Ok, first I'm not crazy, and in DEFINITELY not stupid, so we can eliminate that issue.

I am trying to change the bearings and seals on both on my rear axles in preparation for installing my new gears.

I first got the new bearings and seals from Autozone. They were the standard Timken sealed bearings and inner axle shaft seals that I would expect to buy for a BOP axle. They looked exactly the same as the bearings and seals that we just replaced on a '66 GTO a few months back.

But I have a problem, my axle bearing/seals that I pulled from my current rearend tonight are VERY different from the "normal" 8.2 BOP setup that I am used to seeing.

I read through the other posts here on the site, and EVERYONE swears that the seal fits on the inside of the axle tube before you stick in the new axle/bearing assembly.

/forums/ultimatebb.php?ubb=get_topic;f=23;t=004044#000003

/forums/ultimatebb.php?ubb=get_topic;f=23;t=005125#000000

Then I referenced the photo that shows the seal (part #4) going into the axle tube first.

http://www.1968firebird.org/illustrated/rear/diff1.html

But what I have is totally different.

I have the standard 4 bolt plate that holds in my axles, but when I pulled the plate off and yanked the axles, the seals were on the outside of the axle (between the bearing and the plate). Also, the bearing was an OPEN bearing, meaning I guess it was being lubed by the sloshing fluid in the rear end.

Knowing my car, and it's originality, I would put this at 99% sure this is the original rear end. The code on the axle tube decodes to a 2.78 open, and that is what it actually is.

I don't know if it matters, but I believe my '69 was a very late 69 or early 70 manufacture date. When I replaced my rear end flex brake line before, the "correct" 69 part the store pulled did not match to the piece I had in my hand that came off the car. But it DID match up to a part from a '70 Firebird. Could this have anything to do with the axle bearings and seals being totally different that what is expected on normal FGF's?

Any ideas? Any reason why my rear end would be so totally different that whats in the Service Manuals?

There was a mention on one of the other posts that '69's had either roller or ball bearings. Would this be the difference between the two? If there are two different styles, are they interchangeable (I assume no).

Thanks,
Thomas

Thomas,
The simple answer is that someone rebuilt it the way they knew how to rebuild one with the c-clips. No matter why or how, the bearing needs to be trapped without using a seal as part of the 'stack'. I know this from extensive training and experience with bearings. Even if it were original to the housing you could do a great improvement by getting that seal out of the bearing stack.

Add: There is only one remote possibility that this stack could work the way it is and that would be that the seal is not your normal seal. If the seal is beefed up enough to pass as a spacer it could work. If it's made of your normal sheet metal then it wouldn't have enough structure to hold the bearing in place like it should.

Thomas,

That's exactly like my original rea end assembly. The seal went between the plate and the housing flange. They are still bolt in axles....ie, no c'clip to worry about.

From the axle flange you will have the 4 bolt plate, the seal, then the bearing. The axles slide in and out of the housing without even removing the differential cover, so there are no c-clips.

Drew

So, in essence, the seal is holding the axle in place? ->(Bearing/seal)Plate The seal gets the total side to side force exerted by turning, torque, road hazards.... This takes a great idea of C-clip elimination and weakens it to the point that a C-clip rear end is stronger and less likely for the axle to move side to side.

Obviously, no one can say there are none made like this BUT I can say that the dozen or so I've taken apart had the bearing trapped solidly. Also, the c-clip elimination kits sold to strengthen c-clip rear ends provide the parts to trap the bearing solidly without a seal in the stack.

Jim,

The bearing still is still pressed onto the axle and it is still trapped solidly against the axle tubes, it just looks like it's moved inward slightly on the axle. The plate holds the seal and the seal holds the bearing. So yeah I guess the seal does get all the lateral pressure, but it's of a different design that the inner seals that you are referring to. I can take a picture of the seal if yer interested.

So needless to say, you can't mix the axles and housing from the two different styles that are obviously available on the '69, correct?

Hmmm. All I can say is when rebuilding it, I would get the seal out of the stack. Common sense wise, you wouldn't want the seal detemining how the bearing is being trapped in the pocket. Seals aren't designed for that function. They are not made to take any side loading.

I was part of one of those earlier posts and I finally found the seal that works on the outside as Trauschu seems also to have. It ended up as a Federal Mogul 2148.

I fully understand and appreciate FBody's concern but I had NO machined area on one side to put a seal inboard, and the other side looked suspect.

I have the same setup now Trauschu, Timken style bearing, seal, plate. The seal looks reasonably heavy to take lateral forces, but will certainly monitor everything on a maintenance regime.

I have been thinking about this and you could slightly modify the stock setup by using a heavy plate, 1/8 steel, between the housing and the plate that holds the seal. You could make it like the plate that holds the seal but with a slightly smaller ID on the big hole. I have seen this configuration on machines. Another way to straighten this out would be to purchase the c-clip elimination kit that is available. I have a theory as to how this different set-up may have come about. GM was making these rear end assemblies and then they sold the business to American Axle at some point. Maybe it was an easy, substandard, way to get by when they first took over the business. And since the c-clip rear ends soon followed, maybe the c-clips were an improvement over a set-up where the seal took all the side loading. The solid c-clips are much better suited to hold the axle than a seal. It's an engineering nightmare for a production rear end to be made this way. Hopefully, there aren't many out there. If they are a late 69 thing then it may be that it was only a particial run. Think of it as the 'missing link' between the inboard held axles and the outboard held axles.

Try looking at the bearing and seal for the roller bearing rear. Maybe they fit. (?)
Does the old bearing have balls or rollers in it?
http://www.1968firebird.org/number/abw/abw32.jpg

Ask for 1971 cutlass with 10bolt for late 69 roller bearing axle parts. I think BR9 and 2146 or 48? (alternate seal 16735 0.4700 width or 16747 0.3750 width, NAPA listing)
Somebody here or on the list has pictures of a roller bearing rear axle. I can't remember where the seal was, if pictured.

Here is what Strange has for the problem. It seems like overkill but it does show you that Strange Engineering takes the axle holding seriously. When you look at this serious set-up it shows how silly it is to use a seal in the holding.
http://cgi.ebay.com/ebaymotors/stra...QQitemZ8070778449QQrdZ1QQsspagenameZWDVW

Here is Moser's set-up:
http://cgi.ebay.com/ebaymotors/MOSE...728QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

GM changed the design of the 10-bolt in 1969. That's why the drawing in the 1968 service manual is different. Unless you have a bunch of 1969 10-bolts laying around, you might never see this version. The 1969 service manual also shows the older design.

There are two seals, two bearings and two axle housing designs for 1969. The roller bearing is for the later design and is about 1/16" wider than the ball bearing design. This requires the diferent seal set-up.

There is one reliable way to tell them apart: The bolts that hold on the ring gear are 7/16-20 threads instead of 3/8-24 threads.

Thanks Q.

If I have the choice between the older style 69 rear end (with the seals on the inside) and the newer style (with the seals on the outside), which one would you rebuild with new gears? Is one inherintly better or worse than the other?

Are you ignoring the info? The second is a bad design.

Not ignoring. Exploring. Understanding.

Let's not forget that they made the ring gear bolts larger in the late model 69 rear ends, so in that case, it's STRONGER than the earlier rear ends.

So, it's an open discussion here.

It's debatable whether a fine thread 3/8's is stronger than a 7/16 course thread. The 3/8 has more threads per inch and a shallower thread depth which is stronger and has more holding torque. One thing for sure, the 3/8 cost more so the switch was most likely for cost savings, not to mention how much easier it is on the assembly/machining lines to cut course threads. And since the threads are in the gear does it really matter at all????

I've heard a lot about axle instability but not much about a ring gear coming loose.

I thought 7/16-20 was fine thread and 7/16-14 is course?

Of course. :p And it really doesn't matter because the gears are not part of the housing/axle question.

The c-clip eliminator looks good, wondering if there may be any issues mounting it with the disc setup etc??

I acknoledge that this outboard seal is a weak design, but under light duty driving (ie not racing or high G corners), I assume it would be serviceable?

Heck yes, Dave. It will be fine. We are just beating it to death trying to decide which is best! The axle can't come out, it could squash the seal and move around a little. Maybe make it leak a little.

If you check up on it, you'd see that the seal never takes any real load.

From an engineering analysis point of view:

The load (a force generated by the car's weight while subjected to lateral g's) is transmitted through the outer axle housing tube to the bearing's outer race. The outer race transfers the load through the balls (or rollers) to the inner race, which transfers the load to the axle shaft onto which it is pressed. The axle shaft transmits the load to the hub plate (or rotor plate if you have rear discs) which then transfers the load to the wheel, which transfers the load to to the tire. The tire has to resist that load (the lateral force) while not skidding.

The seal is not in the load path.

Bring a six pack if you want to see it. Extra credit if you notice that the load is in the same direction as the load used to press the bearing in place.

The harder the car corners, the harder the axle is "pressed" into the bearing. (Or vice-versa.)

The lateral loads are NOT shared equally by the bearings on both sides. Because of body roll, the lion's share of the load goes to the outside wheel ... the one trying to push the axle harder into the bearing. In order to pull the axle out of the bearing, the load on that axle has to exceed the press load. What usually happens is that one of the shoulders holding the balls or rollers in place fail from fatigue, usually caused by eccentircity or vibration-driven problems.

The 1964-1969 Seal:



The Later Seal:

I can buy all of that but after assembling so many bearing stacks over the years and the seal never goes up next to the bearing outer race. It goes against all my training and practical experience. If it was on my car I'd probably live with it. If I had the choice I would choose a properly trapped bearing. If I was rebuilding one like that I would find an easy revision.

I have had an axle let loose and there is some side loading because the sucker shot across the street!