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Discussion Starter #1 (Edited)
I'm replacing the flex disc on my '78 Spider. The original flex disc had all six bolts coming into the disc from the front of the car, with locknuts on the back. The bolts that came from the transmission output shaft had washers. The bolts that went into the driveshaft spider did not.

Is that right? I've seen many photos of flex discs with the driveshaft spider bolts inserted toward the front of the car, others with washers on all 6 nuts. What's the definitive answer as to how the bolts go?

I'm currently rejoicing that my olive is in pristine shape (that sounds nasty) but a bit dismayed to find that aside from age cracks, there really wasn't anything wrong with the flex disc, nor were the Ujoints I just replaced showing any wear, so my grinding-howling noise when decelerating from high speeds in neutral still needs to be tracked down.

Thanks
 

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Here's what mine looks like from the prop shaft side.

You can tell that there are washers under the nuts that secure the bolts holding the gearbox tripod spider to the flex coupling, but not under the nuts that secure the giubo to the forward propeller casting.
 

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... so my grinding-howling noise when decelerating from high speeds in neutral still needs to be tracked down
Assuming the noise is not fixed with this driveshaft work, could the noise be differential related and maybe pinion bearings have play, ie. you have no noise why accelerating or cruising but when you lift off the pinion floats forward (due to bearing play) and the meshing is now not 100% correct???

Pete
 

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...aside from age cracks, there really wasn't anything wrong with the flex disc...
If a giubo is old enough to have age cracks, then it's old enough to be replaced. While replacing it may not solve your grinding-howling noise, be thankful you caught the giubo before it failed.

I agree with other responders: usually the bolt heads go forward, nuts go rearward. But honestly, I don't think there would be any problems if you installed the bolts in the opposite direction. Use Loctite on the nuts, as the nylon locking is probably worn out.

How does your rear transmission mount look? A sagging mount can cause driveline problems. Any paint scraped off the driveshaft that would indicate that is where the grinding is occurring?
 

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Discussion Starter #7
I've replaced the center bearing on the driveshaft and the rear transmission support. The motor mounts are a bit squishy, but I don't think that's the problem as the noise comes from the rear. Worn pinion bearings on the differential? Sounds expensive and difficult to fix. So yeah, that would probably be it. :wink2:

Off to change my clothes and take her for a test drive. 64 degrees outside!!
 

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I have replaced several giubos from under the car. All I have ever seen have the bolts facing from the rear of the TX facing toward the rear of the car. All I have ever replaced ended up just the opposite, with the bolt heads in the rear and the nuts behind the TX. The reason for this is that there is only one position at the rear of the TX housing where you can remove the bolt from the TX flange from under the car. I find that it is easier to remove all the bolts, replace the giubo, and then install the bolts from the rear facing forward. this allows you more freedom of movement while doing the hook up of the 2 halfs of the giubo linkage. Just my 2 cents worth for what it may be worth. I can't see what difference it makes after the thing is done and the bolts are properly torqued.
 

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Worn pinion bearings on the differential? Sounds expensive and difficult to fix.
How is the oil level in your differential? Changing the diff oil would be inexpensive/easy - but no guarantees that will fix it. How much iron debris is stuck on the magnetic drain plug? If the answer is "lots" then that tells you something.

If your diff is bad, swapping a good, used, complete rear end is usually simpler/cheaper/easier than trying to repair your old one. Think of it as an opportunity for converting to the later 4.10 ratio.
 

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Discussion Starter #10
Back from the test drive.

:):):):):)


It's like a different car. The original U-joints felt smooth and there wasn't any play apparent, but the new ones, along with the new flex joint, completely change how the car feels. It's not perfect, but I think what I was getting under deceleration was vibration from the back of the car, and a rubbing noise from the front discs. Now, the vibration is gone and the noise isn't nearly as troubling.

And yes, the diff oil was one of the first things I took care of when I bought the car. I changed it out. Nothing was stuck to the drain plug and the oil was clean. Sometimes that makes me suspicious, but in this case the fill plug was so firmly corroded in place that I don't think it had ever been removed.

I'll keep an eye on it, but my $100 in parts and my four hours of labor were certainly not wasted.
 

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Discussion Starter #11
I have replaced several giubos from under the car. All I have ever seen have the bolts facing from the rear of the TX facing toward the rear of the car. All I have ever replaced ended up just the opposite, with the bolt heads in the rear and the nuts behind the TX. The reason for this is that there is only one position at the rear of the TX housing where you can remove the bolt from the TX flange from under the car. I find that it is easier to remove all the bolts, replace the giubo, and then install the bolts from the rear facing forward. this allows you more freedom of movement while doing the hook up of the 2 halfs of the giubo linkage. Just my 2 cents worth for what it may be worth. I can't see what difference it makes after the thing is done and the bolts are properly torqued.
Yes, I thought of that. However, now that I have a perfectly-bent Harbor Freight combination 19MM that can reach those thin bolt heads, a hardwood wedge that holds the wrench onto the bolt head when I'm turning the nut, and scar tissue in just the right places on my knuckles, I figure I'll be OK in 37 years when I need to replace the giubo I just installed.
 

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I agree with other responders: usually the bolt heads go forward, nuts go rearward. But honestly, I don't think there would be any problems if you installed the bolts in the opposite direction. Use Loctite on the nuts, as the nylon locking is probably worn out.
If you install the bolts in the other direction the nuts and bolt shank will hit the transmission case.

If you don't have the washers behind the nuts that tighten the flex joint to the yoke the nut will twist the flex joint as it tightens down. This will give you a vibration.
 

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If you don't have the washers behind the nuts that tighten the flex joint to the yoke the nut will twist the flex joint as it tightens down. This will give you a vibration.
Hi Jim,

What about washers behind the nuts that hold the flex joint to the forward prop shaft? Are washers required under those nuts too?

When I dis-assembled my prop shaft, I only found washers behind the 3 nuts that tighten the flex joint to the gearbox yoke. The other 3 nuts securing the giubo to the prop shaft didn't have any washers and were tightened right up against the prop shaft nose casting. Is that OK, or are washers required under all 6 flex joint nuts?

Thanks,
 

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you need washers between the bolt head or nut when it touches the donut. If you don't you can twist the donut with can cause vibration.
 
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