Our 2008 Denali is experiencing what I believe to be torque converter trouble. Most of the time I notice it when cruising in the 35-40mph range at low rpm (1300 or so rpm) – when you encounter a slight incline it will shudder so bad that it feels like you are driving over rumble strips. As soon as you increase throttle and/or it down shifts - it immediately goes away. I also can sometimes get it to do it at freeway speeds if the conditions are right. (slight incline, not enough to downshift, and light throttle. I did add some lubegard which seemed to help for a couple weeks but didn’t last. It also seems to do it more often when the summer temps are highest with the ac on. The truck just rolled 100k. The fluid is clean and bright red (serviced at 80k) The trans never hunts for a gear. Never slips and otherwise acts totally fine. I’m hoping there is a simpler fix than a full rebuild. I know on the 4L60’s they sell an upgraded tcc valve kit. I have not found anything similar for my 6l80e. Any thoughts on where to start??
2008 Denali tourqe Converter Shudder
- Thread starter pjw67
- Start date
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retiredsparky
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A couple of thoughts: you are describing a situation where the engine is slightly lugging when the crank/flex plate is working against increased torque load until the tranny shifts to a lower gear.
1) Crankshaft dampener starting to de-laminate (watch lower pulley at idle, in gear for wobbling)
2) Flex plate starting to crack
3) Torque convertor clutch/intake shaft bearing in tranny
4) Tranny bearing problems
5) Worn crank bearings (any obvious leaks from front or rear main?)
6) Injection related problems (engine loads, but fuel mapping cannot keep up, causing lugging of engine)
7) Unlikely, but theoretically possible: main bearings not getting enough oil and binding
Because the AC seems to factor in, I'm leaning toward #1 or #6, because of additional stress on engine, but neither implicates the tranny.
1) Crankshaft dampener starting to de-laminate (watch lower pulley at idle, in gear for wobbling)
2) Flex plate starting to crack
3) Torque convertor clutch/intake shaft bearing in tranny
4) Tranny bearing problems
5) Worn crank bearings (any obvious leaks from front or rear main?)
6) Injection related problems (engine loads, but fuel mapping cannot keep up, causing lugging of engine)
7) Unlikely, but theoretically possible: main bearings not getting enough oil and binding
Because the AC seems to factor in, I'm leaning toward #1 or #6, because of additional stress on engine, but neither implicates the tranny.
retiredsparky
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Have you checked air filter, spark plugs for maintenance? How about a dirty intake (MAF)
Hi guys,
Thanks for replies. Retired sparkys explanation is exactly correct. "a situation where the engine is slightly lugging when the crank/flex plate is working against increased torque load until the tranny shifts to a lower gear."
Some more information - I have recently replaced plugs/wires(ac delco factory replacements), fuel filter, air filter and cleaned the maf with proper spray. None of these have made any changes in drive-ability.
To address 1-4.
I will look into the damper and see if I can inspect the flexplate. Do you think if either one of these was problem that I would experience the shake in different situations?. Same with bearings?
5)
I cant check these but have good oil pressure and no leaks.
6)"Injection related problems "
I could see this being possibility. Need to have a good mechanic do a scan that can look into this. I did take the truck in once for a diagnostic and they said they couldn't get it to shake. They said no codes....blah blah.
7)"Because the AC seems to factor in, I'm leaning toward #1 or #6, because of additional stress on engine, but neither implicates the tranny."
My only thought on this is that we only run the ac when it hot outside which raises the tranny fluid temps and theoretically thins the fluid. In which case if a seal in the torque converter circuit is on it way out could cause something.
Thanks for replies. Retired sparkys explanation is exactly correct. "a situation where the engine is slightly lugging when the crank/flex plate is working against increased torque load until the tranny shifts to a lower gear."
Some more information - I have recently replaced plugs/wires(ac delco factory replacements), fuel filter, air filter and cleaned the maf with proper spray. None of these have made any changes in drive-ability.
To address 1-4.
I will look into the damper and see if I can inspect the flexplate. Do you think if either one of these was problem that I would experience the shake in different situations?. Same with bearings?
5)
I cant check these but have good oil pressure and no leaks.
6)"Injection related problems "
I could see this being possibility. Need to have a good mechanic do a scan that can look into this. I did take the truck in once for a diagnostic and they said they couldn't get it to shake. They said no codes....blah blah.
7)"Because the AC seems to factor in, I'm leaning toward #1 or #6, because of additional stress on engine, but neither implicates the tranny."
My only thought on this is that we only run the ac when it hot outside which raises the tranny fluid temps and theoretically thins the fluid. In which case if a seal in the torque converter circuit is on it way out could cause something.
Last edited:
Update
I checked the balancer while running - it looked smooth. Next took the maf out to clean it again. I noticed it was clean but that two of the three little bars with the resistors? on them were black. Almost burnt looking. Must not have noticed when I last cleaned it. Found a new ACDelco MAF on ebay for $25 shipped and figured why not. Since the install I have not been able to get the shudder. Im not 100% convinced as its only been 4days but it behaves totally in the low rpms. Much less throttle response needed to get going. I will let you know if anything changes. Thanks!
I checked the balancer while running - it looked smooth. Next took the maf out to clean it again. I noticed it was clean but that two of the three little bars with the resistors? on them were black. Almost burnt looking. Must not have noticed when I last cleaned it. Found a new ACDelco MAF on ebay for $25 shipped and figured why not. Since the install I have not been able to get the shudder. Im not 100% convinced as its only been 4days but it behaves totally in the low rpms. Much less throttle response needed to get going. I will let you know if anything changes. Thanks!
TheLoveClaw
TYF Newbie
Sorry to re-open an old post, but what you are explaining is exactly what's happening to my wife's 2010 Yukon. Transmission fluid looks amazing, and temps always remain low. Shifting is quick and smooth. Took it in to the dealer and they said I needed an alignment and new tires. There was feathering on the front tires and the alignment was off. Needless to say that didn't fix the problem. I regularly clean the MAF with every oil change and in fact just did that yesterday.
I would assume that because you haven't provided an update that the MAF solved the problem. The wife isn't too happy with all the small things that we have to keep replacing so I just wanted to check and see if the problem came back or if a new MAF fixed it. I would love for it to be something that simple.
Thanks for your time.
I would assume that because you haven't provided an update that the MAF solved the problem. The wife isn't too happy with all the small things that we have to keep replacing so I just wanted to check and see if the problem came back or if a new MAF fixed it. I would love for it to be something that simple.
Thanks for your time.
I never did a follow up. My Maf replacement only fixed/masked it for a month or two. It came right back and comes and goes. I have cleaned the new MAF with no results. The weather was in the 60's this weekend. No AC on - and it was doing it on every little incline with light throttle input. The vibration/shudder is very slight and might not even be noticed by someone else. My wife doesn't notice it. It bothers me because I know something is wrong. At this point Im just going to let it go until something gets worse.
TheLoveClaw
TYF Newbie
Well I'll let you know what we find out. I don't feel comfortable towing my camper with it acting like this. We also have a trip to the Grand Canyon this summer that I don't want to be left stranded on.
How's your gas mileage? Ours is getting really bad. About 12 to 13 in the city and with 3/4 of a tank we averaged only 14mpg on a 120 mile highway trip. Granted we're in Colorado but it's usually around 19 to 20 on the highway.
How's your gas mileage? Ours is getting really bad. About 12 to 13 in the city and with 3/4 of a tank we averaged only 14mpg on a 120 mile highway trip. Granted we're in Colorado but it's usually around 19 to 20 on the highway.
TheLoveClaw
TYF Newbie
We were getting 15 to 15.5. We went from an Acadia to this and my wife was a little worried at first that the gas was going to be way worse. The Acadia actually got 15 in the city so we were quite impressed.
