silversrtman

iTrader: (20)

Hey all. We all have those issues with our cars that really, really get to us. Mine is driveline vibrations. I could never really dial in my pinion angle 100% so a buddy of mine suggested I do a double cardan u joint setup which basically turns a 1 piece 2 ujoint driveshaft into a shaft with a cv joint to which pinion angle doesn't matter. Long story short, I shortened my driveshaft to accommodate what I thought was a double cardan. Upon further research what I did is actually called an H joint setup. After I pressed all the ujoints in I saw that the driveshaft was really floppy. Even though I knew I was screwed at that point I installed in anyway hoping that if its bolted to the rear itll be ok. Well, its not. If I were to drive the car like this at the very least my tailshaft would get destroyed. So my question to any experts out there. Is there anything I can do with my current Hjoint setup that would fix floppiness? A true double cardan would but the parts seem expensive and I don't know exactly what I would need and then I will have to grind the weld down to separate the yoke which is terrible lol. Ive attached pics. Also I know a new driveshaft is an option but I would rather somehow fix mine to make it a cvjoint so I could get rid of my vibes. Worst case Ill buy a new shaft or make my own. Thanks in advance.

Bob@BruteSpeed

iTrader: (16)

You need a new driveshaft, what you currently have is an accident waiting to happen. Bob

silversrtman

iTrader: (20)

Yeah I know it is. As soon as I picked it up to install it and saw how floppy it was I knew I was screwed. Thanks for the reply Bob. Do you think it's worth converting it to an actual double cardan setup with the ball in the middle of the ujoints? Some cars come like this from the factory

Bob@BruteSpeed

iTrader: (16)

No, I would go with a good balanced aftermarket driveshaft in the correct length. Bob

Darth_V8r

iTrader: (4)

My 2 cents - if you're going to dump some coin anyway, consider a carbon fiber driveshaft. It does a few things for you. Shifts the natural resonance frequency higher than the thing will ever spin. Absorbs some of the engine surge if you're cammed. Lighter - though that likely isn't too much a help. And if it breaks, it'll just clean the bottom of the car for you without causing any damage.

It actually helped quiet my car down considerably - and that is saying something!

silversrtman

iTrader: (20)

damn, well it was worth a shot. You know what they say. Desperation is a stinky cologne. I just want to be able to take my car to speed without vibrating like a sharper image chair

when you say it helped you, did you have vibrations? The noise isn't what bothers me it's just the vibes. I can take my car up to 80 and that's basically it without feeling like I'm going to break something. However, my driveshaft from the factory had very tiny little balancing washers welded onto it, when i cut it and shortened it and got it balanced they welded on these weights that were much bigger. I wonder if it was out of balance from the factory

MidwestChassis2

iTrader: (1)

Maybe we can tackle your issue in another way. Give me some details of what all is done to your vehicle as far as suspension, what transmission, and what rear end. Also what driveshaft you have been using and if it was high speed balanced.

This is all assuming you balanced your wheels during this process to rule that out.

MidwestChassis2

iTrader: (1)

Reading your latest response it very well could of been the stock driveshaft giving you issues. Hard to say at this point but like mentioning you need to start with a new and keep your fingers crossed that was it, however if not we could revisit the issue and see if we can help figure it out with you.

silversrtman

iTrader: (20)

thank you. Yes my wheels are balanced correctly and everything is setup correctly to
my knowledge. I got my pinion angle as close as I could in line with my driveline angle and it was still pretty bad. I have a Dana 60 and before I cut it up I had their 3" chromoly shaft but like I stated above after taking 3" off the driveshaft the local place that balanced it put way more weight on it which doesn't make sense which leads me to believe it wasn't balanced correctly. I never even thought to try to have the shaft balanced. I saw the weights and assumed (whoops) that it was correct. As far as suspension I have hotchkis lowering springs, umi adjustable torque arm, umi sways, sfcs, adjustable panhard rod, lower control arms. My rear has lower control arm relo brackets welded on as well. Thanks again for the reply

MidwestChassis2

iTrader: (1)

What transmission? If it is a T-56 that may be your problem and not pinion angle or driveshaft balance. This is the reason we have since gone to Sonnex yokes with any T-56 transmission when we sell a driveshaft.

silversrtman

iTrader: (20)

whoops knowing the tranny is pretty important lol. Yes it's a t56. Why are the sonnex yolks better ?

MidwestChassis2

iTrader: (1)

They have better tolerances.

Darth_V8r

iTrader: (4)

It helped with Noise, Vibration, and Harshness all three in general. MWC is giving you some good info in this thread.

One thing I thought I'd mention is this - At 65 MPH, assuming you're in 3.42 or higher gearing, the wheels are turning roughly 17 revs per second. Think of this as 17 Hz. You can't hear it, but you'll feel every pulse in your gut or on the steering wheel, etc. On the driveline, that 17Hz is more like 55-70 Hz depending on gearing. That's vibrating fast enough to fill the car with a bassy drone, but you won't feel the individual pulses. At 80 mph, the frequencies are a little higher, but the principle is the same. So typically, if you're feeling the vibrations bu not hearing that drone, the first thing I tell someone is to check everything wheel-side. Balance, bubbles in tires, rotors bent wheels, bent axle shafts, etc. If its a shudder that is accompanied by that bassy drone I typically start looking at the driveline

silversrtman

iTrader: (20)

yes midwest has been very helpful. There's definitely a noise associated with the vibes and I know my tires and wheels are in good shape, plus this isn't the only set of wheels and tires that I've had vibes with. Btw I checked out the prices of cf shafts and those are out of the question unfortunately

MidwestChassis2

iTrader: (1)

The carbon shafts are substantially higher than the alternatives for sure and like Darth_V8r mentioned they do give many benefits. I use one for the safety factor myself.

With that said even a PST 3" steel would work for you for a good quality replacement. Keep in mind we are the only ones selling their shafts with the Sonnax yoke.

Don't be afraid to check out local shops for a driveshaft build, just make sure to use a good yoke and I would check the tailshaft for excessive wear to make sure that isn't the issue either.

Bob@BruteSpeed

iTrader: (16)

An aluminum driveshaft is going to transmit fewer vibrations that a steel driveshaft, I'd try to go aluminum if you can afford to do so. Bob

01ssreda4

iTrader: (96)

True high speed balanced PST shaft and zero pinion angle and you can rule that out as your vibration source.