c6 problem, hope its simple

70shortwide · Post by **70shortwide** » Thu Oct 09, 2008 9:54 pm

OK, a little background. this tranny has 3k ish miles. when i bought it, it had been sitting for 3 yrs, had 1k miles on it. drove it a little bit then put it in my truck, changed the fluid at the same time. just in the pan didnt flush the whole thing (convertor should have still been full). so ive been driving it all summer. problem is, after i get on it and run it hard it will stick in either 2nd or 3rd gear (cant tell, it has 3:00 gears, doesnt want to hardly move). if i pull it into 1st it locks up and i skid to a halt.if i try to drive in 1st it has a load on it, but wont move. revese seems fine. this has me really frustrated. i havent done anything as of yet, i know nothing about these things except they are expensive. fluid level is good, has good color and smells fine. i have $3200 in receipts that the PO gave with it. should probly mention that this is a high hp setup.

BobbyFord · Post by **BobbyFord** » Thu Oct 09, 2008 10:00 pm

I wonder if it's got a reverse pattern valve body in it. I would try swapping out a known-good valve body.

70shortwide · Post by **70shortwide** » Thu Oct 09, 2008 10:05 pm

wow that was fast. the shift pattern is normal if thats what you mean. this problem is very intermittant.

Thunderfoot · Post by **Thunderfoot** » Thu Oct 09, 2008 10:15 pm

Sounds like a sticky valve in the valve body for High gear. It could be sticking after it gets warm and something is expanding in the valve body making it stick... When it locks up, that is because it is fighting against itself as it's in 2 gears at once...
You can try some additives to the fluid to see if it will help or will have to take the valve body out and take it apart and find out why the high gear valve is sticking.

70shortwide · Post by **70shortwide** » Thu Oct 09, 2008 10:23 pm

This may sound like i dont want to get dirty , but if i try some additive it wont hurt right? as long as im real easy on it when it gives me trouble? i know nothing about automatics. im not physically capable of gettin under there quite yet, and i def. dont have money for a mechanic right now. this thing might have to sit.. any opinions on additives? safe to use? really dont want to mess this tranny up, its had a ton of work done to it that i cant replace. any brands to make notes of for additives? I really appreciate this guys, im just lost and frustrated. this is my daily ride till i can pull money together for a little car.

70shortwide · Post by **70shortwide** » Thu Oct 09, 2008 11:02 pm

also, i should have mentioned. its a 385 series motor/tranny. i doubt that makes much difference with my problem. but like i said, i dont know much about autos. what i do know about them could fit in a thimble, and youd still have room to build a race track

Thunderfoot · Post by **Thunderfoot** » Thu Oct 09, 2008 11:52 pm

A lot of people have had good luck with the Lucas products http://www.lucasoil.com/products/displa ... 9&loc=show I'm sure some others will chime in

Jake11 · Post by **Jake11** » Fri Oct 10, 2008 2:40 am

Try the slam! Run it D to R back and forth kinda wide open throttle. Sounds like the govenor got stuck.
Works most times. Jake

70shortwide · Post by **70shortwide** » Fri Oct 10, 2008 2:11 pm

ok, i slept on it and from you guys have been telling me this is what i think happens:
the tranny gets stuck in 3rd gear. when i put it in 2nd manually the two gears slip enough to meet in the middle maybe? it acts like your driving with the park brake on.(a strong one) then 1st is so far from the gearing in 3rd it binds and locks up. does this make sense? i want to try an additive, probly will later today. any input is very appreciated.

Thunderfoot · Post by **Thunderfoot** » Fri Oct 10, 2008 3:39 pm

70shortwide wrote:ok, i slept on it and from you guys have been telling me this is what i think happens:
the tranny gets stuck in 3rd gear. when i put it in 2nd manually the two gears slip enough to meet in the middle maybe? it acts like your driving with the park brake on.(a strong one) then 1st is so far from the gearing in 3rd it binds and locks up. does this make sense? i want to try an additive, probly will later today. any input is very appreciated.

Kind of...
This is a really general explanation here...

There are 2 different clutch packs inside the trans and they are inside drums, some of the drums have bands on the outside (depends on the trans) that grab and stop the drum for different purpose (gears)...
Anyway, 3rd and reverse use the same drum but it depends on the band being applied (for reverse) or not for 3rd...
2nd is usually another clutch pack inside a drum and 1st is a band around the 2nd gear clutch pack drum (different for different trans)...
So when it is dragging bad when you put it into 2nd it is slipping one of the clutch packs or the band (not good) wearing it out...

The other thing in there is "planetary gears" this is what changes the ratio (gear speed) of the trans, and the clutches and bands are what is uses to engage these for the gears.
So when you put it in 1st and it doesn't move it is because these "gears" are fighting against each other and the clutchs and or bands are not slipping so it wont move.
Remember this is just a real general idea here...

But basically the drag you are feeling when it is doing this is causing wear/damage to the trans...

Side note:

Drag Racers use what is called a "Trans Brake" this is a modified valve body that has an electric solenoid on it that puts the trans into 1st and reverse at the same time. This locks up the transmission and you can stall (load) the motor up against the trans on the starting line, then when you are ready to go you let go of the button, to release the solenoid, and the trans lets go of reverse and your off like a flash.

70shortwide · Post by **70shortwide** » Fri Oct 10, 2008 4:12 pm

So, that would be a problem with the valve body? maybe? i hate sounding so ignorant, but im lost. could this be the stuck valve we talked about before? should i try some additive or just wait and tear it apart? im sure that i can research enough to manage pulling the valve body, just cant get under there and do it. can anyone rate this 1-10 on difficulty?

Jake11 · Post by **Jake11** » Fri Oct 10, 2008 10:40 pm

Try the slam at 1/2 throttle if your worried. It won't break. Next step is pull valve body and govenor and free up
the stuck valves. Theres some other things it could be. If the high/reverse clutch is fried, it can bind up and drag.
If you pull the dipstick and smell the oil, does it stink? Like its burnt.

A little primer. In reverse theres 350psi or so to lock up the clutch. It can be smoked and still work. When you take off
in "drive" the forward clutch is on. The planets give a first gear. In a C6 second is done with a large "band" that stops
a drum. High gear is a clutch. Same one as used for reverse. These things are all controlled by the valve body.
If two get turned on at the same time, when there not supposed to, it "your trans" can break.

The " slam " sounds kinda crude, but the valves get knocked around a bit and a lot of times it fixes. Not 100%,
but it's worth a try.

70shortwide · Post by **70shortwide** » Fri Oct 10, 2008 11:14 pm

ok, i tried the "slam" thing a little today. didnt seem to do it, although im a little leary of giving it much throttle. did it hard enough to bark the tires real good, but not much harder. took it down the road a ways and it freed up. seems like maybe its worse when its cold out, maybe, could just be gettin worse. its really intermittant, when i give it throttle at highway speeds, not enough to down shift but almost. then ill slow down or give it more and it wont shift again. this thing only has 3k mi. thats what really bugs me. could sitting for a while cause this? it worked fine for 1500 miles or so, after it sat. it also seems like it shifts just a tad later lately, than before. how much work is it to pull the valve body? timewise, for someone whos never done it? is it something that i shouldnt attempt without someone there to supervise? still want to try the additive, didnt get around to it today.

BobbyFord · Post by **BobbyFord** » Fri Oct 10, 2008 11:17 pm

It's very easy to pul the valve body. Do you have a spare known good valve body? It really sounds like a sticky valve problem. I would not recommend any fluid additives

Jake11 · Post by **Jake11** » Sat Oct 11, 2008 1:01 am

After the pans off the valve body comes off in less than 2 min's, unless your goofing off.
Get a shift kit. Tran's go makes a good one and a filter and pan gasket. Oil too, you'll need that.
Read the directions over good and in a afternoon you'll have it shifting really nice. Once you get
an auto trans set up so it shifts right now, you'll love it.

Like Bobby said, the snake oil stuff is a waste. It comtaminates the friction stuff. Then it don't shift right.

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