Two Oddities

[Cougar281]

Mike, I've got two strange things with the trans in my truck (2006 6-speed with a 2002 VB, running a 2002 OS in my TCM). One of them is it seems the TCM has learned a delayed reverse engagement; usually in the area of a second +. The strange part of it is when I clear garage TAPs, the engagement is quick and consistent for the first 6-10 engagements, then it starts taking more time to engage.

The other one (and this may be normal) is I noticed while towing that when I lock out 5th, it unlocks the converter, downshifts, and somewhere near a second later, locks the converter back up. In T/H, isn't the converter supposed to stay locked at all times until it gets back down near 1st? I've logged the TCM, and it commands it, so I doubt it's a mechanical/electrical issue inside the transmission.

On the Other hand, these could just be quirks of running the 06 trans with the 02 VB & OS (Although I can't imagine how considering the C3-C5 should be the same).

 

[duratothemax]

01/02 TCM OS's are more finicky with converter locking/unlocking during downshifts than LLY TCM's are. With the LLY TCM, I can floor it, kickdown, pass, etc in tow/haul or normal mode, and the converter will NOT unlock on the WOT downshift. With the 01/02 TCM, if in tow/haul and I force a downshift at anything above ~30% throttle, it will unlock the converter, kickdown, and then relock. If you do a WOT 5-4 kickdown to pass someone on the highway (with an 01/02 TCM OS), the TCM will drop lockup, and then you are once again greeted with the stupid allison I-wont-relock-until-slip-rpm-drops-below-600rpm problem. So what that means is if you are running a loose converter with decent power and you go to pass someone on the highway, you floor it, converter unlocks, 5-4 downshift.........and then it takes like 5 seconds before the converter relocks (because the unlock under WOT power conditions blew through the converter and pushed it above 600rpm slip).

LLY TCM's dont do this. I dont know why, but it sucks because we all know how nicely the 01-02 TCM OS's shift...but why GM deleted the converter unlock @ WOT kickdown on the LLY TCM's, I have no idea...but its sure as hell much nicer than the earlier OS's.

ben

 

[turbo_bu]

Any know if you can take an LLY TCM OS and put it on an LB7 truck? Maybe it only works on the 04's??? Early 04 = LB7, 04.5 = LLY

Yes, I would like to eliminate the converter unlocking if possible.

 

[Cougar281]

Any know if you can take an LLY TCM OS and put it on an LB7 truck? Maybe it only works on the 04's??? Early 04 = LB7, 04.5 = LLY

Yes, I would like to eliminate the converter unlocking if possible.

An 04+ LLY OS would not work, as it's looking for a "G" Solonoid; a 2004 LB7 MIGHT. You could try it; worst case senario, you get codes for a missing "G" solonoid and you have to go back to an older OS. The only other issue would be you'd loose OD Lockout as it's controled through the BCM in the newer OS.