So, after having driven the truck for three weeks, here's what is happening with my C6.

The shift from 1-2 is just fine. The shift from 2-3 is fine when the transmission is not yet to temperature. when it gets to temp, what happens is that at the point where it would shift, the tranmission appears to slip out of gear (almost like going in neutral), while you're giving throttle, then, it finally goes into third, after letting the motor rev a lot. If you baby the throttle, then it will properly do the 2-3 shift, but that can be annoying. If I simply manually shift 1-2-3, it works OK, but even waiting to shift from 2-3 at around 35-40 mph sometimes does it a little, but usually not.

Does this sound serious? I can't believe this is a modulator adjustment, since the 1-2 shift is fine.

thanks for any help.

 

check trans kick down linkage at the throttle to see if it binds .. make sure vaccum line to modulator is not leaking and has good vaccum all the way to the modulator ..

 

Actually I have no kickdown rod (previous post). But that doesn't affect 'normal' shifting anyway. Vacuum is fine and I have new modulator. Shift from 1-2 is fine, so I sorta ruled out modulator?

 

Sounds like a governor issue. The low speed weight could be okay, and be enough to overcome throttle valve pressure but not enough to overcome TV pressure when the trans is spinning quick. When you baby the throttle there is only a little TV pressure, which makes it easier for governor pressure to overcome, allowing the 2-3 shift.

 

Can flushing transmission help this issue (doubtful)....

 

That's the problem with starting a new thread half the pertinent info is left behind on the other thread and people who are trying to help end up repeating what some one has already mentioned ..

 

It could help but it's a long shot

 

Also do some research on what happens if you lug or bog a motor .. At the moment your relying on your abilities to get the trans shifting dialed in and from reading your other post it's taking you a while .. Leaving off the kickdown linkage for you is probably not a good idea ..

 

__Happens a lot ,irritates me , L.O.L. ,or maybe it's the getting old that does it. ___

 

Hey, apologies if all the info wasn't in this thread. Didn't mean to frustrate. But after doing some research on the function of the kickdown rod, it's purpose is to force the transmission back to second, from third. Delaying shift points, on the other hand, is controlled by the modulator. So really, me leaving out the part about having/not having the kickdown rod doesn't matter. That I had already ruled out

Again, apologies about referring to another thread. Didn't mean to confuse.

 

What makes you so sure its the modulator. I'd bet you a cold one its the governor

 

Correct, I was only saying what the modulator does. But all along, didn't think it was the culprit. Otherwise, I'd see issues with the 1-2 shift too. And it's a new one too.

 

So what happens if the kickdown linkage is boundup at the transmission side in the kickdown posiition ? or if the rod is left off and it is left to be in whatever position ?

 

Hmmm. Interesting. Then wouldn't the truck almost never want to shift 2-3 (would want to stay in 2)? But using the gear selector over-rides what is happening. Also, if the linkage is bound, wouldn't think it would 'rev' out of gear. Also note that at light throttle, shifting is OK. The kickdown linkage wouldn't let that happen regardless. But you raise a good point.

 

A variation of somewhere in between is worth checking making sure the kickdown has no influence on shift points by wiring in the correct position .. Also a C-6 with a valve body and modulator for egr motors is different than without .. So eliminating the egr from a motor without making the changes at the C-6 is an issue that would need to be resolved ..