Transmission shudders at 50mph

[human]

Okay, so I've had this '95 Bonneville for about 3 or 4 days now, and today my girlfriend and I took a little road trip in it. When we came off an exit ramp and onto another road, we were heading uphill and accelerating, and the transmission started shuddering as we reached 50 mph. I gave it a little more gas and it downshifted and smoothed out. After a little experimenting, I came up with the following observations: The shudder happens consistently between 45 and 50 mph when accelerating slowly. If I step on the accelerator at about 35 mph and accelerate hard to about 60 mph, it shifts smoothly. If I put the shifter in "D" instead of "OD", it doesn't shudder.

I checked the transmission fluid when I got home and found that it was at the lower end of the normal operating range (i.e., the fluid level on the dipstick was just above the "add" mark) so I added about 12 ounces of transmission fluid, which brought the level up more squarely into the normal operating range. After doing this, I road tested the car and the shudder subsided but did not go away completely.

So what do you think the likely cause of this is? Is it an easy fix? Do I have a dying transmission? Please say it ain't so. I bought this car because it cost less than it would have cost to fix the oil leak on my Cadillac. I don't need two money pits on wheels.

[Mike Sessei]

How do the motor mounts look? I'm thinking particularly of the front transmission mount. Mine is on its way out, and I feel the vibrations you're talking about, at freeway speeds, at lower rpm, while in OD - not in Drive, however.
How about the color of your transmission fluid? Bright red, or brown? How does it smell? Just smelly or burnt?
Also noteworthy - have you done any tune-up related work since you purchased the car? 00Beast has a helpful and thorough tuneup/maintenance list here:

• 1987-2005 Bonneville / Buick 3800 Maintenance List
  
  Run Seafoam through gasoline and intake every 5,000 miles. One pint of Seafoam in a half tank of fuel is a good mix. The intake is optional, but recommended.
  
  Grease: Ball Joints, Tie Rods Every 8-10k ( Green Grease recommended)
  Air Filter Every 15k (Amsoil EaA, Purolator PureONE)
  PCV Valve Every 30k
  MAF Sensor Element Cleaning/TB Cleaning Every 50k viewtopic.php?f=48&t=1661
  Fuel Filter Every 15-25k (Purolator, AC Delco, WIX)
  Spark Plugs Every 30-50k (NGK TR55 or Autolite 605) (Never Bosch)
  Ignition Wires Every 30-50k (Napa Belden, AC Delco, Autolite Pro, NGK) (Never Taylor or Bosch)
  Oil & Filter Every 5-6k or Every 6 months (Mobil1 or Amsoil)(Mobil1, Purolator PureONE, Amsoil EaO or WIX) (Never Fram) viewtopic.php?f=45&t=214
  *Conventional Oil Every 3k/3 months(Pennzoil with a WIX (Napa), Delco or Purolator filter)
  Transmission Flush or Pan Drop Every 15-20k (Always make sure filter is changed when flushed) http://www.pontiacbonnevilleclub.com/fo ... 45&t=10193
  Cooling System Flush Every 25-50k or 3-5 Years (Peak or Prestone Green Coolant Only) (Never Dexcool)
  Oxygen Sensor Every 80-100k (30k for non-heated) (AC Delco or Denso) (Absolutely never Bosch) viewtopic.php?f=48&t=794
  Accessory Belt Inspect every 15k, replace every 100k, or as needed
  Cabin Air Filter Inspect and Replace every 15k, or as needed in dusty conditions. (Note: 00+ Only)
  Evap Core Cleaning Whenever Needed (Note: 99 and older only) viewtopic.php?f=45&t=2432
  
  *Special Considerations*
  All 3800s, LG3, LN3, L27, L36, L26, L67 & L32, especially important on vehicles factory installed with orange Havoline Dexcool Antifreeze/Coolant: http://www.dex-cool.net/
  Lower Intake Manifold Gasket Replacement, every 80-100k (ignorance of this can allow coolant to enter your engine oil, this happening can cause irreversible lower engine damage, requiring replacement of subject engine)
  
  Series II, Naturally Aspirated, RPO:L36:
  Upper Intake Manifold Plenum Replacement, Every 80-100k (ignorance of this can allow coolant to enter your intake manifold, possible damage to occur can be hydrolock, irreversible damage to emissions devices, misfires, etc. Most times, engine replacement is required if ignored long enough.) viewtopic.php?f=53&t=1061
  
  Series I, II, III RPO Code L67 & L32:
  Change Supercharger Oil; Every 30-50k. (Intense Racing or GM Dealer) viewtopic.php?f=56&t=1690
  Supercharger Belt; Inspect Every 15k, Replace Every 100k or as needed.

10/11/2010 by 00Beast[/quote]

[human]

As far as I can tell, things look pretty good under the hood. The seller definitely cleaned under there as part of pre-sale detailing. Nothing is visibly amiss. I haven't done any "tune-up" type work to it yet. I've mainly been assessing the present state of things to see what needs to be done. I'm not sure what to look for on the motor mounts, so I can't really assess their condition. The serpentine belt looks good—no cracks or visible deterioriation, the air filter is in good condition—looks like it was replaced within the past couple of months. The tranny fluid is nice and pink with no particular odors. The oil, however, definitely needs changing, as the seller pointed out, and will be changed early next week. I'll also be having the air conditioning system recharged at the same time. It's blowing cool, but not as cold as it should be. I'm hoping there's nothing major wrong there. The AC doesn't make any noises or anything, so I'm going to have them recharge it with some stop leak and hope for the best. It's still kind of warm down here in the South.

[Mike Sessei]

For the mounts, you'll be looking for tears in the rubber, separation between the rubber and metal pieces, excessive sagging, and generally deterioration of the rubber. An indicator of this condition if not apparent in the mount itself is more easily viewable as excessive engine movement. You can observe this best while parked, in Park, hood up, revving the engine. I don't recall what most folks here say is and is not passable for engine movement...under an inch, if I recall. Perhaps someone will be kind enough to chime in here with their 2 cents.

[human]

I'll take another look at them tomorrow, but from what I recall, the rubber seems to be intact.

The shuddering sensation feels like when a car with a manual transmission is moving too slowly for the gear it's in. It gives me the impression that something (overdrive?) is trying to engage (or possibly disengage) but is unable to do so. When it happens, it comes on suddenly, lasts for for a few seconds and then stops abruptly.

[stevew9983]

I wonder if it has the same problem as my 00 SSEi with the Transmission Pressure Control Solenoid. I did find these technical serivce bulletin about this issue.

Reference number - 53-65-06 Driveline vibration over 37 mph

I read thru it on my Mitchell On Demand but the program wont let me copy and paste info and it was alot to type out. Anyways, from reading the TSB, I think I would get a scan tool on the car and check the TCC Solenoid. Sounds like this could most likely be the issue

[repinS]

Bonnevilles equipped with the 4T60-E (1996 and older L67, 1997 and older L36) do not have a pressure control solenoid, but rather a vacuum modulator on the front of the trans.

[stevew9983]

I was unaware of that, thank you repinS. Do you believe the TCC Solenoid TSB might be worth looking into a little bit more for his issue?

[human]

I checked the motor mounts this afternoon, and as far as I can tell, they're fine. The rubber appears to be in good shape.

[J Wikoff]

The front tranny mount can look ok, but if you rock the car backwards and forwards, the rubber might pull away from the metal parts of the mount. Worth a look if you didn't try that.

[willwren]

I was unaware of that, thank you repinS. Do you believe the TCC Solenoid TSB might be worth looking into a little bit more for his issue?

No bearing on this trans whatsoever. They are a total redesign (frankly, the 60 is a superior trans to the 65).

Human, set the parking brake, block the wheels, put the car in drive, and power-brake it up to about 3000 rpm's while someone (you) watches the motor to see if it rocks back and forth. It shouldn't move more than 1/2" or so. If it's more, you have a bad mount. Typically front and/or rear trans mounts.

[RJolly87]

I have seen it to many times, uneven firing.

The transmission locks the torque converter at 36mph in 3rd gear <feels like it grabs another gear, but if you tap the brake while still on the throttle some, you will feel the torque converter unlock>, and it shifts into overdrive at 48mph. It may be a good idea to do a few things on the tuneup list <all wouldn't be bad either> as well as a seafoam treatment before tuneup. Also remember you are likely contending with 15 year old vacuum lines, and they may need to be replaced also.

The torque converter acts like a coushin when it comes to engine vibrations. When it locks up, it is a solid connection from the flex plate to the wheels.

[human]

Yes, 48 mph is almost precisely when this shudder occurs! So does that mean the transmission is not going into overdrive properly? That would certainly explain why the problem doesn't happen when the gear shifter is in "D", but only in "OD".

So is this a serious problem? What should I do to fix it? The transmission shifts very smoothly other than this, so I think the torque converter is probably okay. Adding transmission fluid helped the problem a little, but it didn't completely alleviate it.

What is a "seafoam treatment"?

I have seen it to many times, uneven firing.

The transmission locks the torque converter at 36mph in 3rd gear <feels like it grabs another gear, but if you tap the brake while still on the throttle some, you will feel the torque converter unlock>, and it shifts into overdrive at 48mph. It may be a good idea to do a few things on the tuneup list <all wouldn't be bad either> as well as a seafoam treatment before tuneup. Also remember you are likely contending with 15 year old vacuum lines, and they may need to be replaced also.

The torque converter acts like a coushin when it comes to engine vibrations. When it locks up, it is a solid connection from the flex plate to the wheels.

[LeSabre in Buffalo]

Do a thorough tuneup. Plugs, wires, PCV valve, air filter, clean the MAF sensor, new O2 sensor, and fuel system cleaner. That's what he's saying.

[Tuffguy610]

I had the same problem with my car (97' H-body). Staring about six months ago I noticed a shudder when the torque converter clutch locked up in drive and in overdrive. I tried everything to keep it from shuddering. I added lucas transmission additive which didnt do much of anything. So later on I added another additive and it still shuddered. My trans has new fluid in it and the level is good. It also has 135,000 on it so its bound to have issues. I solved the shuddering by installing toggle switches in the 2 wires that control the lockup of the converter clutch so I could disable the clutch and also enable it for passing emissions (having them disconnected throws an SES code). On the front of the trans, you'll see a wiring harness with approximately 8 wires going into the trans. Disconnect/install a switch in these two to get rid of the shudder: Pin C = TCC PWM Sol Valve Control (colour = BRN); Pin D = TCC Sol Valve Control (colour = TAN/BLK). Beware that your engine will rev higher on the highway and cost you about 3-4 mpg (I have witnessed this). Other than that its nice to have the shudder gone! Some advise against cutting the wires because the engine revs higher and causes more heat in the transmission, but my car has been this way for several thousand miles with no problems. Maybe you can try my approach if you run out of options. Here's the link to my thread from a few months ago when I was dealing with your issue. http://www.pontiacbonnevilleclub.com/fo ... 19&t=18768

[human]

Seems like I could accomplish the same thing by driving with the shifter in "D" instead of "OD". It doesn't shudder in "D" and the engine revs higher than in OD.

Just for fun tonight, I took a slightly longer route home from work so I could get the car up to highway speeds for a couple of miles. It went into overdrive at 50 mph smoothly enough, but then began shuddering at 60 and didn't smooth out until I got it up to about 72.

I had the same problem with my car (97' H-body). Staring about six months ago I noticed a shudder when the torque converter clutch locked up in drive and in overdrive. I tried everything to keep it from shuddering. I added lucas transmission additive which didnt do much of anything. So later on I added another additive and it still shuddered. My trans has new fluid in it and the level is good. It also has 135,000 on it so its bound to have issues. I solved the shuddering by installing toggle switches in the 2 wires that control the lockup of the converter clutch so I could disable the clutch and also enable it for passing emissions (having them disconnected throws an SES code). On the front of the trans, you'll see a wiring harness with approximately 8 wires going into the trans. Disconnect/install a switch in these two to get rid of the shudder: Pin C = TCC PWM Sol Valve Control (colour = BRN); Pin D = TCC Sol Valve Control (colour = TAN/BLK). Beware that your engine will rev higher on the highway and cost you about 3-4 mpg (I have witnessed this). Other than that its nice to have the shudder gone! Some advise against cutting the wires because the engine revs higher and causes more heat in the transmission, but my car has been this way for several thousand miles with no problems. Maybe you can try my approach if you run out of options. Here's the link to my thread from a few months ago when I was dealing with your issue. http://www.pontiacbonnevilleclub.com/fo ... 19&t=18768

[Tuffguy610]

Try that and see how it works. These transmissions also lock the converter in 3rd (drive) so you may notice it after some time when driving in 3rd. I know that my car progressively got worse over time, hopefully yours won't do the same. My car used to struggle at 60 mph and "plane out" around 72 just like you described. The faster I went while in OD, the smoother it ran. IIRC, the computer would notice the slippage and disconnect the TCC on its own when on a road trip. But anyway, good luck!

[LeSabre in Buffalo]

Try tuning it up before disabling overdrive.

[human]

Believe me. Disabling the overdrive will definitely be a last resort.

Try tuning it up before disabling overdrive.

[renchjeep]

Try a trans additive called Dr. Tranny's Instant Shudder Fix. I got mine on eBay for just a few bucks. It is in a red plastic tube, only a few ounces. I had the same problem in my 99 Crown Victoria, and it fixed it. I know, a different trans, rwd, etc. But it works with all types of automatics and fluids. I put it in my Vic about 30k ago, and service the trans every 20k. I used it with the last service, and will use it at each one from now on. Trans is original, over 160k miles.

I am not a big beleiver in additives to fix problems, but this one definitely worked for me.

If you try it, please share your results.