Keep in mind, it's all 'anticipatory' whether you're using speed or rpm anticipation and this is all trying to process through a slower processor than what is out there for newer vehicles. The strategy will use the lowest shift point for each gear - either WOT RPM setting or rpm for the desired WOT speed, so try and get your WOT shift settings in the shift tables as close as possible (rpm wise) to your WOT RPM settings. ALso make sure that your TP settings in the shift tables match what you have set in the TP for WOT table - if you have 550 set in that table and your WOT shift settings in the shift tables are 600+, the strategy will use the shift point at 550 TP in the shift tables which usually corresponds to lower rpm shift points.

I've tried it with that switch turned off and don't get as consistent shifts as with that switch turned on, but I'm also running a taller tire than stock setup on the back on the 02 L.

Bird

 

Thanks Bird!!

Arraghh... I was under the assumption those figures,(TPS ad counts for shift rpm) were based on the actual TP ad counts as seen under WOT and not on the WOT specific value for the TP for WOT.... Still learning.

I'll make the changes and report back.

 

Well, that fixed that problem. Now I need to figure out what is making it feel like it is slipping in second after the 1-2 shift....

 

The 2nd gear clutch pack has the least amount of clutches in these transmissions and is 'usually' the first to go out in the stock transmissions under heavy usage, so that is 1 possibility. Does it do it with other tunes also?

Bird

ps - make sure you don't have the 1-2 upshift and the 2-1 downshift curves touching or crossing.

 

I never really noticed it in the other tunes, but it did start doing it soon after I changed the shift points. Also, Just installed drag radials and have been doing 1-2 2-3 WOT tuning. I couldn't before due to excessive wheel spin. (still does but not as bad) Actually, the first time it did it, it was on a 3-2 down shift at WOT. The shift points don't seem to cross.

1-2

636 - 46
548 - 45.5
400 - 42

2-1 (stock values)

600 - 21.5
460 - 16
400 - 16

Thanks again for all your help. Steep learning curve....

engine = easy
trans = :smt089

 

Still running torque reduction ? Might want to investigate that also.

Bird

 

The only torque reduction, IIRC, is on the 3-4 shift. No torque reduction on 1-2 and 2-3.

 

In case anyone ever stumbles upon this and is having the same issue while working on their trans tune, here are the results of what Bird helped me through.

Most tunes for a SBTB will shoot for a lower TP_AD_COUNT_for _WOT value. Stock is 600. I set mine to 550. What this does is skew the trans tune because the new WOT TP_AD_COUNT sets the trans scaler for full TV pressure at a column with less pressure for the 12-21 shift than at the old value for full line pressure at the stock TP_for_WOT. In MY CASE, this change did not allow for full TV pressure because my tune seems to be working off of WOT TP_AD_COUNTS and NOT the actual TP_AD COUNTS as seen under WOT. This was the case with my shift schedule as well. (see earlier posts.) So far, the slip is gone and the truck shifts and engages as it should, although I do get the impression this trans may be on borrowed time.

Keep in mind I am a complete novice at trans tuning. I will say my startup tune was pretty good but the number of changes I have made to it at this point are far too many to list, or remember. I have a ton to learn but this is fun for me so I don't mind the homework.

I will keep updating this as I drive the truck and if the issue returns I will know a rebuild is in the cards.

 

I had good results for years shifting with MPH based settings opposed to RPM but as stated the scaler RPM for shifts as well as the shift/lock tables must match for it to shift where commanded. You need to fully disable torque reduction in all gears as well as increase tv pressures in order to reduce the slip within the clutches, this will ultimately extend transmission life. The stock trans will handle a LOT of power for a long time with a few mods and proper tuning but it it's already hurt you're screwed.

Trans tuning is where the real magic happens with these trucks and a closely guarded secret amongst those who have figured it all out.

 

I agree with the trans tuning being a bit of a black magic. It has been the biggest challenge so far.

As an update, so far the truck is doing great with the new trans settings. One odd thing though on the 1-2 shift and I think it may have something to do with the predictive part of the shift strategy.

Running on 305-45-17 Nitto drag radials.

If I mat the throttle there is quite a bit of wheel spin (obviously) and the trans will shift early, 5000 ish RPM.

If I roll into the throttle to mitigate wheel spin, roughly a 1-1.5 second roll to WOT, there will still be wheel spin, not as much, and the shift will happen right on with my settings of 5300-5400 rpm.

if I roll into the throttle with roughly a 2 second roll into WOT there will be little to no wheel spin and the shift will happen at 5600 RPM. This is quite a bit higher than I have in the tune.

The one thing this quirk has taught me is how to launch the truck on the street with minimal wheel spin...

The second to third shift is great now and It will haze the tires nicely on the shift, even with the drag radials and 3/4 tank of gas.

 

Looks like your predictive speed is doing all the shift control on the 1-2 - Drop your WOT shift RPM 12 by 200, bump your MPH for 1-2 shift at WOT by 1 mph, and bump your clutch fill time 12 shift by 15%

That should straighten it out pretty close to what you want.

Bird

 

Thanks Bird! I'll make the changes and report back.

 

Made the changes, still the same results. Nearly identical. It does all seem to hinge around wheel spin. The more, the earlier it will shift. little to no wheel spin will result in a shift higher in the rev and speed range, with zero wheel spin (1.7-2.0 sec roll on) it will shift outside the set parameters. The up side is it has trained me to be very consistent with my launch. 1.5 second roll on seems to be the sweet spot on the street.

 

Sounds like you might need to be working al little on traction control. These trucks with the suspension dialed in correctly will launch with very little wheel spin.