6spd Allison issues

dirtydriftnutz

New member
Sep 13, 2018
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06 LBZ 6spd Allison trans

Alright let’s get started with the intermittent clunk between 5th and 6th at high way speeds then itt feels like trans/shaft releases and disengages and I watch my rpms spike up to 2500-3000. Was never a problem until about a week ago, then I got the clunk from 4th, 5th and 6th. Bought the truck with 145k on it. Just about at 170k

Tuned by starlight diesel here in Utah, threw codes for p0606, shift inhibitor,,incorrect ratio and 1 more that I’ll post when I get my scanner back. At first all the above issues would disappear when battery disconnected and reconnected. But now after it sitting. For 2 days, as soon as it shifts to second manually or automically it feels like the torque converter is free spinning right at shift and rpms spike to 2500 before I catch it and let off throttle, after rpms drop down trans engages and will go again but just to disengage again a few moments after throttle applied. Any suggestions?
 
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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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Phoenix Az
start searching on here as to what those codes mean. trans is shot. put it on stock power and hope it dont limp or build it
 

dirtydriftnutz

New member
Sep 13, 2018
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Seems every time I see any codes with P06XX, the TCM is involved.

That’s what I am thinking, and I know the Lml had issues with the heat sink. I’m just wondering if it’s electrical related because it’s a different code every time and when it goes to limp I get about 6 codes but when cleared they don’t come back. I’ll be checking grounds on the tcm and voltage tomorrow
 

dirtydriftnutz

New member
Sep 13, 2018
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1
Seems every time I see any codes with P06XX, the TCM is involved.

Is there a common wire that feeds off the ecm. Solus is showing 14v at ignition but with the scanner connected and communicating with the ecm the truck wants to die, drops to about 200rpms but picks back up, now back out of the ecm and go into the TCM and not a problem. Gear command goes 1-6 no problems and 6-1 no problems. 1st solenoid Pressure when put in reverse is 232.5 and 2nd matches. When put into drive it’s only 21.5 while 2nd solenoid pressure is showing 232.5

Bad PSM? But the 4 switches engage according to the Solus

I feel like if the trans needed a rebuild I wouldn’t trying to track down what seems to be an electrical issue
 

dirtydriftnutz

New member
Sep 13, 2018
9
0
1
Seems every time I see any codes with P06XX, the TCM is involved.

update... could have sworn i was getting a signal reading before but took it out today and was not getting any VSS reading. 0.0mph no matter what gear. swapped with a known good one and still nothing. decided to inspect wiring loom that goes back about 12" to connector and all seemed okay. unpluged ISS just a little further to inspect and now not getting a reading from that. wondering if these share a common ground im just not seeing