C6 shifts early

[70shortwide]

I know there are lots of threads on this... Ive read several, however mine is a little different.

This trans was rebuilt and has had a problem with early shifts from day 1. ive put ~1000 miles on it by just shifting manually.

today I got ambitious, looked everything over, decided it must be the modulator. went to the parts house and compared mine to a new one, the pin didnt go into the new one as far. sweet, problem solved. took it home, put it in. same problem.
adjusted it, little gain, if any.
heres where it gets weird...

I pulled the vacuum hose and plugged it. went for a drive, it shifts exactly the same!

I plan to call the rebuilderin the next couple days, but, I would like to educate myself a little bit on possible problems first.. Any thoughts?

[Donnie]

Jeff, there are 3 variables when working with a modulator, they are :
The diameter of the can part of the mod. can vary
The spring strength in the can can vary. noticed by diff. color stripes
The length of the pin /to /the valve in the trans is selectable..you should have a bit of tension when the pin is the correct length, about 1/16 of an inch from the case when installing the mod, you should feel the spring tension
Where I'm lost is with the hose unplugged from the mod & stuffed with a golf tee, or other item of your choosing, your shifts should be LATE & FIRM........yours are EARLY with the hose off????????.....was there any shift programs installed. Was the gov. changed?
This is a fresh rebuild, yes? With the mod. out, can you reach in with a pencil magnet & remove the modulator valve from the trans.?or is it stuck or dragging, or looselike ,side to side. in other words, the valve should slide in & out with ease
Sometimes on high mileage trannys the valve will create a ridge at the base of the bore & the valve can stick in the bore & not move with the vacuum dia........HTH...........donnie

[elgemcdlf]

Do you have the kickdown installed & adjusted properly?

[70shortwide]

Jeff, there are 3 variables when working with a modulator, they are :
The diameter of the can part of the mod. can vary
The spring strength in the can can vary. noticed by diff. color stripes
The length of the pin /to /the valve in the trans is selectable..you should have a bit of tension when the pin is the correct length, about 1/16 of an inch from the case when installing the mod, you should feel the spring tension
Where I'm lost is with the hose unplugged from the mod & stuffed with a golf tee, or other item of your choosing, your shifts should be LATE & FIRM........yours are EARLY with the hose off????????.....was there any shift programs installed. Was the gov. changed?
This is a fresh rebuild, yes? With the mod. out, can you reach in with a pencil magnet & remove the modulator valve from the trans.?or is it stuck or dragging, or looselike ,side to side. in other words, the valve should slide in & out with ease
Sometimes on high mileage trannys the valve will create a ridge at the base of the bore & the valve can stick in the bore & not move with the vacuum dia........HTH...........donnie

With the new modulator there is preload.
Correct, with the hose disconnected it still shifts very early. once I have gotten out of 1st it wont go back to 1st unless I mash it and it kicks down, It will take off in 2nd gear from a stop.
It is supposed to have a shift kit, stage 2 I believe.
I do not know if the governor was changed. could it be possible that they installed a governor for a diesel trans? would it still run out if I manually shifted if that was the case?
I did not try to remove anything after the modulator and pin.
My kickdown is installed and properly adjusted as per lokar

[elgemcdlf]

An easy try would be to adjust the kickdown to a bit longer & see what happens. It should hold it in gear a bit longer.

[70shortwide]

It is my understanding that the kickdown does not control upshifts, only downshifts. That being said I have had it adjusted several ways trying to get a reaction out of it.

[BobbyFord]

If adjusting the modulator has no affect then it back to the rebuilder.

[Donnie]

........Bobby is correct...take it back to the builder....Was it a Pro shop or shade tree? Chances are the former failure left some foreign material in the cooler or lines that got flushed back into the system.....New , clean, & hot trans fluid is the best cleaner for the cooling system.
FYI...most 2nd gear starts are caused by a sticking gov......but your other symptoms indicate that you may have something wrong in the valve body.........donnie

[70shortwide]

cooler and lines were definately not the issue, they were installed new with the trans... Im hoping that it will be able to be fix in the truck, Ive already pulled it back out once. guy rebuilds them in his garage, has a clean work area and very professional. lots of knowledgeable guys out here have recommended him. I feel he is very capable, however, it seems maybe my luck with him isnt as good as others...

[Donnie]

Hi, just wondering what did your builder find wrong with your early shifts? Gov. or valve body mis-assembly?.......Donnie

[70shortwide]

Hi, just wondering what did your builder find wrong with your early shifts? Gov. or valve body mis-assembly?.......Donnie

He claims that the problem is in the valve body. He explained how he found the issue; checked the line pressure and had no response from the valve body. I didnt follow the conversation as well as I wish I could have.... Im definately wondering what could be wrong with it since he expects me to just go buy a new one... it worked fine before he rebuilt the trans and installed a different shift kit..

[BobbyFord]

Go get a valve body out of a boneyard C6 and then go here...> http://transgoonline.com/products.php?h ... rent_id=71 and buy either the SK6 or the 67-1&2 kit and install it yourself. The instructions are so easy to follow, a caveman could do it.

[70shortwide]

at this point Im still expecting the rebuilder to fix it... he installed a transgo kit in it when he rebuilt it, Im fairly certain that is where the problem lies... this trans was built before, I think the issue might be mods done to the valve body that dont work with the transgo kit. I dont know much about automatics, which is why I took it to someone else...

[BobbyFord]

Sounds to me like he's guessing. I've never had an issue with a TransGo shift reprogrammer kit.
Hopefully, he'll figure it out.

[70shortwide]

ive got a little suspicion that he just wants me to throw money at it and hope that it fixes it. Ive already got a pretty significant amount into this trans and it has not shifted right since day one. Ill know in the next couple days what he plans to do...