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U-joints

J

jerry81

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Is there any way to check out u-joints?

I have a stock 1981 automatic with 54K miles. When I put it in gear-either forward or reverse I hjear a clunking noise and the car squats slightly. There is a slight vibration at highway speeds. Occasionally there is a squeaking noise coming from the rear at low speeds. Because of this I suspect the u-joints. But, I would like to verify this before I spend the time and money to change them out. Any suggestions would be appreciated.
 

Yoda

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jerry81 said:
Is there any way to check out u-joints?

I have a stock 1981 automatic with 54K miles. .. ... I would like to verify this before I spend the time and money to change them out. Any suggestions would be appreciated.

Jerry ~ Welcome to The Corvette Action Center ~

U-Joints are very easy to check.. You will need a jack, and two jack stand. If you don't use a Jack Stand DO NOT GET UNDER THE CAR! Just check one side at a time, forget the propeller shaft (main drive shaft).

With the rear wheels off the ground, the car secured on Jack Stands and the transmission in park, move each wheel forward and backwards, listen for the "Clunking Sound" and notice the distance of travel. There should be very little movement in the forward and backward motion of the drive line.

Do this again using very quick movement and observe for the same noise and travel. If one of the half shafts have a bad u-joint you will have excessive travel and that "Clunking Noise".

To check the propeller shaft, you will need to get under the car and move the shaft itself to check for travel and noise. This is probably not the GM recommended proceedure, but it works ;)

Good Luck Jerry, enjoy and I invite you to take a look at The L81VetteRegistry dedicated to the 1981 Corvette :D

BudD
:w
 
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Welcome Jerry! Bud nailed the how, here's the why. Have you ever seen a Shark that lost a U-joint on a half-shaft at highway speed? No, well what you end up with assuming you don't wreck the car is half of the rear suspension in pieces and a new passenger exit through the rear storage compartment from the shaft plowing through everything it hits. Not a pretty story.
 
R

redmist

Guest
Be sure to get new u-joints without the zerk fittings. Buy new french locks as well.
 

Jack

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rusty ... not dusty ... trails

Welcome aboard Jerry:
Bud & the others are so right on all counts. Additionally, if those u-joints are really, really bad ... you may even see small trails of rusty smutz around the inner & outer ('specially) yokes' journals & caps ... from the failed u-joints' bearing needles being ground-up and spewed out; this just one of many t-shirts.
JACK:gap
 
6

69vettester

Guest
Procedure for manual trans??

Im glad this post came up!!Very interesting, safe and economical to look for the potentials of ujoint failure.

Rare81, is the checkout procedure the same for a car like mine with a M20
4sp. or are there differences in the wheel play specs. because of the manual trans.?
seems I remember there being quite a bit of play in the wheels movement while under the car looking at things. But my launches from stop dont indicate anything strange with play or noise? Ive always put the trans. in Reverse before lifting it!
Thanks..
TomC
 

Yoda

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Tom,
Very good question ;)

I have a 4-speed, and to check the u-joints I use the same method and leave the trans in either 1st or reverse as I move the tire/drive shafts.

I should caution that when checking for worn u-joints that it is the travel of the drive shaft before there is movement in the third member that we are checking for.

If you are checking backlash or condition of the rear end, you want to leave the car in Neutral and see how far one wheel moves before the other one starts to move. Having positrac rear ends, both wheels should move in the same direction.

If there is serious u-joint problems it will be very noticable as "Jack" mentioned.

BudD
:w
 
K

kayak

Guest
Bad, bad ujoint

When I started the resto on my '76, this ujoint was one of the things I found upon initial inspection.

Take a good gander and pray you never see one of these under your own Shark.
 
R

redmist

Guest
Wish I had taken a digital shot of mine when I started the restore.
When I drove the car home from the seller the shifter was vibrating so bad I had to take off the shift knob.
On one of the shaft to wheel u-joints tha cap had completely been ground off and all that remained was a cone shaped ground stub.
It is amazing that people can let their cars get to this condition.
More amazing that the whole rear didn't explode on the 4 hour 70MPH ride home!!!!
 
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jerry81,

I agree with all that has been said so far. There are a couple more things I'll add from the "this happened to me " department. The clunking may not be caused by a U-joint. It could be as is mine, caused by a worn out transmission rubber mount, or by a worn differentiential mount bushing. The vibration could be as was mine, a stiff U-joint that when the driveshaft was removed stuck straight out and never dropped down as it should have. Often the only telltale sign is the rust streak around the joint cap seal area. I changed my propeller shaft joints this spring on my 81, at 50,000 miles and checked the rest which were ok. The joints at NAPA were about $15 a piece, all six are the same part number, by the way. Just my 2 cents worth.................
 
R

rpounds

Guest
By the way . . . squatting in the rear when you put the tranny in gear is normal for this suspension. However, the clunking is not.
 
T

tangee-vette

Guest
You gotta love that squat. I know I do.
One of the very first items replaced when a purchased my shark was the u-joints at the half shafts and the drive shaft. Some items of repair just shouldn't be put off and seeing what can happen when a u-joint lets loose, puts these in the top 5. Change them out now and forget about it. :)
 
7

72 Bluz

Guest
Thanks, rpounds

I've wondered about the squatting - Xena goes up in reverse and down in drive. I've thought it might be due to the shift kit - didn't know that was typical. Still going to check my ujoints, though.

72 Bluz
 
R

rpounds

Guest
Because of the trailing arm IRS, the squat happens . . . Corvettes answer to straight axle spring wrap.

I prefer to think of it being like a cat . . . squatting down and ready to pounce!!
 
R

rpounds

Guest
Redmist made a point concerning not buying u-joints that include zerk fittings for lubrication. This is opposite of what I have always considered. Would you please elaborate? I'm interested to know your logic.

Ron
 

AKRAY4PLAY

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Wasilla, Alaska, U.S.A.
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RON,
I HAVE HEARD A COUPLE SCHOOLS OF THOUGHT. FIRST, GREASE IS YOUR BEST FRIEND! SECOND, DRILLING AND FORCING A THREADED WEDGE (GREASE ZERK) IN A CAST HOUSING PROMOTES BREAKAGE. AND LASTLY, IF YOU CAN'T GREASE IT, REPLACE IT. I TRY TO STAY AWAY FROM U-JOINTS WITH "BODY MOUNT" ZERKS. I PREFER THE GREASABLE ZERKS THAT REQUIRE A NEEDLE POINT ATTACHMENT AND SCREW INTO THE ENDS OF THE CAPS. I HAVE NEVER HAD ONE FAIL ON ME, KNOCK ON WOOD!!! DANA-SPICER HAVE BEEN MY FAVORITE FOR A WHILE. THEY SEEM TO HAVE BETTER FITTING TOLERANCES. I HAVE HAD A COUPLE OF NAPA U-JOINTS THAT THE CAPS STARTED SPINNING IN THE YOKES AFTER 6000 MILES. IT WAS VERY HARD TO FIND THAT ANNOYING SQUEAK. BY THE WAY, I HAD TO TRASH THAT DRIVE LINE BECAUSE IT WORE THE YOKES PAST SERVICE TOLERANCES. I DON'T KNOW IF THIS HELPS ANYONE, JUST THOUGHT I WOULD THROW OUT THERE.
BRIAN
 

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