What causes SHUDDERING at 35-40mph (3rd gear) - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-07-2005, 05:06 AM   #1
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Default What causes SHUDDERING at 35-40mph (3rd gear)

I have read a lot of posts about these trannies shuddering or shaking at low rpm with minor torque being applied

It seems to be getting worse on my 94.

When driving at 32-40mph area it is quite easy to feel. It is almost like I am hitting little bumps in the road. It is a minor jerk/shudder/shake that comes and goes, but only when the gas is depressed. When you take your foot off the gas or give it more the problem goes away.


It is ONLY in 3rd gear that I can tell. In OD and other gears I cannot feel any sort of shudder or shake.




I am wondering what causes this problem and what it means for the life of my transmission.
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Old 04-07-2005, 09:31 AM   #2
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Mine does this SOME TIMES around 50 or so MPH like when the TC is trying to engage.
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Old 04-07-2005, 01:14 PM   #3
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This is the reason I had to dump my 1992 leSabre FAST. What had happened in my case, the flexplate in the tranny had warped slightly, so at highway speeds (any consistant speed over 50 actually) It would start to sudder and do exactly what you are describing, except it was very severe and sounded like I was driving over those stop-sign warning ribbs. If I gave it any more gas, it'd stop, if I let off, it'd stop. It was only at consistent speed. Otherwise the tranny was fine, shifted and whatever, the only fix was a rebuild, so instead I sold it. The guy who came to look at it bought it on sight...started it, comment how nice the leather was, liked the dual climate control and keyless entry, so he didnt even drive it out of the driveway, just told me he'd take it. Whatever....he still drives it to this day, I see it all over (we lived in the same building) but I dont know if he rebuilt the tranny or just left it, or if he even ever noticed.

I'd just take the car into a tranny shop and have them give you an estimate, thats what we did, it was free so nothing to lose I guess.
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Old 04-07-2005, 01:54 PM   #4
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http://www.bonnevilleclub.com/forum/...8351&start=120

Read some of my comments on the last page of this thread. I'm 99.9% sure that the shuddering in my case is COMPLETELY induced by heat. Don't ask me why it never did it before, but I know that when my tranny gets hot it starts surging. When it cools down again, the surging goes away. I just ordered a Haynes tranny cooler rated at 22,000 GVW that I'm installing ASAP.
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Old 04-07-2005, 02:04 PM   #5
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Quote:
Originally Posted by STAGED
Tried ignition fixes and trans flush simultaneously. No help. Also if there'* an ignition miss while the TC is engaged you wouldn't see a 200-500 rpm jump. An ignition related chuggle at highway speed with 4th gear/TC engaged can be felt but won't be seen on the tach. A 500 rpm jump corresponds to a large speed difference on the tall geared Bonneville. A 200-500 rpm fluctation caused by ignition issues would correspond to huge speed differences to cause whiplash or seat belt bruise marks.

If there'* a chuggle and no big rpm jump it'* ignition or other stuff.

If you feel a surge/chuggle and you see a 200-500 rpm difference, it'* the transmission TC unlocking/locking.

A local trans guy explained that these higher mileage 4T60-Es have some added clearances between the accumulator and accumulator bore. On hot days, there'* some leakage between the bore and accumulator causing the TC to lock/unlock. Does this make any sense? I don't know transmissions to know. This explains why it happens on older transmissions and it explains why some after fluid changes/flushs notice some improvement due to different fluid properties of fresh fluid although I didn't notice any difference.

I am contemplating rebuilding the valvebody. But interestingly after fall of 2004, it has never done it again. Anybody notice such intermittency?
I like what this guy wrote. This comes from the link I gave you in my previous post. It seems like this would underscore the need for auxilliary cooling with the 4T60.
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Old 04-08-2005, 12:40 AM   #6
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The problem exists only at city speeds from 32 to maybe 40 or so. After that I do not notice it.

On the highway it is smooth as can be.


It is only in very low RPMs in 3rd gear.


Most cars with the 4t60 based trans did this to some latitude as well.



Imagine this drive down a city road and keep constant pressure on the gas maintain 37 or 38 and see if you notice any studder......
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Old 04-08-2005, 04:04 AM   #7
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Could it be the tranny retains more heat with TCC locked up at lower speeds? Less wind through the radiator to dissipate the high temps? Just an idea, I could be way off. I have to wonder if a tranny cooler would help you out. I'm really confident that it will solve my problems, but your case seems weird. Maybe it'* a totally different issue than mine. Sorry I couldn't be of more help.
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Old 04-08-2005, 11:04 AM   #8
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Default shudder

I too had this shudder only when the car was under load 45-50 mph.
When I tweaked the TPS voltage to the center of the book spec. it corrected this.
Must have been something timing related.
My RPMs did not jump when it did this. I also have a tranny cooler but have not changed the fluid yet as I was told it was done at 60k.
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Old 04-08-2005, 01:05 PM   #9
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Hans, I'm placing my bet on something the GM Shop Manuals call "Chuggle." -can be caused by several things,,,

I had experienced the exact same thing years ago on my '87 Olds 88, w/3800, and again on a '93 LaSabre w/3800. For me, the symptoms were what felt like intermittent engine misfire, and it only occured at fairly light to moderate throttle positions. -either press the gas down further, or let up more, and the problem wasn't there. -but a "medium" throttle at about 40 mph in 3rd gear it would do it.

What solved the problem on one car was simply a new set of spark plugs, and on the other I replaced both plugs and plug wires. -problem solved.

Anyway, plugs and wires would be a fairly inexpensive maintenance item, and just may solve your problem.
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Old 04-08-2005, 01:38 PM   #10
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Quote:
Originally Posted by 57chevythunder
Hans, I'm placing my bet on something the GM Shop Manuals call "Chuggle." -can be caused by several things,,,

I had experienced the exact same thing years ago on my '87 Olds 88, w/3800, and again on a '93 LaSabre w/3800. For me, the symptoms were what felt like intermittent engine misfire, and it only occured at fairly light to moderate throttle positions. -either press the gas down further, or let up more, and the problem wasn't there. -but a "medium" throttle at about 40 mph in 3rd gear it would do it.

What solved the problem on one car was simply a new set of spark plugs, and on the other I replaced both plugs and plug wires. -problem solved.

Anyway, plugs and wires would be a fairly inexpensive maintenance item, and just may solve your problem.
Yup there is a TSB on this. GM suggests to change the MEMCal to raise the shift points. I have this problem with my car......its been doing this for a while, with no ill effects
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