driveline vibrations

Topic: driveline vibrations (Read 11095 times) previous topic - next topic

driveline vibrations

May 01, 2008, 08:44:49 PM

Its been awhile since I've posted...lifes had me busy but alas, I've found myself working on the T-bird again. To update I put a 8.8 from a auto TC in the car along with Steeda lowering springs and CHE adjustable lower control arms. After that the car developed a healthy vibration. This only occurs at certain speeds when you let out of the accelerator and/or get back into it and also when you get to higher speeds. I assumed (and had a Ford mechanic friend look at the car) that the pinion angle was way off due to the lowering springs and other changes. I just installed the adjustable upper CHE control arms and took my first drive after adjusting the pinion angle downward...I still have a pretty serious vibration. But now it seems to occur sooner and is a little worse at higher speeds. Obviously I still need to adjust things but I'm concerned it still won't take it all the way out. Previous to this I also lowered the trans crossmember to try and help. Just wondering if anyone has had this problem and how you solved it? Who knows maybe if I simply adjust a little more it will take the vibration out...

On a side note I was impressed on how the control arms improved the ride and handling. A nice little bonus!

driveline vibrations

Reply #1 – May 02, 2008, 09:06:28 AM

I hate trying to get pinion set!
But frist check driveshaft and make sure U joints are all good and its bolted to rearend right.

After that you can redo pinion angle.
Here are tips to doing it right.

Using a gravity angle gauge (Available at hardware stores) to measure the angle between the driveshaft and the ground & the pinion and the ground.

Hold the gauge on the bottom of the driveshaft. Align the gauge front-to-back under the car in line with the driveshaft and read the number from the gauge (Note if angle is up{+} or down{-}). Write down this number.

Next, hold the side of the gauge against the front of the pinion (beside the driveshaft). Write down this number (Note if angle is up{+} or down{-}). Subtract the first number from the second number. This is your pinion angle

Mounts change the degree's

All solid mounting points. -1 to -1.5
Half Solid & Half Poly Mounting points -1.5- to -2.5
All Poly mounting points -2.5 to -3.5
All Rubber mounting points -3 to -4.5
The more you get away from having all solid mounting points the more the rearend is going to try and rotate upward during launch. Therefore the more angle you must start with to prevent the angle from becoming positive (+). The idea is that when the rearend rotates you want the angle between the driveshaft and the pinion would be 0.

driveline vibrations

Reply #2 – May 02, 2008, 09:49:10 AM

Wow thanks man...I will have to work on the car more this weekend. I've spent the last two nights putting the control arms in and working on trying to adjust a little at a time. That gets old; jack car up, adjust arms, drive, repeat. I was getting more than a little frustrated last night.

This should help!

I put all new U-joints in a while back so that should not be an issue...

driveline vibrations

Reply #3 – May 02, 2008, 10:07:01 AM

Totally unscientific input, but when I replaced a soggy oil drenched tranny mount with a new mount (which raised the tailshaft), my vibration levels were reduced significantly. I added some washers to raise it some more and that helped too.

driveline vibrations

Reply #4 – May 06, 2008, 05:24:21 PM

So I've adjusted under the arms several times and never did get it just right. I still had a slight vibration. The last time I was under it I forgot I had it in neutral and the car rolled into my garage door and put a dent in the fender. All these years of babying the car only to do that...man was I pissed.

I think I'm going to take it somewhere where they have a nice lift and let them do it. Thus far I've done most of the work on the car but I've had enough of this pinion angle !!

Once this issue is ironed out and I fix a couple of small oil leaks (rear main, valve covers, etc.) i think I'm going to look into getting the car painted.

driveline vibrations

Reply #5 – January 06, 2009, 09:28:53 PM

Sorry to resurrect one of my old posts. I ended up taking the car to a friend of mine who does rear end work this summer. He adjusted my pinion angle and readjusted the backlash on my 8.8. Once I got it back there is still the same vibration (though not as bad). Couple of questions:

1.) Could a broken motor mount cause a vibration that sounds like it is coming from the rear of the car? I know for sure I have a broken one right now and I guess the sound could travel.
2.) Since the car has the original driveshaft and different rear end should I consider having the driveshaft balanced?

So far I have had the wheels/tires rebalanced, the pinion angle/backlash reset, and new u-joints. I freakin' hate trying to figure this kinda stuff out. Its starting to get expensive too.

driveline vibrations

Reply #6 – January 06, 2009, 10:06:00 PM

Does the vibration occur at a specific RPM? if so your drive shaft is probably out of balance. Also is the dampener on the end of the transmission slip yoke still there? It's a big round donut you can't miss it. If you'd like I can send you a picture of my drive shaft without one. (Don't ask)

driveline vibrations

Reply #7 – January 06, 2009, 10:56:41 PM

From what you described, it sounds like what happened with my TC.

The pinion bearing developed play, and would vibrate, but would vibrate worse if you didn't have a load on the car, like coasting downhill in neutral.

Eventually the pinion bearing exploded at 85mph because the rear had a very slow leak I never noticed.

driveline vibrations

Reply #8 – January 06, 2009, 11:32:57 PM

I was gonna say it's the pinion bearings not the pinion angle.
Replace all the rear end bearings any get pinion bearing preload right

driveline vibrations

Reply #9 – January 07, 2009, 02:53:10 AM

Try a hose clamp on the drive shaft, rotate it a 1/4 turn at a time, see if it gets worst or better. a simple but effective way of checking ds balance. It worked for me I had a vibe at about 70.
actually its still on, Had it with my stock setup and my new one.
I have a aluminum ds to put on someday.

driveline vibrations

Reply #10 – January 07, 2009, 10:42:00 AM

Quote

From what you described, it sounds like what happened with my TC.

The pinion bearing developed play, and would vibrate, but would vibrate worse if you didn't have a load on the car, like coasting downhill in neutral.

Eventually the pinion bearing exploded at 85mph because the rear had a very slow leak I never noticed

I'm fairly confident its not the pinion bearning. The guy that was in the rearend the last time said it checked out fine.

It does it around 70-75 mph and gets worse the faster you go. And it will also come and go as you get in/out of the throttle. I'm gonna crawl under the car this weekend and check for the exhaust rubbing anywhere...who knows it could be something that simple.

driveline vibrations

Reply #11 – January 07, 2009, 10:43:51 AM

Quote

Does the vibration occur at a specific RPM? if so your drive shaft is probably out of balance. Also is the dampener on the end of the transmission slip yoke still there? It's a big round donut you can't miss it. If you'd like I can send you a picture of my drive shaft without one. (Don't ask)

It seems to be more speed specific than RPM specific. The dampener is still there.

driveline vibrations

Reply #12 – January 07, 2009, 11:08:38 AM

Get a carbon-fibre driveshaft - a tiny bit expensive (lol) but it solves all the vibration problems!

driveline vibrations

Reply #13 – January 07, 2009, 09:29:52 PM

lol. yeah I should get a carbon fiber driveshaft...and a '03 Terminator Cobra motor and 6 spd while I'm at it too. lol. I think that would break the budget, but at this pace I will have more than the cost of a carbon fiber driveshaft in figuring it out!!!

What sux is I can't really drive the car to tweak and test...stupid winter time.

driveline vibrations

Reply #14 – January 07, 2009, 09:32:17 PM

Somehow I got in on a group buy for PST carbon fiber driveshafts on a Mustang site - it's definitely nice :D