~79 model trans.
When shifting from 1st to 2nd, what valve(s) actuate to apply the servo? And for the 2-3 shift, which valve(s) actuate to release the servo? I am having a problem that really looks like no band apply and I want to troubleshoot the vb.

Under load, slips 1-2, and flares on 2-3. Trans is fresh and vb NOS from Ford.

Thanks,
Greghttp://www.network54.com/Realm/tmp/1228353581.JPG

You should have bought a Cougar instead of a Mustang. You do know that Cougars are faster than Mustangs, right?

Hmmm...who could this be?

Back to topic: Have you done an air test? This sounds more like the servo is not sealing. With the VB off the body of the trans, you can see an apply and release hole. Use a rubber tipped air gun to apply 40-60 psi at the apply. Is it blowing by? Or barely leaking?
Same with the release. Does it blow by?

If memory serves, a wimpsor dude can't possibly know about a BIG transmission like a C6. Mr. B, how's that 'little big engine that could'
running? Making a grand on the dyno these days? Wouldn't be surprised. Let's catch up off line sometime.

I haven't done a pressure test or any other type of test to date. Just starting to troubleshoot the problem on the trans. My pard in Arlington freshened it for me and had the NOS valve body for it. It is for the 71 with a de-tuned 466 CJ. Under light load, it shifts fine, all gears, but under normal acceleration, slides into 2nd and flares violently on the 2-3. Checked the band adjustment and within spec.

Will try the air check and respond.

Thanks for the help,

Greg

Greg,
Here's a link to a you tube video for air testing the C4. Very similar process for the C6. http://www.youtube.com/watch?v=ucTqlOHhCxM

It should be obvious if the seals are failed.

Bill

Yes, I think I got it, however, whenever I checked all the passages (not knowing which is the servo apply), I don't get any action on the band. I pulled the servo out of the case and air checked the seal through the hole on the side and it seemed to be sealing. I may have an obstruction in the case by some weird occurence.

Man, I could barely keep up with the dude in the video...he was talking so fast! :=) Thanks for the info.

G

Greg,
Here's how to locate the ports. I assume the tranny is in the car?
Looking up from the bottom on the dipstick tube side, VB removed:
Large square opening nearest the dipstick is pump inlet.
Then to the left of it in a direct line towards the dipstick is a threaded hole.
Then to the left of that threaded hole is a small machined hole -- that is the servo release passage.
Just below the threaded hole is a "bent" longer passage -- that is the servo apply. You have to cover up the passage to test. A big fat thumb may work.

To continue air testing, go back to the pump inlet...
Just to the right is REV-HIGH clutch
Next to the right is FWD clutch
Next is converter charge (don't do anything here)

Now drop down to the rear of the tranny and you'll see a threaded hole, open hole, open hole, open hole, threaded hole from side to side.
Starting at the modulator side the first open hole is GOV Pressure OUT
then GOV CTRL Pressure
then, this is what you want, is REV-LOW clutch, test this port for leaks.

HTH
Bill

I did go back, after the video, and found the elongated passage for the servo apply. The band does apply. I poked around on some of the other ports to find the clutches applying. I went ahead and pulled the vb apart to see if any of the valves were sticking. All move freely. Per one of the tranny builders on the 460 forum, I tightened the band to spec with 3/4 turn out. On the test drive, it still slips into gear 1-2 and flares on the 2-3 but not as bad. It may be time to replace the servo to eliminate that variable.

If it was just the flare, I would make the leap that the direct had too much clearance, but since it is common to both shifts, I still believe it has something to do with the servo.......or line pressure, maybe.

Thoughts?

Thanks for the help.
G

Dear Chevy,
Ok, air test 101. When you air tested the servo apply, did it sound "tight" or were you getting a lot of blow-by even though the servo applied? There will always be leakage but a slight hiss is not the same as the air just dumping. How would you describe the apply test?

Next, the backing off of the band 1/2 of its proper setting is a cheat. The servo and lever are designed for the 1.5 turn backoff. I never suggest the 'tighter' setting as it is not necessary.

Flaring into 3 from 2 indicates another source of problem: high clutch piston seal. If the pressure is leaking past the rev-high piston seal then you are delaying engagement of high as the servo is de-applying.

Did you per chance run the full suite of air tests I listed? If not, go back and air test the whole banana and let us know.

IlovChvy

p.s. I heard that TH400s are better than C6s anyway.

Bite your tounge, boy. A turbo water-matic wouldn't make a casting flaw on the extension housing of a C-6.

Otay, the air check was, well, noisy. Guess It'll get a re-do to measure blow by on the servo.....or for $8, I can replace the servo piston. Remember, Sparky, it also has a 1-2 slip as well as the 2-3 flare. Pulling the trans. to check the direct is a last ditch effort.
I realize the .75 turn outturn adj. on the band is only a mask, but wanted to see if there was a linear relationship for both settings. I guess I want it to be the servo, really bad.

btw, why did my name come up as Chevy lover on the last post?

If you don't log in you are named chevy lover.

Ok, everything can be tested in-car. I need you to pull the VB and run the full suite of air tests I provided.

I suspect the 1-2 slip is a bad servo seal. Which model servo is it? Full rubber embossed type or aluminum piston with square cut o-ring?

2-3 flare can be checked by the rev-high air test.

The wrong application of pieces can result in more than one symptom occurring. Usually if the tranny is running great and something fails then it can be pinpointed down to a single item failure.

HTH

$7.60 plus tax. Repairing a transmision problem this cheap is one for the record. Thanks to all for the input!