Quick question about the canned 87 tow

[Jackpine]

Originally Posted by BigSur

I checked it out and I'm not seeing any locking going on b/w 1st and 2nd. The only time I'm seeing it lock is after I drop into OD and I'm on the gas. Seems to be pretty random....in most cases, the shift feels fine. It's really a sweet spot where I'm at just the right speed and RPMs and it only happens when I'm VERY slowly accelerating.....e.g. bumper to bumper traffic where I'm having to creep forward 50 ft and then slow back down again...and there's not much room to really accelerate.

Is it normal to see the comm gear advance prior to dropping into the corresponding gear? If I'm accelerating moderately, the interface shows 4th gear at 32 mph.....I don't actually drop into OD until about 40mph, which is when the TC locking occurs.

Are you sure it's not shifting at 32? If the TC is unlocked, there will be a "gentler" RPM change than if it is locked. It really sounds to me like the shift is happening at 32 and the the TC locks at 40.

But, I don't know that anything is amiss in your truck. I think you are possibly more "sensitive" to its shifting than I am, and I'm pretty "sensitive" too.

- Jack

[BigSur]

Originally Posted by JackandJanet

Are you sure it's not shifting at 32? If the TC is unlocked, there will be a "gentler" RPM change than if it is locked. It really sounds to me like the shift is happening at 32 and the the TC locks at 40.

But, I don't know that anything is amiss in your truck. I think you are possibly more "sensitive" to its shifting than I am, and I'm pretty "sensitive" too.

- Jack

I don't know....unless I'm missing something. I've always thought my tranny drops into OD (or 4th gear) around 40 mph when accelerating moderately. That is when you physically feel AND hear the truck change gear, as well as you'll see the RPMs drop to about 1000; however, of course that changes if I'm on the gas, which in that case, it drops to OD at a higher speed and RPM. When I was running my custom performance tune....the moderate acceleration shift to OD happened closer to 50 mph.

What I experienced today monitoring the comm gear is that it would change to 4th while in mid-acceleration and know noticeable changes in gear. Once I "heard and felt" the tranny drop into OD at 40 mph....the TC would lock. Is it possible that I'm too INsensitive and my truck is changing gears without me feeling it?

[Jackpine]

Heck, anything's possible in these subjective kinds of observations. I don't really have a good reply for you. I would expect though, that the the TC would lock AFTER the shift up had completed in normal shifting, which would reduce strain on the transmission. Likewise, it should unlock BEFORE any downshift.

- Jack

[Longshot270]

I know an easy way for you to check if you have the monochrome Gryphon.

Get a datalog of mph (MPH), rpm (RPM), engine load (LOAD) comm gear (COMM GEAR), and pedal position (APP). While you are sitting still start the logging. Once it starts recording SLOWLY accelerate. One MPH per second is a good rate of acceleration. If you keep an even rate of acceleration you'll get a graph like this...


If you dont know how, read the little article I wrote that is included in my sig. vvvvv

[BigSur]

Originally Posted by Longshot270

I know an easy way for you to check if you have the monochrome Gryphon.

Get a datalog of mph (MPH), rpm (RPM), engine load (LOAD) comm gear (COMM GEAR), and pedal position (APP). While you are sitting still start the logging. Once it starts recording SLOWLY accelerate. One MPH per second is a good rate of acceleration. If you keep an even rate of acceleration you'll get a graph like this...


If you dont know how, read the little article I wrote that is included in my sig. vvvvv

I might very well try that. Seems simple enough. I'm questioning the programmer now though, b/c I remember Jack recommending I monitor comm gear back in the day for a different issue I was having, and I don't remember this happening. Then...the gear would change with the truck. ?????

Maybe I'll try to plot a graph and follow up to this. Much appreciated.

[BigSur]

Guys....I did a bunch of driving around town today and noticed something new. I AM feeling a light shift around 32 mph...and then again at 40mph when the TC locks up. I can only feel the shift at 32 if I'm under very light throttle....otherwise, you almost don't feel it. I can usually pick up on it regardless if I'm paying attention.

This threw me for a loop.....does this mean I have a 5 spd tranny? I'm feeling the shifts from 1 to 2, 2 to 3, NOW 3 to 4? if I'm paying attention, but then at about 40....it drops into OD and the TC locks up. Time to bust out the owner's manual I guess.

[Jackpine]

Excellent suggestion Longshot. Now that I'm using the CTS, I tend to forget about data logging. One day, I'll have to plug it back in and play with it.

But, BigSur - notice the graph of RPM vs acceleration in the plot Longshot posted. The changes in RPM are very small, comparatively at each shift point. They might be somewhat hard to "feel", especially the 3-4 upshift. There was a LARGE drop though when the TC locked, and you'd notice that.

I'm betting that's the behavior you're noticing that makes you wonder if the 3-4 shift is even happening. (As long as the TC is unlocked, it smooths out the shift induced RPM changes, especially during very mild acceleration.)

Edit: And, you slipped in a couple of additional posts while I was composing this and doing some other chores. I'm certain the final thing you are feeling is the TC lockup, not the actual shift into O/D. That happened at 32 mph, just like your Gryphon told you.

- Jack