Duramax Diesels Forum Truck of the Week
Old 06-19-2017, 07:52 AM
cm2500hd cm2500hd is offline
Join Date: Jun 2017
Posts: 1
Default Allison extension housing replacement procedure

ok guys I have a cracked extension housing. I know I have to pull the trans to fix it but Im looking for more information on how to do it?
Old 06-19-2017, 12:10 PM
JoshH's Avatar
JoshH JoshH is offline
Daggum farm truck
Join Date: Feb 2007
Location: Texas!!!
Posts: 13,018


Drain fluid
Remove transmission
Remove torque converter
Stand transmission with tail housing end up
With transmission in park, remove output shaft nut
Remove tailhousing bolts
Remove tailhousing making sure the park pawl pin doesn't try to come up with the tailhousing
Remove old tailhousing gasket
Remove C5 apply piston if your new tailhousing doesn't come with one
Install new lip seals on C5 apply piston
Install piston into new tailhousing
Place new gasket on rear of transmission
Install new tailhousing
Torque bolts to 42 lb-ft
With transmission in park, install output shaft nut and torque to 45 lb-ft
Stand transmission with bellhousing up
Measure input shaft end play (I usually shoot for around .035")
Correct end play as necessary with shim under output roller bearing
Lie transmission down
Install torque converter
Install transmission in truck
06 Silverado 4x4 CC/SB

06 Express 2500 Duramax Van "The Dumpster"

Last edited by JoshH; 06-19-2017 at 12:23 PM.
Old 06-19-2017, 12:17 PM
Mike L.'s Avatar
Mike L. Mike L. is offline
Got Sheep?
Join Date: Aug 2006
Location: Disneyland, CA
Posts: 14,986

Josh, make this a sticky here. Save a lot of time and trouble for us.
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