Shift/throttle response post Vector Tune - Page 2 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2006 - 2009 TrailBlazer SS Tech > 06-09 SS Engine and Drivetrain > Engine Tunes/Mods

Engine Tunes/Mods Engine tuning and/or modifications

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  #11  
Old 03-31-2006, 11:46 PM
PEDRO PEDRO is offline
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  #12  
Old 04-01-2006, 01:30 AM
EssEss EssEss is offline
 
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Quote:
Originally Posted by TonyGXP
you're pretty good in getting the truck to behave in a way that 8 out of 10 of us could never do...right in that "no man's land" and you say your wife got it to happen as well?? any vehicle will do that given you are right at the "max" rpm for a lower gear...I've done it in my work car numerous times at 35mph & 75mph, granted I am pounding on my work car probably 10-15x a night, so the odds are increased that I will have that situation a couple of times..now that you know where the threshold is for the 2 to 1st downshift try easy the pedal down taking about a full second to lower the hammer, bet you don't have anymore issues..
The point is though, my Silverado SS doesn't have this problem and I don't want this problem on my TB either. I don't want to have to ease in to it. I mentioned in my post that I observed a steady opening solves the issue so I know that is a work-around but that still sux. I want to drop the hammer and hope that I am pointed in the right direction. And, based on comments, I'm not sure that it has anything to do with the tune either, to Kirks point on Page one. Maybe the tune just moves it to a different spot. I only had 700 miles on my TB when I put the tune on it, most of which was spun by my wife and none of which was at full throttle, so I don't have a lot of pre-tune experience. I am anxious to see what Kirk's findings are.
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  #13  
Old 04-01-2006, 10:52 AM
Vector MS Vector MS is offline
 
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Quote:
Originally Posted by steined
I don't think this is a problem with the tranny or stock tune or VCM tune.

Here is what is happening.

You are in say, 3rd or 4th at about 1700 - 2100 RPM @ 38-41 MPH.

You floor it and the transmission grabs 3 - 2 - 1 or 2 - 1 or for sake of argument, goes directly to 1st. The engine needs to spin up to about, oh 5700 - 5900 RPM from 1700 RPM.

This takes time and is what you are feeling. I'm guessing the flywheel and the like on this engine aren't exactly vette light and this is what everyone is feeling. When the engine hits the speed of the transmission so to speak, you feel the acceleration.

That's my take on it.
I have found that this is what is happening.
When you are driving at 40mph you are in 3rd gear. You are also at the top limit of where a 1st gear downshift will take place.
When you hammer the gas the engine has to downshift from 3rd to 1st and the engine has to go from 1500 rpm to over 5000 rpm. This is the delay you feel. This also happens on a stock calibration. You can feel it slightly more with the tune because we raise the upper limit on the downshift causing the engine to have to spin higher.
Kirk
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  #14  
Old 04-01-2006, 02:13 PM
TonyGXP TonyGXP is offline
 
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Quote:
Originally Posted by Vector MS
I have found that this is what is happening.
When you are driving at 40mph you are in 3rd gear. You are also at the top limit of where a 1st gear downshift will take place.
When you hammer the gas the engine has to downshift from 3rd to 1st and the engine has to go from 1500 rpm to over 5000 rpm. This is the delay you feel. This also happens on a stock calibration. You can feel it slightly more with the tune because we raise the upper limit on the downshift causing the engine to have to spin higher.
Kirk
and that's the point, any car/truck will do this, just has to be at the right speed for the particular vehicle, when you try to make it happen..
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  #15  
Old 04-01-2006, 02:33 PM
EssEss EssEss is offline
 
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While I intend to accept this as the explanation, I would like to go on record to Chevrolet that I think this is lame. My Silverado SS doesn't do it and I will continue to believe this shouldn't either. Right after GM and Delphi figure out if they will still be in business next year, I expect them to get right on this issue.

BTW, I'm still going to tinker with it at different speeds to see if it happens anywhere else.
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  #16  
Old 04-01-2006, 05:21 PM
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TBSS TBSS is offline
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I tried this test a couple times this morning on my way back from a meeting. I have a stock tune (stock everything, actually).

When cruising at 40 mph, if I floor it, it only goes into 2nd gear not first. So I don't have this problem at this speed.

Now that I've read this thread, I will try the same thing at incrementally lower speeds (i.e. 38 mph, 36 mph) sometime this weekend.
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  #17  
Old 04-01-2006, 05:29 PM
steined steined is offline
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The SSS has a 4L80 right? Different gear ratios right? So the feel will be different. Look at the gear spread on the 4L70 we have. Not exactly tight and part of the reason there is a 4.10 back there...

Not saying it is ideal, but it isn't a problem per say.
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  #18  
Old 04-01-2006, 05:39 PM
B52GUNNER B52GUNNER is offline
 
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I'm pretty sure the SSS is a 4L65E.
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  #19  
Old 04-01-2006, 06:11 PM
ScarabEpic22 ScarabEpic22 is offline
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Quote:
Originally Posted by gunner
I'm pretty sure the SSS is a 4L65E.
Thats what I remember hearing too, it is a 4L60E tranny beefed up (like the TB SS 4L70E) but not as beefy as the 4L70E TB SS tranny. As for rear gears, I have no idea, but I bet they are at least 3.73s.
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  #20  
Old 04-01-2006, 08:51 PM
Juniorss Juniorss is offline
 
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Quote:
Originally Posted by EssEss

Say I'm cruising along steady at 40 mph, 20% throttle. If I crack it wide open, there is a noticeable delay, borderline confusion in how my SS responds, specifically what gear choice it wants to make. Don't get me wrong, once it figures it out that I want to go fast, it does not disappoint, but this lag is kind of a bummer. If I am in the throttle from the line or under slight acceleration to full throttle, it doesn't do it. It only seems to be from a steady speed to WFO.
My GTO does this but not as bad as my dads Silverado SS. Both of them have stock tunes on them. I was told that if you have it in "3" it doesnt do it because all it does is realease a clutch pack or something to that effect.

Also on the issue of pining, my dads Silverado SS does it terribly and like I said, its totall stock. The thing sounds like its going to blow itself to pieces and it doesnt stop until you lift off the gas. We took it to the dealer and they dont hear anything . O well, it should be much longer until its traded in for a TBSS
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