'96 Bonneville shudders

I have a 1996 Bonneville with 100,000 miles. At speeds above 50 the whole car shudders when the throttle is depressed just slightly, such as when trying to maintain speed. The only way to stop the shudder is to back off the throttle or accelerate harder. It accelerates hard as well as ever. The engine has had a head gasket replaced and the upper intake replaced for the coolant leakage problem common to the 3.8 engine. The problem existed before these repairs were made. Any ideas?
Thanks

well if it's only in ONE place on the pedal, i'd check for the throttle position sensor.

deadring

OK dudes,I myself have a 96 bonneville that had the same prob.good thing i'm a mechanic and can fix it using a lift where i work.I got the car from a dealer auction with 94 k on it,I tried many things and one thing that worked temporarily is putting in a bottle of lube guard in my tranny.what it does is cleans out the thick crut between your selenoids for your gears so that they engage properly when needed.I can't believe you said tps can cause the shudder man :nono: Now what it can be is a faulty (tcc) which stands for torque converter clutch selenoid which is located at the valve body,and that you can get to where that side pan is on your tranny which is pretty visible when you take the drivers side wheel off.Allthough ther is quite a bit of work involved to do that so i wouldn't recommend doing that by yourself if you don't have much experience with mechanics and certain tools you might need.Worst case scenario man is that either your tranny is shot or your torque converter itself!(which is a involved job since you gotta rip the tranny out to change it).Welllllllllll i hope this helps you,and i would say try that stuff i said called lubeguard for the tranny which is used by tranny rebuilding pro's and not that easy to find unless you order it from the net. P.S. OH yeah a simple tranny service might work for you too if your tranny filter is clogged and you don't have adequate pressure going through your valves.Keep in mind that if you do a tranny service and flush when your current fluid is brown,stinks,and you most likely won't be able to move!!!!!! this is due fot the reason that a car with alot of mileage on it gets used to a certain type of viscosity of the fluids.GOOD LUCK MAN!

I support the Torque Converter Clutch being shot or lacking proper pressure.. When you back off the throttle, it is no longer sollicited so it does not slip/shudders. When you accelerate, the TCC opens and reverts to unlocked torque converter operation, so no shudder. A classic.

my 1995 has started the same problem,,where can you get this "lubeguard"?? is this the product name?? about how much do you use?? and the cost??

I am having a similar problem on my '97. Driven it for years like this, mostly just annoying. Would like to sell, so I'd like to fix the problem. Any additional info appreciated!

I tried the LUBEGARD, and I think that this product makes it a little less noticeable, however, in my vehicle it did not fix the problem. I think that my next try may be the TCC module. May try the junkyard first.

my problem was the spark plug wires the hadnt ever been changed in that car once i changed them no more studder.

I have unplugged my tcc sensor on the transmission and the shudder is gone.I have also tried the lubeguard and it did not work for me.I had the same symptoms on my car.

Depends on exactly what you mean by shudder ?but my 85 pont.does kinda the same thing,only at a low speed(10-25 mph)really more of a{wobble ?in the front end}.What i found out is that a rear tire being out of round or just plain shot will cause it.
I have had this happen on my current car as well as others,replace the bad rear tire problem solved.
May not be your problem(speeds seem at diff.end of scale)just something to think about. good luck!!
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I have a 92 Bonneville and when i hit about 60km/hr it starts to shake and progressivly get worse, when i get up to about 130km/hr it starts to go away, dont matter if the gas pedal is pressed or not if im going in that speed range it shakes, and bad. We put 4 new tires on it, the rims are good, all balanced, replaced axels, wheel bearings and rotors and the shake is still there. I`m readig about a lot of people having this problem and would like any help you can give.I just bought this car weks ago and already spent more on trying to fix the shake than i pid for the car, gotta get it fixed tho, such a beautiful ride.

heres what we did so far.

We jacked up the front end, one side at a time so the wheel was off the ground and brought the car up to 80 kms/hour, on the passengers side its as smooth as can be, when we do the same thing for the drivers side you can see the car shaking real bad, thats why we are trying parts on the drivers side. It also looks like the wheel itsself has a up asnd down and side to side shake/wobble.

I`ve already spent 8 hrs at the garage trying to figure out this problem and am going back today fopr probally another 4 hrs or until we find it.

heres what we did and found out Friday.
Ok, at the garage we put the car on the drive on hoist, lifted the front end right up and spun it up to 90kms, shook like a b*****d, the back transmission mounts seems weak so we put a piece of rubber under it spun the car back up to 90kms and not one bit of shake, had to order a new mount, anywhere between $95.00 for a solid one to $330.00 to a liquid filled one, i went for the cheaper one, getting it in Monday morning, hopefully this will cure the nasty shaking.

.Ok, we tried tranny and motor mounts and did not help, one thing i`ve noticed, when i hit around 80 kms/hr just b4 it shifts it makes like a grinding or chattering type noise, then the shake gets worse as i go faster, 90kmh is really bad and it now stops at around 105km/hr. just cant figure it out, starting to think its in the tranny itself

Since it seems limited to one side and according to the description you give, I would consider the c.v. joints as a serious target. However, since you changed hub assembly, I supposed that would have been checked at same time, wasn't it?

there were new axles put in both sides and still does the same thing, the shake does not seem to be limited to one side tho, kinda hard to tell where it comes from, lots of shaking trough the seats but not much shaking coming from the steerinjg wheel.

Ok guys we found the problem, both rear brak drums were off balance , put 2 new ones on and the car drives like new, never ever seen drums like that before, they were excellent when braking and were in excellent shape, but were completly off balance, 5.75 ounces on one side and 3.5 on the other.