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 Post subject: Powerglide problems
 Post Posted: Sun Dec 30, 2007 10:37 am 
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Pulled the glide out of my footbrake car, about 300 passes on it. It was working perfect the last race of the season. I was expecting only new seals and cleanup. Instead I have dark, slightly burned forward clutches and heat marks around the drum, what did I do wrong. My other glide at this many passes using a transbrake has always looked new. Is this a lube problem, burnout technique? Pressures were in spec. when I built it, didn't check before I pulled it, didn't think I had a problem. I use about .010 per friction and that is still in spec.
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Greg

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 Post Posted: Sun Dec 30, 2007 10:57 am 
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Greg, how many clutches are you using in this and how much hp?  Also, any possibilty that the band is a little too tight?

George


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 Post Posted: Sun Dec 30, 2007 11:41 am 
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It has 5 clutches George, it only runs 6.80s , I don't know how much horsepower that would be. I wondered if the band was dragging on the 1-2 shift. I think it was set around 3-1/4 out from snug.

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 Post Posted: Sun Dec 30, 2007 1:37 pm 
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StrokerCamaro wrote:
It has 5 clutches George, it only runs 6.80s , I don't know how much horsepower that would be. I wondered if the band was dragging on the 1-2 shift. I think it was set around 3-1/4 out from snug.


I'm sure Ken will give his opinion when he sees this but it sure sounds like to me the band is dragging.  Although 3 1/4 turns should be enough.  I usually set mine at 3 1/2.

George


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 Post Posted: Sun Dec 30, 2007 3:29 pm 
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I know people that run them tighter than that O:) I do think the band caused all of the problems. Looks like too loose would cause slippage at the line also. Am I thinking correct on that also?

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 Post Posted: Sun Dec 30, 2007 3:33 pm 
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The stuff it shows is from slipping so it's either a pressure problem or possibly lube depending on what you are using.  What kind of fluid was in it?

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 Post Posted: Sun Dec 30, 2007 4:22 pm 
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Ken0069 wrote:
The stuff it shows is from slipping so it's either a pressure problem or possibly lube depending on what you are using.  What kind of fluid was in it?


It had dextron 3 in it, never got around to the tractor fluid.

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 Post Posted: Sun Dec 30, 2007 4:38 pm 
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Ken0069 wrote:
The stuff it shows is from slipping so it's either a pressure problem or possibly lube depending on what you are using.  What kind of fluid was in it?


I agree it's from slipping but my thought process is that if the band is too tight for a clean release, at some point it will slip prior to releasing.  By the same token, the high gear clutches will slip some upon application if working against the low gear band.  His comment "slightly burned" would indicate to me it's happening in a very short period of time right at application/release.  Just a possiblity but as you say it could be a pressure problem too.  Don't you just love it when your "student" gets to diagnosing this stuff?? =;  =;

George


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 Post Posted: Sun Dec 30, 2007 5:51 pm 
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Hey George, your guess is probably as good as mine at this point.  Not a problem Bubba.

The band adjustment is close enough to be OK, IMHO.  

At any point did you have problems with the transmission not going into high gear, ie, was the shifter ever out of adjustment?  BTW, this only has to happen once to possibly hork up stuff.

Pressure holds the servo in to apply the low band.  Pressure also pushes the piston out to apply the direct clutch.  If pressure is down then both will or can slip.  

You have to remember that there are two circuits to the servo.  One is apply and the other is balance?  The reason I say "balance" is because hyd pressure isn't what actually moves the servo piston away to release the band.  That large spring actually does that when hydraulic pressure is "equalized" on both sides of the servo by the direct clutch apply circuit.  The balance side isn't fully pressurized until the piston has applied in the direct clutch.  At that point both move at the same time, which makes the shift.  

So, having said all that, I'm still leaning toward the pressure thingie and the clincher is you really don't know which place to look.  Could be the pump or could be the relief valve in the valve body.  

Oh, and if you HAVE to run regular ATF, please use TYPE F in the future. ;-)

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 Post Posted: Sun Dec 30, 2007 9:40 pm 
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At any point did you have problems with the transmission not going into high gear, ie, was the shifter ever out of adjustment?  BTW, this only has to happen once to possibly hork up stuff.


There was no known problems with the trans or shifter. It probably had 300 plus passes. I am switching my silver car over to the tractor fluid. I will have a good hard look at the pump and gears. I will look at the PR valve and spring. Thanks Guys...especially Ken, who probably don't feel well enuff to be thinking about this stuff.
Greg

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