1968 DeVille Convertible - Restoration

[Roger Zimmermann]

On my ex-1956 Sedan de Ville, the backing plates has similar grooves. We used also to weld them and removed the excess weld with an hand tool. You did the luxury variant!
Why are you replacing the bearing at the rear axle? Do you have the impression that it was damaged?

[DeVille68]

Hi Bruce,
ok, strange. Maybe someone in the past tried to repair something? Maybe putting JBweld on it?
Thanks for your kind words.

Hi Roger, no I am leaving everything in place. I just noted the markings and part numbers. Maybe helps someone else, because the manual is no help at all. They just say its not rebuildable.

Continuing on the axle:
While cleaning the inside of the diff the front pinion bearing actually "dropped" out, I did not plan on removing it but without the flange there is basically nothing to hold the bearing in place. Turned out to be a good thing because I was able to clean between the bearings too, which is otherwise impossible to get to.
You can see the collapsible spacer that sits in front of the bearing. My axle rebuild book says to not reuse those - well I have no choice. But its nice to see this here, which means that the bearings are designed just like any other diff and it should be possible to find new bearings for it.

After cleaning it, it installed the front seal with some permatex around the outside ring. Then I positioned the diff into the axle housing. I installed the gasket also with permatex on both sides (just a thin strip). I then snugged the nuts down, but did not yet torque them to allow the sealant to set. I used some copper paste on the splines, washer and pinion nut. I then mounted my holding tool and torqued the pinion nut to 200Nm. Takes quite a lot of force. I then checked the preload, but was again unable to measure this. I think its now somewhere around 15 inch pounds. But I guess this is mostly due to the new seals on the pinion and the two axle bearings.

After installing the axles and all the rest of the parts on the axle I was able to use three jacks to maneuver the axle into position. With the help of three jacks it can be done by one person. First task is to mount the shock absorber mounts, then the spring insulation and then the spring itself. After this it is just a procedure of slowly rising the axle to align the spring in the top mount and then continuing rising the axle until the bolts of the suspension arms can be slipped in. Actually the shock absorber will mount first and give a good insurance to keep the axle from jumping out if something goes wrong compressing the springs. Be careful, those springs are like a bomb!

Today, I will work on completing the install and mounting all brackets, brake, driveshaft etc..

Best regards,
Nicolas

[Roger Zimmermann]

Over torque or under torque at the pinion is not desirable. Usually, the position of the nut is marked before removing it. Installing the nut at the same position once the seal is replaced is giving good results. It's what was done on my own rear axles. I hope that you did not torque the nut too much!

[The Tassie Devil(le)]

Nicholas,

With regard to the collapsible spacer, I have had to re-use them at times, and what I do is to get a piece of shim steel, around .010 thick, and cut it out so that the ID fits the spaft, and the OD does not interfere with any part of the bearing.

Then, it is a simple matter of reinstalling the original Crush Sleeve, bearings and flange, and then tighten up everything (the nut) to the correct tension, as per factory specs.   Plus, before assembling the flange, I put some Loctite sealant on the spline so that there can be no oil leaking out sad spline.

The only way to obtain the correct tension is with the axles out, and with a gauge, measure the pressure.

The tool I made is a piece of wood, with a groove (to stop the piece of string falling off) and a piece of string to wrap around it, and a spring gauge to measure the pull, and then divided the number to get Foot Lbs, or Inch Pounds.

I never go by Torque Wrench specs unless I am using a Solid Spacer, as in a drag racing diff.

Bruce.

[DeVille68]

Hi Roger and Bruce

I did mark the flange relative to the shaft and I measured how deep the nut was on the threads. I measured about 3.6mm.
I don't have a "pointer" torque wrench only the common click type. But Bruce, your idea with a scale is perfect. I need to keep this in mind for future projects.

I measured the distance now again, its roughly 3.7mm. It took slightly more than 200Nm to get it to this setting.

Maybe one day I go through the controlled differential again and use your trick with the shim on the crush sleeve. From an engineering standpoint what you want is preload between the bearings. So, the need to replace the crush sleeves goes away when you use a proper amount of shim and torque wrench. There is a point where you cannot crush the sleeve anymore to give some preload and "spring" action but I guess with one shim one should get away with it.
Just a pity you mentioned this not earlier as I could have made such a shim! 

I am more concerned about the backlash, it is way more than the recommend 1/8''. Could this be a consequence of reusing the crush sleeve? With my measurements of the contact area and the larger than recommended backlash I try to think why this is the case. Looking at this situation it seems to me that I would need to move the pinion slightly more rearward.
What are your assessments of the situation? Has anyone a recommendation on what to do next?

On to the update on progress:
I installed the axle completely, all screws are just hand tight. They will be torqued once on the ground. I fabricated a hand brake cable holding strap, because mine was missing. Fits quite well and should solve the pounding noise of the handbrake cable when it is cahted between the floor and the suspension arm.

I also assembled the brakes, but it took me almost an hour to mount the handbrake cable. Do your self a favor and attach the handbrake cable with the braking back plate removed. You don't have enough room between the suspension arm and I made the situation worse by creating special rubber seals. Anyway, I got it done. Ready to bleed the brakes tomorrow.

I also got my insurance activated again even picked up my license plates.

Best regards,
Nicolas

[Roger Zimmermann]

Why don't you ask before you do something you are not sure?
My suggestion was to mark the nut in relation to the shaft and torque up to that point, period, no matter of the torque at the nut. Now you may have the pinion 0.1 mm towards the front, which is increasing the backlash in consequence. What I would do: loose the nut again a bit until you have the 3.6mm.

[The Tassie Devil(le)]

........Maybe one day I go through the controlled differential again and use your trick with the shim on the crush sleeve. From an engineering standpoint what you want is preload between the bearings. So, the need to replace the crush sleeves goes away when you use a proper amount of shim and torque wrench. There is a point where you cannot crush the sleeve anymore to give some preload and "spring" action but I guess with one shim one should get away with it.
Just a pity you mentioned this not earlier as I could have made such a shim! 

I am more concerned about the backlash, it is way more than the recommend 1/8''. Could this be a consequence of reusing the crush sleeve? With my measurements of the contact area and the larger than recommended backlash I try to think why this is the case. Looking at this situation it seems to me that I would need to move the pinion slightly more rearward.
What are your assessments of the situation? Has anyone a recommendation on what to do next?   Best regards,  Nicolas   

Nicholas,

The only way to adjust the pinion rearward is to install a shim between the rear pinion bearing inner and the pinion gear itself.   This moves the bearing forward on the shaft.   With other diffs, like the Ford 8 and 9", there is a shim that moves the whole pinion bearing mount to where it is required.

As for the crush spacer, that can be crushed a really long way (shorter) simply by turning more and more on the pinion nut.   You would be surprised just how much a press can squash a tube when sufficient pressure is supplied.

One of the reasons I only use a .010" shim is simply to squash it a bit more, than a lot more.

When initially beginning the initial crush of a new spacer, I find that it needs a lot of pressure on the wrench to get it to begin the squash, but then it is easier.

I don't use a torque wrench to do this part, as torque wrenches were never designed to perform such tasks.   I use a breaker bar with socket, and to make it easier on me, I place a length of tubing over the end to increase its' length.

The tool pictures is for holding the pinion "flange" on a Universal to pinion diff, and I have another one with a circular piece welded to the handle, which bolts to the flange, and that one has a hole in the centre to allow access to the socket.

The longer the handles, the less effort required.

Bruce.

PS.   I apologise for not reading your mind.   Maybe I was asleep?

[DeVille68]

Hi Bruce

ok, I guess I would have to remove the complete differential gears (ring gear and pinion) to slide a shim between pinion head and first head bearing. Shimming the crushsleeve only preloads the two bearings on the pinion shaft but does not change backlash or gear pattern.
Indeed, I measured about the same backlash as before. There is slightly more torque required to turn the pinion, I am assuming due to new seals. The runout of pinion flange and axles also stayed the same.
So in summary I guess I am good to go. I will measure the backlash again with the tire mounted, the larger diameter makes for an easier measurement.

Regarding gears and splines: this is what I have counted:
Number of pinion splines = 16
Number of ring gear splines = 47
Number of axle splines = 26

Axle Ratio: 47/16 = 2.9375


Regarding the dimples on the brakes. I found a picture in my documents from a guy here on the forum. He posted his rear brakes and I saved the picture. Looking at the picture you can see the same kind of dimples. And also the same kind of grooves due to wear. I wonder what those dimples are good for?

Best regards,
Nicolas

[Roger Zimmermann]

To keep some lubricant?

[The Tassie Devil(le)]

Dimples are usually placed in a piece of metal to simply try and build-up the surrounding metal, as in if the centre punch is pushed in, with a solid anvil at the back, then metal will rise up around it, as it cannot get deeper.   Plus, it is done when people haven't got a replacement part, or don't want to buy one, or is selling the car/item.

I have seen many attempts at tightening bearings in holes where they were spinning on the outside, and the cup gets tightened a bit, but it is only a stop-gap.

A new seal does create a bit of resistance, but there shouldn't be any reason to remove the crown wheel to allow the pinion to spin freely.   The tension is normally done before the crown wheel is installed.

Bruce.

[DeVille68]

Hi guys,

First test drive was a success! Brakes are great, suspension and ride comfort is amazing. What a difference replacing those bushings makes! wow. Gas gauge works nice. Limited slip seems to work, I tested it on a gravel road.

However, work is not over. I have a huge exhaust leak. The vibration around 60 is still somewhat there. Not sure what the problem is. Need to investigate further. The propeller shaft still needs to be replaced. I hear clicking of the u-joints. My new shaft is currently in Germany, due to the virus I can't go and get it.
I also have some tuning issues with the carburetor. Something is not right with the choke.
The radio was working fine, but now its dead?! Also the climate control does not work anymore. Must have developed some vacuum leak somewhere.

Well I guess the work does never stop! 

Below a picture from the mountain region where I life. Behind the car in the valley you can see the end of a glacier. Those mountains can actually be climbed, but there are obviously no roads up there. 

Best regards,
Nicolas

[Cadman-iac]

Beautiful area Nicholas,
As well as your car.  Congratulations on getting it out and taking it for a drive. Looks like you had some good weather as the top is down.
Keep plugging away and you will have a great car you can take anywhere.

Very nice,

Rick

[Roger Zimmermann]

If you look at picture two you see some dimples within the surface. Maybe to lower the contact area and thus the friction?

Nicholas, I had a look at the pictures done in the US during the refreshment of my '72 de Ville. The backing plates have the same dimples. I don't know the reason. As the car had only 20'000 miles at that time, I'm sure it was done at the factory.

[The Tassie Devil(le)]

Ah ha...... equidistantly spaced, which would suggest that their purpose is to allow lubrication to remain in the depressions as against a flat piece which would not retain said lubrication after a short time, and "fall" away.   Plus, seeing as lubrication was a part of brake servicing, it would be renewed at normal intervals as per the Shop Manual.

Bruce.

[DeVille68]

Hello,

Very interesting. Thanks for checking too! This hypothesis of keeping grease in place makes sense.
Well, my backing plate was welded with pure nickel and should be hard or at least as hard as the steel backing plate. Well, if the brake pads create new grooves, I can weld those again. No big deal.

Rick, thanks for the compliments!

So, now that the car is running I was finally able to fix some issues with the quadrajet. I noticed that the acceleration pump was not working right. After a few shots it seemed dry. The reason was that the lever would not allow the plunger to come up enough to reliably fill the reservoir below. I fixed this by bending the lever. I must have bent it wrong a few years ago.

Then I had an issue with the choke flap, it would somewhat bind. The reason was that I made a wrong bend into the choke flap lever, it would hit the casting and bind up.

With my O2 meter I can analyze the driving situations and noticed that the off-idle transition was not satisfactory. This is due to the changes made to my engine, raised compression, different camshaft. I made idle bypass air modifications last summer and this helped to bring the idle speed down and the mixture correct. But I did not change the idle fuel. Well, now the off-idle was too lean.
The only way to fix this is to remove the idle tubes. They were very very tight, but I got them out in the end by heat, and driving them down, drilling the top part and trying different drywall screws.
Unfortunately, I damaged one of the tubes. But not a big deal, because I did want to get rid of that pressed in tube anyway. So my plan is to make the tubes with a thread a the top. This way I can just unscrew them and redrill for a different fuel flow.
The first attempt was not successful, because I tried to press the brass tube I made into a threaded aluminum part I made.  However, the aluminum was not able to hold the turning force by a screw driver. So now I need to buy proper brass material ( 5mm diameter, 0.2'') and make the idle tubes out of one piece instead of the three part piece like original.

The original metering hole is 0.035'' but I am going to enlarge it to 0.040''.

Best regards,
Nicolas

[klinebau]

That's too bad that the idle tubes got messed up.  I sometimes mess up the original idle tubes when I take them out the first time, but usually they are still salvageable.  After I have had them out once, I don't usually have problems removing them after that.

There are other ways to increase idle fuel if needed.  You can increase the size of the down channel restriction or you can reduce the size of the idle bleed.

[DeVille68]

Hi Kurt

Yeah, first time doing this..
Idle channel restriction has been enlarged already. Also idle mixture screw hole. And the idle "venturi"
Idle mixture screws are too far out anyways.
If I am not successful, it was at least an interesting experiment. :-)

Best regards,
Nicolas

[DeVille68]

Hello followers,

here is a success story. First attempt failed with using pressed in threads.
I decided to make the tubes out of brass on the lathe in the experimental work shop of my company. But the second attempt  failed too because I was not familiar with the machine and it was not set up correctly making it very hard to machine a precise part.
With the third attempt I finally succeeded in creating the custom idle tubes I needed.
I made a idle tube out of 6mm diameter brass rod, cut the top 8mm back to tap a #10-24 thread on it. Then the next 1cm was a diameter of about 3.6mm and then to the top about 3mm. I drilled a 1.5mm hole from the top about 25mm deep. And then from the other side a 1.5mm hole about 3mm deep. The overall length is 38mm.
This made sure that the hole was straight because drilling such small holes that long of a distance is always a problem. You will face the problem that the hole will not be straight.
So I relocated the "calibrated hole" from the tip to about 4mm into the tube. Then I used a 1mm drill (thats about 0.040'') to create the new larger idle tube restriction. Originally a 0.035'' hole was drilled.
I notched the top of the idle tube to be able to use a Phillips screw driver. Cleaned everything up and installed the Quadrajet again.

--> Wow, what a difference in driving this modification makes!  No stumbling from a stop with little gas, it just goes. Very very nice. The car now drives as I have dreamed about two years ago.

Without a O2 sensor these kind of modifications would have been very difficult to make, because it is hard to judge the combustion condition from the driver seat. Also WOT performance was not very good, I noticed that the mixture was about 10.5 air fuel ratio.  Way too rich. Probably caused by the various modifications, bending the hanger I now have a WOT mixture of about 13.0. And it really goes. pretty cool.

As you can tell I am really excited. The suspension is nice and soft, gas tank shows correct amount of fuel, brakes are fantastic (straight and strong), rear end is sealed, as is the transmission output shaft. Performance is way better than before. Even the limited slip works and leaves two black strips on the ground....   (I only tried this once for about 2m)

A few pictures below.

Before making the idle tube with the thread on it I turned to google to see if this is a idea someone else had. Turns out that you can buy idle tubes with a thread on them: https://allcarbs.com/product/threaded-idle-tube-kit/ The kit costs 45$ but only the tubes is about 10$.
Finding those showed me that my idea would work out - with it did!
The tubes from allcarbs use fine thread (juding from the pictures), which I think I wrong because we are dealing with aluminum and brass. Hence you need as much material as possible to make a strong edge of the thread.
Exactly the same conditions made a bad reputation of the early Northstar, for example the 93 Allante used fine thread head bolts. There is a kit available which replaces those with a larger side coarse thread head stud.

Best regards,
Nicolas

P.S Now what is left to do: fix the radio, fix the heater / air conditioning, replace the drive shaft, fix the exhaust leak, replace the muffler, change out the ignition for my new unit, restore the power seat, restore the autronic eye, replace and fix rust on the driver side floor pan, restore and recreate the interior panels, and some smaller issues! 

[klinebau]

Very cool!  Glad you got this sorted.

[DeVille68]

Hello,
here is an update about my replacement driveshaft. This post was also posted here:
http://forums.cadillaclasalleclub.org/index.php?topic=161346

So good and bad news. I was at this special shop (truck rebuilder) that also makes custom driveshafts. We made sure that driveshaft tube was straight and then we run an initial calibration. Check out the first three pictures below.
Then we ran an initial measurement at 1000 rpm which (when I calculated correctly) is about 30 mph. The machine said to remove 9gr at the rear and 19gr at the front. So we decided to remove all the original weights and over. Then the machine said to add 14 gr at the rear and 11 at the front. We added 15gr and 10 gr, and after a verification run the machine showed to add 3gr at the rear and 2 at the front. So we called it a day.

We experienced one strange phenomena though. As few minutes in the run we heard some strange contact noise coming from the front third of the tube. So we lubed the ball and greased the cv joints. We noticed that the sound disappeared when introducing a deflection of the driveshaft. It was installed in the machine totally straight, which should not happen in the car because then the cv joints are not lubed enough and can get damaged. So I suspected that a cv joint had a problem. And indeed after removing the shaft we noticed that one of the front cv joints made these contact noises. We greased it some more and the noise disappeared. Very strange! I hope this sound does not return.



So far so good. So, I put the car up on my ramps and removed the old original driveshaft and but it side by side. Check out picture one.
Well, what do you see? Nothing at first, but I noticed that the slip yoke looked strange, that is kind of small.

And indeed when measured with my caliper I got about 1.850'' O.D. on the original yoke but only about 1.690'' O.D. on the replacement yoke! 
(picture two and three).

Strangely all other dimensions checked out to be exact. Spline count is 31 +1 = 32 (+1 means the missing spline for the air to escape to the end of the yoke). The I.D. is also correct at about 1.4''.
Length and cv joint size is all the same. Total length of the driveshaft is also correct.
Last two pictures show the double cv joints, the replacement shaft looks a bit different but the dimensions are the same.

So, now I tried to figure out what went wrong here.
From my master parts catalog I can find the part number for the front yoke, its 7812171 and is used from 68 through 73, below it is used on 74 exc. Eld. On the web I found that this very number is also used from 76 through 79. So first, I thought I miss-ordered and made a typo like 78 or 86. But that was clearly not the case.
When searching online for a slip yoke for a TH400 all the results give the larger yoke style.
I read somewhere that the small yoke was used up to year 65.
Maybe the rebuilder took the wrong slip yoke to put this driveshaft together?

So, now I kind of not know what to do next. Clearly this driveshaft is just junk now. (costed me with shipping and labor about 1000$!! )

Any advice on where this yoke was used would be highly appreciated.

Best regards,
Nicolas