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Discussion Starter · #1 ·
Alright guys I need a little help. I have a customer with a PG that went to the track and it performed great for 5 runs and then backed up out of the lights. So I had him check the band adj. and it was 3 to 3 1/2 turns out. So I ask him to hook up a gauge on the servo port and 1st gear has 245psi but when you apply the transbrake the pressure drops to 50psi for about 1.5 seconds and then comes back up to 245psi. I've ask him to put it on stands and check the pressure on the shift from 1st to 2nd to see if the pressure drops, but it will be a couple of days before he can get to it. It has a dual ring servo with steel rings and a jw case. I'm wondering if it could be in the valve body. Any help would be thankful.
thanks Steve
 

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mine did they same thing (backing out of the lights ) very goofy it endned up being the front pump on mine was cracked and was not keeping enough pressure applied to the forward band to hold it ?
 

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Generally what you have described is due to a worn pump.
If it is backing up, the band is not applying enough to hold low gear
Sounds like you have plenty of pressure, but your TB action sounds slow if it really takes 1 1/2 seconds to rebound the pressure after application of the TB.
As you tear down, verify the shift spool is indexed properly, the band apply tube in to the servo is in place.
Or the band is completly gone and the adjustment was not done correctly.
Hope this helps.
 

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Discussion Starter · #5 ·
Generally what you have described is due to a worn pump.
If it is backing up, the band is not applying enough to hold low gear
Sounds like you have plenty of pressure, but your TB action sounds slow if it really takes 1 1/2 seconds to rebound the pressure after application of the TB.
As you tear down, verify the shift spool is indexed properly, the band apply tube in to the servo is in place.
Or the band is completly gone and the adjustment was not done correctly.
Hope this helps.
Hey thanks for the help, but what do you mean by verifying that the shift spool is indexed properly.
 

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Hey thanks for the help, but what do you mean by verifying that the shift spool is indexed properly.
I will try and explain, but may be hard with out some pictures.
With the trans pan off and trans in park, the shift spool should be flush with the edge of the valve body. If it is in too deep or too shallow it may not be positioned properly inside the valve body for the correct flow of fluid for the gear selected.
Hope this explanation is not to confusing.
 

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Discussion Starter · #7 ·
I will try and explain, but may be hard with out some pictures.
With the trans pan off and trans in park, the shift spool should be flush with the edge of the valve body. If it is in too deep or too shallow it may not be positioned properly inside the valve body for the correct flow of fluid for the gear selected.
Hope this explanation is not to confusing.
Your talking about the manual valve correct.
 

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Yes, he's referring to the manual valve. They call it the shift spool and we call it the manual valve. Just like they say "tomato and potato" and we say "mater and tater". LOL
 

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Come on Hutch, have you ever had this happen?
Sorry for the delay, I took a week off in 13 years and neglected this free tech forum.

Yes I have had this happen and it is usually caused by improper converter to flexplate clearance causing the pump to get destroyed.
Although it has 245 psi does not mean the pump can keep up when volume demand is increased.
I doubt its the valve body but it could be a blown VB gasket at the reverse feed port if the valve body uses gaskets or someone has not installed the proper VB bolt in the VB at that location (shorter) causing the VB to not seal correctly at the reverse feed port.
The other possibility may be a leak in the governor support gasket causing a leak into the tailhousing area.

Hutch
 

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Discussion Starter · #10 ·
Sorry for the delay, I took a week off in 13 years and neglected this free tech forum.

Yes I have had this happen and it is usually caused by improper converter to flexplate clearance causing the pump to get destroyed.
Although it has 245 psi does not mean the pump can keep up when volume demand is increased.
I doubt its the valve body but it could be a blown VB gasket at the reverse feed port if the valve body uses gaskets or someone has not installed the proper VB bolt in the VB at that location (shorter) causing the VB to not seal correctly at the reverse feed port.
The other possibility may be a leak in the governor support gasket causing a leak into the tailhousing area.

Hutch
I picked up the trans today and the front pump looks great, no gasket on the reverse feed port. But I will make some when putting it back together. VB bolts are correct and has a good seal to the case. I have a aluminum rear governor support with a solid gasket, no problems there also. I'm going to try another VB just to see if it fixes the problem. This only happens when the trans gets HOT! He ran it this past weekend and the trans worked perfect for 2 rounds and then it backed up at the lights. Put a fan under the car and cooled it down and worked for 2 more passes and then backed up again. I will let everyone know after this weekend if that fixes it. Thanks for the help. Steve
 
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