I guess I'm bringing this one back from a few months ago.. I need answers, hopefully someone can help..

I have a long story that goes along, that has a lot of insight, so please bear w/ me..

All started 2-3 years ago... I had to get the rear diff rebuilt since the whirring was terrible. Turned out to be an axle seal went bad, and I lost all the fluid over the course of a few months..

Well, shop rebuilds the rear-diff, but incorrectly. It slightly damages my 3.73's but as long as my Eaton LSD is fine, I don't mind a little gear noise.. Problem is, ever since then, I've had the vibration coming from what seems to be the middle of the car..

Fast forward to last Fall. Since I was sick of the noise, and it seemed to get slightly worse, I brought it to a good friend who took a look.. He recommended U-Joints. initially, since he didn't really get dirty that day.. After swapping them, I notice the vibration is a little worse.. He gets back under the car w/ me, and sees the tranny mount is trash..

I replace it. Most of the vibration is gone, but it's still pretty bad from 50-85mph, then it goes away. Gear noise is still present, so I re-shimmed my rear-diff. Noise is still there...

So.... Recently, I got a bunch of money, and decided to do the right thing.. Replace my entire suspension. Well.. No dice.. STILL have vibration, and I think it's causing the pinion seal to separate from the housing, and I'm getting a little oil spray right about the diff..

I replaced the U/LCA's, Shocks/Struts, Rims/Tires, Tie-rod ends, brakes, wheel bearings, hardware etc.. I mean, the only things original about my car are the engine itself, driveshaft and the paint on the rear of the car...

So I searched for rear-axle alignment, to see if maybe that is off. How does one go about aligning a solid rear axle?? Is it all toe-in/caster adjustments??


Any help would be huge!!!


JT

 

I have had extensive rear end rebuilds myself and from what you've said I can't think of anything that would be causing the issue without being there myself.
Is it just a whine, is their clunking? What specific sounds can you elaberate on?

 

It's all sorts of vibration and whirring.. The whirring DEFINITELY sounds gear related, however, the vibration feels more like U-joints or driveshaft issues..

This is why I'm thrown.. After 2 complete rebuilds w/ in a year of each other, and a completely new Suspension w/ wheels and tires, new transmission/mounts, wheel bearings/axle bearings, I was hoping that would have gotten rid of any vibrations.. Was I wrong.. Didn't do a damn thing..

It's not going to make a difference, but I'm putting the rear Diff. Girdle on in a few minutes.. I'll see of maybe a little more firmness gets rid of some of the vibration, although I'm not holding my breathe..


JT

 

The bushing in the tailshaft of the trans could be the problem, seen it a few times and it will vibrate until replaced.

 

Ok if its in the middle of the car, not sure how you figured its in the mid rather than front or rear, then theres one thing in all your tries you havent checked or replaced. The driveshaft. Take it out and take it to a driveshaft shop, have them balance it for you. THey might tell you that its so far out that it cant be and youll need a new one.
Also, I dont think that a rear end itself can cause a vibe unless it binding. And at that point I would imagine that you wouldnt be able to turn it by hand. But at any rate by reason of deduction, new gears, t-lok unit, axles, rims tires, all thats left is the driveshaft.
-P.

 

Not a bad idea.. The other idea I had was if I had put the pinion flange/slip yolk on the D/S in reverse (front to the rear, rear to the front) or backwards... Problem was, I had too many variables from the start.. Now that I've gotten rid of most of them, I think it's either gears or Driveshaft..


Funny thing is, I kept listening to a few other friends of mine who kept striking down the idea that the Driveshaft is no good... Time for Aluminum I guess, if that's the issue...


What I don't get though, is why the vibration goes away around 85-90mph, and comes back around 100.. Don't ask how I know...



JT

 

there's a driveshaft vibration damper (i don't know the correct name for it) that installs near the end of the driveshaft - towards the diff area, you might want to check to make sure its present because the shop you had the work done at may have removed it and not re-installed it.

 

Hmm.. Interesting.. I think I know exactly what you're talking about.. Isn't it a little rubber, well, thing that goes towards the slip yolk, instead of the diff??


First thing tomorrow, the Driveshaft comes out.. I'm sick of dealing w/ this sh-t.... [:@]



JT

 

Sometimes when you go to a lower rear gear you'll get driveshaft vibration... What is actually happening usually is that the vibration you may have not noticed at 100+ mph is now at 70+ er so... The driveshaft is turning extra revolutions, which at high speed may have some vibraton. I have a small one myself at about 90-100 mph.
Try removing the weight off the bottom of the diff. Sometimes this helps, sometimes it makes it worse.

If nothing else you may look into buying an alluminum driveshaft..... nice, light, and balanced..

 

Is anyone still following along??


So yesterday I installed the Rear Diff. Girdle, and between getting Permatex in my hair, and about an accidental 2qts of Gear oil on the street, it wasn't such a bad day after all..

I switched to 80-145w Gear oil, just regular Petro, and it quieted down a lot of the gear whine. It's funny though, I thought I wasn't going to feel a difference, but when the car shifts, and launches now, it feels so much more firm...

Anyway, after inspecting the gears, there isn't much crowning, or any burrs, however, there was quite a bit of metal "dust," floating around in the old oil...

On top of all of this, the original PI Intake mani, has developed it's standard crack near the T-Stat housing..

So, either I'll roll the car off a cliff, after I set it on fire, or I'll have to wait until the Spring to rebuild it..


4.30's or bust..



JT