Lately my vette has been making a clunk noise when I punch it, doesnt matter what gear but most pronounced when in a low gear. I'm worried that my mods may have killed the u-joints or something even worse. Also the trans has always made a bad clunk sound when I put it in D. Does it sound like all of my u joints should be replaced? Can you visually tell if one is bad? Will increased power from mods do them in?

 

Not sure what your power level is but yes power kills everything in the IRS. There are too many angles and everything including your wheels are changing angles as you drive down the road. All this angle changing and additional power causes problem eventually.

I fought with the IRS for YEARS and used to get literally 1 run on a set of spicer u-joints. They seem to be hit or miss as to the punishment they can take. Again my situation might be a bit to the extreme, but peope making much less power have broken the cases whereas I never had that misfortune - how I do not know, but as I said it seems to be hit or miss. Which is why I came up with the bolt in solid axle setups for these cars. No more worries and add as much power as you like and not worry about anything breaking.

With your particular situation, you need to get under the car with it off the ground and try to identify which ones are bad...there may be more than 1. Take it out and replace it following the torque specs of the manufacturer of the caps and joints. Another problem you should look for is the stub axles themselves get oblonged and do not support the joints properly. I went through several of them as well.......all I can say is I am pleased to not have that POS under my car anymore

If I were near you I would be more than happy to help you change them out, I was like a nascar pit crew changing tires with my ujoints. Not a single wasted motion, that is what happens when you do it 15+ times a summer.

 

I wouldnt say my power level is anywhere near what your car is making let alone extreme. I'd say I have about 310-330 HP at the crank(judging by how well I stack up against LSx cars). I dont plan on adding anything else for a while. I'm afraid that if they are worn out that they might lock up or break and tear up the rest of the drivetrain

I tried to replace the u joints on an old pickup truck I used to have but couldnt figure out you get the thing out of there. The setup looks the same on the corvette except it has halfshafts and the truck had a solid rear.

 

Like I said its hit or miss with the level of power. I have seen stock powered cars break stuff - just all depends on how the stars align and for me they often do not align for good fortune when it comes to breaking stuff.

To replace them you have to press them through to one side and pull that cap off that is exposed, then push it back to the other side and you should be able to weasle it out from between the two ears. It takes some practice, on the last one if you replace all 6, you will do it pretty efficiently. To replace them you reverse the process and try not to knock the little roller pins over in there which will cause you to not be able to press the caps all the way on again. Then you get to try to stand them all back up again. I used to use my 6 yr old to realign them...his little fingers fit in there perfectly.

They make a tool too that I had that makes pressing them in and out much easier. Looks like a large C-clamp, napa has them as well as harbor freight and other tool supply places. You can probably rent one from autozone for free if you return it. But if your like me - I end up keeping them ( you pay full price for it when you rent it, so they don't care or at least our local store doesn't)

 

A bench vise and a huge socket works good too!
A little word for wisdom; do not buy Napa/Auto Zone/etc. u-joints. Stick with Spicers... I had to replace some Napa "heavy duty" u joints on the half shafts after 2 years of use, one of the joints I took off didn't have any bearings left!

 

Your lucky if it's just the U-joint. I replaced the U-joints on a friends 84 that was make the same sounds your Vette is making. It turned out to be a bad pinion and ended up replacing the diff.

 

An automatic transmission doesn't "clunk" when you put it into gear. The clink you hear is slop being taken up in the drive train, behind the transmission. That can come from any, or combined from every, of the many points where there is slack in the drive train. Such as, u joints, (6 in a C4), the slip yoke, the ring gear back lash and even the hubs on the spindles. You should caerfully inspect the whole drive train for any excessive play in any of the connection points. Excess power isn't the only cause of the demise of u joints. Every day use and plain old wear and tear will do them in. Added power certainly can accelerate the process. For severe service, you want the genuine Spicer brand u joints, the ones without grease Zerks.

RACE ON!!!