Rebuilding Rear Uprights and rear discs

Before you do anything, I'd try a different gear oil. Try to use one that says it's specifically designed for use in manual transmissions or transaxles. The ZF and RBT spec. calls for a GL-4 oil but many people use GL-5 oils without issue. Many 80W90 GL-5 gear oils are designed to be used in differentials only and are too slippery for use with synchros.

I have bearing Option B in my 74 Euro Pantera.  Wilkinson installed them for me.

I have bearing Option D in the project Pantera that I received in February.  The work was originally done by Dennis Quella.  In the photo below, one of the uprights is partially disassembled and the other is fully assembled.  I spoke with Dennis about reassembly and he essentially said to put it back together.  Wilkinson also spoke to Dennis about and then helped me reassemble it.  The bearings are readily available from Temkin.  The Temkin seals were harder to find.  I can dig up the part numbers.  I think Dennis no longer does this.  The spacer between the two tapered bearings needs a specialized machining process in order to size it just so.  Perhaps call there and leave a message if you want to know more.

I admit that I don't understand how a system with two tapered roller bearings can work without machining the hub to create a stop for the inner bearing cup.

There is also the option of machining the hub in order to install a double row ball bearing (reference 3308-B-2RS) on the outer side of the hub, where the forces are greatest.

Hi this is the first I’ve heard of this option. To help keep track of the available options let’s call this option “E”. This looks like a single machining setup and would certainly help carry the load.

The reason Dennis Quella no longer does the tapered roller bearing conversions is, it’s a lot of work for very little benefit. There’s really nothing wrong with the OEM ball bearings, as long as everything is done correctly; the critical elements being the axles and proper torque. If you feel you need more, do the (easy) double row inner bearing mod. If you want to make the assembly more serviceable, convert to two piece rear rotors mounted on the outside of the hub. This way, you can service the rear rotors by simply removing the calipers. The only caveat is, it pushes your rear wheels an extra 1/4” outboard.

This seemed to me to be the easiest to achieve based on the machines I had at the time. Now that I have a milling machine with a boring head, I might choose another solution.

Just to throw another option into the mix; GT5-S’ have a larger OD inner bearing but still a single row bearing. I had a machine shop modify my uprights to use a larger OD inner bearing. My understanding is, they used a very large lathe to machine the uprights. In hindsight, probably not worth the effort.

FWIW, Wilkinson has the double row bearings and correct spacers on the shelf.

But the double row Wilkinson bearings are the inner bearings, it is better than the OEM but it is not the best.

Rene, it is the inner bearing that has historically been more prone to failure. I suppose that's simply because it's smaller.

On 4406 it was the outer bearings to the point of having damaged the axle because the inner race had rotated around it.

When you look at the geometry it is clear that the outer bearing supports more load and I guess that is why it is bigger.

But I also think that the "huge" tightening torque has not always been respected on all our Panteras over the last 50 years, which has caused many failures.

Amazing - was just discussing this subject over the phone, and look what popped up on my Facebook Feed...  You don't think they are listening?

Nevertheless....

The person posting says all the bearings and seals are still available....

We jumped into rebuilding the uprights, no one has mentioned the obvious, a bad half shaft u-joint!

Joules - Don't you think we all want to make this as hard, and as complicated as it could possibly be?    And we haven't even had a chance to begin listing the catastrophic consequences that could possibly occur!

(Smiley Face - Joke, Joke!!!)

Rocky

PS>  That's a good suggestion you provided.

@joules posted:

We jumped into rebuilding the uprights, no one has mentioned the obvious, a bad half shaft u-joint!

Just asking… how would a half shaft U  -joint know if you drive straight or around a corner… is there a load difference on the shaft I don’t see?

no noise straight but noise around a corner regardless left or right or of any load or speed..

I can’t figure it out… 🤪

Cornering the car will unload weight on one side, compress on the other and one wheel turns faster than the other. Re-reading I see the half shafts were rebuilt so maybe not that, but also no information on type of noise.

Another option while you are in there is to switch from half shafts to full CV axles.  I have them in my 74 Euro Pantera that has the Option B double row bearings.  It is a very smooth setup.

Where did you find the CV joint locking tabs?

I think the tabs are there to stop the sealing cap deforming and leaking grease, they are somewhat useless in locking a round head Allen (socket cap) bolt, to ensure security the way to go would be drill and safety wire. I always change the boots for the Aero style, much less prone to tearing and can work at more acute angles.

They are torque distribution plates and are intended to be used with Schnoor single use lock washers.  The M10 10.9 allen head bolts should be of the length where a few threads extend out of the CV joint.  This helps maximize strength of the joint.   The bolts are then torqued to 62 pounds.  You can get the M10 Schnoor washers at McMaster.  These bolts have not come loose on my car.

The bolts and torque plates are reusable to a point.  The Schnoor lock washers are single use.

Using the Schnoor washers without the the thick plates would quickly tear up the thin sheetmetal cover.  The washers make a serrated imprint on the metal they are torqued onto.

They use Porsche 930 CV axles quite a bit in the off-road world and this seems to be their standard setup.

Links to these parts are below.  I got the allen head bolts at McMaster as well.

https://www.mcmaster.com/produ...rs/?s=safety-washers

https://dunebuggywarehouse.com...6ZRtASnMUyPltvAfx-Nr

Also, the allen head bolts are actually 12.9 tensile strength, not 10.9.   That's why they can be torqued to 62 pounds.

Disassembled the rear uprights from the car and I could clearly hear bearing noise. Oddly enough the bearings were louder from the driver side of the car on the bench. To a lesser degree on the passenger side even though on the road the passenger side was noticeable loader. Clearly these have been replaced before.

Digging deeper today and removing the axles (impact wrench and proper socket used; they were damn tight) there is noticeable wear on the mating surface at the outer bearing on the driver side. This axle also appears to be the newer design with a full thickness front flange and a shallow rear hole. The passenger side is of the original design and showed no signs of damage. The spacer tubes had light compression on them from the bearing retainer plates and were able to be pushed around after the screws were removed. There was also no interference between any of the bearing ID’s and any of the axles (slide right apart).

The lower bronze bushings were a mess although they had installed grease fittings a poor job of drilling them through to the shafts didn’t help much. Getting the bearings removed at the shop and start the rebuilding process next.

With the bearings out you could plainly hear the rumble noise in the outer driver side bearing! Cleaned up everything will be replacing the expendables. Have a question about axle diameter. It looks to me that the non contact area of the axle measures 1.5743 inch on both my new and OEM style axles. Does anyone know the target diameter for the proper running fit to the bearing ( 40mm x .03937 =1.5748 )? Our driver side axle at the front bearing measures 1.5702 and is grooved and will need replacing. My concern is the passenger side axle. The rear bearing interface measures 1.5742 ish (great!) but the front area interface measures 1.5726 no galling or tracks. I’m inclined to replace that axle as well or does this still have life left in it?  

For reassembly I found an old infopop that talked about after installing the bearing in the upright first then placing the upright in the oven at 150 degrees for 30 minutes and the axle in the freezer. Pressing them together with the help of expansion/contraction. Is this the best way or has someone come up with something better?

Finally back to this project with the two new axles and necessary parts. We cold pressed everything together and the Uprights with the axles are back together with stock replacement bearings; but not without some issues. Our uprights had been apart before for bearing replacement. The shields were not reinstalled which is common today but someone put a .032 inch shim to help take up the missing outer shield space. Does someone know how thick the outer shield is? Knowing this thickness would help with getting the caliper centered over the disc. During disassembly I noticed I small contact gouge from the rotation of the back side of the disc/stud area in the bearing retaining plate on one upright. Nothing much just a scrape thru the retaining screw faces. We corrected the depths of the counterbores and used flat head cap screws to secure the bearing retainer plates. However we had a few original wheel studs that had goofy threads and new studs were installed. When pressed it all together everything bound up! We found that the heels on the new studs (with the flat on the diameter) were approximately .016 inch taller than the production wheel studs. We had new spacing shims made from hardened blue tempered flat stock at .026 inch thick. We installed two shims per side (.052 total) and removed the original shim of .032. We now have full rotation with the bearings fully seated. On to the lower shaft assembly.

Ken - Sounds like you know more about this than 99% of the rest of us Pantera Owner’s, because you’re elbow deep in it!

Keep up the great work!

Rocky

Just goes to prove that there is no such thing as a bolt on? Granted, the Pantera rear is just a little bit unique.

Personally I like making everything work like you have to.

Just an after thought, are you sure that the noise when turning isn't from the limited slip unit itself?

Hi, yes my first thought was “oh Lord not the gearbox”! Thinking maybe the diff clutches started acting up with the new pressures from spirited corners after years of not being used. I knew the bearings in the uprights had no movement while doing the classic 6/12 and 9/3 o’clock pull testing by heavy hands. So before I started tearing the uprights out I spoke with Dennis Q. We did a couple of tests Dennis suggested (they all showed a worn but fully functional diff section) and he said without opening it up he strongly suggested the bearings in the uprights. Another friend ex-Porsche racer turned early 911 restorer also strongly suggested the bearings in the uprights. Knowing our OEM rear discs were at the low limit we decided to go in and replace axles, bearings, discs to eliminate that concern and hopefully clear up the issue. I’m not holding my breath because further inspection of the old bearings showed no rust, dirt or damage with the shields removed. However as above one of the axles was badly beaten up and the other showed minimal wear/damage.

@KR500 posted:

Hi, yes my first thought was “oh Lord not the gearbox”! Thinking maybe the diff clutches started acting up with the new pressures from spirited corners after years of not being used. I knew the bearings in the uprights had no movement while doing the classic 6/12 and 9/3 o’clock pull testing by heavy hands. So before I started tearing the uprights out I spoke with Dennis Q. We did a couple of tests Dennis suggested (they all showed a worn but fully functional diff section) and he said without opening it up he strongly suggested the bearings in the uprights. Another friend ex-Porsche racer turned early 911 restorer also strongly suggested the bearings in the uprights. Knowing our OEM rear discs were at the low limit we decided to go in and replace axles, bearings, discs to eliminate that concern and hopefully clear up the issue. I’m not holding my breath because further inspection of the old bearings showed no rust, dirt or damage with the shields removed. However as above one of the axles was badly beaten up and the other showed minimal wear/damage.

What rear discs did you use?

Are they dimensionally a substitute for the originals?

The discs came from Larry at Pantera Parts Connection in Carson City NV. Larry sells these as the stock disc replacements. I checked a few dimensions and they look to fit nicely. I wanted stock size discs for the rear in case maybe someday I would go with stock wheels for the full restored look. We also installed (earlier this year) Wilwood six piston calipers all around which also clear stock wheels from SACC.