Heavy vibration when accellerating slowly

[chengny]

http://www.gmsquarebody.com/threads/rattle-in-oil-pan-below-700rpms.19010/

The ratlle was solved half way the thread. After that he developped a vibration very like mine.

I am assuming that you eliminated all the basics - as the cause of your vibration - before jumping straight to the TCC. Right? For example:

1. Motor and transmission mounts in good shape

2. U-joints tight and correctly phased

3. Wheels and tires are properly balanced and rotors are true

4. Drive shaft true and balanced

5. Front end suspension/steering components tight and properly adjusted

 

[Camatruder]

First off, thanks for the very great info on the previous post. i will print these schemas as i can read it better that way. Thanks ! It will be clear how to perform the test you proposed.
The truck has had this issue ever since i bought it a couple of years ago but untill 3 months ago it was a hobby truck and almost never saw highways. Now it has become my daily driver and she's on the highway 5 times a week. In the last year i changed motor and tranny mounts, u-joints and rotors. I had the tires balanced and the steering aligned. I have no obvious reason to think the drive shaft is out of balance but if nothing comes up i'll bring to a shop. As mentioned earlier all suspension bushing and front stabilier bar bushing are very worn and will be replaced at the end of the year.


As i mentioned in post 10, i'm now more leaning more to the idea that accelerating in lock up is only exposing an other issue more violent.

 

[chengny]

First off, thanks for the very great info on the previous post. i will print these schemas as i can read it better that way. Thanks ! It will be clear how to perform the test you proposed.
The truck has had this issue ever since i bought it a couple of years ago but untill 3 months ago it was a hobby truck and almost never saw highways. Now it has become my daily driver and she's on the highway 5 times a week. In the last year i changed motor and tranny mounts, u-joints and rotors. I had the tires balanced and the steering aligned. I have no obvious reason to think the drive shaft is out of balance but if nothing comes up i'll bring to a shop. As mentioned earlier all suspension bushing and front stabilier bar bushing are very worn and will be replaced at the end of the year.


As i mentioned in post 10, i'm now more leaning more to the idea that accelerating in lock up is only exposing an other issue more violent.

Wait a minute, don't print them yet - unless you want to. I meant to attach bigger, more legible versions of them...but I spaced it. Here, try these:

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[chengny]

And the rest:

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[chengny]

Oh yeah, and to answer your question about test driving with the TCC manually engaged: I can't think of anything to be concerned about. When you think about it, doing that is essentially the same as releasing the clutch on a manual transmission. If folks can remember to disengage the clutch when coming to a stop, I'm sure they can handle flipping a switch.

 

[kenny78]

On locking out the Tcc, it will build more heat but not a problem for testing. A trans expert should be consulted but I doubt it would measurably decrease trans life even if left off indefinitely. Fuel mileage will suffer some.

 

[Camatruder]

@chengny

If you’re ever visiting Belgium, i’m gonna buy you a couple of bears, that’s for sure !

English is not my natural language, so i did not understand the concept ‘hot wiring’ fully, In my twisted mind that meant someting completely different . So now i do and i will test it that way. However if the problem remains, nothing is gained. It still can be the solenoid, the check ball mechanism or another not related problem that only gets more noticeable. If i could do the test with the rear axle on jack stands (so there is almost no load to the engine and driveline) that would be better but i’m not sure that’s a safe thing to do. Would the VSS work that way?

I’ll perform the test in the flowchart first with a helper driving on the highway.


Going through the schema on top of page 10-4 i notice the TCC is not vacuum controlled and also that whenever you’re in 4th gear with engine temp above 149°F and not touching the brake pedal, the TCC is always on (4th gear oil pressure switch is grounded in tranny).

 

[Camatruder]

Ok, i did all tests i could and found nothing wrong. The resistance of the solenoid is 30 ohm (must be more than 20). The current through it when it's on is 0,4 A. All tests of the flowchart were good meaning the solenoid comes on when it should and the 4th gear switch works as it should. All these measurements stay the same when the vibration is present.
I hot wired the solenoid like Chengnie suggested but i can still trigger the vibration.
So i think it's safe to say the TCC lock up system is not at fault but slowly accelerating in 4th gear with the TCC engaged exposes another not related problem more definite.
i'll be changing those worn bushings as soon as possible and may be taking my drive shaft to a balance shop. Other than that i have no clue.
Flexplate? Harmonic balancer? Diff ?

 

[Camatruder]

Since this thread hasn’t been updated for a while I recapliate in short. I have a very sudden speed related heavy and fast vibration (like driving over a washboard) when pulling up gently with the TC locked up in such a manner that it stays locked up. This happens always at the same speeds : 65 and 75 mph. Playing with the gaspedal or brakes so the TC clutch disengages immediately solves the problem. Driving at any constant speed, pulling up aggressively or driving with the lockup connector not attached never gives problems.

Tires are balanced and good. Lock up system in the tranny works as it should (see previous replies). There seems to be no shop in Belgium that can check the balance of my drive shaft, they all need flenses at both sides of the shaft.

Anyway since this only occurs with the lockup engaged, the TC clutch is probably the culprit. Is that something that can be repaired or do I have to replace the hole unit? Should i replace the flexplate while I’m in there or is that a ‘don’t fix if it ain’t broken’ thing?

I know spall speed is the rpm on which something behind the TC has to move even when applying the brakes. I understand that can be important when doing power take offs , but it doesn’t mean the car won’t move at lower rpm when nothing is blocking it. So how important is stall speed for a daily driver that is not doing off road or burn outs and stuff.

The Monster Transmissions B29DLLF heavy duty torque converter with a stall of 1650 seems a good deal at 175 USD. Any other suggestions. Since I’m overseas and this is my daily driver I cannot remove the drivetrain in advance but the 30 splines will be the right one for my stock 1991 K5, right?

Still, i hate throwing money at it if i'm not sure it's gonna solve the issue. Is there any way i can confirm the TC clutch is the culpritt before removal and order?

Thanks.

 

[Honky Kong jr]

From what I've read and heard I'd stay away from anything Monster.

 

[74 Shortbed]

From what I've read and heard I'd stay away from anything Monster.

X1000....

 

[Azathoth]

Just found this thread. I had exactly the same problem with my 700r4 for about 3 months before it grenaded. The trans shop guy said it was the lock up clutches letting go.

 

[yevgenievich]

Shudder like that usually indicates failing tcc. Likely need to replace the torque converter

 

[chengny]

Since this thread hasn’t been updated for a while I recapliate in short. I have a very sudden speed related heavy and fast vibration (like driving over a washboard) when pulling up gently with the TC locked up in such a manner that it stays locked up. This happens always at the same speeds : 65 and 75 mph. Playing with the gaspedal or brakes so the TC clutch disengages immediately solves the problem. Driving at any constant speed, pulling up aggressively or driving with the lockup connector not attached never gives problems.


Anyway since this only occurs with the lockup engaged, the TC clutch is probably the culprit. Is that something that can be repaired or do I have to replace the hole unit? Should i replace the flexplate while I’m in there or is that a ‘don’t fix if it ain’t broken’ thing?

Still, i hate throwing money at it if i'm not sure it's gonna solve the issue. Is there any way i can confirm the TC clutch is the culpritt before removal and order?

Thanks.

Before you commit to a new TCC (and the associated labor costs to change it), be sure to first change your transmission fluid/filter and then get your line pressure checked - that check should be week one stuff for any competent mechanic:

Oil pressure can be checked with the transmission in the vehicle, using a 0 to 300 psi pressure gauge.

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1. Clean dirt from line pressure plug, located on left side of transmission case, and remove plug.

1. Connect pressure gauge hose fitting at pressure plug bore in case and place gauge in vehicle so it can be seen from the driver's seat.

1. Drive vehicle until transmission fluid has reached operating temperature.

1. Check and correct fluid level.

1. Road test car and check pressure as follows:

Engine Idle Pressure Check
With selector lever in Direct Drive position, operate vehicle at approximately 30 mph with throttle closed. Line pressure should be 70 psi. When a selector lever has been moved to Intermediate range with vehicle operating at a stead road load (25mph), line pressure should e 150 psi (plus or minus 5 psi).

Pull Throttle Pressure Check
With vehicle on jackstands, disconnect vacuum line from carburetor and place selector lever in Neutral and in Reverse. Operate engine at fast idle (700-1000 RPM) in each position. Neutral pressure should be 145 psi, and Reverse pressure 230 psi. Connect vacuum line.

If either pressure check was low, check vacuum modulator for loose attaching bolt, collapsed bellows, or stuck modulator valve. Also check pressure regulator valve and spring for sticking, plugged orifice, or collapsed spring. Check regulator boost valve for sticking.

If either pressure check was too high, check vacuum line and vacuum modulator for leaks or sticking valve. Also check pressure regulator valve and boost valve for sticking.


A couple of relevant items:




30 Common 4L60E Transmission Problems & Repair

25. Torque converter shudder in 4th while lockup is engaged; problem goes away when the brake pedal is pressed slightly to unlock converter: Need to verify line pressure, and provided no valves in the TCC (Torque Converter Clutch) hydraulic circuit are worn, replace the torque converter.


Transmission shudder is a recurrent problem that afflicts millions of vehicles nationwide. But while the issue is common, its causes are not always easy to find. Here’s a look at how to troubleshoot this frequent complaint.

What Is Transmission Shudder?

Drivers usually notice transmission shudder when they are driving between 40-60 mph. They feel the vehicle begin to shake, as if they just drove over a rough patch of road. The sensation lasts for 3-4 seconds, then everything returns to normal – for the time being.

The cause may seem clear: transmission issues caused by failing fluid or a slipping torque converter clutch (TCC). But is this necessarily the case? Here’s a step-by-step process for getting to the root of the problem.

• Check trouble codes, as the vehicle’s computer may tell you all you need to know about what’s causing the shudder. It may also reveal other issues with the automobile. In either case, it’s important to fix all trouble codes before proceeding further.

• Use your shop scanner to monitor the vehicle when the shudder occurs. Note whether or not the TCC slips at the same time. If so, then you have located the problem. If not, then the issue may not be with the transmission at all, but with the engine. Common engine-related causes of shuddering include: misfiring plugs, a miscalibrated vehicle computer, and poor fuel intake. Monitor the engine during shuddering to detect these issues.

• If the TCC does slip during the shuddering, then it is almost certainly at fault. But, before you begin replacing parts, check online for any technical service bulletins (TSB) released by the manufacturer. This may point you to the real cause when nothing else will. For example, GM recently issued a TSB for it 6T70/75 unit, explaining that shuddering is often caused by poorly connected ignition ground coils. Only after checking for a TSB-related issue should you proceed to additional troubleshooting steps.

• Shuddering is often caused by a loss of transmission fluid pressure. Adjusting the EPC solenoid to increase this pressure may eliminate the shudder. If you suspect that the fluid is at the root of the problem, then flushing the system and adding new oil is the next step most shops take. But, before doing so, drop the pan and look for debris in the fluid. If you see this, or if you have other reasons to suspect worn components, then you will need to replace parts as necessary.

• There are additives that promise to “instantly fix” transmission shudder simply by adding them to the fluid. However, these compounds are, at best, only a temporary fix. Using them is like putting an adhesive bandage on a cut that needs stitches. A professional transmission technician should never rely on these products.

Transmission shudder is a common problem with many possible causes. It’s vital that the technician carefully troubleshoot the issue before attempting to resolve it. Taking the time to ensure that the root issue has been found will pay off in the long-term, both for the customer and for the shop’s reputation.

 

[chengny]

Torque converter shudder is usually caused when there is a buildup of contaminants in your automatic transmission fluid. This is the way it happens: let’s say there’s a buildup of deposits somewhere in the transmission that is freed up by the detergent properties of the automatic transmission fluid. And, let’s say further that the contaminants begin recirculating throughout your transmission as they are likely to be microscopic to small in size so they will easily get through things like the valve body and they will likely get by the filters because they are too small, at this point.

As time passes on and the contaminants continue to circulate they begin to fall out of the transmission fluid again, this time on other parts of the transmission, say a gear or a clutch pack or, perhaps, on an impeller turbo vane. Over time, other contaminants are attracted to the new buildup like metal is attracted to a magnet (look at the magnetized screw in your transmission pan for confirmation the next time you change fluid. If there are small shards on it, the plug is doing its job of taking metal out of the fluid and holding it safely out of the way).

Now, let’s say there’s enough contaminant buildup on one of the parts mentioned earlier, let’s further say, it’s an impeller vane, and so what happens when the buildup becomes large enough to effect the part? The part slips briefly causing a shudder through the whole transmission. It is easy to feel as the vibration goes through the entire structure of your car. (The reason this happens is the way cars are built today. Car frame members are attached to one another throughout the body of the vehicle. This increases tortional strength or resistance to breaking and shearing. It also increases intrusion protection. The downside is that if there’s a resonant vibration anywhere in the frame, it is felt in all parts of the frame equally.)

The funny thing about transmission shudder (torque converter shudder) is the quick nature of the whole thing. Usually, the buildup, when it reaches the stage where it can become a nuisance in the transmission, breaks down and goes away as quickly as it appears. It may take several driving cycles as the problem breaks down for it to go away fully, but it usually does. Note that this type of problem can happen anywhere in the transmission. Sometimes, buildups can become troublesome. In that case, you’ll have to employ a quick fix.

The fix is relatively easy. Swap the old transmission fluid and filter. (Don’t rely on a drainage and replacement; you will have to drop the transmission pan to get all of the automatic transmission fluid out as well as to access to filter). Then, replace it with fresh fluid and a fresh filter. If the problem repeats, repeat the process. Yes, it is costly in terms of transmission fluid and filters, but, think of it this way. By paying $30 to $50 for the proper fluid and another $35 for the filter, you are ultimately saving because, even if you invest $200 in new fluid and filters, you are saving yourself about $2,800 in major work to the transmission.

Here’s an important thing to note: while some authorities say it’s best to remove all the fluid by using a blast of compressed air on one side of the transmission and draining things off, it actually can cause damage. If a part is dislodged or a major clump of something breaks off and travels through your transmission along with the rest of the evacuating fluid, it may cause damage downstream. All it takes to remove the total amount of fluid is patience. First drain the fluid, let the vehicle rest as all of the fluid will drip down to the pan and second remove the pan over a bucket to keep the floor clean. That’s it and your transmission is safe.