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Username Post: Bearing seat offset        (Topic#360260)
4dr 57 
Valued Contributor
Posts: 4667

Loc: Texas Hill Country
Reg: 11-10-04
03-24-20 05:15 AM - Post#2789349    


What is the reason the 57's have 3 different bearing seat offsets?
Thanks.
Stan

It's all good. mostly




 


acardon 
Ultra Senior Member
Posts: 11364
acardon
Loc: DFW TEXAS
Reg: 03-25-05
03-24-20 07:04 AM - Post#2789359    
    In response to 4dr 57

What bearing are we talking about?

Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
toms57 
Senior Member
Posts: 529

Loc: Caney, Ks, USA
Reg: 10-28-01
03-24-20 07:48 PM - Post#2789402    
    In response to 4dr 57

Been at this for a lot of years. I don't understand your question.




 
Shepherd 
Frequent Contributor
Posts: 2067

Loc: Lake George, NY
Reg: 11-11-15
03-25-20 02:24 PM - Post#2789461    
    In response to 55MAS

How about we put this on hold til the op responds with a clear description of what he is talking about.



 
4dr 57 
Valued Contributor
Posts: 4667

Loc: Texas Hill Country
Reg: 11-10-04
04-07-20 07:03 PM - Post#2790598    
    In response to Shepherd


Sheperd, tom's57, acardon, I APOLOGIZE! For being a week lateon my reply to ya'll questions!

Hope everyone is safe and well-

If one were to meazure from the outside of the rear axle flange to the bearing seat you will have measured the Bearing Seat Offset of the 57 Chevy. There are three of them. I'm looking for a reason there are three different measurements.

Yeah different mgfrs. does come to mind right away, however being an armature enthusiast I'm wondering if there could be a definitive reason that to date, eludes me. I know it can make a difference when it comes to tire removal on my 8 window as the clearance is different now that I have changed axles.
Thanks.
Stan



 
acardon 
Ultra Senior Member
Posts: 11364
acardon
Loc: DFW TEXAS
Reg: 03-25-05
04-07-20 08:03 PM - Post#2790612    
    In response to 4dr 57



Maybe post #12 in this thread will help. Link to axles. I still don't know what you mean by 3 offsets.

Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
4dr 57 
Valued Contributor
Posts: 4667

Loc: Texas Hill Country
Reg: 11-10-04
04-10-20 12:27 PM - Post#2790827    
    In response to acardon

Unfortunately as righteous as that information is, there is no mention of the 3 rear axle bearing offset measurements in 57.

There are three different measurements found on 57 Chevy rear axle bearing seats. This has nothing to do with the length of the axle itself. Although it can effect the amount of axle engagement with the spider gears on an "open" type rear differential, and probably the posi gears as well. How critical it is I have no idea.

As pretty common knowledge it's no big deal.
I simply wanted to know why GM did it this way.
Perhaps they represent the allowed tolerances, how should I know? There are just 3 however.

(This fact is not nearly as obscure as the length from the end FRONT axle to its bearing seat and the wear-in limits allowed before the axle is worn out.)

Thanks.
Stan

It's all good. mostly




 
acardon 
Ultra Senior Member
Posts: 11364
acardon
Loc: DFW TEXAS
Reg: 03-25-05
04-10-20 12:55 PM - Post#2790828    
    In response to 4dr 57

I still don't know what you mean by 3 offsets???

The bearing will only go on one place on the axle shaft. The inside bore of the ONLY 57 bearing (RW307R) is 1.3780" rounded off to 4 places. Bearings are held to very close tolerances and do not vary. It is a press fit which means the shaft diameter where the bearing is pressed on, up to the shoulder, is approximately 1.3781 or 1.3782" which is followed by the retainer which is an even tighter press fit. These parts will go on in ONLY one place on the axle and there will be no axle wear as long as the bearing is not frozen up and turns on the axle.
The shoulder determines the location of the bearing on the shaft and establishes a constant location of the axle flange to the housing/backing plate.


Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
4dr 57 
Valued Contributor
Posts: 4667

Loc: Texas Hill Country
Reg: 11-10-04
04-10-20 08:02 PM - Post#2790867    
    In response to acardon

Thanks acardon

All True

3 different offset measurements
means there were three different locations from GM, of just exactly where the bearing seat is located when measured from the outside of the axle flange.

Both axles of a rear assembly "probably" had the same measurement.

However a different pair of axles can have a different measurement hence the location will be different.

And still another set/pair of axles can have an even different measurement. There are just 3.

But definitely 3 were used through the production year.

This probably isn't a coincidence since there were 3 Series of car made with differences like rear bumper ends and other changes/improvements.

I was told that on a 4drht for example there was only one escutcheon shaft/pin holding the rear corner bracket to the body. The second Series has 2.
There are probably other differences as well.

Again, I am simply interested in why they did it that way? Was it just a matter of being within tolerances?
Were there 3 different axle suppliers?
Was there some actual purpose other than it can be done that way?

Thanks.
Stan




It's all good. mostly




 
acardon 
Ultra Senior Member
Posts: 11364
acardon
Loc: DFW TEXAS
Reg: 03-25-05
04-10-20 08:35 PM - Post#2790868    
    In response to 4dr 57

  • Quote:
But definitely 3 were used through the production year.



I don't believe that could be even remotely possible. That would mean the axle flange would be a different distance from the backing plate with different axles. The brake drum fits on the axle flange. It HAS to be a certain distance from the backing plate for the shoes to contact it and not rub on the backing plate.
They deffinately did not have different backing plates, brake shoes, drums, or axle housings, to compensate for what you are suggesting. There's just too many parts depending on the location of the axle flange, not to mention wheel backspacing.

Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
4dr 57 
Valued Contributor
Posts: 4667

Loc: Texas Hill Country
Reg: 11-10-04
04-11-20 12:14 PM - Post#2790904    
    In response to acardon

acardon

I guess I have actually answered my own Original question UNLESS there is some other reason other than the two I mentioned.
Would you have any other explaination?

At this point I should just say Thanks Again acardon for the lesson in critical/logical thinking!!!





 
Rick_L 
Member #409
Posts: 27716
Rick_L
Loc: Katy, Tx, USA
Reg: 07-06-00
04-11-20 02:32 PM - Post#2790912    
    In response to 4dr 57

There is only one, you are dreaming.



 
4dr 57 
Valued Contributor
Posts: 4667

Loc: Texas Hill Country
Reg: 11-10-04
04-12-20 06:43 AM - Post#2790950    
    In response to Rick_L



=GAK!! Ya'll are absolutely right!!!

Yeah, I'm embarrassed - but it was a good dream - but it was wrong as they come -





 
acardon 
Ultra Senior Member
Posts: 11364
acardon
Loc: DFW TEXAS
Reg: 03-25-05
04-17-20 08:12 AM - Post#2791371    
    In response to 4dr 57

Stan, in your study of axles, are all open rear axles the same length and all posi rear axles the same length?

Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 


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