Vibrating/knocking feeling when accelerating... I'm clueless!

[deevergote]

While driving today, I noticed something new... Between 2000 and 4500 RPM, especially in 3rd, 4th, and 5th gears, I would feel a knocking vibration through the steering wheel... enough to slightly shake the whole car. It feels almost as if I had a bald spot on one of my tires.

However, this ONLY happens while accelerating. While the engine is under load. Revving the engine in neutral or with the clutch pedal depressed did not produce the vibration. Rolling while in neutral at any speed did not produce the vibration. Rolling in gear within the problem RPM range did not produce the vibration.

The vibration was only felt when I was on the gas, and it got stronger the more I opened the throttle. At high speeds (80mph, around 4500 RPM) the vibration was unnoticable.


This has me scared, since I don't know what it is. I assume it's something with either the engine or the transmission, since a suspension, axle, or bearing problem would be evident at a roll.

My H22 has over 100,000 miles on it (assuming it had 40k or more when I got it). It's been over-revved once many months ago with seemingly no damage (valves need adjusting, but that's it). I have an Unorthodox Racing crank pulley. I have an XTD Stage 3 clutch and XTD 12lb flywheel (installed without a torque wrench, as cpmike's torque wrench was worthless). My transmission has synchronizer issues in 3rd and 5th gears (not bad, but present). I occasionally have trouble getting the car into first and second (2 weeks ago, the transmission made a noise that sounded like small chirping birds when I tried to put it in 1st or 2nd from a stop... hasn't done it since). I'm currently running GM Synchromesh in the transmission, and Mobil Clean 5000 in the engine (and is almost ready to be changed). I never installed a balance shaft seal retainer on the motor. I recently replaced the driver's side axle.

That's all that I know has been done to the motor/trans that could possibly be related.

My biggest fears are internal issues... rods or transmission guts. Next would be the clutch...


Any help would be appreciated! I don't have AAA just yet, and I'm not ready to depend solely on my Volvo without heat!

[deevergote]

Yeah, tranny was my first thought.

Another idea that AccordWarrior suggested on IM was that it could be a bad inner axle joint due to my motor moving (my rear mount is shot).

[cp[mike]]

deduce

1. drivetrain related, not engine, as it has to do with speed, not RPM

2. not the brakes, as they would be deceleration.

3. whats happening during acceleration? flywheel/clutch turns the gears, diff, turns the axles, then the wheels.

4. its not the clutch or flywheel, as its only under load and not in neutral

5. leaves the tranny, axles, wheels. wheels dont "go bad" and make a knocking based on speed.

6. tranny vs. axles. unless its making noises, not going into gear, or having other problems, it doubt its tranny. you say its only under load. which is when the axles are turning the wheels, were all of the engine torque is applied through the... ding ding ding... CV joints!

my answer: axles

i havent looked at the car and dont really know exactly what youre feeling, but thatd be my guess.

also the fact that mine are bad and i get similar feelings helps. others called it "thumping" but under full load acceleration, its a crazy strong vibration that shakes my entire car. door panels and windows especially. my cv joints are bad, but the boots arent torn

IIRC yorue on autozone axles. likely.

[deevergote]

I have one autozone axle that's "new" (recent install, reman) and one that's a Napa axle (passenger side... also most likely a reman). That Napa one is at least 4 years old, with well over 60,000 miles on it. And the feeling DOES seem to come from the passenger side (though those feelings are often misleading)

[owequitit]

I think it is your motor mount.

The primary function of the rear is to control torque AND vibration.

As the rear mount goes bad, the vibration will start at a narrow speed range, gently and usually at a high speed.

As it gets worse, the speed range will start to widen, and then eventually, so will the severity.

Here is what may be a partial contributor: the front dogbone mount on CB7's is whimpy. Once the rear stops doing its job, the front dogbone usually follows shortly thereafter.

Once this occurs, you now have the two side mounts attempting to control all forces, only they aren't able to control or stop everything, so you end up with some fore aft movement, and some side to side movement.

It will eventually get to the point where the car shakes so bad, you won't be able to read the gauges.

That is why I am in the middle of my swap...

It is possible it is an axle, but my first guess would be motor mount.

[gloryaccordy]

My votes were axle and motor mount...in fact, I was gonna ask whether you had ever poly'd your mounts. A bad mount and a crappy axle both exacerbate each other...

Good luck.

[flight50]

this is some good info. i will know what to look for when i run into this problem. again. while i am in the process of doing my swap i found out that both my front and rear mounts were shot. so maybe this swap will kill two birds with one stone for me.

[phatdoughnut]

get under there and check to see if maybe any of your boots are ripped.

[deevergote]

Well, the good news is that I have a poly'd dogbone and rear mount in my basement, waiting to go in (I've been too busy, lazy, and cold... ) I'm hoping it's not an axle... I can change it, but it's no fun in the street in the middle of winter!

[deevergote]

Well, using my new Craftsman jack, I took a look under my car today. What did I see? A loose exhaust hanger! The exhaust moves pretty freely at the flex pipe, as there is only one rubber piece there, and it's not connected. The piece in question is in the picture. The part you can't see (the part attached to the car) is where the rubber is not connected. I couldn't pull it into place myself, so I'm going to have to get someone under there with me pushing on the exhaust a bit. Another quarter inch and it'll be back on.

Hopefully that is what I'm feeling! A vibrating exhaust would certainly be felt!

[deevergote]

Sorry for the HUGE pic... I put it from my camera directly onto the CB7tuner server...

[NAiL05]

Yea my car does that too. =D Even with the rubber hangar it decides it wants to knock on the floorboard sometimes. But just not as high of an rpm. Mine is usually around 2000-2500 or so. I got used to it so just said fuck it,

[cp[mike]]

thats normal for an h22 dp. i doubt a missing hanger is your issue.

[deevergote]

Well, I checked the passenger side axle (the area that it seems to be coming from... and it hasn't done it since the other day) and it seems absolutely fine. The driver's side axle should be fine, since it's only a couple months old. I'll fix that hanger and we'll see! Best to have it fixed anyway, even if it isn't the issue. Regardless, a turbulant exhaust flow coupled with an engine under load (hanging on lousy mounts) would probably cause the exhaust to wobble if it was free to do so.

[owequitit]

A good test while you were down there would have been to grab the header (assuming it wasn't hot) and try to move the engine back and forth.

It it really rocks freely, you have a bad mount.

You can also put your hand under the IM and try lifting up. If the engine rocks back and forth, same thing.