shudder while cruising
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Joined: Apr 2012
Posts: 87
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From: Midway Ga
shudder while cruising
I have been experiencing some shuddering while cruising in my 92 lt1 automatic. It only happens within a narrow rpm range for example when Im cruising @75 mph and I give it a little throttle it will shudder at @2400 rpm at @55 it will shudder @1800 rpm. I replaced the plugs and wires several weeks ago thinking that I may have had an issue with old wires or plugs but it made no difference except for a smoother idle. Normal accel or hard accel seem fine. I have a feeling that it may be tranny related and not the engine. The trans fluid is red and clear but was high up on the dipstick when I checked it right after a 30 mile run. I'll recheck it tomorrow after it has cooled down.The car has 80500 mi
Anyone here had any experience with this issue.
Thanks
Anyone here had any experience with this issue.
Thanks
Safety Car
Joined: Aug 2009
Posts: 3,752
Likes: 276
From: Melbourne, Victoria, Australia
I have been experiencing some shuddering while cruising in my 92 lt1 automatic. It only happens within a narrow rpm range for example when Im cruising @75 mph and I give it a little throttle it will shudder at @2400 rpm at @55 it will shudder @1800 rpm. I replaced the plugs and wires several weeks ago thinking that I may have had an issue with old wires or plugs but it made no difference except for a smoother idle. Normal accel or hard accel seem fine. I have a feeling that it may be tranny related and not the engine. The trans fluid is red and clear but was high up on the dipstick when I checked it right after a 30 mile run. I'll recheck it tomorrow after it has cooled down.The car has 80500 mi
Anyone here had any experience with this issue.
Thanks
Anyone here had any experience with this issue.
Thanks
As 383vett said perhaps your torque converter lock up may be the culprit, if your trans fluid is still bright red perhaps get it serviced, they can check the converter lock up solenoid/wireing while they replace the trans filter and replace the fluid.
Good luck
Thread Starter
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Joined: Apr 2012
Posts: 87
Likes: 16
From: Midway Ga
I pulled the fluid down to the cold level last night and did another run but no change in performance.
The fluid is red&clear when blotted on a white paper towel with a very slight grayish tinge around the edge of the blot
I read through the FSM section for the auto trans symptons and diagnosis and also made a call to an old childhood friend who is in the trans business up in ATL.
The fluid is red&clear when blotted on a white paper towel with a very slight grayish tinge around the edge of the blot
I read through the FSM section for the auto trans symptons and diagnosis and also made a call to an old childhood friend who is in the trans business up in ATL.
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Joined: Apr 2003
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From: moraga ca
I pulled the fluid down to the cold level last night and did another run but no change in performance.
The fluid is red&clear when blotted on a white paper towel with a very slight grayish tinge around the edge of the blot
I read through the FSM section for the auto trans symptons and diagnosis and also made a call to an old childhood friend who is in the trans business up in ATL.
The fluid is red&clear when blotted on a white paper towel with a very slight grayish tinge around the edge of the blot
I read through the FSM section for the auto trans symptons and diagnosis and also made a call to an old childhood friend who is in the trans business up in ATL.
Last edited by 383vett; Mar 5, 2013 at 10:27 PM.
Racer
Joined: Sep 2010
Posts: 325
Likes: 8
From: Princeton Jct. New Jersey
I had similar symptoms when I was getting my '84 running again but the problem turned out to be a low fluid level, not high fluid. I added over 2 qts. and the shuddering was gone. Since you have checked the levels this probably isn't the cause, but low fluid pressure due to a failing pump or valving might be. In my case the pump was starved and not able to deliver high, constant pressure when accelerating, hence the TC disengaged/slipped intermitantly.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
I had similar symptoms when I was getting my '84 running again but the problem turned out to be a low fluid level, not high fluid. I added over 2 qts. and the shuddering was gone. Since you have checked the levels this probably isn't the cause, but low fluid pressure due to a failing pump or valving might be. In my case the pump was starved and not able to deliver high, constant pressure when accelerating, hence the TC disengaged/slipped intermitantly.
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Joined: Apr 2011
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Check the TCC plug on the tranny...
take a drive and see if the symptoms are exactly the same if you drive for an extended amount of time in 3rd, as it behaves if driving in OD all the time.
The stick position dictates to the ECM how or when the TCC operates. In 3rd it will lock in early to act like a direct drive or manual trans. This is for enhanced fuel economy and performance. But if the stick is left in 4th all the time, traffic and hiway, the TCC is less aggressive and behaves more like a typical auto trans with a lock-up thats a little softer and higher up IIRC. If the TCC plug or switch is faulty or loose it can do weird things like this. The shudder can also come from engine stumble, clogged cats, poor fuel inj performance, low fuel pressure. Immediate response slowly goes away as the engine ages...but its not mechanical as much as it IS bad data or sensor input from not being used much.
Re-reading your post, it also sounds like timing could be retarded...not enough advance for the engine to want to accellerate.
take a drive and see if the symptoms are exactly the same if you drive for an extended amount of time in 3rd, as it behaves if driving in OD all the time.
The stick position dictates to the ECM how or when the TCC operates. In 3rd it will lock in early to act like a direct drive or manual trans. This is for enhanced fuel economy and performance. But if the stick is left in 4th all the time, traffic and hiway, the TCC is less aggressive and behaves more like a typical auto trans with a lock-up thats a little softer and higher up IIRC. If the TCC plug or switch is faulty or loose it can do weird things like this. The shudder can also come from engine stumble, clogged cats, poor fuel inj performance, low fuel pressure. Immediate response slowly goes away as the engine ages...but its not mechanical as much as it IS bad data or sensor input from not being used much.
Re-reading your post, it also sounds like timing could be retarded...not enough advance for the engine to want to accellerate.
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Joined: Apr 2012
Posts: 87
Likes: 16
From: Midway Ga
I talked to my old friend today who has been doing trans work for the last 25+ yrs and I must admit that I felt kind of awkward since I haven't talked to him in several yrs and out of the blue I call him to ask him tranny ?s so we did some catching up before I hit him up with the Q&A session. I'd also like to add that he still has the 92 LT1 that he won from the 96 rock radio station in Atl , so he's no stranger to Vette's either.
He told me to do a fluid/filter change and try a product called lube guard and see if that cures the problem and said that the 4L60 is a very reliable trans.
If I wasn't so far from the Atl(@6hrs) I would just take it to him and my Snap on dealer gave me some good info on some reputable trans shops in the Savannah area.
I appreciate all the feedback from you all and really glad that my post got such a great response.
Steve
He told me to do a fluid/filter change and try a product called lube guard and see if that cures the problem and said that the 4L60 is a very reliable trans.
If I wasn't so far from the Atl(@6hrs) I would just take it to him and my Snap on dealer gave me some good info on some reputable trans shops in the Savannah area.
I appreciate all the feedback from you all and really glad that my post got such a great response.
Steve