Since I last posted on this subject Ive done some extensive test driving and have come up with a better explaination of the problem and its symptoms. Forget what I said before. I should have done this first before asking questions but heres the new info.

First of all heat is not a factor because the trans will act up weather warm or cold. Now, I can leave from a stop, and as long as I dont give it more than 1/4 throttle the trans will function normally and upshift thru all gears perfectly. I can do this all day long without any problems. Now, the symptoms of failing to upshift to 3rd will arise whenever I either, get on it good with more than 1/2 throttle, or if I punch it from a roll and cause a kickdown. After doing either of these the trans will act up and not upshift under light throttle. So, half throttle thru first and into 2nd then let off. One would expect it to then eventually go into 3rd. But it wont. I also discovered how to make the symptoms and problem go away, and I did this a dozen times with the same results. When the trans acts up and wont shift, I pull over and come to a complete stop, put the trans into reverse for a second, pull it back into D and go. Upshifts fine and problem is gone, so long as im easy on the throttle. Something about putting into reverse must be raising the pressure and causing a sticking valve to be pushed back to its normal position. When it acts up and I come to a complete stop and "dont" first put it into reverse then back into D before pulling away again, it will shift very very hard into 2nd but then fail to shift into 3rd. So, when it acts up, its obvious that the pressure is really high, even at light throttle, hence the very hard shift from 1st to 2nd. And this is with light throttle so the pressure shouldnt be that high at that throttle position. One transmission guy has already suggested that the throttle valve might be hanging up in the valve body, and by selecting reverse the pressures are raised enough to push it back where it should be. He said that its possible that each time I push the pedal down far enough the valve gets to the point where its hanging up, and that when I stay on light throttle it doesnt bind and functions normally. Makes sense to me. Whatta you think? Im gonna drop the pan and valve body, and remove the throttle valve components, clean and polish them and make sure the bore is clean. Ill give this a try anyway. Ill try anything to avoid pulling this tranny. Ill also check really good for metal filings and whatnot since its possible that something else is failing and debris got in there to hang up the valve. Could be a piece of dirt from cooler line or convertor or anywhere else. Could have got in there thru a dirty funnel when filling. So to the tranny experts, whatta do you think? Does this senerio of symptoms match a sticking throttle valve? Im goin in there to check and clean up and ill post back and let you know if it does or does not solve the problem.

 

Jvette, keep in mind I have a 700, and know it fairly well by now, unfortunately....and have never owned a 200 so for me to say specifically...

but from what I know and hear....it's the throttel valve sticking...sure enough...

GENE

 

john what did you find out?

 

Nothin yet pat, I got side tracked on the caliper O-ring conversion and repairing my trouble light. Lettin the trans drip dry and ill tear into it tommorow. I want so bad for it to be this hung up TV valve. I can handle that one myself, with the tranny in the car. Ill definatly post back with an update when I get done.

 

Something from http://www.transmissioncenter.net :
Sometimes on a newly rebuilt 700R4 or 200-4R transmission, it may not make the 3-4 shift when first installed. A stuck valve, trash in the fluid or an air pocket, usually causes this. Raise the rear wheels off the ground, place the transmission in overdrive position. Run the speedometer as high as 100 miles per hour, pop the throttle on and off and see if you can force a 3-4 shift. Once it makes the first 3-4 shift, work the shift lever back and forth between drive and overdrive until the 3-4 shift works correctly.

 

Has anyone tried this? That sounds pretty scary to me...

 

Sounds like an idea but im not gonna try that. Not with a vette and its IRS. Maybe with a solid axel car I would try it. When the rear wheels are hangin unsprung on a vette, the halfshaft u-joints are angled too much to run the rear wheels at any speed, let alone 100mph. Anyway, I did this same sort of test today on the road to no avail. Some piece of crud is up in there hangin it up. At least thats what i hope to be the case.

 

Hopefully youll find something stuck in it. :thumbs:

 

Actually I dont need to find "something" since it could be microscopic debris. Tiny little crap to small to see. I quarantee you when I put it back togeahter its gonna be spit shining clean and buffed to a sheen. Im gonna make sure its free. Hope I dont find a bunch a crap in the pan. If so, the TV valve would likely hang up again when crap got to it. We'll see. Im on a mission tomorrow.

 

Another tip from PATC:
If your transmission doesn’t shift out of first gear or shifts hard at too high a R.P.M. this doesn’t always mean you have a problem. This could be a stuck throttle valve caused by a small piece of trash. This sometimes happens after a rebuild. Sometimes the throttle valve can be unstuck without removing the valve body. Get up to about 20 to 30 M.P.H. and hit the gas pedal on and off hard with your foot. This might do the job. If that doesn’t work remove the throttle valve cable end from the throttle, with the motor at idle in park, pull the cable in and out very fast, this might work, if not the valve body must be removed by a transmission shop to be unstuck.

 

Thanks joe73vette, Thats some good info. But now the pan is already drained and im knowledgable enough to drop the valve body and dis-assemble and clean. I woulda tried that trick you just noted had I heard it 4 hrs ago. At least when im done ill be sure its clean in there. Thanks for the input. :cheers:

 

Problem solved. Trans works great. Heres what it was. The TV valve function is made up several parts. Theres a bore, a plunger, and the TV valve itself, which is burried deep in the valve body, and some springs that make it retract when you let off gas. Now, a popular modification is to add a washer between the plunger and spring which increases the tension and raises the pressure higher. BTO had made this mod to the TV valve setup. Later on I installed a shift kit from PTS. He too had me add a washer in the same place. The thing is I didnt see the one that was already in there. These doubled up washers were not allowing the TV valve to rerturn to rest all the way. I tossed one of them out, put it back togeather and bingo, problem solved. But I cant figure out why it took so long for it to act up. Anyhow its workin great now. Its also possible that the washer That BTO used was binding since it was barely small enough to fit into the bore. The washer from PTS was smaller in diameter and would no way bind. So now theres one washer in there and its the smaller diameter one from PTS and everythings back to normal. Thank GOD I didnt have to pull this thing and send it out. I was sweatin for a while there.

:cheers: :smash: :D

And by the way, the trans is spotless inside, no evidence of unusual wear or signs of anything being torn up.


[Modified by Jvette73, 4:37 PM 4/2/2003]

 

:thumbs: :cheers: ,John!


[Modified by 69er, 5:57 PM 4/2/2003]

 

way to go john :thumbs: :cheers: a big sigh of relief

 

Gettin better n better. Earlier today after finished working on it I test drove it during rush hour. I just wanted to make sure it wasnt actin up anymore and I was able to establish that fact. I couldnt really get on it too much cause all the traffic. I just took it out again and all I can say is FRIGGIN WOW!!! Its workin much much better than ever before. It shifts a bit smoother and sooner on light throttle now. But when you nail it from a stop it hangs in 1st till about 5k then shifts up to 2nd very positively without any hesitation at all producing a bark at the rear tires. Still down on it and climbin thru 2nd, it goes to about 4800 and again upshifts fast and positive causing the back of the car to squat down at about 70mph. Almost feels like someones hitting yur rear bumper. The 2/3 shift was never that good before. Havnt had a chance yet to run it up thru 3rd and into 4th since that requires about 110mph at the top of 3rd. Maybe ill test that on the highway tomorrow. When I first got the tranny from BTO it was snappy shifting on part throttle but mushy and slippy on WOT upshifts. The govenor and shiftkit from PTS helped that, but remember I had doubled up that TV washer by mistake. Now that ive corrected that error, this thing is doin what it should, like it should, when it should. I was happy with it before, but im way happier now. :D :D :D