MORE rear end noise and vibration

7991LXnSHO · Oct 21, 2010

My 91 LX just started having problems at 70 + MPH after some "enthusistic straight line acceleration" tests. Around town I may hear a little grinding rumble out of the rear, but the fun does not start until fast speeds. 1. At 80, it was hard to find the next gear because the shifter was vibrating so much! It is dependent on road speed, not engine speed. 2. At 65+, I am hearing some grinding or other noises - hard to hear above the mufflers and other shaking noise. it is only when warm and at steady speed or letting off. Not under acceleration. No whining, except from me.

HELP!
What did I break??? (tranny mount, crush sleeve/pinion bearing, or more than just a worn wheen bearing?) How do I check it out in my garage before sending it to the mechanic?? Can i jack up both back wheels, put it in neutral, and spin the wheels? I have a mechanics stethascope and am not afraid to use it.

7991LXnSHO · Oct 26, 2010

TRANSMISSION MOUNT SYMPTOMS?

PLEASE someone help take a guess for me!

How is it like to have a ripped tranny mount?

Can I jack it up with both rear wheels in the air, put it in neutral and listen for bearing noise by turning a wheel?

MFE92 · Oct 26, 2010

Check your driveshaft bolts.

Kdubslugga · Oct 26, 2010

Sure, put it up in the air ON JACK STANDS, and have a buddy bring it up to 60 or so MPH and use your stethoscope to check things out.

89drop · Oct 26, 2010

Kdubslugga said:
Sure, put it up in the air ON JACK STANDS, and have a buddy bring it up to 60 or so MPH and use your stethoscope to check things out.

youre gonna get someone killed! hahaha!!!

Lawbreaker5.0 · Oct 26, 2010

Plus the speedometer will not be right with out the wheels loaded. I wanna say when the speedo reaches 30mph with the rear end off the ground is like going 50-60mph on the ground.

TRWXXA · Oct 27, 2010

Lawbreaker5.0 said:
Plus the speedometer will not be right with out the wheels loaded. I wanna say when the speedo reaches 30mph with the rear end off the ground is like going 50-60mph on the ground.

You're kidding, right?

7991LXnSHO · Oct 27, 2010

I jacked it up (and used jack stands) for an inspection. You can not see anything past the X pipes with it lowered and on the ground. The driveshaft flange bolts are tight. I do not feel brave enough to rev it up in jack stands.

The transmission mount looks worn, probably the factory one. A Pro-thane one is on the way. I'll let you know if this fixes it.

The only other parts I saw problems with are the upper control arm bushings on the pumpkin end are badly cracked.

I am thinking about going with Poly Graphite bushings. I do not want a harsh ride or squeaky one. Has anyone had good or bad experiences with Performance Suspension Technology Performance Suspension technology?

Lawbreaker5.0 · Oct 27, 2010

TRWXX, no I'm not. Please tell me how spinning a wheel off the ground won't spin faster an easier (showing more speed) then when it's loaded on the ground genius?

MFE92 · Oct 27, 2010

Lawbreaker5.0 said:
TRWXX, no I'm not. Please tell me how spinning a wheel off the ground won't spin faster an easier (showing more speed) then when it's loaded on the ground genius?

Did you move from Massachusetts?

Lawbreaker5.0 · Oct 27, 2010

I ment the opposite going 60 on the speedometer(with the tires off the ground) gonna be way less (prob 30-40mph) then if the tires are on the ground because there is no weight on the vehicle and the rotational mass is way lighter.

MFE92 · Oct 27, 2010

...eat a lot of paint chips when you were a kid?

89drop · Oct 27, 2010

no disrespect to anybody, but if the spedo reads 60, then the tires would be going 60, as the spedo would be driven by the gear in the tranny...right? sorry, im just confused and just thinking that the weight really wouldint make a difference... again, not trying to get on anyones bad side, or call anyone out, im just thinkin that it wouldint really matter if there were weight on the tires.

Lawbreaker5.0 · Oct 28, 2010

Let me clarify. I DID NOT mean to say the speedometer would be OFF.

MFE, no I did not eat paint chips as a kid, I did bang your Mom as kid and she was dry as *****.

89drop · Oct 28, 2010

Lawbreaker5.0 said:
Let me clarify. I DID NOT mean to say the speedometer would be OFF.

MFE, no I did not eat paint chips as a kid, I did bang your Mom as kid and she was dry as *****.

TRWXXA · Oct 29, 2010

Lawbreaker5.0 said:
Let me clarify. I DID NOT mean to say the speedometer would be OFF.

MFE, no I did not eat paint chips as a kid, I did bang your Mom as kid and she was dry as *****.

Wow... You're a class act.

Tires bolted to axles...
Axles splined into differential...
Differential geared to driveshaft...
Driveshaft bolted to transmission output shaft...
Speedometer geared to output shaft...

Why would you think that just because the tires are turning easier since their off the ground the speedometer would be indicating a speed different than it would if they were still on the ground?

And please try to answer without bringing my mother into it.

hotcobra03 · Oct 29, 2010

problem

7991LXnSHO said:
My 91 LX just started having problems at 70 + MPH after some "enthusistic straight line acceleration" tests. Around town I may hear a little grinding rumble out of the rear, but the fun does not start until fast speeds. 1. At 80, it was hard to find the next gear because the shifter was vibrating so much! It is dependent on road speed, not engine speed. 2. At 65+, I am hearing some grinding or other noises - hard to hear above the mufflers and other shaking noise. it is only when warm and at steady speed or letting off. Not under acceleration. No whining, except from me.

HELP!
What did I break??? (tranny mount, crush sleeve/pinion bearing, or more than just a worn wheen bearing?) How do I check it out in my garage before sending it to the mechanic?? Can i jack up both back wheels, put it in neutral, and spin the wheels? I have a mechanics stethascope and am not afraid to use it.

its that time of the year for stuff to go wrong.........

what you describe sounds like a frozen ujoint...can only be found by removing drive shaft from car,,

tires would be next to look at,,, than a good check for things that might be loose

good luck

JadeGT · Nov 4, 2010

Lawbreaker5.0 said:
Let me clarify. I DID NOT mean to say the speedometer would be OFF.

MFE, no I did not eat paint chips as a kid, I did bang your Mom as kid and she was dry as *****.

Good job on trying to run off a Mustang expert.

7991LXnSHO · Nov 4, 2010

Frozen U Joint symptoms?

"what you describe sounds like a frozen ujoint...can only be found by removing drive shaft from car,,

tires would be next to look at,,, than a good check for things that might be loose"

I looked at the U joints thinking about wear, but did not think about a frozen one. I have NO idea how many miles are on these, but they do not show play. What really caught my attention about this idea is on the rear U joint, one of the four caps is shiny on the end and the other three are surface rusted. I'm used to someone bringing the trashed out reminants into the parts store and demanding a new one - with no idea what the drive shaft is really off of.

SO ANYWAY, can a U joint be frozen and still be driveable around town??? I picture there being some serious binding over any kind of bump. It would be a cheaper solution than rear end bearing issues!

7991LXnSHO · Jun 23, 2011

Follow up since snow is gone and car is out

The u joints seemed to move smoothly, so the drive shaft went to a driveshaft shop to check for an imbalance and run out. One u joint cap at the rear had damaged the flange that bolts to the rear end. (It may have spun and broke loose again.) And they felt there was something damaged in the slip yoke. So for half of the cost the Ford dealership wanted for the two OEM end parts, I have a complete, new Ford Racing Aluminum shaft assembly on the way for Monday.

The mechanics think it should be fine with the new shaft and new mount.

BUT if it is not, since the vibration is only through the shifter, it gets MUCH worse as speed goes up and is worse on acceleration and deceleration than coasting; they think the next steps are 1. there may be something wrong with the tranny output shaft area or 2. less likely - in the rear end. I hope to know by Tuesday. Does this sound likely in anyone’s Mustang accelerator pedal mashing experience?

Also, I want to to postpone any future leaks by getting a new seal for the T-5 tranny output for the new slip yoke. Is it just an inexpensive, press in seal????

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