Driveline Vibiration - GONE - TCCoA Forums
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post #1 of 40 (permalink) Old 02-12-2005, 01:26 AM Thread Starter
 
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Driveline Vibiration - GONE

When I bought my 95 last year it had a bad driveline vibiration. I checked the u-joints, (look & shook) and they seemed ok. I then went about checking the driveline angle and found it out almost 3deg.

All I had time to do was a quickie shim and let it go. The vibe was better, but far from gone.

Last week I was able to get all four wheels on ramps so as to have all the weight sprung from the wheels. I checked the angle of the crankshaft pulley, and then the rear carrier u-joint.

The engine and trans. was 1/2 deg. up, while the pumpkin pinion was 2 1/2 deg. up. I loosened the bolts holding the front of the pumpkin and lowered it until I achieved the correct 1/2 deg. to match the engine.

I then measured the distance between the isolator and the sub-frame. I went to the hardware store and purchased enough thick washers to make up the difference in the space.

I removed the pumpkin bolts and placed the washers between the isolators and the subframe, checked to make sure the angle was still correct, and then tightened the bolts using high strength locktite, just to be safe.

Test drive, NO VIBE!! I usually don't run over 75 , so I went to just over 80 to check. Smooth as silk, and the car is much quiter without the harmonics of the vibe echoing throughout the car.

Those with the vibe should check you pinion angle. It sure is nice to no longer be a member of the "Vibe Tribe".

Tool Used:
http://www.sears.com/sr/javasr/produ...id=00939840000
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post #2 of 40 (permalink) Old 02-12-2005, 07:43 AM
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So in order to measure pinion angle, you put the magnetic protractor on the pinion itself where the drive shaft attatches, correct?

<----not throwing rocks at girls anymore
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post #3 of 40 (permalink) Old 02-12-2005, 02:49 PM Thread Starter
 
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The way I measured the angle was to jack one rear tire up, spin the wheel until a u-joint cap that is attatched to the pumpkin yoke is facing straight down. Then lower the wheel to have equal force on the rear sub-frame.

I then removed the clip that holds the u-joint cap in place, and found a good straight socket that would fit into the yoke and rest on top of the u-joint cap. Then I held the angle gauge aganist the exposed end of the socket.

The u-joint cap is flat on top, and is the exact angle of the rear pumpkin yoke. (if you don't mess up and use the cap attached to the driveshaft)

There are adapters that you can buy or make, but this is as accurate as anything.

Since a dial gauge is not as accurate as a digital, you just have to hold it solid and steady, and be sure that you get the crankshaft and pumpkin degrees as close to each other as possible.

If you must be off some, make the rear angle lower than the front, as the rear will have a tendency to rotate up from d/s torque, but be within 1/2 degree.

I had to lower the front of the pumpkin so much that I needed to take a crow bar and spring the d/s loop down to keep it from rubbing the d/s.

This is very simple and quick to do. I just wish I had a digital camera to post pics.

BE SURE to replace the u-joint cap clip when finished.
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post #4 of 40 (permalink) Old 02-13-2005, 02:56 PM
 
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Quote:
Originally Posted by yardbird82056

This is very simple and quick to do. I just wish I had a digital camera to post pics.
TECH ARTICLE ATTENTION MODERATORS

I will perform this soon !! as Alot of us have vibs when swapping gears and
removing pumpkins - I used the mn-12 performance bushings " might be
different size than stock"

Thank You yardbird
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post #5 of 40 (permalink) Old 02-13-2005, 04:15 PM
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Yeah, I am convinced this is my problem now. The diff was recently set up so it is fine. The Mark VIII drive shaft was smooth as butter up to 145mph with stock diff. I am thinking that combination of different diff is a different angle.

Thanks!

Big-Al

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post #6 of 40 (permalink) Old 02-15-2005, 11:02 PM
 
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Wow, too bad you didn't come up with this in '94 or '95. A friend bought a brand new Cougar with bad vibes. It spent more time at the dealer getting pumpkins and driveshafts swapped than on the road. They put all kinds of 'doo-ma-hicky' weights on the trans and exhaust that were filled with steel shot. The people at the Ford dealer must've hated him. One day he took it back because the bearings were bad in the diff [whining sound]and presto...it was fixed. They must've got the pinion angle correct when the new diff was installed. That was almost 3 years after he bought the car.
Just wondering if shimming the trans mount would work too?
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post #7 of 40 (permalink) Old 02-16-2005, 12:15 AM Thread Starter
 
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Quote:
Just wondering if shimming the trans mount would work too?
It would only work if the pumpkin pinion angle is up more than the transmission angle. eg: trans down 2deg. pumpkin pinion 0deg. Raising the rear of the transmission would then bring the angle of its pinion up to 0deg.

"Always measure the slope of the drivetrain going from front to rear. A component slopes downward if it is lower at the rear than the front. A component slopes upward when it is higher at the rear than it is in front.

In a conventional two joint driveline, the center line of the driving device (transmission) and the center line of the driven device (axle) are usually parallel.

As a U joint moves through its operating angle, it moves through an elliptical path that causes the velocity, or surface speed, of the driveline to increase (and decrease) two times per revolution.

If the U joint operating angles are equal on both ends of the driveline, you will have smooth power flow through to the pinion. The system will run smooth because the second U joint will be decelerating at the same time the first U joint would be accelerating the drive line."

In other words, if the transmission yoke is 2deg. down, make the pumpkin yoke the same. It is easy to get confused about up and down on the pumpkin angle. The u-joint may be facing up toward the transmission, but the angle is considered down because the rear of the yoke is pointing down, through the pumpkin, toward the ground.

Some text copied from: http://www.sixstates.com/modules.php...howpage&pid=32
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post #8 of 40 (permalink) Old 02-16-2005, 07:47 AM
 
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In other words, if the transmission yoke is 2deg. down, make the pumpkin yoke the same. It is easy to get confused about up and down on the pumpkin angle. The u-joint may be facing up toward the transmission, but the angle is considered down because the rear of the yoke is pointing down, through the pumpkin, toward the ground.

I read something about pinion angles in Hot Rod, 4X4, ect magazines, saw it on reality tv . I realized the centerline should be the same but the terminology went in one ear and out the other
I'm pretty sure 0* between the yoke and shaft is bad. Like in front end alignment....0* makes things wobble. Don't the u-joints need a slight angle with the non-moving diff to get the rollers rolling and making even wear pattern?
After reading what I typed it may be confusing.
What I'm trying to say is both yokes should be at the same centerline but not exactly straight with the driveshaft.
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post #9 of 40 (permalink) Old 02-16-2005, 02:59 PM Thread Starter
 
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What I'm trying to say is both yokes should be at the same centerline but not exactly straight with the driveshaft.

You are correct. Both pinion angles should be the same in normal driveline setups, be it 2deg, 0deg, or whatever. The driveshaft should be at an angle off of centerline. This can be achieved by one yoke being lower than the other, or offset to one side, such as a pumpkin yoke not being exactly centered on the rear axle.

The theory is a minimum 1deg working angle to keep the u-joint needle bearings rolling, so as to not wear ridges in the joint, and to keep the grease moving.

All factory cars "should" have this build into them. What I believe happens is the tolerances are not checked when assembled, this will cause a vibration when new. Also, as time goes on you will have bushings, mounts, and springs wear and sag, which will cause a mis-alignment and vibration that comes on with age.

Lets say your yokes are both at 3deg down, and the driveshaft is 1 1/2deg down. Subtract the smaller number from the larger number: 3 minus 1 1/2 equals 1 1/2 deg. This means you working angle is 1 1/2 degrees. This is more than enough to keep things greased without undue u-joint wear, but still deliver a smooth driveline at speed.

After setting mine up I had a working angle of around 1 1/2 degrees.
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post #10 of 40 (permalink) Old 03-26-2005, 04:07 PM
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Quote:
Originally Posted by yardbird82056
When I bought my 95 last year it had a bad driveline vibiration. I checked the u-joints, (look & shook) and they seemed ok. I then went about checking the driveline angle and found it out almost 3deg.

All I had time to do was a quickie shim and let it go. The vibe was better, but far from gone.

Last week I was able to get all four wheels on ramps so as to have all the weight sprung from the wheels. I checked the angle of the crankshaft pulley, and then the rear carrier u-joint.

The engine and trans. was 1/2 deg. up, while the pumpkin pinion was 2 1/2 deg. up. I loosened the bolts holding the front of the pumpkin and lowered it until I achieved the correct 1/2 deg. to match the engine.

I then measured the distance between the isolator and the sub-frame. I went to the hardware store and purchased enough thick washers to make up the difference in the space.

I removed the pumpkin bolts and placed the washers between the isolators and the subframe, checked to make sure the angle was still correct, and then tightened the bolts using high strength locktite, just to be safe.

Test drive, NO VIBE!! I usually don't run over 75 , so I went to just over 80 to check. Smooth as silk, and the car is much quiter without the harmonics of the vibe echoing throughout the car.

Those with the vibe should check you pinion angle. It sure is nice to no longer be a member of the "Vibe Tribe".

Tool Used:
http://www.sears.com/sr/javasr/produ...id=00939840000

SWEET! I have been fighting vibrations for a LONG time! Some of you may remember my posts. Anyway, my car had this EXACT same problem. I just checked it today and had to put some washers between the isolators and the subframe - NO MORE VIBES! THANKS FOR THE HELP!

Randy

Randy
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post #11 of 40 (permalink) Old 04-02-2005, 07:49 PM
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I wish someone would post some pic's. And where and how much can I get a Mark VIII drive shaft for. That's the aluminum one right?
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post #12 of 40 (permalink) Old 04-02-2005, 08:03 PM
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Originally Posted by conradcliff
I wish someone would post some pic's. And where and how much can I get a Mark VIII drive shaft for. That's the aluminum one right?
Sorry, I didn't take any pictures. But, I was able to do it without removing ANYTHING (with the exception of the U-Joint clip. I measured the front angle from the crank. As far as the MK8 driveshaft - just hit the salvages. Remember that you want a '93 ONLY! '94 up driveshafts are a two piece design where the '93 is a ONE piece!

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post #13 of 40 (permalink) Old 04-02-2005, 08:22 PM
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That's ok, after reading that last one the picture finaly popped into my head. you are just measuring the angle of the drive shaft and comparing it to the angle of the side of the u-joint that's attached to the pumkin. But what do you measure the angle against? A level? Also, is there any validity to this? http://forums.tccoa.com/showpost.php...5&postcount=27
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post #14 of 40 (permalink) Old 04-02-2005, 11:26 PM Thread Starter
 
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Detailed instructions for dirveline angle adjustment:


Start off by getting the car raised up so you can get under it. Make sure all the wheels are on ramps or something sturdy. You want weight on all four wheels so the sub-frames will be sitting as they would when driving.

Jack up one rear wheel(make sure car is chocked and will not roll) and turn the driveshaft until the rear pumpkin yoke u-joint is facing straight down. Make sure it is the pumpkin yoke, and not the D/S yoke. Lower the wheel.

Remove the bottom u-joint clip and place a good straight socket against the u-joint cap. Place the angle finder against the socket and record the reading. The socket acts as an extention of the u-joint, which will give you the actual angle of the pumpkin when the angle finder is used.

You get the transmission yoke angle by placing the angle finder against the front of the crankshaft vibration dampner. Since the engine is attached to the transmission, it will have the same degree angle as the transmission yoke.

Record this angle.

Both should be the same, example 2 1/2 degrees, or whatever yours happens to be.

If both are not the same, you will need to shim the pumpkin. Most likely you will have to lower the front of the pumpkin to get the angles together.

To do this you will loosen the bolts holding the front of the pumpkin and lower it until the correct degree to match the engine is achieved. It would be better to get the front of the pumpkin 1/2 degree lower than the engine angle, as the pumpkin will rotate up as torque is applied, making the driving angle more even.

Measure the distance between the pumpkin isolator and the sub-frame. Go to the hardware store and purchase enough thick washers to make up the difference in the space.

Removed the pumpkin bolts and place the washers between the isolators and the subframe, check to make sure the angle is still correct, and then tighten the bolts using high strength locktite, just to be safe. Recheck angle.

I had to lower the front of the pumpkin on mine so much that I needed to take a crow bar and spring the d/s loop down to keep it from rubbing.


This is the angle finder:http://www.sears.com/sr/javasr/produ...00&bidsite=&BV


I posted most of this earlier, but this is more complete.

Last edited by yardbird82056; 04-03-2005 at 01:14 AM.
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post #15 of 40 (permalink) Old 04-02-2005, 11:41 PM
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...and what are the measurements when your car is under acceleration? There can be asevere change in pinion angle as soon as you touch the gas pedal.

This has been a controversial discussion amoungst many drag racers in the past. Now, I am not entirely sure, but I do know for a fact that there is some pinion angle built into the car(pre-load) to compensate for center-section rotation.
How does your adjustment affect that? Do you know what the pinion angle is under acceleration? I hate to see folks destroy axles, and u-joints, plus lose some torque do to parasitic drag from too little pinion angle.

Please advise, so I know. My driveline vibrator has switched to high at 80mph+
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post #16 of 40 (permalink) Old 04-02-2005, 11:52 PM
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Wow, thanks for all the detail!
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post #17 of 40 (permalink) Old 04-03-2005, 01:12 AM Thread Starter
 
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The amount of pinion rotation will be in relation to the amount of give in the front isolator bushings, and as to how worn the rear pumpkin mount is. If the rubber in the rear mount is weather cracked and soft, then the pumpkin will rotate more.

If the pumpkin is pointing up too much to begin with, as mine was, then accelleration torque would really make it bad. Too much down angle would make for a decelleration vibiration. As long as the D/S is smooth during accelleration and decelleration, then you are right.

All of the driveline specialist and websites I have researched say that the max difference betwen the front and rear yoke angle should be 1/2 degree for the smoothest operation.

The 1/2 deg lower for the rear is a suggestion to compensate for pumpkin wrap. Mine is set even, but that is because my isolator bolts were too short to drop it any more. I haven't bought any new bolts as it runs pretty smooth now.

If you have poly bushings on both ends of the pumpkin, then 0 to 1/2 degree lower should be right on. I am sure that even with the pumpkin bushings tight, the rubber bushings on the sub-frame will flex, so the 1/2 degree lower might be best. It is easy to change if that is too much.

I do need to change my rear pumpkin mount, as when I would back up the D/S would rub the D/S loop from the flex in the old rubber mount . I bent the loop lower to stop this until I replace, or put a bolt through the rear mount.

Mine was out well over 2 degrees up to start with.

Last edited by yardbird82056; 04-03-2005 at 01:23 AM.
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post #18 of 40 (permalink) Old 04-03-2005, 06:39 PM
 
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Quote:
Originally Posted by Blackicelsc
...and what are the measurements when your car is under acceleration? There can be asevere change in pinion angle as soon as you touch the gas pedal.

This has been a controversial discussion amoungst many drag racers in the past. Now, I am not entirely sure, but I do know for a fact that there is some pinion angle built into the car(pre-load) to compensate for center-section rotation.
How does your adjustment affect that? Do you know what the pinion angle is under acceleration? I hate to see folks destroy axles, and u-joints, plus lose some torque do to parasitic drag from too little pinion angle.

Please advise, so I know. My driveline vibrator has switched to high at 80mph+
This isn't generally a problem with IRS systems (there is no spring wrap).

By-the-way...This subject was brought up a long time ago.
Here

Last edited by BMan; 04-03-2005 at 06:50 PM.
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post #19 of 40 (permalink) Old 04-03-2005, 09:59 PM
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I've been chasing a vibration for a while, going to be checking this out idea this weekend. Got a question too, where did you feel the vibration the most? Hope I can lessen or solve my vibe issue. Already replaced the entire front end enclusing all bushings, ball joints, and the steering rack because I believed it was originating from the front end. It vibrates the same with any set of balanced rims and tires I put on, I also have a metal matrix shaft, so the motor mounts and pinion angle is my last ideas...........

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post #20 of 40 (permalink) Old 04-03-2005, 11:20 PM Thread Starter
 
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I could feel my virbation from around 45 mph on up, with 65-75 being worse. I don't drive much faster, so I can't tell you what high speed wound have been like.

The vibration sounded and felt like harmonics cycling from rear to front every second. I could feel it in the seat, floorboard, and steering wheel. The steering felt like bad wheel bearings, though it wasn't.
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post #21 of 40 (permalink) Old 04-04-2005, 06:20 AM
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That sounds nearly exactly like my vibration, it just feels like it's coming from everywhere. I kept telling people it's not my front end EVERYTHING is new, tight and balanced. Ok this is getting checked out sooner than this weekend I hope. Thanks a lot man we'll see where this takes me.

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post #22 of 40 (permalink) Old 04-04-2005, 07:15 AM
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I'm gonna be checking this out this week hopefully. I need to get me some ramps first.
Thanks for posting this up.
My vibe is either this or the driveshaft. Since I'm getting a driveshaft in the GP, I'm also gonna check the angles to see if I have a problem.
Thanks again, yb
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post #23 of 40 (permalink) Old 04-04-2005, 10:14 PM Thread Starter
 
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Let me know if you angles are out, and if this helps.

Good Luck.
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post #24 of 40 (permalink) Old 04-05-2005, 08:29 AM
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I picked up the tool yesterday afternoon, I'll be checking it out this weekend or sooner. Man I hope this finally does it, you have no idea all the things I've gone through to find this. Keeping my fingers crossed!!

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post #25 of 40 (permalink) Old 04-05-2005, 05:55 PM
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Well I got the car up in the air today. I spent a lot of time with a aluminum straight edge and the protractor I picked up at sears. With all four wheels on ramps (pretty close in height) I got a reading of 2.5 up for the engine and trans and about 1-1.5 deg up( tough to read) on the center section. So that's at most 1.5 deg difference. I ran out of time to try shimming but is 1-1.5 deg enough to cause the vib? Just seems like such a small amount but in the next few days I'm going to shim the rear slightly to bring it in line better. I'll report back. I was hoping to see like a 2-3+ degree difference so I really knew it was the problem but it doesn’t seem as likely now. I'll know for sure in a few days.

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post #26 of 40 (permalink) Old 04-05-2005, 06:10 PM Thread Starter
 
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Is the 1 to 1-1/2 degree up on the center section measured off of the u-joint that is attached to the yoke of the rear pumpkin? If it is, it sounds like your pinion is at a lower angle than the trans yoke, which is unusual, but could be.

As little as 3/4 degree will cause a vibration. Recheck your readings, and make sure you have the right u-joint cap you are measuring off of on the rear. The first time I measured mine I accidentially checked the u-joint cap connected to the driveshaft and kept wondering why the angles were not chancing as much as I was dropping the pumpkin.
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post #27 of 40 (permalink) Old 04-05-2005, 09:20 PM
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I measured right from the input flange on the center section that the driveshaft bolts to. Also what I mean by positive degrees is that the front is up. So I measured the +2.5 on the crank pully. This means the rear of the engine is down 2.5, or the front is up 2.5 from a horizontal refrence, which ever way you want to think of it. And the center section input is 1-1.5 up from horizontal refrence. To bring them both the the same angle I will have to shim the rear of the carrier.

I mean we want to get the carrier and the engine/trans assembly at the same angle to minimize vibrations correct?

While I was looking around under there to see if there was anything else that might need replacing I noticed the crossmember that holds the rear of the trans up has some crappy looking bushings between the crossmember and the frame rails. (I know it's a unibody but what the hell else do you call them??)
Anyway I'm going to be replacing those too.

This is pretty much how I measured the pinion angle:

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post #28 of 40 (permalink) Old 04-05-2005, 10:33 PM Thread Starter
 
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Putting shims in the rear will be easier than the front. Mine had the front up too high. The sub-frames, or the sub-frame bushings must be giving on these cars to have some off to the up side, and some off to the down side.

Then again, it could be the way the pumpkin mount is made. If the rubber bushing in the mount is not made exactly the same on every mount, then the angle would be different on every car.

Keep me posted on how it works.
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post #29 of 40 (permalink) Old 04-07-2005, 04:36 PM
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Well, I got under the car today with the angle finder. I'm not sure how you did that but the gas tank doesn't leave ANY room to check for an angle. And I am NOT dropping the gas tank for this. So I decided to go ahead and shim the front mounts on the diff. I used some fairly thin washers. I put two on each side just to start with. It seemed to be a bit smoother up til about 70, then the vibe took over again. So either I do need a smoother drive shaft (which will get as soon as the GP goes thru) or I need to shim it more. I'll prolly not touch it until I get the drive shaft then I'll work on the angle.
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post #30 of 40 (permalink) Old 04-07-2005, 04:48 PM
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Quote:
Originally Posted by Big-Al
Yeah, I am convinced this is my problem now. The diff was recently set up so it is fine. The Mark VIII drive shaft was smooth as butter up to 145mph with stock diff. I am thinking that combination of different diff is a different angle.

Thanks!

Big-Al
I'd bet $20 it's a runout problem - play around with the indexing.

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