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Thread: Upshifts Too Late, Downshifts Too Soon In One Truck But Works Great In Another

  1. #1
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    Default Upshifts Too Late, Downshifts Too Soon In One Truck But Works Great In Another

    I've had an absolute motherfucker of a time trying to get this stupid big block to act like a big block. For the longest time I blamed the stock tune, this truck drives unlike anything I've driven GM or otherwise. With a 4000 RPM big block, this thing sure seems to love its redline. Part throttle it REFUSES to upshift and the thing also will NOT hold a damn gear past what feels like 40% without reaching for the next so it's never at atmospheric at torque peak, rather revving its face off at 4000 RPM for no reason. I based a lot of my trans stuff on my 1500 as it moves with much less throttle input, upshifts far more aggressively, doesn't take 10 seconds to lock the converter, and doesn't downshift at the sight of a damn hill. One day I had an epiphany as I suddenly realized this truck was not hitting atmospheric prior to a downshift. Made sense to me that WOT seemed on par with what I expected and part throttle sucked so damn bad. Both 350 and 454 came stock with a 75mm TB, so I bought an 85mm for the 454. Slightly better response, but nowhere near what I was expecting. I figured it'd artificially fix the upshifts and downshifts but it had very little effect on those whatsoever. I calculated that the 85mm would have around a 27% increase in airflow, maybe I should have sprung for the 90. It just seems like the speed values I program in, no matter how I skew them, are simply ignored. My logs indicate that the speed EFILive displays on its dash is accurate within a couple and the speedometer in the truck is within 1 mph so I really don't know what to make of this. The 1 ton will, at this point, get out towed by a half ton simply because the half ton will lug a damn gear. It's pretty sad that I'm about to change plans this weekend to tow with the otherwise inferior truck simply because it won't piss me off by making me listen to it at 4000 RPM for 5 hours. Attached is the current dually tune and the current 1500 tune.

    Dually Attempt #15 Timing Bump.tun
    411 Whipple V18 Stomp + 20%.tun
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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    Quote Originally Posted by Supercharged111 View Post
    I've had an absolute motherfucker of a time trying to get this stupid big block to act like a big block.
    That "stupid big block" is only doing what you're telling it to do. Have a look at the WHOLE tune, not just two or three parameters.

    Start off with this...

    {D0960}... change ALL values to 100
    {D0961}... change ALL values to 100
    {D0962}... change ALL values to 100

    See if that helps at all.

    I'll have a good look at your tune after YOU'VE had a good look at your tune.

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    If those are the kickdown tables I have modified them. They're similar to the tables that work well on my 350.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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    According to D0962, at 103kph (~63mph), I should not downshift from 4-3 until 70%. According to D0908, at 105kph, I should not downshift until 75%. This is more than I want, and it does not deliver in accordance with what I am commanding. Less aggressive downshift tables on my 350 work much better, this is what's confusing the hell out of me and pissing me off. When I look at what's commanded in the tune, it's not what I'm getting when I drive. I must be missing something critical that's skewing everything and for the life of me I just don't know what it is. I'll get a log later after I fix all the issues with the new throttle body.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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    Well I figured it out, wasn't the tune after all. While response was improved with the larger throttle body I installed, it was nowhere near what I wanted. New TB had progressive linkage installed which didn't strike me as the stock TB was also progressive. When I compared it to a small block TB though I noticed that that had linear linkage so I changed the arm out and just like that the engine responds, upshifts sooner, downshifts later, locks sooner, EVERYTHING this thing absolutely sucked at stock (Plus TPS read in the teens at idle so I modded the TPS to clock it properly). As happy as I am I figured out what the holdup was, I'm kind of pissed at the same time that they'd intentionally make this thing suck so hard from the get go.

    The problem I'm left with is the slam-bang shifts at mid/higher throttle angles. It must pertain to the added airflow at lower than stock throttle angles, something that was precluded in the factory tune, but I'm not too sure what to do about it since the blue truck never did this even after adding a blower to it. If I grab a handful to get up to speed and then let off it hits the next gear hard enough to break stuff. If I just stay in it it just hits more like a shift kit. Definitely didn't hit this hard with the stock throttle body and I got it to do it on the 1-2 shift so that eliminates locked TCC on upshift. For tomorrow I think I'll just turn shift times back to stock to soften things up, but I'm not sure even that's gonna fix it. IIRC I left TM intact on the upshifts.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  6. #6
    Joe (Moderator) joecar's Avatar
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    Which table has priority, D0901 or D0960...?
    What about D0902 and D0961...?
    D0903 and D0962...?

    It turns out that in different OS's the answer is different.

    Look at attached graphs drawn from your file 411 Whipple V18 Stomp + 20%.tun

    If you want predictable shifts, then set the throttle kickdown tables to 100%.



    Click image for larger version. 

Name:	D0901-D0906-D0960.png 
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Size:	61.1 KB 
ID:	21934Click image for larger version. 

Name:	D0902-D0907-D0961.png 
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Size:	63.6 KB 
ID:	21935Click image for larger version. 

Name:	D0903-D0908-D0962.png 
Views:	261 
Size:	65.4 KB 
ID:	21936

  7. #7
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    ( and should also do same with TCC Throttle Release tables D1007,8,9 )

  8. #8
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    To soften the harsh shifts, add some Torque Reduction back in, right at/around the places where it shifts harsh...

  9. #9
    Joe (Moderator) joecar's Avatar
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    Set the shift times to 0.2 or 0.3 seconds.

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    Set TCC release to 100%? Here I've been setting a curve via trial and error to get it to jive with the downshifts. Statesman did get me to thinking when he posted about the kickdown, I even did a search and that seems to be the common thing to do. Now that the throttle body has completely transformed how this truck acts, I can work on tweaking up and downshifts. Before the TB and linkage no tune in the world was going to give me what I was after. Have any new products popped up other than that handy Excel spreadsheet?
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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