While I know an order of magnitute more about these transmissions now than I did even 4 weeks ago (as I'm still learning this thing, I don't know it like I do a TH350 which I can build in my sleep), I still have one question. The one that's in my car now (new sun shell, 9C1 calibration, OD in WOT yada yada yada) had an erm, "feature" that I've been debugging - one that I would guess would be related to low line pressure, but the throttle valve spring checks OK and the adjustment is done per GM recommendations (adjust all the way out, WOT at the carb to "click" it in). Although it felt as though there was some slippage at certain RPMs (no engine flaring, but a definite difference in the feel of power transfer) and there was a "click-clack-click-clack" coming from the front pump while it felt as though it was slipping. When the chattering noise went away, I could feel the full power transfer. Anyways, the 1-2 shift has been a lot softer than before, due to the old stiff 'orange' 1-2 accumulator spring being broken (what led to the sun shell failure) and my selection of a much softer spring than what it had (a purple spring).

A guy at Cottman told me that you can firm up the 1-2 by flipping the 1-2 accumulator piston over, so that front is back and vice versa. Enter tonight. I decided, what the hell, I'll give it a shot because even I didn't like the 1-2 shift and that orange spring is apparently made out of unobtainium as it cannot be found at any shop I go to. So, I got smart last time I pulled the pan and put a drain plug in the pan which made tonight's job almost grease-free for me. Upon pulling the pan I notice the condition of the fluid and rethink my entire 'slippage' theory. I've put almost a thousand miles on it since installing it two weeks ago and the fluid was a nice, sweet-smelling, crystal-clear cherry red and there was no trace of anything in the pan. Generally if there's slippage, there will be a varnish on the inside of everything (prior experience tells me this) and there will be gunk in the pan and the oil will be cloudy from the clutch material, but this was not the case. I take the accumulator off, flip the piston over, put it back together with the same purple spring, and put everything back together.

Not only has the 1-2 shift seriously improved, but the noise and "slippage" is totally gone. It's acting like a real transmission now. My one (well, two) question(s) is(are),

Does this make sense?

Could the 1-2 accumulator have caused a low-line-pressure condition in the condition it was, due to valving and calibration within the transmission?

Am I talking out of my butt?

I'm not sure what means you might use to verbalize, and really don't need the details...

Back to the trans, IF the 2nd accumulator piston were installed incorrectly, flipping it would make sense. Installed upside-down (if it's even possible) would tend to reduce the volume of oil available to drive the 2nd apply piston - The spring rate controls the apply pressure.

Unless this a a '93-later trans, the accumulator piston should have an extended hub that is supposed to face the spring side. If you were to flip the piston away from the spring, the piston could not travel as far downward (away from the valve body) and some more oil would always be retained in the accumulator cover. This would reduce the volume of oil necessary to build pressure, but would also reduce the volume of oil available to drive the 2nd apply piston when the valve cycled. I would think this would tend to slow the application of the 2nd apply servo, not speed or firm it up.

How was your's installed?

While I know an order of magnitute more about these transmissions now than I did even 4 weeks ago (as I'm still learning this thing, I don't know it like I do a TH350 which I can build in my sleep), I still have one question. The one that's in my car now (new sun shell, 9C1 calibration, OD in WOT yada yada yada) had an erm, "feature" that I've been debugging - one that I would guess would be related to low line pressure, but the throttle valve spring checks OK and the adjustment is done per GM recommendations (adjust all the way out, WOT at the carb to "click" it in). Although it felt as though there was some slippage at certain RPMs (no engine flaring, but a definite difference in the feel of power transfer) and there was a "click-clack-click-clack" coming from the front pump while it felt as though it was slipping. When the chattering noise went away, I could feel the full power transfer. Anyways, the 1-2 shift has been a lot softer than before, due to the old stiff 'orange' 1-2 accumulator spring being broken (what led to the sun shell failure) and my selection of a much softer spring than what it had (a purple spring).

A guy at Cottman told me that you can firm up the 1-2 by flipping the 1-2 accumulator piston over, so that front is back and vice versa. Enter tonight. I decided, what the hell, I'll give it a shot because even I didn't like the 1-2 shift and that orange spring is apparently made out of unobtainium as it cannot be found at any shop I go to. So, I got smart last time I pulled the pan and put a drain plug in the pan which made tonight's job almost grease-free for me. Upon pulling the pan I notice the condition of the fluid and rethink my entire 'slippage' theory. I've put almost a thousand miles on it since installing it two weeks ago and the fluid was a nice, sweet-smelling, crystal-clear cherry red and there was no trace of anything in the pan. Generally if there's slippage, there will be a varnish on the inside of everything (prior experience tells me this) and there will be gunk in the pan and the oil will be cloudy from the clutch material, but this was not the case. I take the accumulator off, flip the piston over, put it back together with the same purple spring, and put everything back together.

Not only has the 1-2 shift seriously improved, but the noise and "slippage" is totally gone. It's acting like a real transmission now. My one (well, two) question(s) is(are),

Does this make sense?

Could the 1-2 accumulator have caused a low-line-pressure condition in the condition it was, due to valving and calibration within the transmission?

Am I talking out of my butt?

Blue Bowie has some good info there
I am bowing out of that one.
But if you need more info on it here is a good trans link.
http://www.batauto.com/cgi-bin/Forum/db_TalkToMeV2.cgi?forum_name=trans

I'm not sure what means you might use to verbalize, and really don't need the details...

Back to the trans, IF the 2nd accumulator piston were installed incorrectly, flipping it would make sense. Installed upside-down (if it's even possible) would tend to reduce the volume of oil available to drive the 2nd apply piston - The spring rate controls the apply pressure.

Unless this a a '93-later trans, the accumulator piston should have an extended hub that is supposed to face the spring side. If you were to flip the piston away from the spring, the piston could not travel as far downward (away from the valve body) and some more oil would always be retained in the accumulator cover. This would reduce the volume of oil necessary to build pressure, but would also reduce the volume of oil available to drive the 2nd apply piston when the valve cycled. I would think this would tend to slow the application of the 2nd apply servo, not speed or firm it up.

How was your's installed?

I'm sorry about the non-sequiturs above - I was half asleep when I wrote that (and soaking wet from a storm that gave us 2" rain in about 40 minutes)...

The 1-2 accumulator is a bolt-on unit behind the valve body. The piston goes within this cylinder, and is held to the bottom with the spring.

The piston is pushed upwards toward the valvebody during the 1-2 shift (2nd apply). Remember that the servo receives apply pressure, and the accumulator "softens" the apply by taking some of the apply pressure from the servo. If you can somehow limit the amount going to the accumulator, you can have more to the servo.

It (the piston) was installed in the "correct" position (concave area with legs toward spring), and now it is installed in the "incorrect" position. This stiffens the spring rate and lowers the amount of travel. I still consider this to be a "band-aid" until I can get a proper spring.

My original question was if an accumulator that's too soft could cause a pressure rise problem.

O/K/ From your descripton, it sounds like the older version ('87-92) trans.

Perhaps the unobtanium part could be replaced with a Chinesium part - Or was that the initial problem? Actually, you should be able to get the accumulator spring for about $2 in several places:

http://www.bulkpart.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=2&Category_Code=4L60-700R4servo

http://www.redrider.us/700r4_performance_transmission_p.htm (About halfway down the page)

Just about any color spring you want.

MT - Good link. I'll be saving that one.