[DML] Transmission Shaft Couplers

[tobyp@xxxxxxxxxxxx]

Hello List - As you might recall, there was a lengthy flurry of 
messages regarding failures of input and main transmission shafts.  I 
took a good look at the reports, and have decided to do something 
about what appears to be the primary failure mode in this area - the 
splined coupler that connects the input shaft to the main shaft.  I 
have focused in on two components; the coupler itself, and the roll 
pin that is used to fix the coupler to the main shaft.  In a recent 
local failure, the coupler stripped out, and the roll pin sheared.  
The sharp fragment of the pin caused irreparable damage to the 
splines on the main shaft, resulting in the expensive replacement of 
the main shaft.  The failed coupler is made from mild steel, possibly 
4130 alloy, with a heat treat of about 115,000 PSI ultimate tensile 
strength (very soft).  It is only partially splined internally 
(perhaps 50%).  The theory has been proposed that this is supposed to 
be a "fuse" of sorts to protect the main shaft from damage.  So far, 
not so good.  The "protection" has become the primary failure of the 
transmission, which is not acceptable.  I have commissioned custom 
couplers made from 4340 alloy at a heat treat of about 150,000 PSI 
ultimate tensile strength, and are fully splined for maximum 
strength.  They are nearly done, fit the shaft splines better than 
stock, and are beautiful!  I have also obtained a stronger variety of 
roll pin that is much more resistant to coming out prematurely, and 
also cracking.  For those of you who are contemplating  horsepower 
increases, or want a better load path into your transmission to avoid 
future expensive failures, I will have a limited number available by 
mid next week.  Please contact me off-list for further information at 
toby(at)delorean-parts.com.  We will have some available at PF, 
unless they are sold out immediately.  See y'all there!

Toby Peterson  VIN 2248 "Winged1"
DeLorean Parts Northwest, LLC
www.delorean-parts.com
     




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