Clunking noise from the rear end???
 

August 20th. I drove her down to PIR and everything was fine. Got to the burnout box for the first time and started to heat up my Summitomo HTRZ rear tires and I felt the rear end make the usual drift to the right because I don't have C4 beam plates yet. But during the burnout, I felt something break. The car snapped sideways about six inches further to the right and stopped as if the body of the car hit something (which of course it didn't).
I made my pass very gingerly and got back to the parking lot and jacked the car on both sides and could not feel any play in any drive shaft or half shaft. Could not feel any play in any of the suspension components. Yanked on both wheels in all directions with the car in the air and could not feel anything out of the ordinary. I decided to drive the car home where I could take a closer look but slowly got it up to free way speed without anymore noise or other issues. I have a spare six speed corvette parts car at home so I got on the throttle harder and harder but everything seemed fine. Go ahead and feel free to cringe but I took the car back and raced it more than ten more passes at PIR. I felt and heard a "clunk" several more times from the rear of the car throughout the night but it never broke. I ran 12.6 @ 114mph multiple times and drove it home. Turned into the driveway which was a tight, slow, right hand corner and heard it clunk three or four times. Clearly there is something that needs repair but I had to head out to Eastern Oregon to help my parents out and heven't had a chance to look at it since. Any ideas? On the way home, I went over several speed bumps with no nothing noticably wrong with the supsension. I would think that anything in the drivetrain that would be causing the car to make that much noise from the rear would have broke with the amount of extra abuse that I put on it. So the only things I can think of that might be causing it would be a wheel bearing or something. It shimmies a little while turning but still goes in a straight line pretty good. Penny for your thoughts???

Re: Clunking noise from the rear end???
 

Just guessing, but my thinking is that it could be as simple as a U-Joint gone bad or as ugly as problems in the differential, i.ed, broken spider gear or clutch pack.
I've never broken a spindle so I don't know what the symptoms are, but I've read they are a weak point.

TomC
'Crabs

Re: Clunking noise from the rear end???
 

Sounds like either a spider or side gear in the differential unit has split a tooth.
I would definitely tear it down and check it out thoroughly otherwise you run the risk of wiping out the gear set and differentila case when it finally lets go.

Re: Clunking noise from the rear end???
 

Okay, my two cents, fwiw.

On my C3...waaaay back in the late 70's before synthetic gear lube the rear would start to make clunking noises as the fluid lost it's lubricity when taking slow corners. Further lube degradation would eventually yield a loud banging noise from the clutch pack. Have you checked the fluid level and or do you know when the last change was performed? You could feel the rear slewing the car to the left or right randomly, and this symptom would get worse as the fluid degraded also.

A second thought, but this is way out in left field, are the C-beam bolts at proper t/q spec?

:cheers:
Tom

Re: Clunking noise from the rear end???
 

My money is on a toasted U-joint. Mine made the same noise also. Put new U-joints in and no more clunk. Your going to go through U-joints pretty often when you drag race. It just comes with the territory.

Re: Clunking noise from the rear end???
 

I just got home 30min ago from eastern oregon. I will take a look at the differential fluid later tonight. The car does have a very noticiable "slweing" from left to right in conjuction with weird noises. I am probably going to replace all my u-joints and the diff fluid and take it for a spin and see if the problem has corrected itself. Thank you guys for your input. :thumbsup:

Re: Clunking noise from the rear end???
 

chris if you do the u joints use the 799 series spicers they are the best money can buy

Re: Clunking noise from the rear end???
 

my car is making the exact same noise. Rick and I are going to replace the u-joints and hopefully that solves it. The U-Joints aren't to pricey, so if I am going to throw some money at a noise then they make perfect sense. I also think my problem began after doing some burnouts and drag racing.

Re: Clunking noise from the rear end???
 

I got a tip from a friend here on the registry to go with the spicer differentials from dennys driveshafts. Not sure if they are the ones you recomended but Here is the link for the half shaft u joints i ordered. I also bought the drive shaft u joints too and parts are on their way. I also bought a poly bushing kit for the car and that is on the way too. http://www.dennysdriveshaft.com/p443...build_kit.html

It is somewhat comforting that my car isn't the only one having this issue. keep me posted on your situation.

So far, I have only gotten the exhaust out of the way. I pulled the bottom differential bolt last night thinking that would drain the fluid from the diff but it didn't. I am thinking since I have C4 beam plates ready to go in, a bushing kit on the way, and a spare 3.45 geared Dana 44 ready to go, I am going to pull the bat wing out today and split the differential case and have a look today. Thats a little ambitious, don't know if I will get that far but I will keep you guys posted.

Chris

Re: Clunking noise from the rear end???
 

I ran out of time today to pull the diff, Should have it out pretty quickly tomorrow morning though.

I was talking with my dad who test drove the car several days ago to see what he thought of the issue and he told me that he backed the car down the hill out of the driveway and stopped, pushed in the clutch, and the car rolled "UP" hill... that sounds like something is binding up in the rear end to me and makes me highly doubt the issue is being caused by a U joint (but new u joints wont hurt a bit). I have a 3.73 gear dana 44 installed in my project car so I am going to pull that pumpkin and put that in the Z. That will get rid of my problems for sure and give her a little more pep. Then at some point I will rebuild the diff that is coming out of the Z with 4.10 gears for the project car. Will let you know what I find tomorrow when I pull apart the suspected bad differential.

Re: Clunking noise from the rear end???
 

Chris, the "backing up hill" symptom could/has to be a problem in the clutch hydraulic system. It's loosing PSI to keep the release bearing engaged. Of course that is assuming that the trans was in a gear when the clutch was depressed and the car moved by itself.

I would just recheck that road test to make sure that the symptom was happening, or not happening. The zf's syncros do not react well to malfunctioning or degraded clutch hyd system performance....they usually get toasted!

http://zfdoc.com/ here is Bill's link to his zf site.

:cheers:
Tom

Re: Clunking noise from the rear end???
 

Another road test to ensure the car was or wasn't rolling up hill is not going to be possible. I have already pulled the diff out and seperated it for inspection. The car was backed down the hill and then when the clutch was depressed, it rolled a few inches forward (up hill). The transmsission would have been either in nuetral or in reverse at the time, so correct me if I am wrong but that doesn't make sense for a faulty clutch hydraulic system. It also doesn't make sense for that to have caused the rear of the car to feel like its moving around underneath the car accompanied with popping and or clunking once in a while.

The differential is appart and I did find a little bit of metal dust in oil but not as much as I was expecting. Beyond that, my untrained eyes cant find anything wrong. All my ujoints are solid (they are not sloppy, worn out, or broken in any way). I have no idea at this point what actually went bad. I can only assume the differential needs to be rebuilt. If you have any ideas, please let me know.

Re: Clunking noise from the rear end???
 

I was a little shocked to find so many different options for ring and pinion gears so I have done some research on the Dana 44 to try and sort through the mess. Here is some of the really good info I found on some forum posts accross the net. Maybe most of you already know this stuff but I figured I would post it anyways.



the vette d44 is actually a half-breed....d44 ring gear with a d60 pinion gear.

the d44 used in jeeps,international, chev pick-ups, etc can be installed in the vette housing, using the vette carrier...done that years ago before true vette gears became available...need the jeep yoke and front seal, bearings from any industrial bearing supply house (off- the-shelf bearings, simply cross from dimemsionals)...the smaller pinion shaft of the jeep is obviously not as strong...there are ''sleeved'' jeep pinions being sold, beware.

4.09's have a smaller (STD D44) pinion diameter with a tack-welded sleeve, and are your least desirable (but still perfectly functional) option.

4.10's are *marginally* stronger than 4.09's/4.11's, but require that you purchase a 4-series carrier.

4.11's are available in a "thick-gear" configuration which will use the 3-series carrier you already have. "Thick-gears" are available from many different companies now days.

Richmond's R&P sets are inherently noisy. Other than that *I* am aware of no other manufacturer having noise issues with a proper setup.

I am running 4.11 "thick gears" from Tom's Differentials in the stock 3-series carrier. I R&R'd the diff myself and sent it to DriveTrainSpecialists (whom I highly recommend, BTW) for the actual swap/setup. The entire project (new gears, rebuild kit, installation, shipping, etc.) ran ~$450. <---in 2006 so prices may have changed.

I have the 4.09 gears. For all of the above reasons I would choose the 4.10 dana viper gears. But I do have to say, the problems I have had with the dana 44 have not been ring and pinion related. It has been spider gear and pin problems. Oh, and IMHO and experience dont believe all the hype about the dana 44 being bullet proof down to 1.30-1.40 60ft times. Believe me, if you beat on them enough, high 1.6x times will break them and its not just me. There are others such as Mackey who ran regular 1.5x times and broke them as well.


the rear cover (batwing) for the d36 is different from the d44 bat , but can be used with an adapter plate (i have an adapter on my spare d44 rear/ d36 bat)...the d44/ d36 / adapter is a stronger assembly than the d44 chunk/ d44 bat in the gear case area, but the bat ''outriggers'' of the d44 bat are slightly heavier --welding flat bar reinforcements to the d36 bat gives it the edge....outriggers probs are rare but have occured.


There is a carrier break between gear ratios equal to 3.73 and numerically lower and gear ratios equal to 3.92 and numerically higher. Gear ratios equal to or numerically lower than 3.73 require a 3series carrier (bolt size 3/8 in diameter). Gear ratios equal to or numerically higher than 3.92 require a 4series carrier (bolt size 7/16 in diameter). THICK gears with a ratio equal to or numerically higher than 3.92 are designed for the 3series carrier.

Re: Clunking noise from the rear end???
 

For thoe who care, I got the car back on the road today. It apears to be fixed. But I installed a whole different Rear suspension, differential, and driveshaft. Along with C4 beam plates and poly bushings. I have an appointment tomorrow at 2pm for an alignment. Then I will take it out for a cruise and make sure she is all better and also to test out my new 3.73 gear ratio change.

Re: Clunking noise from the rear end???
 

Did you ever nail down what ever it was that was "clunking" and causing the rear to step out?
Just curious.

TomC
'Crabs

Re: Clunking noise from the rear end???
 

I did not figure out what was causing the issue. Since I was in there, I replaced everything with spare parts from my race car project. I am assuming the problem was in the differential which is going to get rebuilt with a gear ratio change for the race car.

Re: Clunking noise from the rear end???
 

Great synopsis on the ZR-1 D44. It's all going in my Tech subdirectory.

Thanks for taking the time.

Re: Clunking noise from the rear end???
 

Half-breed?

Your comments regarding the D44 are quite applicable to the D44 used in everything EXCEPT VETTE/VIPER! The IRS 44/44HD (216) and the Super 44 (226) I wouldn't consider "half-breeds" at all but "purpose built" units.

Yes they share pinion diameters and spline diameter of the D60 and in the early years many D44 pinions were sleeved or specialty bearings used to assemble ratios other than those offered by OEM. You also when using these installation procedures had to use the "lesser" D44 pinion flange, less splines and a substantially smaller diameter stem but adequate it seemed.

The ring gear bolt diameter has absolutely nothing to do with a 3 series or a 4 series carrier and I don't recall ever seeing a 4 series carrier offered for a VETTE/VIPER. Would a 4 series from a conventional D44 do? Certainly not! To the best of my knowledge and all I've ever seen offered for a VETTE is a single carrier that the correct ring/pinion gears are manufactured for. Adjustment of ring gear thickness of course is required for various ratios and pinion diameters required but there's not 3 series or 4 series case. You referenced Tom's and I believe if you check their applications you'll see only a single case application!

A VETTE 44 is/was only manufactured in a 216mm configuration with 3/8 ring gear bolts. The VIPER was built with both a 3/8 bolt thru MY 2000 and 7/16 MY 2001 +. The Super 44 226mm configuration is also shared with the Grand Cherokee & SRT Jeeps and there are a few different axle ratios available for it. The VIPER/MOPAR performance ring gear packages are mostly built with a 226mm configuration and "may" when used in a VETTE application require a "massage" of the case/housing. You need to make sure you buy a correct 3/8 bolt ring/pinion package if you elect to use the VIPER/MOPAR gear kits.

The D36 cover with an adapter/plate for a D44 adding strength? Really?

The differential pinions, side gears and cross-shaft are for sure the weak link. There's often little attention paid to the "fit" and the condition of the pinion thrust washers, the pinions and the cross-shaft fit to the bore of the carrier.

------------------

Chris -

A comment in your post looked familiar and it was by a friend/acquaintance on the Corvette Forum in '06. Most but not all of your "researched" comments were from that thread.

The only direct comment of yours I find fault with I guess is your reference to ring gear bolts! That as I pointed out is "erroneous".
Ring gear bolt size has nothing to do with a 3 or 4 series build. Just "ain't so"!

There are options for the Vette/Viper 44 but not ever having a "hands on" I'll not comment other than to their expense.

The Eaton - reasonably priced and a recent addition to their applications

OS Giken LSD - exotic, expensive and likely requires some modifications. Theirs is "serious stuff"!

Re: Clunking noise from the rear end???
 

We are also experiencing a "clank" sound when going over small bumps, potholes, sewer lids etc, not speed bumps tho, just uneven smaller stuff in the road.

For me it sounds like it's coming from the rear on the driver's side. It's just like someting small is loose and hitting another metal part when the car is passing uneven surface....sometimes more of a "pling" than a "clunk" if you know what I mean.

Only had the car for a few weeks, but we have driven it both often and hard for around 1000 miles or so.

Going on a 3 week roadtrip soon and would like to find out before leaving.

About the car itself, it's a 91 with 57k miles on it. in 2005, at 50k miles, it went to Haibeck's for a 4:10 gear change, new injectors etc. In 2007, at 53k miles, it went back to get the engine powder coated and a performace chip installed.

As you can see it's not been driven very much since (we bought it at 56k miles in may).

It had all brand new tires and brakes + oil/filters when we bought it.

It runs and drives like a madman and everything is fine, just not that annoying sound we have noticed lately...

From reading here and many other threads online, we will put it on a hoist and check for loose bolts etc, but all and every tip from you guys are highly appreciated :fahne:

Re: Clunking noise from the rear end???
 

Check the spare tire area for the tools and the compartment is tightened down.


Lou

Re: Clunking noise from the rear end???
 

Marc Haibeck told me this:

"The number one cause is a loose rear sway bar link bushing. They are difficult to see with the wheels on the car. Look for missing bushing rubber and/or red dust in the area from high pressure fretting corrosion."