Shake with acceleration... Trans or Engine?

[IsaacHayes]

Ok, first of all I have a noise like a wheel bearing is going out. The wheel bearing is not loose, but I read they can still make noise. I replaced the passenger side one when it was a little loose, and maybe it's just time for the drivers side to go only it is making noise instead of being loose.... I'll find out if it's the wheel bearing or transmission making the noise when I replace the bearing this weekend.

Next, I have a vibration/shaking when accelerating. Sometimes it does it with a load going up a hill for example. Sometimes it does it when gunning it a little. Sometimes it only does it at the upper RPMs when downshifting into 2nd at 65mph (4200 PRM) for example. Sometimes it doesn't do it. Sometimes it does... Is this something transmission related or is it just something as simple as crappy plug wires. I can't tell that the engine is miss-firing bad or anything, and I don't feel a loss of power really, but I have plenty to spare. Should I throw money towards plug wires or is the trans about to blow?

It shifts perfectly fine and behaves great.

Plug wires are many years old, around 8 give or take. Plugs are new.

[torq455]

doesn't make sense that you have intermittent shaking or vibration during both accel and decel. maybe your motor mounts are weak and bumping the mount housing. still a good idea to replace those wires. for the tranny, i can only think of the shudder description where clutches aren't working smoothly. i don't know that much about the autos though. just something for you to inquire about.

[91LQ1Lumina]

My 99 grand am had a not so smooth idle, and a stumble every once and a while. After replacing the plugs and wires it felt like a new car, the drop in performance was so small I didn't notice it but after I replaced them, WOW.


Don't know if this helps or not.

[IsaacHayes]

My mounts are good, I even had a poly/CNC aluminum dogbone in but I took that out for winter so that I could have more torque absorbed before going to the wheels so that traction would be improved on slick conditions. That is when I could feel the vibration since before it shook a lot with the poly one anyway.

I have a poly insert in the upper mount. It does look a little sagged as the bracket for the dogbone is near the subframe, (probably the poly dogbone made more stress go to the upper mount and pulled it down some). It looks like there was some rubbing but I would hear/feel that differently than this sound. this sound is not going through the subframe like the vibrations from the poly dogbone did (subframe is bolted right to unibody with no bushings).

I might try the wires and see. It has no affect on power I can tell. I will see about the noise /wheel bearing soon enough. If the noise doesn't go away with the wheel bearing then it's probably the tranny

The car has no stumble, and no idle issues. The tach doesn't jump or rise up, no slipping I can tell unless the rumble/vibration is enough to feel but not enough to slip and show up on the tach. I will hook up my laptop and scan the TCC slip % and log that and see if I notice anything strange there.

What about torque converter shudder? What is that and could that be it?? Or is that only a lockup issue?

[IsaacHayes]

OK on the way to lunch today I went WOT and I felt some tremendous vibration (for the stock dogbone) through the body of the car. I'm pretty sure now that part is the dogbone bracket that bolts to the engine hitting the subframe. As I could feel it rattling through the unibody. I will get some paint marker and paint those areas then re-check them and see if they are rubbing. I probably didn't feel that with the poly dogbone because it limits the movement in that area, but the poly dog bone probably put more stress on the upper mount and wore it out by not letting the engine rotate so then it "pulled" downwards on the upper mount when it tried to rotate and couldn't. Instead of all of the mounts flexing some, it transferred all the force to the weaker one. (even though it has a poly insert). The other side is held up by the trans mount, which IIRC how it's made it will rotate freely so it shouldn't be affected.

Now as far as the slight vibration during part throttle on hills and such, I'm not sure. I guess the stock dogbone compresses enough that it could just cause the bracket to touch the subframe and rest on it and shake but not really whack it hard quickly like it felt like when I went WOT earlier.

So I guess I'm going to start with wheel bearing for the growling noise, and then replace the upper engine mount with a new one and transfer my poly mount over to it. I'm not sure to go with a stock hydraulic one or a solid rubber one now. I'm thinking right now price will be my deciding factor. Unless I can grab another whole mount from the junkyard for cheap ($15) like last time. That will save me time from installing it and knocking out the center section. I'll just have to transfer the poly insert. I might do that. Hell, this one lasted me 100,000+ and it had over 100,000 on it when I got it from the yard!

I hope that's the only problem and not the trans. I'm not in a position to be rebuilding a spare and swap it in right now. I'm loosing where I'm staying and it's middle of winter and things just are too chaotic right now. Plus I have 2.5" custom mandrel bent exhaust to put on in spring!!!

[3400-95-Modified]

Is your downpipe close to your swaybar? or are you still running the stock downpipe?

My liquid filled replacement upper mount made the motor sit very high, like 1" higher than the factory one... With the 95 the cap on that mount comes off so you can see the two bolts holding the aluminum bracket to the mount, and there is a rubber insulator on top of that, well when I put the new mount in, that rubber insulator stuck above where the cap was bolted down to so it actually had to get squeezed in there when I put that back on. It was a very tight fit and I feel that it was made completely wrong for my car... not sure why.

I thought maybe it would settle down but I don't think it has any... This is why I haven't replaced the mount on pinky yet... no need since it only had 74k on it, and I don't want to deal with that again.

All I can suggest is to get a factory mount, bring it with you and compare heights with what they have in stock, or just measure it...

[IsaacHayes]

Stock downpipe and exhaust right now. I have wicked_irocz's 2.5" stainless mandrel bent sitting the garage waiting for warm weather to go on complete from manifold to tail pipe. It has enough pipe I may run cat and mufflerless for a short while for shits and grins. I did put on a 28mm bar but the downpipe is no where near it.

Hmm. I will measure them then and check in store. Do you remember what brand it was? I can bring in my old 94 busted mount. It's jacked up but the height should be ok. LOL

Hopefully Friday I can put on the wheelbearing. I just don't have access to my own impact tools or big sockets for the axle nut or it would be on now. When in parking lots and turning I hear a "squeaky" rubber on metal sound, but nothing is rubbing (185/75 R14 lol) but not just when moving the wheel. Its when the wheel is turned and the car moving. So it's not steering related since that isn't moving when the noise happens. I'm thinking maybe a dry spot in the bearing and that's what I hear there, and that would explain the noise and vibration (really high freq vibration in the wheel) while driving. And if I'm not mistaken when I hit the brakes last night the sound changed, and if I let off the brakes the noise changed right back to what it sounded like before the brakes were applied. I could see that as being wheel bearing there...

The other vibration I think is a motor mount is a different vibration. It's defiantly motor shaking type of vibration. Closest thing I can relate it to is a bad off balance tire/wheel. But the tires are not doing it.

3400- do you recommend the OEM fluid one or the solid rubber one they offer? You think the solid rubber with poly insert (but stock dogbone) would shake the car a lot?

Thanks.

[IsaacHayes]

Ok I replaced the wheel bearing and the noise and vibration is still there if not more.

No way this could be a CV axle, and there is nothing else that roatates that would make this noise other than an output bearing in the trans itself. It sounds really bad now like it could explode at any second despite it working perfectly.

Great. The only thing I can think of is buying another car right now and putting this one in storage some where. This came at the absolute worst time the way my situation is right now.

[torq455]

why not a cv? they have bearings in them too. maybe one is worn out. you should be able to hold both ends of the tripod and twist back and fourth with slight play still being acceptable.

[IsaacHayes]

When you are going straight a CV's bearings are not moving. Only when it's angled/bending does it turn. It doesn't have needle or ball bearings like a wheel bearing does.

I guess I should do the motor mount thing next too to rule out that is indeed what is causing that shake. It could be the loose bearing in the transmission too under power causing shit to move around. Close to top of 2nd and the car really shakes.

[torq455]

the cv's will move when going straight. if the axle is perfectly parallel to the ground, perfectly perpendicular to the output housing AND the spindle, then they don't move. bumps, dips in the road and hard acceleration will cause them to move. my car sits slightly higher than level. i have also seen the bushings at both inner cv axles inside the differential housingt have enough play to cause vibration as well. that caused more of an out of balance feeling at higher speeds though.

[IsaacHayes]

Right but its not going to be a movement like a bearing on say an alternator would be. The axles are one "solid" unit when rotated, they just flex. The noise sounds like a wheel bearing type of sound, does not change with steering braking or acceleration, and shakes the steering wheel with a high frequency vibration not an out of balance feel.

[torq455]

ooohhhhh that's not good. spose you could take it apart and inspect, or wait until something happens.

[IsaacHayes]

I have a 95 trans w/137,000 for $150 waiting to be picked up from a guy I know. With that many miles I'm going to rebuild it and document everything that I learn from 3400-modified. For $150 that's not a bad price for a core to build up at my own leisure. The trans was working when pulled.

No way I can pull the trans, take a look and put it back together in time for work in one weekend... LOL. This is my DD so I have to plan ahead for things like this. That's why I'll be fixing up a spare Trans to swap in one weekend.

[torq455]

haha oooo nooooo. the swap will be a whole weekend. $150 huh? damn, i got mine delivered to the shop with 38,000 miles for only $250! people don't want a Buick LeSabre tranny. it has the 2.86 FDR! it's cool though. with the gear conversion, that would make my FDR a 3.20. IF i were to reinstall that. lol