the two sensors were switched and that is throwing things off. Try unplugging the rear sensor. If the speedo stays at 0 and the transmission won't shift, then that is correct. If it still shifts normally, then it's picking up the speed from the front sensor. In that case, swap the connectors. It can happen, I've seen it before but not on an AWD like this one.
Click to expand...
Im going to try to get it up in the air today, i will check the sensor placement, i did find a tccm from an 08 97x at the junkyard, was only $20, worth it to rule it out, if thats not it i have a spare.
 
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trandy45 said:
Im going to try to get it up in the air today, i will check the sensor placement, i did find a tccm from an 08 97x at the junkyard, was only $20, worth it to rule it out, if thats not it i have a spare.
Click to expand...
Just an update, i never got around to swapping the tccm or anything else but the problem is about 98% gone the last few days, ive only noticed it less than a handfull of times in 3-4 days
 
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