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RarlyL8 RarlyL8 is offline
Crotchety Old Bastard
 
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Join Date: Jan 2000
Location: Huntsville, AL
Posts: 14,101
Garage
The weak points of the 915 are:
> small bearing retainer - torque warps the retainer causes the pinion to move.
> side plate cover - as the torque moves the assembly towards the side plate the shims are crushed and the side plate cracks.
> LDS - this will more equally load both sides easing the pressure on the side plate.
> small gears/teeth - the long throw on boost from 2-3 can shuck the teeth right off 3rd gear.
> wheel hop - can instantly warp the bearing retainer smash the shims and crack the cover plate.

The worst I have seen is a drag racing incident where the actual housing cracked on the 1-2 speed shift.
To combat these things I used a WEVO bearing retainer, HD side plate, custom gears, LSD, and made a cradle surrounding the R&P housing. That held 400HP on the street. Still not the strength of the 930/4spd.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 10-30-2014, 03:53 AM
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