th350 clutch pistons air check video

[stevef]

About 6 weeks ago, I posted a question about my th350. To review, I have a th350 that I rebuilt, but on the maiden voyage it wouldn't shift out of first gear. It runs in first and reverse. So, I've removed the transmission from the car and opened it back up. When I rebuilt it, I noticed during the air checks that I had some air leakage, but the pistons were still applying the clutches. I didn't know how much air leakage is acceptable, and Cliff said it should be minimal. But I'm not sure what minimal is. So, I made this video to show how they are. Does this look and sound okay, or should they be more air tight? Thanks.

https://www.youtube.com/watch?v=as81X1cRI8s&feature=youtu.be

[Cliff Ruggles]

All is fine from what I can see in the video.

If you had enough leakage to be a problem the transmission would still have shifted, but slipped and smoked the clutches. 

Not upshifting, or only having low and reverse is a problems someplace else with the build......Cliff

[stevef]

Thanks for your quick reply Cliff! I really appreciate your help. Now, I can concentrate on looking elsewhere for the problem.

I'll be calling you to order some more q-jet stuff in the next day or 2.

Thanks again. Steve Fountain

[77cruiser]

Check the gov. make sure it's not stuck or the lands aren't wore too much. Vacuum modulator OK?

[stevef]

I did look at those when the problem happened, hoping to not have to take the transmission out. The vac modulator is new, and just to make sure, I swapped it for a known working unit, and no difference. I pulled the governor and it was free with no wear, and I tried another good looking one and no luck there either. I'll double-check those things again though. Thanks.

[Cliff Ruggles]

Aside from stuck valves in the VB or springs on the wrong side of them there are three things that will prevent upshifting.

No vacuum to the modulator, governor stuck or not spinning, or kick down valve applied. 

On the TH400 we see this more than with TH350's because it's a solenoid instead of a manual valve for kick-down.

I typically don't use the kick-down feature in either one of those units here, unless it's a pretty much stone/stock set-up and the owner requires or wants forced heavy throttle down shifts for some reason.

Since I drag race my car and it uses a TH400 I haven't had the kick-down feature hooked up now some thirty something years and don't need it for any reason.

Anyhow, let us know what you find, I'm sure you'll nail it down pretty soon.......Cliff

[stevef]

Thanks again Cliff. I'll be double-checking all those things.