Transmission shudders at 50mph

[willwren]

This Is most likely a problem with the torque converter and/or valve body.

Also, listen to the other advice in here and make sure all of your preventive maint. is done. You will be amazed how much they can restore a car.




Refer to the topic below for some help with TC problems



viewtopic.php?f=19&t=14338&start=0&hilit=1870

I disagree. The 4T60E transmission the topic author is talking about is not as prone to TC shudder issues as the 4T65E. His symptoms are typical of a misfire issue. 95% of all 'shudder in OD or lockup' issues on 4T60E transmissions are ignition related.

[blazerk5drew]

I think 95% would be a bit much to say. if the missfire is strong enough to cause shudder/surge symptoms. the SES light would immediatly flash. Granted a transmission problem will only be amplified by a missfire. The car must be tuned up and all p ms' done in order to complete this diagnosis. There are plenty problems with the 4t60 e valve body. and plenty with the 65' as you said.

please refer to this This TSB if a complete tuned up/coils, transmission goo or kicking and screaming does not change the problem: 87-71-75 (If you want i can send you it in an email) if you cant find it online.

[willwren]

95% isn't a bit much. I've been on this Forum for 8 years, and have watched hundreds of similar cases solved. A slight misfire is not enough to set off the SES, particularly on a 95 or older OBD1 PCM. And it's plenty to be most obvious at low RPM's under load (OD/Lockup). I have 3 cars with 4T60's and all have had these symptoms caused by mild misfires, as well as a good dozen others I've repaired myself, and hundreds I've seen here over the years.

95% is a fairly accurate number. Ignition misfires must be ruled out completely before further troubleshooting or guessing. And don't use any more "Mechanic in a can".

[blazerk5drew]

It was stated that adding transmission fluid changed the symptoms slightly. This, along with the speed noted caught my eye as something ive had to fix on two of my 4t60 transmissions. My bonneville even had a newer goodwrench transmission with all updates "supposedly" done. I really hope for the sake of this 95 and Humans pocket that it is not the transmission at all. I really wish there was a way I could share my database with you guys easier.

Get back to us Human

[enslow]

95% isn't a bit much. I've been on this Forum for 8 years, and have watched hundreds of similar cases solved. A slight misfire is not enough to set off the SES, particularly on a 95 or older OBD1 PCM. And it's plenty to be most obvious at low RPM's under load (OD/Lockup). I have 3 cars with 4T60's and all have had these symptoms caused by mild misfires, as well as a good dozen others I've repaired myself, and hundreds I've seen here over the years.

95% is a fairly accurate number. Ignition misfires must be ruled out completely before further troubleshooting or guessing. And don't use any more "Mechanic in a can".

Add me to your list. My shuddering was so bad I could hardly accelerate up a hill, yet I had no SES light. It seems the comptuer must catch consecutive misfires on one plug before setting a code. If 3 -4 plugs have weak connections to the wires, you can have lots of misfires but no codes.

However, after I took care of the ignition on my wifes car, I still had a rolling rpm at about 60-65 km/h under slight load. So even in the 4T60, the TCC can cause trouble. After I dropped the pan and changed the fluid and filter those symptoms went away.

I'm not sure if this is on the mark or not, but are TCC problems more likely to cause a rolling rpm under load in the 4t60?

[blazerk5drew]

In my olds 88 i originally started out with a rolling surging. after the transmission was rebuilt it then had a shudder. I went through the entire engine and ignition system trying (wishing) that it wasn't yet another transmission problem. turns out that the updates were never done to the valve body and it had to come back out and be fixed along with the brand new smoked converter. now that the updates are in the car the tcc applies much better than it ever did stock in either of my cars. I gotta say that even though i love these old tanks i dont quite get them sometimes. Working as a mechanic i would see some of these cars come in with 250,000 miles on all original drivertrain and a lead foot driver. Other days I would be installing a transmission on a 97 buick lesabre with 60,000 grandma miles. I cant complain i got one of those grandma olds 88s for 400 bucks with only 60k miles....and guess what it needed transmission work for the tcc. go figure another grandma car

[human]

I just got back from my little trip down to my parents'. The car did okay on the way down. It shuddered some, but not too bad. I drove around town down there today and the shuddering got progressively worse! The car felt like it was missing horribly when I was sitting at stoplights, and then would shudder and barely accelerate when the light turned green. At one point, I had the car revving at almost 4,000 rpm. and unable to get above 35 mph. Ironically through all of this, the "check engine" light never came on.

The drive home was a bit dicey to say the least. At times, it was all I could do to get the car up to 60 mph without the car feeling like it was going to shake itself apart. I kept the cruise control on as much as possible as it seemed to shudder less that way, but I eventually started downshifting to "D" whenever I went up a hill. Eventually, things smoothed out a bit and 45 minutes or so of the two-hour trip home, the car did okay as long as I didn't attempt any hard accelerations.

I truly don't believe Dr. Tranny did any good at all in this instance, but I'm not exactly surprised by that. 'Snake oil' doesn't make worn parts go away. Tomorrow afternoon, I'm going to install the new plugs and wires I bought Friday afternoon. I'm hoping that will help smooth out the apparent misfires, but I don't have any illusions about it helping the transmission issues. The thing that frustrates me is that had I known the car had these issues, I would never have bought it in the first place. I was trying to avoid dropping a couple thousand dollars--money that I did not have in the first place--to get a major oil leak fixed on my Cadillac. Now, it looks like I'll end up spending even more by acquiring and and having to fix this car.

[human]

The AC 41-606 spark plugs are basic, copper core plugs that are shown in NAPA's computer system as the stock OEM part for the car. I had already confirmed on their web site, as well as Advance Auto Parts' O'Reilly's, and AutoZone's, prior to going to the store, but I did not give the guy at the counter that information. I intentionally let him access it himself for additional confirmation. There were supposedly several higher performance alternatives available, but the guy at the counter said that if it were his car, he'd be inclined to go with what the factory put in, especially at that price. He had the perfect opportunity to 'up-sell' me into a more expensive alternative, including a set of AC "Rapidfire" plugs at almost three times the cost of what I bought, but he didn't even try to push anything but the basic AC's. We both agreed that if the car was engineered for those plugs, then they ought to be good enough.

I should add that I grew up in a GM family. My dad worked for GM for 32 years as a district sales manager for Oldsmobile and he has always been a firm believer in using the OEM parts whenever possible.

I didn't remove the strut tower bar to replace my plugs, I just reached back there blindly and did them. Somewhere there is a classic photo of Bill standing on his engine to get to the back plugs. (Anyone? Anyone?)

You said you got AC plugs for $1.97 each. That seems amazingly inexpensive to me, I'm wondering if the plugs you bought are going to be okay for your engine or not. Anyone else worried about this? There are many many plug threads on this forum. If you search, you'll find recommendations on which plugs to use and not use.

(I just wanted to raise a red flag on this before you install them; just get some confirmation here that the plugs you're going to put in are okay.)

[human]

I put the new plugs and wires in this afternoon. It wasn't as bad a job as I'd feared. Still, it took about three hours. The AC 41-606 plugs I got at NAPA were identical to what was in there. The electrodes on the old plugs didn't look all that bad, just a little bit of white residue, but some of the wires were in kind of bad shape. I'm pretty sure five of the six wires were the factory originals, as they had cylinder numbers printed on them. One was a NAPA wire like what I was putting on. In removing the old plugs and wires, I figured out why it was running so badly. The no. 5 wire was just barely making contact with the plug.

After we got everything buttoned up, we took the car for a brief road test, and all I can say is ! Everything was smooth as silk. The car had much more pickup and no shudders whatsoever. In the end, I guess it was at least as much an ignition system problem as it was a transmission problem, so maybe Dr. Tranny did do some good after all. I know my comments last night had a bit of a harsh tone to them, but I was tired and frustrated.

While I feel good about what I accomplished today, I'm not going to pronounce it completely healed until I've driven it for another week or so. I'll let you know how it goes. Meanwhile, a big thank-you to everyone who contributed their experience, wisdom, and expertise. I am in your debt . I hope I'll be able to reciprocate by contributing my modest knowledge to help others with their issues.

[willwren]

This is exactly why I pushed you to rule out ignition problems FIRST. I'm glad the car is running good, and I'm sure you're grateful none of the doom-and-gloom in this topic applied to your issue.

[Bugsi]

Regarding the plugs: I'm glad to hear you did your research and knew you were getting the correct plugs. I think you got a great deal at under $2 per plug. For what it's worth, I also use the OEM AC Delco spark plugs when I replace mine, and I'm in 100% agreement with you about using them. If you're running stock or nearly stock without major engine performance modifications, I'd totally stick with the OEM plug.

I seem to recall paying more than you did when I did plugs, so I raised the flag to just have you make sure you weren't using the wrong plugs. Sounds like you were good to go already.

*REALLY* glad to hear that your shuddering problem appears to be solved. I experienced first hand that plug wires are a primary cause of misfires on these engines. This engine design seems to be particularly sensitive to spark plug wire issues, seemingly moreso than any other car I've experienced; but it might simply be because the rest of the engine is so much more reliable. It's actually pretty rare to find a misfire on this forum that isn't related to a plug wire or an ignition coil.

Enjoy your Bonneville!

[human]

The price of those plugs varied quite a bit between the stores' Web sites that I checked. The high was somewhere around $2.50. The $1.70 I paid was by far the lowest price I saw for any plugs, AC or otherwise, for that car.

I'm still amazed at the difference the plugs and wires made. It was $35 well spent. I usually dread getting up for work on Monday mornings, but today I was almost eager to get out of the house and on the road. My commute was silky smooth.

Willwren, thanks for pushing me to do the plugs and wires. I was more than a little skeptical going in; it just seemed a little counter intuitive that bad plugs and wires would cause the transmission to malfunction, but now I'm a believer.

Regarding the plugs: I'm glad to hear you did your research and knew you were getting the correct plugs. I think you got a great deal at under $2 per plug. For what it's worth, I also use the OEM AC Delco spark plugs when I replace mine, and I'm in 100% agreement with you about using them. If you're running stock or nearly stock without major engine performance modifications, I'd totally stick with the OEM plug.

I seem to recall paying more than you did when I did plugs, so I raised the flag to just have you make sure you weren't using the wrong plugs. Sounds like you were good to go already.

*REALLY* glad to hear that your shuddering problem appears to be solved. I experienced first hand that plug wires are a primary cause of misfires on these engines. This engine design seems to be particularly sensitive to spark plug wire issues, seemingly moreso than any other car I've experienced; but it might simply be because the rest of the engine is so much more reliable. It's actually pretty rare to find a misfire on this forum that isn't related to a plug wire or an ignition coil.

Enjoy your Bonneville!

[willwren]

The plugs and wires didn't cause the transmission to malfunction at all. There was never anything wrong with the trans to begin with. When the trans is in OD with the torque converter locked, the engine is at a low RPM under load, which is the best time to 'feel' a misfire. Another good time is climbing an incline under load and low throttle. Your car was misfiring at all times, but was just easier to feel under those circumstances.

[blazerk5drew]

Glad to see that the car is back in buisness. Wish I had the same luck back when I went through this. BTW Human, you said your dad worked for olds? Does he maybe still have a hookup for olds bodyparts from the late 90's? let me know and we can start a new thread.

[willwren]

FYI, we've seen cases of certified mechanics at dealerships misdiagnose these TCC lockup issues as well. This is a common thing, and it is FAR more common to be an ignition issue particularly with the 4T60 - equipped cars than it is to be an actual trans issue.

Rule of thumb, always VERY carefully rule out ignition/misfire issues first when you feel any surging/stumbling under load at low rpm's or in OD/TCC lockup.

[human]

Unfortunately, most of Dad's contacts have dried up. He's been retired since 1991, and with all the shake-ups and downsizing since that time, he doesn't know anyone on the corporate level anymore. Even most of the people he knew at the dealerships he called on have retired or moved on.

Glad to see that the car is back in buisness. Wish I had the same luck back when I went through this. BTW Human, you said your dad worked for olds? Does he maybe still have a hookup for olds bodyparts from the late 90's? let me know and we can start a new thread.

[Lavecchia]

Did you have any problems with the trans over heating when those two wires were disconnected ?