[Rovernet] P6 final drive

[Fletcher Millmore]

The people who do this know the answers about what can be done, given 
the application.
These shafts should really have the splines cut away outside the mating 
gear, with a round end tool, down to the root of the spline, and out to 
near the bearing seat. This has proved to help a lot in similar 
applications - ie, Spridget halfshafts. Commonly referred to as 
"Growlerizing" after a guy who popularized the procedure. It turns the 
small diameter area of the shaft into a sort of spring, but with no 
stress risers to initiate cracks. About halfway down this: 
http://www.mgexp.com/article/midget-rear-axle-knowledge.html
you will see some info and a little pic of a not great example.
Then you ought to peen the machined area at least.
Cryogenic treatment adds a bunch more, and is not all that expensive, 
certainly cheaper than busted parts. It is used in all sorts of high 
performance industrial and racing applications. Cryo is good for nearly 
all metal parts, especially including gears.

FRM

On 3/3/2015 5:49 PM, Dermot Harvey via Rovernet wrote:
> Sounds really interesting.  As I recall, the drive shafts shear at the point where the splined shaft enters the differential wheel. Would the shot peening damage the splines on the shaft?
>
> Dermot Harvey
>
> On Mar 3, 2015, at 4:57 PM, Fletcher Millmore via Rovernet wrote:
>
>> Look into other treatments - stress relief, cryo, peening all help, especially in combination. See Metal Improvement company etc. Much of this stuff was first done by SoCal hotrodders so they could abuse final drives - ie putting 1000hp through a 40's Ford axle.
>>
>> FRM
>>
>> On 3/3/2015 4:34 PM, Scruggs Family via Rovernet wrote:
>>> Ah, thanks, Vern...  I'd forgotten about those things.  I suppose it
>>> wouldn't be too difficult to have a good set of 2000 axles shot peened...
>>> which reduces the likelihood of surface cracks.  Never had that problem but
>>> have had the differential mounting bracket develop stress cracks.
>>>
>>> Said the one-armed alligator wrestler, "We learn as we go."
>>>
>>> Gross
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: Vern Klukas [mailto:vern at inkspotco.com]
>>> Sent: Tuesday, March 3, 2015 4:13 PM
>>> To: Scruggs Family; Rovernet
>>> Subject: Re: [Rovernet] P6 final drive
>>>
>>> Dermot meant what I would call the stub axles on the diff that the half
>>> shafts bolt to. Rover calls them drive shafts.
>>>
>>> Yours
>>> Vern
>>>
>>>
>>>> On Mar 3, 2015, at 1:02 PM, Scruggs Family via Rovernet
>>> <rovernet at rovernet.org> wrote:
>>>> Dermot,
>>>>
>>>> Clarification please... you said "drive shafts"... did you mean to specify
>>>> "half shafts?"  Was there a common point at which these failures took
>>> place?
>>>> Thanks,
>>>> Gross Scruggs
>>>> Annapolis, MD
>>>>
>>>> -----Original Message-----
>>>> From: Rovernet [mailto:rovernet-bounces at rovernet.org] On Behalf Of Dermot
>>>> Harvey via Rovernet
>>>> Sent: Tuesday, March 3, 2015 1:19 PM
>>>> To: Rovernet at rovernet.org
>>>> Subject: [Rovernet] P6 final drive
>>>>
>>>> There is another factor with P6 final drive - the differential drive
>>> shafts
>>>> are different! The 3500S drive shafts are shot peened which is supposed to
>>>> make them stronger. I think these drive shafts are a weak point in the
>>> rear
>>>> end. I had a 3500S once where the drive shaft completely sheared leaving
>>> me
>>>> stranded. I like to take these drive shafts out and see how 'upset' the
>>>> splines are before using or selling a rear end. I have seen quite a few
>>> that
>>>> are well on their way to twisting off!
>>>> Thank you David Walter for the harmonic balancer info.
>>>>
>>>> Dermot Harvey
>>>> Spectral Kinetics
>>>>
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