DrkPhx
February 12th, 2011, 12:20 PM
Hi,
This is just for reference, but I thought I would post it in case someone stumbles across the same issue. Other's may already know this, but anyway here it is.
I've been tuning a friend's 00 4WD Silverado in which he installed a 6.0L with LS3 heads, L99 intake and a LS6 cam. All went well except for a nagging problem where the truck wouldn't WOT downshift at certain speeds. After multiple attempts tweaking the various trans tables (and a lot of time searching various boards and threads) I couldn't nail it. I've tuned muitiple A4 cars (and my TB SS) without this problem, so I was baffled. Well I finally figured it out.
The mph values in the WOT Downshift Shift Speed tables in this particular PCM are a ceiling and not a floor value. Example: WOT 2>1 table is set at 30 mph. The PCM will allow a 2>1 downshift at any speed under 30 mph but will not WOT downshift above that value. So this is the maximum speed the PCM will allow a 2>1 downshift; nothing more. Same applies to all of the WOT Downshift Shift Speed tables.
While this is hardly ground breaking, consider the same table in my 98 TA is a floor value; meaning you set the value purposely low (if desired) so the PCM will WOT downshift at anything above the mph value.
I didn't realize the same trans tables in different PCM's have different qualifers. That's what was driving me nuts. Once again, hardly earth shattering and may be well known to others, but it was something that just hit me so I thought I would pass it along.
This is just for reference, but I thought I would post it in case someone stumbles across the same issue. Other's may already know this, but anyway here it is.
I've been tuning a friend's 00 4WD Silverado in which he installed a 6.0L with LS3 heads, L99 intake and a LS6 cam. All went well except for a nagging problem where the truck wouldn't WOT downshift at certain speeds. After multiple attempts tweaking the various trans tables (and a lot of time searching various boards and threads) I couldn't nail it. I've tuned muitiple A4 cars (and my TB SS) without this problem, so I was baffled. Well I finally figured it out.
The mph values in the WOT Downshift Shift Speed tables in this particular PCM are a ceiling and not a floor value. Example: WOT 2>1 table is set at 30 mph. The PCM will allow a 2>1 downshift at any speed under 30 mph but will not WOT downshift above that value. So this is the maximum speed the PCM will allow a 2>1 downshift; nothing more. Same applies to all of the WOT Downshift Shift Speed tables.
While this is hardly ground breaking, consider the same table in my 98 TA is a floor value; meaning you set the value purposely low (if desired) so the PCM will WOT downshift at anything above the mph value.
I didn't realize the same trans tables in different PCM's have different qualifers. That's what was driving me nuts. Once again, hardly earth shattering and may be well known to others, but it was something that just hit me so I thought I would pass it along.