C6 not downshifting until complete stop

[dsrtjeeper]

My freshly rebuilt C6 with Transgo shift kit and Hughes 2500 stall converter won't downshift until I'm nearly at a dead stop. My Cruisomatic did the same thing in stock form. I roll up to an intersection and the light is green. I slow way down to negotiate the turn. I then throttle when headed straight and the tranny is still in Drive. It does the same thing when slowing way down for speed bumps. Could the shift kit or stall converter affect downshifts? Just a typical C6?

[Donnie]

Hello Jeeper, did you build this trans yourself? The shift kit installer may have made an error someplace in the build.
My first guess is that your governor is hanging up...Try manually shifting it with the shift lever for a while, it may free up.
Is this a 2WD or 4x4..???
The converter is not your problem.
If you didn't build this yourself, did you install it yourself?............post back ............Donnie

[dsrtjeeper]

Hello Jeeper, did you build this trans yourself? The shift kit installer may have made an error someplace in the build.
My first guess is that your governor is hanging up...Try manually shifting it with the shift lever for a while, it may free up.
Is this a 2WD or 4x4..???
The converter is not your problem.
If you didn't build this yourself, did you install it yourself?............post back ............Donnie

Hi Donnie. I had it professionally built. They are going to make it right but I wanted to go in there armed with a little knowledge. When I test drove it after installation; it wouldn't shift down at all. It would always take off in Drive. I manually shifted it for a few miles and it started downshifting automatically. Would it upshift fine if the governor is sticking? I spoke with Transgo today and the tech guy was great. He wanted to know at what speed the tranny is shifting from 1-2 and 2-3. I'll check that tomorrow. He said the C6 downshifts into low anywhere from 7-1mph. I guess that's just about stopped. I guess I'm use to these newer vehicles. The tranny staying in drive when I make a slow turn through an intersection; puts quite a load on the engine.

[BobbyFord]

I have a TransGo kit, too. I like how it shifts. First IS there if you mash it, so don't worry where it is on decel, when you don't need it.
I suspect you've grown accustomed to stock shift points.
Reprogram your brain.

[dsrtjeeper]

I have a TransGo kit, too. I like how it shifts. First IS there if you mash it, so don't worry where it is on decel, when you don't need it.
I suspect you've grown accustomed to stock shift points.
Reprogram your brain.

The C6 with shift kit operates the same as a stock Cruiso when it comes to downshifting. I have to be nearly stopped for tranny to shift down. If cruising through a green light and say taking a slow right turn; the tranny remains in Drive. This lugs the engine when accelerating from a slow speed in Drive. True if I put her to the floor after the slow turn; it fries the tires and takes off violently. Not exactly what I want for street cruising. The tranny should drop to second at least in a slow speed turn. No?

[BobbyFord]

I have a TransGo kit, too. I like how it shifts. First IS there if you mash it, so don't worry where it is on decel, when you don't need it.
I suspect you've grown accustomed to stock shift points.
Reprogram your brain.

The C6 with shift kit operates the same as a stock Cruiso when it comes to downshifting. I have to be nearly stopped for tranny to shift down. If cruising through a green light and say taking a slow right turn; the tranny remains in Drive. This lugs the engine when accelerating from a slow speed in Drive. True if I put her to the floor after the slow turn; it fries the tires and takes off violently. Not exactly what I want for street cruising. The tranny should drop to second at least in a slow speed turn. No?

My trans shifts very differently now that it did before I rebuilt it. Yes, mine does drop down to second at low speed with moderate gas pedal. How are your shift points under normal acceleration? Perhaps a modulator adjustment is in order.

[Donnie]

Hello Jeeper, Bobby is correct, it COULD be a modulator problem, either the wrong one or a mis-adjustment....Your trans should at least downshift to 2nd at intersection's...I neglected to ask about any engine mods. which would affect the engine vacuum...
I also neglected to ask you about your up shift points, my fault..........Hi Perf. cam will lower engine vacuum which the trans. uses to interpret the engine load,,that is why you get a downshift when you add more throttle...Engine vacuum drops. Your modulator reads this & will signal a shift, but if the gov. is sticking...A fairly common problem if a proper flush was not done. You will not get a downshift. In your case you need to add too much throttle to force a downshift....This could very well be vacuum related as Bobby said.
My original thoughts were that if it was a" home built " unit, that the cooler was not flushed properly, thus the questions that I asked..
Your trans uses engine vacuum to tell the trans how hard the engine is working--------and the trans uses governor signal to tell the trans the speed of the vehicle...There is a balancing act between these two components to control the shifting of the trans.
I hope that this bit of tech helps you when you discuss this with the builder or Trans-go,,,,,,,,,,,Donnie

[BobbyFord]

Nice info, Donnie

[dsrtjeeper]

Hello Jeeper, Bobby is correct, it COULD be a modulator problem, either the wrong one or a mis-adjustment....Your trans should at least downshift to 2nd at intersection's...I neglected to ask about any engine mods. which would affect the engine vacuum...
I also neglected to ask you about your up shift points, my fault..........Hi Perf. cam will lower engine vacuum which the trans. uses to interpret the engine load,,that is why you get a downshift when you add more throttle...Engine vacuum drops. Your modulator reads this & will signal a shift, but if the gov. is sticking...A fairly common problem if a proper flush was not done. You will not get a downshift. In your case you need to add too much throttle to force a downshift....This could very well be vacuum related as Bobby said.
My original thoughts were that if it was a" home built " unit, that the cooler was not flushed properly, thus the questions that I asked..
Your trans uses engine vacuum to tell the trans how hard the engine is working--------and the trans uses governor signal to tell the trans the speed of the vehicle...There is a balancing act between these two components to control the shifting of the trans.
I hope that this bit of tech helps you when you discuss this with the builder or Trans-go,,,,,,,,,,,Donnie

Engine is modified. I run 18"hg vacuum at cruise. 13"hg stopped at idle in Drive. The tranny cooler and lines are all new and the tranny is fresh out of the shop. Of course that doesn't guarantee that there is no small pieces of crud in there. Driving it like a granny; it shifts 1-2 at about 12mph. 2-3 at about 23 mph. If I'm cruising along and kick it down into second at WOT; it shifts back out to Drive at 5500rpm. I'll have to crawl under there and see which modulator I have or if it has any paint markings on it at all. I know they usually have a colored stripe. Not sure which one should be on a '69 C6 out of a F100. Do they get changed to a different one when one adds a shift kit?
Thanks for the help!
Eric