no 2>3 shift at WOT

[Nickvrebel]

I'm trying to help my bro-in-law, he's got a 2000 Silverado 5.3L with a about 212/218 cam, 2800 vig. stall and shift kit.

Our problem is that he gets no shift at WOT from 2-3. 1-2 is fine, looking at the logged data the RPM's shoot up to the rpm limiter at the shift mph speed and it refuses to shift bouncing off the rev. limiter. We even tried lowering the mph and shift rpm down and left the rev limiter as described below, it still release at the mph and rpm's shoot right up and bounce off rev limiter:

Original:
84 mph shift 6000 rev limit 6400

also tried:
80 mph shift 6000 rev limit 6400
and:
70 mph shift 5500 rev limit 6400

any ideas? we haven't messed with the TCC settings, from what I've seen I understand that is just for poor driving problems, the truck seems to drive fine at part throttle. I'm very new at this so I'm not sure where else I should be looking.

[Nickvrebel]

ok, I'm not getting any responses so maybe I can throw up a few possiblities:

maybe the transmission's 3rd gear clutch band is going out?

maybe it's in the torque converter?

I'm thinking it my not be in the tuning, every setting I can find seems to be in a logical place, it's just not going into 3rd at WOT as best I can see by reviewing logs. I'm open to any suggestions, any tranny guys that have an idea please speak up. I think (please clarify if you know) that the clutch band for 3 and 4 are the same, maybe it doesn't have enough to hold on at the power the motor makes at WOT? maybe I could just up the line pressure to get it to engage?

an suggestions welcome from any level of tuner / transmission guru

[Zick]

Try putting the stock tune back in it and see if that fixes it. If it does, then you know its something in the tune.
If you want, you can send me the files and I'll compare it to mine. I've got a similar setup as his.

[backpurg3]

I'm having the exact same problem with a Corvette. I have a feeling my problem is mechanical so I'm going to be throwing the stock transmission tune back on this week. I'll let you know.

[Nickvrebel]

thanks and thanks.... I'll hold off and see what backpurge3 comes up with, I'm really thinking it's mechanical, which isn't a big deal b/c he's not scared to put the truck out of commision to fix it, we just need to know where to target our attention..

thanks again guys, I'll be watching for backpurge3's results

[backpurg3]

thanks and thanks.... I'll hold off and see what backpurge3 comes up with, I'm really thinking it's mechanical, which isn't a big deal b/c he's not scared to put the truck out of commision to fix it, we just need to know where to target our attention..

thanks again guys, I'll be watching for backpurge3's results

Threw the trans tune on the Corvette we were working on back to stock and still had WOT upshifting problems just like you're having. Talked with a few places that build up 4L60E's and they all said the bands were going out in the transmission. Time for a build up.

[TheDastardlyDuo]

Have had this problem with a 2000 corvette that already had a built transmission. Put the car back to stock shift points (reloaded previous file) and the car still wouldnt shift at 100% TPS, but would shift at 95% TPS.

Need help on this one.

[jimmyblue]

Check the WOT MPH table as well as the part throttle
MPH/TPS. They should have consistent values.

Check that the force motor table, for the WOT line%
seen, does not put a high current (low line pressure)
out. For that matter just log the force motor current.
Some models have an insane "blow-off" value in the
100% line column and if you get over the 94% mark,
you start interpolating toward Slip City. Cute.

Log the "Current gear" PID and this will tell you if it
meant to shift but can't get it done, or if it's holding
back for some reason. That will help you focus in on
(tune related) causes.

[TheDastardlyDuo]

So if Force Motor Current table has a value of 1245 for the 100% TPS value, while the 95% TPS value is 98, that would most likely be the problem?

[jimmyblue]

If you are commanding 98mA at 96% line column (it's the
line pressure as percent of max, not TPS) and 1245mA at
100%, any commanded line value above 96.000% will be
going the wrong way; command 98% and you will be back
to half max line pressure or thereabouts, wrong answer to
haul down 350lb-ft of torque.

There is a max line pressure value that clips the index and
if it's all stock you'll never see the "blowoff". But if you went
and changed that to 100% thinking you were going to get
more line pressure, surprise....

Can't say for sure without seeing all of the PIDs but it's one
possibility. If you set that 100% column to all "98" like its
neighbor and it gets better, that'd nail it down (not to
mention, it's just a sensible thing to do).

[TheDastardlyDuo]

Sounds like that would be the answer, funny thing is that I never went into that table until you mentioned it in this post. as I look at the table though, must of the numbers are greater than 100, could this lead to any other problems?

[jimmyblue]

Force motor is mA. The larger the value, the lower the
line pressure delivered. There is a sticky about the real
pressure vs current profiles.

What you want, is for it to be bottomed out at WOT
(blowing off minimal pressure) and in the low-midrange,
providing the minimum real pressure needed to fully
avoid any slip in the frictions (clutch-packs and TCC).

I wouldn't touch it unless you see the mA in logging
are not under 100mA, at WOT; then you would want
an idea as to why, before trying to fix it with the force
motor table. Have to see what in the chain is responsible
before trying to crutch it.