General Category > Quadrajet Carb Talk and Tips

th350 question

<< < (2/3) > >>

stevef:
It was just like driving around in 1st gear. Now that you mention it, it might have gone to neutral a couple of times, when driving around the block, but I was able to get back in gear to get home. It's been a couple months since I drove it, so it's hard to remember exactly how it was acting. I just know that it never shifted up.

I don't think it's the governor, since I checked the valve inside it, and it's moving freely, not sticking.

Thanks for replying.

stevef:
Okay, I found a pretty good way to air test those 3 holes. I took a piece of small diameter rubber fuel hose and cut a small notch in one end. I slid the other end of the hose over the end of the air nozzle tube. I inserted the notched end of the hose into each cavity aiming the notch at the hole in the cavity. When holding the hose tight into the cavity, it seals up pretty good and blows air into the hole. So, I did that for the 3 holes, using 25-30 lbs air pressure.

Referring to the pictures on page 103, from left to right: 
Applying air pressure to the hole in the left picture, I can see the intermediate clutch moving as the book says. It seems to work strong without significant air leaking.
Applying air to the middle hole, I hear the clutch applying, but there is the sound of air leaking. Is that the forward clutch pack?
And putting air to the right side hole, I hear the clutch applying. It's a duller thud when applying than the 2nd one. It has air leaking too, but not as loud as the 2nd one. Is that the direct clutch?

So, what would you conclude from this test?

stevef:
I'll answer my own question. If I'm not supposed to hear much air leakage, I think there's too much, even though the clutches do engage. I've got a new seal kit, so I'll have to see if I can get those clutch packs as air tight as possible this time. So, this was a helpful test that seems to be confirming my suspicion of what the problem is, before taking everything out.

Cliff Ruggles:
Leakage should be very minimal during an air pressure test.  I've never tried low pressure air, we use 125-140psi when testing them here. 

The metal hooked end sealing rings seal pretty tight but you can here very minor leaking with each test. 

We air test every unit we build here during the rebuilding process.  A very easy way to test the fwd and direct are to invert the pump is a large shop vise with soft jaws and air test thru the supply holes in the pump.  This is described in my TH350 book, Chapter 5 page 90......Cliff

stevef:
Thanks again for responding Cliff.

The reason I used the lower air pressure was I figured if air leakage was the problem, then the clutches wouldn't apply with lower air pressure and I'd know that's the problem. But, I hear leaking, and even with low pressure they're applying anyway, which I didn't expect if the leaks were too bad. 

I thought if I use high pressure, even if it leaks badly, the high pressure would overcome the leakage and make the clutches apply anyway, which would defeat the purpose of the test. But if you do it that way, I guess that's not the case.

During the rebuilding, I did do the forward and direct air test on the bench. I got a little leaking at that time, but the clutches applied so I thought they were okay. I was using higher air pressure then, and afterwards, when the transmission wouldn't shift, I was thinking maybe I used too much air pressure, which was overcoming the leaking and making the clutches apply in spite of the leaking, making it a false test.

Now, I have a better idea of how much air leaking is normal. I suppose even if the clutches apply with a bad air leak during a test, the apply could be too weak to work when the transmission is in actual operation.

So, I'll re-seal them and test them again. And I'll double-check the other things that you listed that could go wrong too. Thanks a lot for the help!

Navigation

[0] Message Index

[#] Next page

[*] Previous page