Powerglide Issues

sc3912 · 05-28-2011, 07:16 PM

I got a problem with my glide. Dont know what would be relevent info, so bear with me if I give more info than needed. Dedenbear case, Coan pro brake, stock pump and Coan converter. Worked fine last year. Took it to my trans guy this winter so I could send the case in for a recert. Put it back in the car and was going to change from shift by rpm to shift on time. First pass transbrake worked fine but car broke a rocker arm. Fixed that, and when I went to back away from the trailer, the car wouldnt go into reverse. Kept wanting to go forward with the trans brake button pressed. Had low and high but didnt feel right. Would not engage the trans brake in low and just kept moving forward. Checked solenoid and was working correctly. Checked pressures at the port in the case and the plug in the servo. Transbrake engaged in low or reverse........barely moved the gage at idle and about 60 lbs at 2000. In the servo port, I had the same pressure readings, barely any at idle and around 60 at 2000 when I had the trans in either low or high. I took the trans back to my guy and we pulled it apart. Everything air checked ok, no signs of anything wrong or broken. Moved the valves in the body and in the pump, but did not disassemble the valves. The gears in the pump were good. Rechecked everything and thought we found a voltage problem to the solenoid, that might not have allowed to engage all the way. Didnt think that was the actual cause of my pressure problems, but put it back in the car anyway. Still does the same thing. I am sure we are missing something simple and was hoping for a little advice and a different perspective. I didnt have the converter checked , nor have another one to try, but a converter shouldnt cause a problem like I am having, would it?

SST 3728 · 05-29-2011, 10:19 AM

It should have at least 180 psi at idle, and around 225 above 1800rpm, sounds to me like the pressure bypass is stuck open in the pump or the roll pin holding it in has broken.

63corvette · 05-29-2011, 12:06 PM

First thing to check is your shifter linkage and if it is set correctly.
Always setup the shifter in high gear then check the other gears and if the pin into the trans linkage goes in freely in all the gears.
I have seen this before. Being off just a little is a big thing when the port sizes in the valve body are so small.
Good Luck with the fix. These things can be so frustrating.
Rick Cates

sc3912 · 05-29-2011, 05:55 PM

Found the problem, like I said, something simple. We decided to try the valve body. Had an identical one in an old spare I had. When he disassembled the replacement valve body, he noticed the pressure valve was all the way to the end of the bore, where as the problem one was about a 1/4 inch from the end. He had noticed that when he took it apart the first time, but the valve moved ok and always came back to the same position. He assumed that maybe that was how Coan did it back in the day, as everybody used to do things a little different back then, to arrive at the same result. Couldnt really find a reason why the other valve was acting up, so we put the spare valve body in. 180 lbs of pressure at idle and everything works fine. Thanks for the help.

63corvette · 05-30-2011, 10:12 AM

Good to hear you found the issue.
There is always something new and to learn about a race car....
Rick Cates

05-28-2011, 07:16 PM	#1
sc3912 Junior Member Join Date: Apr 2006 Location: illinois Posts: 99 Likes: 0 Liked 6 Times in 1 Post	Powerglide Issues-Fixed I got a problem with my glide. Dont know what would be relevent info, so bear with me if I give more info than needed. Dedenbear case, Coan pro brake, stock pump and Coan converter. Worked fine last year. Took it to my trans guy this winter so I could send the case in for a recert. Put it back in the car and was going to change from shift by rpm to shift on time. First pass transbrake worked fine but car broke a rocker arm. Fixed that, and when I went to back away from the trailer, the car wouldnt go into reverse. Kept wanting to go forward with the trans brake button pressed. Had low and high but didnt feel right. Would not engage the trans brake in low and just kept moving forward. Checked solenoid and was working correctly. Checked pressures at the port in the case and the plug in the servo. Transbrake engaged in low or reverse........barely moved the gage at idle and about 60 lbs at 2000. In the servo port, I had the same pressure readings, barely any at idle and around 60 at 2000 when I had the trans in either low or high. I took the trans back to my guy and we pulled it apart. Everything air checked ok, no signs of anything wrong or broken. Moved the valves in the body and in the pump, but did not disassemble the valves. The gears in the pump were good. Rechecked everything and thought we found a voltage problem to the solenoid, that might not have allowed to engage all the way. Didnt think that was the actual cause of my pressure problems, but put it back in the car anyway. Still does the same thing. I am sure we are missing something simple and was hoping for a little advice and a different perspective. I didnt have the converter checked , nor have another one to try, but a converter shouldnt cause a problem like I am having, would it? __________________ Jeff Spierling 2007 Div. 3 S/C Champion Last edited by sc3912; 05-30-2011 at 03:18 PM.

05-29-2011, 10:19 AM	#2
SST 3728 Junior Member Join Date: May 2004 Location: Mansfield, OH Posts: 72 Likes: 0 Liked 0 Times in 0 Posts	Re: Powerglide Issues It should have at least 180 psi at idle, and around 225 above 1800rpm, sounds to me like the pressure bypass is stuck open in the pump or the roll pin holding it in has broken. __________________ Alex Miller

05-29-2011, 12:06 PM	#3
63corvette Senior Member Join Date: Mar 2007 Location: Canyon, Tx Posts: 535 Likes: 117 Liked 281 Times in 88 Posts	Re: Powerglide Issues First thing to check is your shifter linkage and if it is set correctly. Always setup the shifter in high gear then check the other gears and if the pin into the trans linkage goes in freely in all the gears. I have seen this before. Being off just a little is a big thing when the port sizes in the valve body are so small. Good Luck with the fix. These things can be so frustrating. Rick Cates

05-29-2011, 05:55 PM	#4
sc3912 Junior Member Join Date: Apr 2006 Location: illinois Posts: 99 Likes: 0 Liked 6 Times in 1 Post	Re: Powerglide Issues Found the problem, like I said, something simple. We decided to try the valve body. Had an identical one in an old spare I had. When he disassembled the replacement valve body, he noticed the pressure valve was all the way to the end of the bore, where as the problem one was about a 1/4 inch from the end. He had noticed that when he took it apart the first time, but the valve moved ok and always came back to the same position. He assumed that maybe that was how Coan did it back in the day, as everybody used to do things a little different back then, to arrive at the same result. Couldnt really find a reason why the other valve was acting up, so we put the spare valve body in. 180 lbs of pressure at idle and everything works fine. Thanks for the help. __________________ Jeff Spierling 2007 Div. 3 S/C Champion

05-30-2011, 10:12 AM	#5
63corvette Senior Member Join Date: Mar 2007 Location: Canyon, Tx Posts: 535 Likes: 117 Liked 281 Times in 88 Posts	Re: Powerglide Issues Good to hear you found the issue. There is always something new and to learn about a race car.... Rick Cates