noise from trans/driveline when gas petal released while in gear

What is happening to these shafts? Has the car been lowered?

it has a mild lowering spring with upgraded shocks. I was told the lowering of the car would cause inward pressure on the axels causing the inside cv axel to fail prematurely. on that note almost any Honda that is lowered will have chamber issues unless addressed with a performance adjustable chamber kit. the rear chamber is adjustable but not the front. the axels I ordered were a 1/2 inch shorter on each side and also rated for double the hp which the car does not have. also on a side note it was much warmer today as I was checking the oil ect... I was looking around the transmission and axels from the top of the engine bay. the 99 civic si has an extra engine/trans mount from other civics or cars with a DOHC VTEC B16 B18 ect... I found a long engine mount bolt wedged in the corner near the mount. once I got it out I thought ahaaa theirs my problem the bolt is rattling on the trans. left it out ..drove car still has the noise just once again quieter but now more distinct. also noticed vibration coming from the stick more than it did before from what I can remember. nothing violent just slight vibrations. have not reinserted the bolt yet so maybe the mount is causing the noise. strong chance. I will be replacing the mount tomorrow and will check back, in the meantime any feedback is greatly helpful.

It's not the length of the shafts; it's the angles they're going through. As a suspension and alignment specialist, I am strongly against any alterations to ride height on car and trucks. Besides the reduction in braking ability, steering response, handling, tire wear, and comfort, if I were to even work on an altered vehicle for any reason, I'm leaving myself open to be party to any future lawsuit. Lawyers and insurance investigators know all about this, and wheels and tires with different offsets, widths, and circumferences that are not stock, and they'll use it to convince a jury that you were partly at fault for the crash their client caused by running a red light, because you were less able to avoid it, and they will be right.

Also, the auto marketing business is so extremely competitive, if a manufacturer could offer a raised truck or a lowered car to the public that wants these vehicles, you can be sure they would do it. They know it can't be done without compromising safety. To do so would leave them open to lawsuits too.

That said, there is a range of travel designed into your suspension system, and the inner cv joints are designed to accommodate that range. By raising the wheel bearing, that range is extended on one end and may cause the shaft to hit on the inside of the housing three times per revolution.

The joint is expected to change length in two ways also. As the suspension goes up and down as you go over bumps, the shaft is supposed to move in and out of the housing. That's why it's spring-loaded and free to move. Second, due to there being an angle difference between the shaft and the housing, each of the three rollers rolls one way, then back, once per wheel revolution. If altering ride height causes the shaft to be too straight, or in-line with the housing, its length won't change much as it rotates. That concentrates all the stress and wear in one tiny area. That will not result in catastrophic failure of the joint but that barely-detectable wear will cause a steering wheel shimmy during acceleration, and that will be much worse anytime anything is done with the engine mounts that moves the engine sideways as little as 1/16", or raises it back to proper height when replacing a collapsed mount. Anything that results in those rollers running back and forth in a new spot will cause that steering wheel shimmy. That is due to the rollers binding during acceleration since they're not free to roll back and forth over the ends of the worn spots.

Part of the problem in finding this is if you jack the car up, the suspension will hang down, and that knocking of the shaft on the housing might not be there. There is a tool you might be able to borrow or rent from an auto parts store that borrows them called the "Chassis Ear". It is a set of six microphones, a switch box, and headphones. You clip the microphones to suspect points, then drive around while listening with the headphones. You can move the microphones around to zero in on the source of the noise. Be aware that many mechanics have never seen or even heard of this tool. Suspension and alignment mechanics use it to find rattles, squeaks, and other noises.

much appreciate the feedback as I am open to any opinion or even facts. I do as well agree with you on the lowered vehicle concept being an issue in MANY circumstances much in which you talked about. HOWEVER I have heard it go both ways as far as lawsuit and whose at fault. with that said I want to make it clear im not arguing at the fact that any alterations to ride height up or down as well as camber angles offset wheels and the will not cause issues, flaws, premature failer, excess wear...ect. I for one respect your expertise in the alignment suspension field greatly as their are so many factors that can play in to cause the smallest fraction of difference when it comes to alignment and measurement aspects accidents, upgrades, modifications, worn parts ect, but I will point out that some of your argument is one sided. sure on the legal end of things one could argue a lowered car with altered suspension and incorrect camber/alignment from factory specs can affect handling/breaking on LEGAL US ROADS/HIGHWAYS but in a track/off road setting stock alignment is almost always altered for obvious reasons. Now I can understand why this subject has come up as ive had CV axel problems recently on that note I also may add their has be multiple lawsuits on behalf of customers suing car manufacturers for flawed designs, excessive wear ect. ive seen many cases won in this case. I am pretty well knowledge on how suspension works, how wheel alignment changes over road surface especially with suspension travel. As I said before I still think we are straying away from my current problem and addressing possibly an unfixable problem or ongoing problem without proper ride height correction. The thing that confuses me when it comes to the CV Axels is im the 3rd owner of the car. I purchased the car with 87,XXX miles on it. besides excessive tire wear from the lowered ride height, CV Axel problems didn't first occur until the first set obviously were replaced because they were original from what the service record has shown since the car was brand new. Your point taken and it makes much sense that the set that was installed after that had worn so quickly was due to already worn engine mounts. as well as the set after that and the like. It still confuses me however what the problem is that im dealing with now is which I will address in a new post.

I've worked with race cars too, and that is a totally different ball game where lawsuits aren't a concern. For street driving I normally get a lot more vehement about this issue because I wouldn't be looking out for my new friends if I didn't make them aware of the potential pitfalls of making modifications.

In your case, if this was a design issue or strictly a ride height issue, everyone would be having the same problem with the same model car, and I haven't heard of that. We need to go back to the basics. If this is a noise concern AND a half shaft concern, I'd start with engine mounts and looking at the angle the shafts come out of the inner housings. Next, loosen the axle nut, then push in on the shaft and see if it pops back out under rather hard spring pressure. Be sure the tire is off the ground anytime that nut is not fully-torqued, otherwise the wheel bearing will become noisy. You should be able to push the shaft into the inner cv joint housing at least a good half inch. This most likely isn't the problem because if the shaft was bottoming out in the housing, you'd have a horrendous steering wheel shimmy. Look instead for signs the shaft is rubbing on the housing.

Be aware there might be different inner housing designs too. Chrysler, for example, had three or four different cv joints that interchanged for a given model. That was because sometimes one supplier couldn't keep up production, and it eliminated the worry about one supplier going on strike. Honda usually makes their own parts, but you never know if there was some mid-year design change.

Don't forget my Chassis Ear recommendation. I used to use one a lot, and it helped me find some things I never would have unless I was running alongside the car at highway speed!

Unless I missed it, you never said how the shafts are failing. What is happening to the joints?

The current problem that has arised stated in the original post I will go into detail about again as I have done further more research today. Now before I go into some detail I will explain the problem again.

-car is running at idle not moving with no abnormal sounds/no difference with clutch engaged or disengaged.

-car is moving (in any gear, with trans in neutral clutch engaged or disengaged, at any speed ONLY with RELEASING foot from gas) the noise is still heard.

-noise is much quieter after taken out of gear (while moving with foot off gas only) it is also a lot louder in 1st and 2nd gear at high rpm engine breaking with gears and is heard most distinctive in 4th gear around 50-70MPH and noticeably quieter when trans is taken out of gear with clutch or trans but is still audible until the car is stopped.

-noise has been described by many people with all makes and models modified or unmodified cars with MT/AT AWD/RWD/FWD. noise has been described as follows, playing cards against bicycle wheel spokes, grinding noise, rattle, trans gears non lubed with no whine, and tapping with almost perfectly exact consistency and frequency both effected by vehicle speed and rpm mainly speed both neutral or in gear MT/AT AWD/FWD. (Slower the speed slower the tapping or rattle, higher rpm faster and louder, higher speed louder faster ect) noise also described as almost always coming from trans/driveline from front of car alternating from left or right side.

-I have noticed a slight vibration from the stick alternating with speed and volume of the noise described following the stipulations above especially pulling it out of 4th gear into neutral from 50-70 the vibration is noticeably less. the vibration has only been described by 30% of people INCLUDING myself. vibration is almost completely gone and back to normal when car is stopped.

-CONDITIONS 1 no change in sound when car cold or normal 2 has been cold here 3 no change from road bumpy smooth ect

with all detailed above I will share some things ive found on the internet regarding what people have commented on what this noise could be.
-Exhaust rubbing or rattling
-Resonator separation (Noted TSB on 99-00 Civic Si for stock exhaust, but noise seems to always come from front of car)
-Subframe bolts lose (bolts rattle after load is taken off driveline by releasing gas pedal)
-carrier bearing
-lose rattling heat shield (I would think it would be too irregular of a noise, more distict, happen under acceleration as well not just decel)
-Clutch Disk Springs rattling (many people with same clutch installed as me "Exedy OE Replacement"+"Lightweight Flywheel" have described this happening shortly after install, didn't start happening to me for 3-5kmiles as well as I would think it wouldn't be as consistent of a sound and more irregular
-exhaust (cat breaking apart) lose bolt or separation from header/manifold at cat
-lightweight flywheel + clutch pressure plate combination is unbalanced together or install of lightweight flywheel altogether (claimed to be unfixable issues/normal without factory parts) but as I described the sound is still heard with the clutch is engaged or disengaged, sound only gets quieter by trans being put in neutral. almost makes me rule out clutch or flywheel
-timing belt or timing belt tensioner or pulley bearing
-EGR Cooler flex lines (releasing gas petal causes backpressure or a stuck throttle plate or intake exhaust flutter inside intake manifold)
-loose bolts somewhere on suspension

I cant rule out some of these without further Inspection of the car. with the warmer weather on its way it will be put on a lift and looked over entirely I will also attempt to move the car down a hill without the engine running to duplicate the sound. with more inspection I will check back and rule out some noted things as well as note findings or fix.

Please any feedback or thoughts/questions are greatly appreciated I also promise to help pass this on to whomever is having similar problems as it seems to be effecting a lot of people without many really having answers
some people also have done transmission replacements and still have had the same problem with even a brand new transmission. thanks again

interesting ... that's a great idea and I will most definetly try that when I am looking over the whole car. a close friend owns a general repair shop with both 4 post lifts as well as alignment racks, I am arranging a time to see him after hours to look over the car. as for the headphones I have actually heard of them now also made with a video option for optical and audible feedback. ive never used them personally but have seen and heard a lot of positive things about them. as far as the cv joints and axel shafts I haven't had any noticeable problems since the stronger Cv Axels have been installed, I agree and have also had my own experience with too aggressive or not enough of an angle at the CV joints on either end mainly caused by altered ride height as we both agree on, my experience has mainly been with Honda/acura both 4dr 2dr and hatchback. inside joints almost always show signs of problems with clicking on turns and inner joints almost always terrible steering wheel vibration across different speed ranges mainly on acceleration as you mentioned as well. I will be back soon to note my findings as always any ideas would be a great help.
As you can see ive opened pandoras box after 2-3hrs of research on all makes and models. what I can say from what ive read most of the people having the same issues almost all have had foreign cars consisting mainly of JDM and German cars with a pretty even balance between Modified Unmodified cars (suspension & performance upgrades) MT/AT AWD/FWD mostly some being older cars with miles like mine as well as cars with less than 5kmiles bone stock having almost similar issues. their may be documented manufacturer TSBs on some but I haven't gotten that far. looking forward to getting to the bottom of this wish me luck!!!

I was going to suggest coasting with the engine off. It appears to me you don't really have a half shaft problem. You just replaced them in an attempt to locate the source of the noise / vibration.

Do the Chassis Ear. They used to cost $200.00 from the guys who drive the tool trucks around to the repair shops each week. I've seen them on Amazon for less than 70 bucks. That's for the wired version with six microphones. If you want to hook one to something that is rotating, the newer model has four wireless microphones and two with wires.