Add the high octane for a couple tanks then load the 91 tow and see what it does

 

Hello Bradley,

Though this may come as a shock to you, I am sitting here looking at your files - and there is absolutely ZERO difference between your stock tune and our tuning in the 4th gear torque converter lockup schedule & 4th gear downshift schedule, too - none whatsoever - it is all *stock*. I just checked all 3 tunes, and there is no change whatsoever from stock. There is no additional line pressure there, either - that too, is stock.

This is at extremely low speed and very little throttle - the engine is turning *maybe* 1000 rpm at that point, a point at which Overdrive simply has no business being engaged.

For example, at 29-92 TP (throttle pressure) in your code, it will lock up the TQ at 41 MPH, for example - so if you want this to go away, you need to simply disable the O/D.

As we have been telling people, remember - Overdrive was NEVER INTENDED to be used all the time like that, or at such low speeds & light throttle openings - expecting it to be relevant at low speeds & light throttle like that is simple wrong, that will cause 3-4 4-3 cycling, and/or TQ lock/unlock cycling - by now just about everyone here knows that, as does Bradley from the wording of his original post, obviously.

Overdrive is intended for use under the same circumstances it was originally invented for back in the 1920's - to be used only at higher speeds once your cruising speed has been reached & when the load is down, to reduce engine rpms to save gas. It is NOT intended to be used at very low speeds - nor is it intended for towing loads up grades at 70 mph, where the engine is turning *maybe* 1800-2000 rpm, and thus making *maybe* 80-100 HP if you are lucky at part-throttle at 70 mph, for another example that one of our other customers is trying to blame on us (and quite incorrectly). It doesn't matter that the factory sets them up so that the Overdrive is enabled by default, it still irritates the heck out of some people, and understandably so.

In this example, at 41 mph you are turning all of barely 1000 rpm in 4th gear - let's get real, nobody should expect the transmission not to cycle or the TQ not to lock & unlock under those conditions, at 1000 rpm - it does it stock, too - it doesn't only do it with our tuning, as I said, those areas are not changed at all from stock in your tunes - I'm looking at it right now, and there is ZERO difference from stock in those areas.

Now one thing that a lot of people ask is, well, if that is the case, then can we make it so that the Overdrive is disabled at startup in the tune? And the answer is, unfortunately, no - we cannot do that, that is not something under our control. What you need to do is to simply turn Overdrive off until you are operating in a situation in which Overdrive is actually relevant - that applies any time the tranny is cycling 3-4 4-3, or the TQ is cycling between lock & unlock - this is the nature of the beast when you have a 3-ton truck with a very tall final drive ratio, as all of these trucks do from the factory.

So *that* is the actual scoop - your settings in this areas are NOT changed at all from stock.

 

Hey Mike, thanks for looking into it for me... The only reason that I questioned it is because there is definately a noticable difference from stock. I realize that you said you double-checked, and there's no difference... But on Friday I went back to the stock tune because I didn't like the way it locks up, and it does not do it with the stock tune. Since the tunes themselves are the same, is there possible something else that could cause the difference?

If you get a chance, could you give me a call? Crystal has my phone number. Thanks!

 

Also, is it possible to tweak the tunes so that , for example, at 29-92 TP it won't shift into 4th/OD until, say, 50 MPH?