Is this Normal?

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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I do have an Autocal. But I talked with Mark wal ago and he said it's normal, the tcm unlocks the converter as a failsafe when it sees the wheel speed jump suddenly.

better to keep that then. it will save on the trans/drivetrain.
 

Chad006

Drag racer wannabe
Feb 12, 2015
311
5
18
Goodlow, B.C.
Yup we have horrible frost heaves up here north of the border and mine does the same. Makes for a bad time when your racing someone up a hill and converter unlocks sending ya straight to the rev limiter. Allilocker fixes that though, just don’t really recommend it for street use lol
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
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At Da Beach
I wonder if some tuners turn that off and contribute to excessive wear on bearings and cranks? You would think that would be a pretty big shock to the motor if the converter did not unlock.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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im sure it doesnt help but the stock P2/C2 will go before the crank will (most of the time, i would bet. no hard evidence on that). bearing wear in the engine isnt going to change much. id expect more on the thrust side but ours do a decent job at handling the loads.
 

2004LB7

Well-known member
Dec 15, 2010
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I do have an Autocal. But I talked with Mark wal ago and he said it's normal, the tcm unlocks the converter as a failsafe when it sees the wheel speed jump suddenly.
where is this in the tune? or is it something others have mapped outside of EFILive?
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
5,013
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At Da Beach
I was wondering if the original TCM tune from lb7 has it? I used to use that calibration in a bunch of trucks bc it was a more basic tune and didn't do a lot of the random stuff the newer calibrations would do.
 

cdbright

JUST RENT IT
Dec 16, 2008
1,009
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Salt Lake City, UT
if it is a hard enough bump and the rear tires spins just a tad more than the front since you are pulling hard, it think you are spinning so it lets off , I bet it wouldn't do it if you had traction control off ?
 

2004LB7

Well-known member
Dec 15, 2010
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I'd like to see the logs of the converter and wheel speed/mph. I'm having a hard time seeing the wheels ramping up in rpm fast enough during this split second on a bump with the inertia of the whole drive train, wheels, drive shafts, transmission and engine all locked together to be anything noticable
 

gmduramax

Shits broke
Jun 12, 2008
4,042
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Nor cal
I'd like to see the logs of the converter and wheel speed/mph. I'm having a hard time seeing the wheels ramping up in rpm fast enough during this split second on a bump with the inertia of the whole drive train, wheels, drive shafts, transmission and engine all locked together to be anything noticable
I don’t think efi live would recognize it. I think it would be possible for the ecm to see the speedo pulses being say 40 a second then randomly jump to 45 pulses a second and maybe that’s what’s causing it to unlock the converter. Just using random numbers I don’t know the exact count.

Didn’t someone at one point say that the ecm limits how fast the rpm’s can increase?
 

gmduramax

Shits broke
Jun 12, 2008
4,042
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Nor cal
I would think under full power and at a good speed the ecm wouldn't do much to hold the engine, trans and rear in the event of wheel spin at 60.
Probably not but the ecms do weird things sometimes for no reason, or maybe there is a reason we just don’t know 🤣
 

DAVe3283

Heavy & Slow
Sep 3, 2009
3,670
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Boise, ID, USA
Didn’t someone at one point say that the ecm limits how fast the rpm’s can increase?
I think Mr. Jack Stand Racer said something like that, but it isn't true for the LB7 ECM at least.

I have a log of my brother's LB7 breaking traction and picking up RPM at IIRC over 2500 RPM/sec. So quick it spun the balancer (sheared the pin).

Neither the ECM or TCM did anything to attempt to limit power once the wheels broke loose. Might've saved me a lot of effort replacing that balancer if it had, but they let it go to the moon.

I can't say if the newer ones do weird things to protect the drivetrain. But an 03 will let you do any dumb thing you want with a couple limits raised...

Sent from my FlashScan V2 using Tapatalk
 
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Dozerboy

Well-known member
Jun 23, 2009
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I can't say that I've ever noticed it on my LBZ, but I try to get out of the throttle on bumps while accelerating hard. I'm way too worried about breaking something.
 
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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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I can't say that I've ever noticed it on my LBZ, but I try to get out of the throttle on bumps while accelerating hard. I'm way too worried about breaking something.
its very hard on parts. good way to kill trans parts or t-case parts.
 
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