Change TCC Setting?

[ol9465er]

Can you change the TCC setting to something greater than stock, around 50mph (80km) I believe and would there be any problems with any other issues. I would like to set it to 55mph (90km).

I've searched TDP and found info about manual switches for lockup, but sounds like there have been problems. I would just like to change the automatice setting.

I will be receiving GMTDScan Tech soon and was wondering if that would let me do it.

Thanks in advance.

[Robyn]

This sort of data is in the software programing in the ECM
I dont believe its an item that can be changed.

John Kennedy, Bill Heath or others that mess with the programing may be able to answer this question but to my knowledge its non adjustable.

best

Robyn

[SwedeBurb]

http://www.thedieselpageforums.com/tdpforum/showpost.php?p=244946&postcount=8

[JohnC]

TCC lockup is based on engine RPM (transmission input shaft speed), not MPH. Put on bigger tires and it'll go up...

[SwedeBurb]

I beg to differ. TCC On/Off is based on %TPS and MPH.

/Stefan

[JohnC]

I beg to differ. TCC On/Off is based on %TPS and MPH.


Why then when I went from 245-75 tires to 255-85 tires did my lockup happen at the same engine RPM but ~5 mph higher?

Also, I believe that a truck with 4.10 axles will lock up at a slower speed than one with 3.73 axles, but at the same engine RPM.

I agree that more throttle will delay lockup.

Also, stock HD (VIN F) programming locks up at a higher speed than LD (VIN S) programming.

Now that I think about it, I think the 3rd gear lockup occurs at the same speed as 4th, so more likely it's output shaft speed, proprotional to but still not equal to MPH.

[SwedeBurb]

When I make changes to lockup I do it based on speed and throttle. I have never seen that RPM has anything to do with it. Logically that would just mess things up since RPM drops significantly when lockup kicks in... how is the ECM to know that it should stay in lockup after the RPMs have dropped?

Example of stock F...
http://www.enghsmotor.se/_stuff/Stock_F.gif

Example of stock S...
http://www.enghsmotor.se/_stuff/Stock_S.gif

/Stefan

[JohnC]

Where does the speed data come from? If it comes from the transmission output speed sensor and not the VSSB, how do axle ratio and tire size figure into the equation?

If this information is duplicated in the PCM programming, then changing one without changing anything other than the VSSB would result in the same behavior: proportional to shaft speed, not MPH, as the PCM's MPH calculation would be in error.

TCC lockup should not have a significant effect on either transmission input or output shaft speed. I didn't mean to imply it was engine RPM, rather one of the transmission shaft speed sensors.

So, I guess the question I have is "if I change my tire size and correct the VSSB accordingly, won't my TCC lockup speed change?"

[SwedeBurb]

I helped a guy with a 2000 6.5TD G2500 this weekend. He had gone from 4:10 to 3:42 gears and his speedo and shift points got "messed up". We reconfigured his VSSB and things went back to normal... speed was 3mph off compared to a GPS and shiftpoint and lockup speeds was back to what he had before the gear change.

/Stefan

[JohnC]

I'm still confused. I changed the tire size on my '95 (twice) and each time I got the VSSB dead nuts on. One time it was consistantly within 0.1 miles on the odometer over a 100 mile trip based on the highway markers. Anyhow, when I increased the tire size all the shift points moved up and shifts occured and the same engine RPM given the same throttle settings. Vice-versa when I changed tire size down. FYI, I went from 245-75 to 255-85 to 265-75. Also, when I switched from a stock "S" chip to a stock "F" chip lockup speed went up about 5 mph.