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View Full Version : 4L60 Kickdown problem - TC??



Boost
November 26th, 2010, 12:15 PM
I have been searching here and that's how I came up with some of the ideas I will mention in this post.
My truck has developed a very noticeable and annoying transmission malfunction. The symptoms have appeared gradually and I am thinking and hoping they are related. Recently I have noticed that any time I floor it does not downshift into 2nd or 1st gear like it used to, rather it hesitates for 2 seconds then goes into a high gear like 3rd or 4th. It also hesitates for 2 seconds from a very low rolling speed before it goes into 1st gear and starts accelerating hard when floored. And I notice that now when I hit tow/haul the rpms don't increase and I don't feel a lockup although it still holds the gears longer. That's why I thought it was the TC. The engine is fine and accelerates very well for what it is when it goes through the gears.
The truck is a 2003 4.8 with 3.42s and mostly stock. A crappy loud exhaust system and a home made tune is about all the mods. While the tune is wack, it was shifting fine on the same tune for a long time, so it has to be a mechanical malfunction.
The first thing I noticed months ago was that it doesn't shift hard enough on the 1-2. Also, tow/haul acts really funny and too jerky / bumpy on shifts. Next, regular shifts became harsh, especially cruising into 2nd, a big bump. Now this no downshifting at all deal, as if I'm not flooring it. Some variables are that a while ago I changed the filter and swapped some new fluid in. I know that can dissolve more crap in the trans and plug the valve body and new filter. Also, I have a mass airflow code P0101 due to massive VE table mods in my tune, but before you think anything the truck ran and shifted fine for a long time on the same tune before this issue developed.
My truck has 110,000 miles and I drive aggressively. I have all tranny protection removed from the tune. I am thinking the TC can't make enough pressure?? I would love to replace it with maybe a 3000 Yank stall?? Thanks!

Taz
November 26th, 2010, 01:02 PM
It appears you may have multiple issues currently - you will need to address the P0101 DTC before being able to make an accurate diagnosis of a possible transmission issue.

Judging by the thread attached below … you’ve had this happen before.

http://forum.efilive.com/showthread.php?4775-4l60-going-bananas-!-(maf-sensor-)&highlight=4l60+sd

When the P0101 (MAF sensor performance) DTC is set - the PCM goes into SD mode. Those you have elected to operate in SD mode know this affects the transmission shift quality - requiring changes to the tune.


Regards,
Taz

Boost
November 26th, 2010, 01:57 PM
Fair enough. So you are confirming my suspicion that the MAF code can cause these symptoms. Weird however, that the shifting problems did not start right after setting the code. Does the PCM not go into SD mode as soon as it determines a mass air flow inconsistency? Also, this VE modified tune runs harder than one that does not set a MAF code. How can I determine what adjustments I need to make to the MAF settings to match my crazy VE table? Lastly, soes anyone have a nice new (higher OS#) stock or stockish tune for my 4.8? I kind of took the crazy route and just "landed" on this setup and left it alone because it runs HARD except the intermittent trans. issues. Thanks!

Boost
November 26th, 2010, 02:00 PM
Oh and the thread you posted was my nitrous NBS, when I was just learning the relation between MAF and trans. shifting. I have never had THIS issue before, but thanks for the info and making me miss my "ninja: '07 :( just joking :) LOL

Taz
November 26th, 2010, 02:19 PM
By no means did my previous post imply the P0101 DTC was causing ALL of the transmission issues, there may be another (or others) – or not. But it will be more difficult to accurately diagnose any potential transmission issue, with an active P0101 DTC.

Regarding your VE values - obviously you want these to be as accurate as possible for proper fueling, to avoid unnecessary DTCs being set, and to minimize driveability issues.

Regarding your previous thread where you had a broken MAF sensor - the “link” to your current issue is that a P0101 DTC amounts to the same thing as a broken MAF.

Good luck getting things sorted out …..


Taz

Boost
November 27th, 2010, 12:45 AM
Got it, that makes sense. The most common sense thing to do would be to go back to a tune the doesn't set DTCs, especially ones that are directly related to driveability and see if this latest downshifting problem disappears. I know the tranny is old and sloppy anyway, but so am I and I work ok most of the time ;)
Thanks Taz!
:cheers: