727 sometimes not going in reverse
Still seeing tons of needle jump. It seemed like the more I added and Warner it got the pressure dropped but still in spec though it was still jumping like crazy. When the reverse seemed like it wasn't activating I could give it alot of throttle and then it would grab....
That sure sounds like the pump is sucking air.I don't know what to tell you, except If the pump is sucking air, the fluid will be aerated. You will have to check it immediately after trying reverse with warm fluid. Just pull the stick and check out what's there. If it looks the same as what you just poured in there, then its normal and the pump circuit is fine.If it's foamy with lots of bubbles, that would be no good. ATF has anti-foaming agents in it, so you will need to be speedy in the checking. Leave the engine running.
If the oil is fine; I would be dropping the pan, and checking the band and the servo. I would pressure test that bad boy to within an inch of it's life and if there was any doubt at all;I would pull the servo right out for inspection. But before that, I would study the band as you work that servo. Use a blow-gun with a rubber tip and at least 100psi. Watch the band for monkey business.If it is one of those triple-wrap bands, pay extra attention.If it split off one side of the anchor you'll see it.
If that's all normal, I would check the manual valve operation.
Stop! I think it just came to me.At least the jumpy needle. Here's my theory;
The pressure builds up in the circuit. Then there is a sudden drop in pressure, right? That's what you are seeing on the gauge; and then the pressure builds back up again. This happens continuously.So the needle is jumpy.
Ok so what could cause this? First off, it did this before the rebuild. I assume you replaced all the sealing parts in this circuit, which ain't much. So it has to be in the hard parts. Well you swapped out the VB so that ain't it. That just leaves the servo, the band, and the case.
Since we're having an issue with the clamping of the rear drum, at the same time, but it's a different band....... I'm gonna go with servo and case.
So drop the VB and crank up the air compressor to the max.
Put the pressure to that circuit and hold it. Listen. Something has to be leaking,suddenly, like a blow-off valve, Nothing? Back off the band adjustment and let the servo come all the way to the full applied position and retest. Still nothing? Swap in a different servo.Set the band and put it all back together. I know this is getting old. Fill'er up and retest. Same problem? replace the case, it has to be porous or cracked in the servo house, Problem gone? go find that old servo, and a big hammer and you can guess the rest.
But if you didn't replace the servo seal, or you nicked it on the install, your compressor may not have had enough pressure to make it show up. Remember the pressure on the gauge was hitting 250 to 275 before blowing off.
Now before you do any of this, wait a couple of days. There is a chance I'm wrong . Maybe someone else will chime in with a new thought or experience.
Just bump your thread back to the top every now and then.Don't be shy.