WOT Shift, 1-2, 2-3

[arubenstein]

I've been tuning the WOT shifts on a T42 / 4L70E.

For instance, in the 1-2 upshift WOT tables (D1011 and D1021), which does it use?

I had D1011 set to 43 MPH and D1021 set to 5800. I hit the rev limiter at 6000, which I don't understand. I was at about 41 mph.

What is the logic here? Is it 'AND', 'OR', or 'HIGHER OF THE TWO' ?

[joecar]

The logic is AND.

This is the same problem seen with LS1/LS6 PCM's...

The PCM somehow misses when to shift...

you may have to set one of those parameters low (e.g. set to 30 MPH), and fine tune the other one (e.g. start at 5000 RPM, test it, bump it a little, test it...) to where it shift's where you want it to.

[N0DIH]

Which rules first? rpm or speed? I tune my OBD1 and it doesn't go by rpm, speed only.

[ScarabEpic22]

Its kinda whenever both get hit. i.e. set upshift rpm to 6100rpm and speed to 40mph, hit 40mph first and then when the rpms hit 6100 it shifts. At least thats how my 4L60E works...

[N0DIH]

So if I set rpm to say 2000 rpm, and shift mph to 41, it would pass 2000 rpm and then shift at the moment I get to 41?

Not really sure what the value having both and an AND logic on it.

IF rpm = x AND mph = y THEN shift
ELSE wait and keep revving
IF hits rev limiter, oh well!

Correct?

[dc_justin]

IF rpm = x AND mph = y THEN shift
ELSE wait and keep revving
IF hits rev limiter, oh well!

Correct?

Yep, that's correct. And always take TCCSlip into account when setting the MPH value.

[arubenstein]

Yes, which is the problem I hit.

So, i created a spreadsheet which calculated this all out, and subtracted about 15% from anticipated MPH. This seems to work well. I will share when I get home.

[arubenstein]

Actually, I have access to it from work.

[joecar]

Yes, which is the problem I hit.

So, i created a spreadsheet which calculated this all out, and subtracted about 15% from anticipated MPH. This seems to work well. I will share when I get home.What are your current WOT MPH/RPM points set to, and what MPH/RPM are you actually shifting at...?

Do you have a stall converter...?

[arubenstein]

Don't know yet. Just loaded this in this morning and will do some scanning tonight.

The transmission was done by a local guy, it has a Vigilante Triple Disc 2500.

I will report back my findings later.

[joecar]

Ok, thanks.

[arubenstein]

OK, so I was able to go out for a small test drive.

First, find attached my t42 tune, and the log. But the summary is this...

In normal (not tow/haul), I said 37 mph / 5800 rpm for shift; according to the log, it commanded the 1-2 shift at 40 mph / 5564 rpm; however, rpms did not begin to drop before hitting 42 mph / 5901 rpm.

In tow/haul, I said 35 mph / 5500 rpm; it commanded at 37 mph / 5235 rpm; however, rpms did not begin to drop before hitting 40 mph / 5597 rpm.

It must predict the shift point based on rate of increase, or something.

For 2-3 in normal, I said 69 mph / 5800 rpm, it commanded at 75 mph / 5567 rpm, rpms did not begin to drop until 76 mph / 5643 rpm

For 2-3 in t/h, I said 66 mph / 5500 rpm, it commanded at 70 mph / 5229 rpm, rpms did not being to drop until 71 mph / 5318 rpm.

Attached is my T42 tune, and the log file. Log file has two WOT acceleration scans, one with normal, the second with T/H.

Please comment.

DISCLAIMER: don't use this tune for you, all torque management on upshift has been removed, and shift points are significantly changed from stock. This is on a built 4L70E.

[dc_justin]

Hey Alex,

Did you alter your tire size in the engine calibration? What are you using to base your commanded shift MPH on, the calibrated rev/km or based on another?

Justin

[arubenstein]

H0104 (Trans Output Shaft Revs/Mile) is 640. This is topic of other discussion, because this seems wrong -- TOS is before the diff, so it seems this should be times 4.10.

H0135 (Tire Size Correction) is 106633 which is factory stock.

H0136 (Tire Revs per Mile) is 640.

I'd love for someone to tell me about H0104 and why it is 640 and not 2624.

My Suburban is not factory in that regard; it is a LTZ but I couldn't stand the 20 inch wheels. So, I bought a set of Z71 18" wheels and put Goodyear SilentArmor Forteras on it; great ride, looks great, handles great.