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Mopar Rearends


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#16 Savageman OFFLINE  

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Posted March 23, 2014 - 09:12 AM

OK.  For what Chris and Joe Mopar has shown explains the timeline and the earlier question about what did '54/'57 Copars use .  Older stuff from the 40s & 50s was definitely more available.   But they didn't introduce the 8 3/4" rears til 1957.  So that being said, the Panzers do not have these bigger 8 3/4" rears.  Agree?

 

Now for the ratio question, If I tried to find my ratio and turned my smaller Panzer wheel and tire which is 21" tall I would get less turns of the pinion then the original 1940/1950 model car tires that were 710-15 and 28" tall (info obtained from Coker website).  That 7" difference in height should answer that question.  Agree?

 

The only other question I have is a statement from fzrs55 on these being open rearends.  I have never heard this term and my mechanic buddies at the coffee shop this morning haven't either.  Can you explain more clearly?

 

Dave


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#17 Canawler OFFLINE  

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Posted March 23, 2014 - 09:45 AM

Now for the ratio question, If I tried to find my ratio and turned my smaller Panzer wheel and tire which is 21" tall I would get less turns of the pinion then the original 1940/1950 model car tires that were 710-15 and 28" tall (info obtained from Coker website).  That 7" difference in height should answer that question.  Agree?

 

No.  As far as the ratio goes, the wheel height has nothing to do with it.  It's strictly number of turns.  One revolution is one revolution regardless of height.

Now where it will come into play in an automotive setting is speedometer calibration.  They had multiple speedometer drive gears available for various ratio and wheel combos.

 

 

The only other question I have is a statement from fzrs55 on these being open rearends.  I have never heard this term and my mechanic buddies at the coffee shop this morning haven't either.  Can you explain more clearly?

 

Dave

 

Open rear is just another name for the normal differential.  As in, not positraction, or in Mopar's case Sure Grip.  In the open rear, torque will be transmitted to the wheel with the least traction while the Sure Grip rear will drive both wheels equally.


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#18 fxrs55 OFFLINE  

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Posted March 23, 2014 - 09:48 AM

That is an old term I guess.  Open means  non possitive traction,  not a limited slip differential.

Just one wheel gets power.  We also called it single wheel pull back in the old days.

This is a general explanation and everyone has an opinion.  A large percentage of

most cars are built this way.  Cheaper to build.

 

 

How old are your mechanic buddies?  ( Ha Ha )


Edited by fxrs55, March 23, 2014 - 09:51 AM.

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#19 Savageman OFFLINE  

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Posted March 23, 2014 - 10:41 AM

Just a group of old retired guys.  One of them still runs a Ford Model T rebuilding business.  We are all in the 70s. 


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#20 toppop52 ONLINE  

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Posted March 23, 2014 - 10:55 AM

The term "open rear", is what I always heard as well. The 8 3/4" rear is a very strong rear and was used behind 440 engined cars. They were available in a bunch of ratios from at least 2.56 all the way to 4.88, there may have been some below and above that.  The rear in my old Panzer was a 3.91 ratio. Don't remember the model or tire size, it was  a 6 h.p. B & S motor.

I don't know that the 8 3/4 was ever available with anything but the 4.5" lug pattern, all the smaller  wheel lug patterns I ever saw were in the 8 1/4" rears. As for what they used in older tractors, no idea, they could have bought them from Chrysler as early as 1956 when the '57 production began.


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#21 fxrs55 OFFLINE  

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Posted March 23, 2014 - 02:12 PM

 

Now for the ratio question, If I tried to find my ratio and turned my smaller Panzer wheel and tire which is 21" tall I would get less turns of the pinion then the original 1940/1950 model car tires that were 710-15 and 28" tall (info obtained from Coker website).  That 7" difference in height should answer that question.  Agree?

 

 

 

 

Ahh, Now you are talking two different things.

One is gear ratio which is what is the ratio of the ring and pinion gear inside of the diff.

 

the other is final drive ratio which varies with tire size.

how far does a 21" dia tire travel in one revolution ?

how far does a 28" dia tire travel in one revolution ?

 

 

 


Edited by fxrs55, March 23, 2014 - 02:14 PM.

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#22 Canawler OFFLINE  

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Posted March 23, 2014 - 04:30 PM

I don't know that the 8 3/4 was ever available with anything but the 4.5" lug pattern, all the smaller  wheel lug patterns I ever saw were in the 8 1/4" rears.

 

A-body vehicles (Dart, Valiant, Duster, early Barracuda, Demon, etc.) used a 4" bolt circle and were available with 8 3/4 rears in the high performance versions.


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#23 stiemmy ONLINE  

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Posted March 23, 2014 - 05:58 PM

Up in this neck of the woods, they are often referred to as a " one wheel wonder ". LOL
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#24 Savageman OFFLINE  

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Posted March 23, 2014 - 06:24 PM

This note is for fxrs55.  (I wish I had a first name).  So, there is no way to tell what the ring & pinion ratio is without disassembly.  I've learned one thing, if things are working good don't take them apart.  The answer to the final drive ratio is  28" rolls 7.3'  and 21" rolls 5.5'.  Diameter X  Pi  (3.142) divided by 12 = circumference

 

And this note is for stiemmy.  (no first name here either).  Back in my racing days we called them "one legged burn out" LOL

 

Dave


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#25 toppop52 ONLINE  

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Posted March 23, 2014 - 06:28 PM

A-body vehicles (Dart, Valiant, Duster, early Barracuda, Demon, etc.) used a 4" bolt circle and were available with 8 3/4 rears in the high performance versions.

My '72 Demon 340 did have a 4" bolt circle, so my memory was off and it's only been 40 years! That being said, it appears that there were also large bolt circle 8 3/4 rears used in some Imperials and trucks, 5" pattern.


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#26 toppop52 ONLINE  

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Posted March 23, 2014 - 06:31 PM

This note is for fxrs55.  (I wish I had a first name).  So, there is no way to tell what the ring & pinion ratio is without disassembly.  I've learned one thing, if things are working good don't take them apart.  The answer to the final drive ratio is  28" rolls 7.3'  and 21" rolls 5.5'.  Diameter X  Pi  (3.142) divided by 12 = circumference

 

And this note is for stiemmy.  (no first name here either).  Back in my racing days we called them "one legged burn out" LOL

 

Dave

It doesn't matter what tire size you have in determining gear ratio, one full revolution of the wheel/tire is going to turn your pinion and yolk a given amount, whether the tire is 20" or 40". The distance it would travel on the ground is another matter, so you can still use the two revolutions of the wheel vs number of revs for the pinion yolk.


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#27 stiemmy ONLINE  

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Posted March 23, 2014 - 07:20 PM

This note is for fxrs55.  (I wish I had a first name).  So, there is no way to tell what the ring & pinion ratio is without disassembly.  I've learned one thing, if things are working good don't take them apart.  The answer to the final drive ratio is  28" rolls 7.3'  and 21" rolls 5.5'.  Diameter X  Pi  (3.142) divided by 12 = circumference
 
And this note is for stiemmy.  (no first name here either).  Back in my racing days we called them "one legged burn out" LOL
 
Dave

Lmao
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#28 fxrs55 OFFLINE  

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Posted March 23, 2014 - 08:56 PM

It doesn't matter what tire size you have in determining gear ratio, one full revolution of the wheel/tire is going to turn your pinion and yolk a given amount, whether the tire is 20" or 40". The distance it would travel on the ground is another matter, so you can still use the two revolutions of the wheel vs number of revs for the pinion yolk.

This is correct, gear ratio can be determined as stated in this post by toppop52. very well put by the way.

 

My first name Don.


Edited by fxrs55, March 23, 2014 - 09:03 PM.

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#29 Panzerguy OFFLINE  

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Posted March 24, 2014 - 05:59 AM

DSCF2159.JPG DSCF2161.JPG DSCF2162.JPG DSCF2160.JPG Rear end of my T-70 yard ornament.

 

Couldn't get a couple of these to rotate for some reason. They were in the proper position when I attached them. Sorry about that.

 

AL


Edited by Panzerguy, March 24, 2014 - 07:45 AM.

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#30 toppop52 ONLINE  

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Posted March 24, 2014 - 06:45 AM

Since we're confessing, I'm Randy! :D


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