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Discussion Starter · #1 ·
My '73 Gt has a whine when I let off the gas. It doesn't seem to do it under power. In fact the whine will continue even if I shift to nuetral. I rebuilt the torque tube thinking that was the problem. Nope. Chis from Loveland Ohio replied to a post from someone else abut having a bearing go bad where the driveshaft connects to the pumpkin. Anyone think this might be a possibility with my car? How do I go about replacing that bearing?

Thanks
 

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Dave,

Is this the same problem you reported last year? (http://opelgt.com/forums/showthread.php?s=&threadid=384)

Can you further describe the problem? You say it only whines when the drive-train is "unloaded", and I presume the car is moving forward. No whine when the car is stationary and in neutral, or in gear with the clutch depressed? Does it change pitch according to speed? Have you changed the differential and/or tranny fluid, and if so, did it affect the pitch or loudness?

It's odd that it only happens when the drive-train is "unloaded". It sounds more like a gear problem than a bearing. Bearing noise is usually constant, or gets worse under load. Worn gear teeth or improper gear pre-load sometimes can cause a noise when running unloaded.

But if you want to try replacing the central joint bearing, it is fairly simple (but not easy) to do. Drop down the torque tube, then remove the the big nut on the forward end. You usually need a puller to remove the pinion flange (where the U-joint bolts to), but a well placed hammer blow to the end can sometimes pop it off (be careful not to damage the threads). Then use a rubber mallet to drive the extension shaft (the rear drive shaft inside the torque tube) and bearing out of the central joint.

To remove the bearing, you have to pry open the sheet-metal casing and then press the bearing off the shaft. Look to see if sand or mud has gotten into the space between the bearing case and the bearing. It is supposed to be filled with grease to prevent this from happening, but when my bearing became rough, it was only dirt inside the case. The bearing was otherwise fine.

Good luck and tell us the answers to the questions above.
 

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Discussion Starter · #3 ·
Keith,

Yeah it's the same problem as last year. I rebuilt the torgue tube, although nothing really looked suspicious. I'll try and answer your questions.

The whine is when the car is moving forward. It doesn't matter if the clutch is depressed or not. Nor does it matter if it's in gear. The whine tends to slow down as I decrease speed.

I haven't changed diff fluid or trans, but both are topped up. I will try that. Do you have a suggestion on the correct weight fluid or brand to use?

I can't really say about the whine on jack stands. I'll try to check that out more but I don't think I noticed it.

On the torque tube---When I replaced the bearing and the bearing didn't look bad, I don't remember having to 'press the bearing off the shaft'. I basically followed instructions from the OGTS flier. I know I didn't press it back on the shaft. Do you think my problem could be with the bearing sliding on the shaft?

The only thing suspicious that I noticed was when I replaced the seal to the rear end, there were some shavings in the oil that ran out. Not a lot but enough to notice.

Any help would be greatly appreciated.


Dave
 

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A whine while decelerating sounds like an improperly meshed/clearanced ring and pinion. Too much backlash likely, but if it's been this way a while the damage is done. I'd go with Keith's recommendation and flush the housing and replace the fluid. You should probably at least increase the viscocity to 90-140 gear lube.

If that does not do it, then Redline makes a synthetic gear oil called 'ShockProof' for high stress situations. It has a tendency to cling tenaciously to the gears, so it will dampen the noise somewhat. A bit expensive, but you don't need much to fill the rear axle.

Bob
 

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Discussion Starter · #5 ·
Bob and Keith,

I'm going to give the gear lube change a try this week. I'll give you a report after changing to the 90-140 gear lube.

Dave
 

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Discussion Starter · #6 ·
differential

Still working on the vibration noise from the rear. I did take the opel to a mechanic for diagnosis. He said he was pretty sure the noise was from the differential. I took off the rear cover to the differential. I don't see any chipped teeth as I spin the tires. Aso didn't find any parts in the bottom of the case...Yeah. I'm a decent shade tree mechanic but have always shied away from differentials. When I rock the tires in and out I get no play or noise. When I shake the tire back and forward I get a little noise from the left side and none from the right. When I put it in gear and rock the tires forward and back I have some play and of course hear the gears clicking.

So if any of you are more experienced than me with the GT differentials, I'd appreciate the help. By the way it's a '73. I haven't tried the heavier oil yet. I wanted to hear back from the forum.

Dave
 

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PrOpeller
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Dave,

Did you ever find out what was causing the whining noise from your axle?

Well, my car just started exhibiting the EXACT symptoms when decelerating. (It started exactly after downshifting into fourth while climbing). I suspect it is incorrect rear-end back lash (as RallyBob suggested) that causes this condition since my axle was JUST rebuilt 500 miles ago.

How long did you drive with the noise? Did it finally go away when you used heavier synthetic fluid?

I had to drive the car home 30 miles with this whine. Basically, kept the axle loaded as much as possible and decelerated VERY slowly to minimize the whirr sound. I plan to have the car towed back to the rearend shop for them to inspect. I just hope I haven't done any long-term damage. :(

So did you eventually have to put in new gears? For both of us... I hope that's not the case!

Walter
 

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Discussion Starter · #8 ·
Haven't been Opelling for awhile. No I haven't found the source of the noise but haven't really tried either. Putting in the heavier oil didn't help. I don't think it's the rear end gears. As it the noise pretty much happened all at once.

In looking over the manuals it talks about adding weight when removing the driveshaft...torgue tube etc. Actually when putting it back together. I'm wondering...does the weight or lack of it affect the alignment of those parts. Could that be the source of the noise? As it starts to warm up a little more in the Chicago area that's my next step. Tear it apart again, but pay attention to the adding the weight part when I put it back together. I really suspect this as when I leave it on the jack stands and run it through the gears I don't have the noise. I only get it when the weight of the car is on the wheels. So I'll post again in a couple months when I can lay on the concrete without fear of frostbite on my male extremeties.
 

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Dave,

I found the source of my problem; so maybe this will help you, too...

The pinion nut had loosened up and backed off enough to affect backlash. The gearshop tack welded the nut to keep it in place (which sounded kind of extreme to me). But it has solved my noise problems and apparently no harm was done to the gears. HTH.

Walter
 

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DaveKayson said:
I don't think it's the rear end gears. As it the noise pretty much happened all at once.

I only get it when the weight of the car is on the wheels.
Sounds suspiciously like a wheel bearing "gone bad"
Does the sound increase as you corner or varry as you saw the steerng wheel from side to side thus alternately loading the wheel bearings?

Worth checking them, at least, because they are easiest to get to.

We used to pack old SV Ford V8 diffs with banana skins to stop gear noise - just before we sold them:eek:

Walter - that is WORSE than banana skins! Haven't they heard of loctite or lock washers????
 

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Discussion Starter · #11 ·
Walter, Thanks, I'll check the pinion nut.

Jim, I don't think it's from the front. I've pretty much pinpointed the noise to behind the doors, but I'll double check the front wheel bearings. Could it be a rear bearing? I'm not quite ready for the banna peels yet.

Dave
 

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Rear Wheel Bearings!

Dave,

Was refering to the Rear wheel bearings - the ones at the outside end of the diff axles, just behind the brake backing plates.
If you have an early (pre-1971) GT then the bearings run directly on the axles without an inner race. Later model diffs have conventional style ball races with integral seals.

If one of those bearings gets rough the noise can transmit through the diff housing and up the torque tube to sound quite bad at the rear of the car.

Sorry about the banana peel revalation - just an old battered concience surfacing!
 

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Discussion Starter · #13 ·
Jim,

Thanks, it's a '73 with about 108,000 miles. I didn't do anything to the rear axle except put on brakes. How much of a job is it putting new rear bearings in the '73?
 

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Unfortunately the first thing is to take off all the brakes you just put on, the back anyway. Then there are 4 bolts that hold the backing plate you need to remove through the cut outs in the axle. From there it can be a tap and it all comes out or a slide hammer affair. Either way the axle comes straight out. Then the bearing and retaining ring have to be pressed off. You will need new retaining rings and there is also an O-ring that should be replaced. From there it is pressed back together and carefully reinstalled. Use of axle grease or some good lube to keep from pinching the O-ring is recommended. On the 73 there is no outer seal other than what is on the bearing. Ok with that said I'm gonna play devils advocate for a second. When you installed the brakes is it possible something there might be causing the noise? It's just an idea and easier and cheaper to fix if it is. If it is the axle bearing you really need a new retaining ring it's what keeps the axle shaft in there, it's not something to take a chance with.
Here sawdust is easier to get than banana peels, then again I filled a land cruiser motor with vactra to quiet it down and sell it. To explain vactra is a machine way oil about the consistancy of mollasses at 40 degrees. I used 90 weight to thin it.
 

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Rear Wheel Bearings

Dave,

Put the car up on jack stands under the diff tubes then grasp the rear tyre in the 1/4 to 9 position and attempt to move the wheel in and out. There should be no slack or movement at all.
Rotate the rear wheel while applying inward and/or outward pressure and "feel" any roughness or looseness in the rear wheel bearing. the wheel should turn smoothly without and "notchiness"
Take the car for a drive and do a bit of weaving from left to right like a slalom course through road markers at about 20 to 30 MPH and listen for any varrying bearing sounds. If the bearing is loose it will "change its tune" as it is alternately loaded left and right.

Dud rear wheel bearing sounds are unmistakable once you recognise them.

The 1973 diff has conventional style bearings BUT the actual bearings are for Opels only as far as I know. OGTS and other Opel stockists should have them plus the retainer rings.
Any Ford or Chev manual should have a section on replacing rear wheel bearings if you do not have a GT Manual yet. ( inch Ford diffs have a very similar setup holding the wheel bearings on.

Generally a quite powerful hydraulic press is required to remove them. A local automotive repair outfit or small engineering shop usually have a press that can do the job for a few bob or a beer or two!

If they check out OK that eliminates something else.
 

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jim you know you will only confuse our american cousins by talking £.s.d. beer yes
shillings no
 

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Mea Culpua!

Replace with: "A couple of nickels or a Bud or two"
 

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Discussion Starter · #18 ·
I know this seems like ages ago but I finally fixed my rear end. Well not mine but the GT's. I swapped out mine with another '73 rear differential. The only thing I found in the process was that the "thrust cap" on the pinion end of the differential was mushroomed and the replacement was not. I don't know if that could have been my problem or if it was actually something with the gears. It's running and not whining. woo!woo!
 

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Spring ... ??

Was there a spring inside the yoke at the back of the gearbox? This spring pushes on the end of the gearbox output shaft and loads the driveshaft back against the button on the front of the pinion. If it is not there the driveshaft moves back and forward - like a steam hammer - and mushrooms the button. Which is why I ask .......
 
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