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JoshH

Lock the converter early for better economy

9 posts in this topic

I did a little experiment the other day that seems to have paid off in slightly better fuel mileage. I do a lot of low speed driving (in town and on base) so my converter is unlocked a lot. If I put it in T/H mode it will lock, but my shifts are so drawn out it really doesn't help my mileage any. The other day I decided to play around in the TCM some and copy my converter locking tables from the T/H shift pattern to the normal shift pattern. This resulted in my converter locking at around 22-24 MPH. The only modification I had to do to my shift points was raise the speed at which it shifts into and out of 5th gear because it was shifting so soon that the RPM would drop low enough to trigger the release of the converter clutch only to have it lock again almost immediately.

It doesn't look like it gave me a huge gain, maybe 1 mpg better, but with fuel prices what they are, every little bit helps.

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Man, so you guys can set the vane position like rob talked about, advance the timing a little, and throw in this T/C lockup. That whole deal has got to be worth about 3 to 5 mpg. With a 25 gallon fillup that is another 75 to 125 miles per tank. That is NOTHING to scoff at.

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Great info Josh. How does it drive with the converter locking early?

I haven't noticed any drawbacks from having it lock early. The only thing I don't like is aparently there is a table somewhere that makes it unlock if you let off the throttle at 46 mph or slower. I looked and couldn't find anything though.

It also seems to have helped my harsh converter engagement a little.

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I'll mess with the T/C later, but sounds like a hell of an idea... Good info brotha...

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I've been running this way today and babying the truck. The DIC has improved +2mpg, but that is also with a new economy ecm tune installed. Getting 17+ in the city. I need to fine tune the shift points, wants to short shift and I feel lugging the engine may have the reverse effect on economy.

DIC should be right on because I'm running stock fuel tables in the driving range.

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