8 3/4 tapered axle center section question.

[Nate S]

It’s an interesting set of reasons. Certainly some I wouldn’t have thought of. That said they seem to cause more problems than they cure.

They do have their place in rear disc setups I suppose.

As before, I’d like to do the bearing calcs. If someone can spring the real bearing number (not the kit or package number) it would be interesting to see how they add up. Certainly seems like some improvements were made going from the old version to the new.

 

[RJRENTON]

No one is saying that the sealed ball bearing is better than the taypered roller bearing, although the sealed ball bearing has found it's place in the hobby mainly for ease of installation and in some cases it's the only way to upgrade to newer components like changing to a flanged axel from the taypered axels on 1964 and earlier housing.



Here's an explanation from Cass (Dr. Diff) on what has taken place with the bearings in question.

Unfortunately, the original Mopar Green wheel bearing design has 2 problems.

First generation (RP-400) Green bearings, still sold by Mopar Performance and others, are problematic because the crimped-on flange will not allow the bearing to wiggle around inside a housing that is not perfectly straight (none are).

In addition, the design causes the axle to be inserted DEEPER into the housing than necessary. This results in pre-loading against the differential thrust block and early bearing failure.

Second generation (MO-400) snap-ring style Green bearings are forgiving because they can move around inside the housing and they do not preload the differential thrust block in a stock application.

Most guys who have problems with Green bearings are running the RP-400 first generation version or incorrectly made aftermarket axles or housings or poorly designed rear disc brake kits, all of which cause pre-loading and premature bearing failure.

http://www.doctordiff.com/blog/tech-info/why-green-bearings/

IMO...
With regard to the MO400 bearing with the snap ring allowing axial movement "inside the axle housing" an unspecified amount, to avoid differential thrust block preloading, any axial movement, over time would wear the bearing's fit area, requiring repairs or machining. The bearings outer race hardness exceeds the hardness of the axle tube, causing premature wear in the axle tube. This "movement" relieves any axial loading imposed on the bearing. Whereas, with the tapered roller bearings dedign, it is absorbed.
I realize that Dr. Diff provides a worthwhile service. I'm reasonably sure that he has a higher margin with the green bearing package than the Timken Tapered Roller Bearing assembly. Rhetoricly speaking, why would Chrysler engineering design a rotating axial and radial load bearing assembly using tapered roller bearings in lieu of single row ball bearings? Was cost the only objective or was longevity and performance the more important consideration? I vote for the latter.
I've yet to see any actual load calcs of the differences between the two designs, both the B10 and L10 life considerations, to convince me. Would I use the Green bearing design....NO. BUT, I'm not considering changing to rear caliper brake system for my Dana 60 rear axle assembly, nor have I experienced any operational issues with the OEM design and parts. For those people that have converted to the ball bearing assemblies....great....I wish you well. I'm also reasonably assured that IF they did or do have issues, those problems would not be disclosed, to avoid the "I told you so" syndrome.
Just my opinion of course.
BOB RENTON

 

[khryslerkid]

With regard to the MO400 bearing with the snap ring allowing axial movement "inside the axle housing" an unspecified amount, to avoid differential thrust block preloading, any axial movement, over time would wear the bearing's fit area, requiring repairs or machining.

Mr. Bob,
Actually the MO400 with the snap ring allows for a better axle alignment being that the tubes are rarely square with each other and not always being square with the center housing area. That's the only movement that the bearing will have and that takes place when they are installed and they won't move after everything is tightened. As far as thrust block preload, it's recommended to remove the thrust block buttons when using the Green bearing. Then theres no thrust block contact. The block stays in the spider gears, just the buttons are removed.

The older RP 400 was problematic with this along with not having the snap ring which allowed it to move in and out of the axel tube making contact with the thrust block.

Rhetoricly speaking, why would Chrysler engineering design a rotating axial and radial load bearing assembly using tapered roller bearings in lieu of single row ball bearings? Was cost the only objective or was longevity and performance the more important consideration? I vote for the latter.

And you would be correct. It's the perfect bearing with having side load and center load capabilities. Rarely do they ever fail unless moisture gets in them. Almost every one that I replaced were rusty and or completely dried out. Then you have the newer vehicles of today that are using sealed ball bearings in almost everything. The most abuse would be front wheel drive units that have the weight of the engine and trans plus the constant weight of turning the vehicle. Most are a double row ball bearing but do alright in most cases. I'm betting you'll have to replace them before you hit 100k miles in a lot of cars. I deliver auto parts part time and they are constantly being sold to the shops everyday.

I'm not considering changing to rear caliper brake system for my Dana 60 rear axle assembly, nor have I experienced any operational issues with the OEM design and parts.

There's people using the original taypered bearings with their rear disc brake conversions. There was a thread on here not too long ago with a member doing this. It's recommended by most rear disc conversion manufactures to use the Green bearing, probably for the rigidity of the rotor not walking but does a taypered bearing have that much side to side walk? Then you might have to check the alignment of the rotor with the caliper that probably would need to be shimmed if it wasn't true with the adjustable axle side.

As before, I’d like to do the bearing calcs. If someone can spring the real bearing number (not the kit or package number) it would be interesting to see how they add up.

I'll try to find those numbers if I can but I would be pretty sure the outcome would be in favor if the taypered roller out lasting the ball bearing. This is almost a given.

The thing is, in this hobby, your not going to drive your classic as your daily driver and get that many miles per year on it. In a normal circumstances don't replace your original bearing with the sealed ball bearing.

The Green bearing is a fix for "out of the norm" situations as what us early car owners have to deal with updating the taypered axel rears or maybe rear disc brake conversions or probably what really started the use of these bearings, Drag racing. Makes it easier to swap out a different gear ratio or replace a unit that just let go with a replacement unit.

I'm using a set of the MO 400s in the '62. Have about 1500 miles on them. I'll be the first to post on here that one failed, I'm not scared!

(I really hope this is the last time we kick this can down the road but I'm not holding my breath.)

 

[RJRENTON]

Mr. Bob,
Actually the MO400 with the snap ring allows for a better axle alignment being that the tubes are rarely square with each other and not always being square with the center housing area. That's the only movement that the bearing will have and that takes place when they are installed and they won't move after everything is tightened. As far as thrust block preload, it's recommended to remove the thrust block buttons when using the Green bearing. Then theres no thrust block contact. The block stays in the spider gears, just the buttons are removed.

The older RP 400 was problematic with this along with not having the snap ring which allowed it to move in and out of the axel tube making contact with the thrust block.



And you would be correct. It's the perfect bearing with having side load and center load capabilities. Rarely do they ever fail unless moisture gets in them. Almost every one that I replaced were rusty and or completely dried out. Then you have the newer vehicles of today that are using sealed ball bearings in almost everything. The most abuse would be front wheel drive units that have the weight of the engine and trans plus the constant weight of turning the vehicle. Most are a double row ball bearing but do alright in most cases. I'm betting you'll have to replace them before you hit 100k miles in a lot of cars. I deliver auto parts part time and they are constantly being sold to the shops everyday.



There's people using the original taypered bearings with their rear disc brake conversions. There was a thread on here not too long ago with a member doing this. It's recommended by most rear disc conversion manufactures to use the Green bearing, probably for the rigidity of the rotor not walking but does a taypered bearing have that much side to side walk? Then you might have to check the alignment of the rotor with the caliper that probably would need to be shimmed if it wasn't true with the adjustable axle side.



I'll try to find those numbers if I can but I would be pretty sure the outcome would be in favor if the taypered roller out lasting the ball bearing. This is almost a given.

The thing is, in this hobby, your not going to drive your classic as your daily driver and get that many miles per year on it. In a normal circumstances don't replace your original bearing with the sealed ball bearing.

The Green bearing is a fix for "out of the norm" situations as what us early car owners have to deal with updating the taypered axel rears or maybe rear disc brake conversions or probably what really started the use of these bearings, Drag racing. Makes it easier to swap out a different gear ratio or replace a unit that just let go with a replacement unit.

I'm using a set of the MO 400s in the '62. Have about 1500 miles on them. I'll be the first to post on here that one failed, I'm not scared!

(I really hope this is the last time we kick this can down the road but I'm not holding my breath.)

I appreciate your comments and candor. Regarding the movement of the installed bearing assembly, what you note is true, if the movement is parallel to axis of rotation as a ball bearing assembly can accomodate a slight axial load to the limit of the bearing's design maximum. Offset mis-alignment introduces additional considerstions to both axial AND radial load capabilities. Any repeated axial movement of the bearings outer race in its containment (axle tube) will result in premature wear, over time.
As far as a drag racing application, as you noted, YES but only if the participant is using a 8 3/4" differential assembly. A Dana 60 is much more difficult to swap out for just a ratio change (IMO).
I wish you well with your '62 and the MO400 bearing installation and as you noted, time and use will tell...
BOB RENTON