'02 TB EXT transmission "hunting"

[traumadog]

I've been trying to tweak my wife's EXT for a while now, hoping to get a few more MPG out of it (about 15 MPG, now), but what's starting to happen is a "hunting" while cruising...

This happens around 60-65 in 4th, in a light cruise. The RPM's vary by about 300 rpm, bouncing up and down. I can't seem to find it while logging - the logging software doesn't seem to pick up the RPM changes that well. It also notes that the trans is in fourth, with the TCC locked.

Now I thought that if the TCC remains locked, that the engine RPM wouldn't change much relative to the vehicle speed (isn't it the point of having a locked torque converter?) - but I'm wondering if there's a feedback loop I've caused somewhere.

Any ideas or tune files you guys can put up is appreciated.

Thanks!

[ScarabEpic22]

Hey man, I have an 02 SWB TB and have had this problem before when my 4th servo was improperly installed and the TCC wasnt locking up properly. Im going to guess its your TCC going out, or the solenoid not commanding enough pressure. With 3.73 gears at 65MPH I run ~1980rpm and is the sweet spot for mileage. I get about 14-15 city but at 65 I get ~23-24.

Post up your tune and Ill tweak the trans a little to see whats up. Ive also gone to more of an "On/Off" TCC setting vs the ramp-in that GM gives stock and prefer it more.

[joecar]

Log TCCDC, TCCMODE, TCCSLIP.

[traumadog]

ScarabEpic - This is the .tun it was doing it the worst - I backed off of this one a bit.

Joecar - good idea, will do.

[ScarabEpic22]

Hey man, I went ahead and changed some of the TCC settings to what Ive been running (and got the idea for from here) plus I went ahead and removed some Torque Management and quickened up the shifts. These should help you out a little on your quest for mileage. I couldnt help but notice the weird hump in your Low VE table, did you get that via WBO2 data?

[traumadog]

OK - thanks. And yea, I have to look at the VE again - it's been a while since I've had the WBO2... I've not dynoed it - just street stuff, so I really don't know what the upper range is.

Oh, and just out of curiosity - have you noticed a big difference with the 'Vette 1-2 servo?

[ScarabEpic22]

OK - thanks. And yea, I have to look at the VE again - it's been a while since I've had the WBO2... I've not dynoed it - just street stuff, so I really don't know what the upper range is.

Oh, and just out of curiosity - have you noticed a big difference with the 'Vette 1-2 servo?

No prob, I was just curious about your VE table, havent seen an I6 one like that before.

The vette 1-2 servo makes the 1-2 shift a ton better, it shifts smoothly and reasonably fast with a stock tune. With a normal set of line pressures, 0 TM and 0 shift times it will snap your neck so if you get it be ready to tweak the LPs.