Re: [Chrysler300] 64 K Rear Diff

["charlies@xxxxxxxxxxxx [Chrysler300]" <Chrysler300-noreply@xxxxxxxxxxxxxxx>]

Hi All,

In regards to axle length, be advised of the following, taken from Auto Hobby Digest. See   https://www.bigblockdart.com/techpages/875axle.shtml

There was a difference in thrust blocks prior to 1964 that make center section interchange, as well as axle interchange problematic. The thrust block, or "axle shaft thrust spacer", it thr block that both left and right axles butt up against inside the center of the differential. Prior to 1964, all open differentials used a thrust block was approximately 1/8" to 1/4" thicker than units made after 1964. The Sure Grip thrust block prior to 1964, however, was indentical to all 1964 and later Sure Grips and open differentials. In 1964, the thrust block width was changed to match the Sure Grip thrust block width.

This difference in thrust blocks between Sure Grip differentials and open differentials required that two different axles be produced for each 8-3/4" housing manufactured. This is true of all 1959-1963 cars with 8-3/4"s.

A 1964 and later differential, or any Sure Grip differential, cannot be used with 1959-1963 rearends and axles originally equipped with an open differential. The original axles must be machined or original Sure Grip length axles must be used.

Section 3 contains housing and axle sizes and part numbers for these early 8-3/4" rearends.

Charlie in Ottawa

 

On 2020-12-10 3:16 pm, 'Rich Barber' c300@xxxxxxx [Chrysler300] wrote:

 

Rick:

 

The 1964  "Service Technical Manual" shows the 2.76:1 differential was standard in Newport's and New Yorkers so should be easy to source.  I believe the pinion shaft and U-joints in Newport's were of smaller diameter than those in NY's.so you might take that into consideration for strength and boltup to your K's rear U-joint.  Your speedometer pinion would need to be changed from 19-tooth dark blue to 16-tooth brown. Axle lengths are same for conventional or Sure-Grip.  You are probably aware that the rear brake drums on our '64's are hard to remove.  Special tooling and techniques may be required.  Ask if you need guidance.

 

Do let us know how much greater MPG you get after the change and whether top-end speed was increased or decreased. 

 

Rich Barber

In sunny CA, surrounded by Covid 19 cases and Governor's lockdown.  So far, so good.

 

 

From: Chrysler300@xxxxxxxxxxxxxxxx <Chrysler300@xxxxxxxxxxxxxxx> On Behalf Of Rick King rickking952@xxxxxxxxx [Chrysler300]
Sent: Thursday, December 10, 2020 10:38 AM
To: chrysler300@xxxxxxxxxxxxxxx
Subject: [Chrysler300] 64 K Rear Diff

 

 

Hi everyone, I am looking for a rear diff. & axle shafts for my 64 300 K. Would like a gear ratio around 2:76 . Also need a Posi unit as well.

 

Thanks, Rick King

 

 

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Posted by: charlies@xxxxxxxxxxxx

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