PDF User Manual

COA-COA-12025 

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08/31/2018 

 
 

Figure 1. 

 

 

INSTALLATION INSTRUCTIONS FOR POWERGLIDE 

PRO TREE LOW AND HIGH GEAR BRAKE KIT (#12025)

 

 

Thank you for purchasing a Coan Racing performance product.  Since 1976, Coan Engineering has been 
the leader in hi-performance race transmissions and converters.  Our ongoing research and development 
assures that you have purchased the best products available.   
 

* COMMITMENT * PERFORMANCE * RELIABILITY * 

* A WINNING COMBINATION * 

 
Caution: Trans-brake can be activated in low and high gears.

 It is imperative that you install a 

power 

interrupting device

 between trans-brake solenoid and 12V source. A power-interrupting device will 

totally disable trans-brake solenoid for a predetermined amount of time.  This device will prevent 
accidental re-engagement of the trans-brake in high gear during the run.  Re-engagement of the trans-
brake in high or low gear will cause the rear tires to lock up. 
 
The scope of these instructions will be aimed at the installation of this kit and it is assumed that the 
transmission will be rebuilt properly to work with this valve body.  If necessary refer to a transmission 
manual for detailed instructions on disassembly and reassembly of the Powerglide transmission. 
 
The transmission needs to be completely disassembled, including the reverse piston, and thoroughly 
cleaned. 
 

1.  Next it is necessary to drill the reverse passage.  

With a 3/16” drill, drill all the way through the case 
as shown [(Figure #1, & Figure #2,) (2 places.)]  
Then, from the inside, of the case, open up the 
holes to 13/32”, until the drill intersects the ports 
from the bottom of the case (Figure #3).  

 
2.  Now drill 13/32” hole from the bottom port, until you 

intersect the previously drilled holes (Figure #4.) 

 



  After deburring the holes and cleaning the case, 

reassembly can be started. 

 
3.  It is recommended to stack the reverse pack with 5 

frictions and 6 steels.  With a reverse piston 
thickness of .900” you should get a clutch pack 
clearance of .050” - .060” which can be checked 
through the inspection hole in the bottom of the 
case.  Replace the stock return springs with the 
springs furnished in the kit and reassemble the 
transmission. 

Figure 2. 

 

COA-COA-12025 

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5.  Install new valve body.  You must have the brake 

valve and spring in its bore as you put the valve 
body in place.  

The brake valve will not fit through 

the hole in the case.

 Make sure the

 

manual 

selector valve is properly aligned with linkage pin.  
Tighten valve body bolts to 132 in-lbs 

 
6.  Install solenoid and gasket/o-ring. 
 
7.  On a shorty transmission, install a gasket 

between shorty plate and case.  The block off 
plate is 

not 

required.  On a standard length 

transmission, install block off plate in between 
rear support and case without gasket.  This will 
prevent pressure leak in the reverse apply 
circuits.  An improper seal between the case and 
rear support will cause trans-brake failure.   

 
8.  Install filter and tighten bolts to 36 in-lbs. 
 
9.  Reinstall pan and tighten bolts to 72 – 108 in-lbs. 

 

10.  Proper low band adjustment is crucial.  Tighten 

adjusting screw to 70 in-lbs.  Loosen screw 3 ½ 
turns and tighten lock nut. 

 

11.  Check and maintain proper fluid level 

 



 

*NOTE:  

Cooler fittings should never be plugged.  

If a cooler is not used, connect the lines 

together with a loop. 

 
After assembly of transmission is completed, necessary wiring for the solenoid can be done.  Position the 
momentary switch on the shifter or wherever it is comfortable.  Run a wire from lead of switch to a twelve 
volt source, the other lead is connected to the red (+) wire on the solenoid.  The black (-) wire on the 
solenoid should be connected to a good clean chassis ground.  Be sure to use good wiring connections. 

 

Adjustable Regulator Pre-Set at 235-240 PSI, Approximately 8 PSI Per Turn. 

Adjustable operating range is 185 min. - 290 max.  PSI. 

 
 

Your Pro Tree Low and High Gear Valve Body is designed to have a reverse lockout safety feature.  To 
engage reverse, the shifter must be placed in reverse and the trans-brake switch must be depressed 
simultaneously.

 

 

Pro Tree 5 Kit Components

 

1.  Valve body assembly with manual valve. 
2.  Modulator gasket/o-ring. 
3.  Solenoid. 
4.  Pro Tree brake valve and spring. 
5.  Rear block off plate. 
6.  Rev. clutch springs. (17) 

 
If you have any questions regarding the proper installation and/or operation of a Coan Racing product, 
please call (765) 456-3957.  You may also fax us at (765) 456-3960, or e-mail at 

coan@coanracing.com.

 

 

Figure 3. 

Figure 4. 

 

COA-COA-12025 

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Warranty 

 
Coan Engineering offers a limited warranty covering all new products for ninety days and all repair service 
for thirty days from the original date of purchase to be free from flaws in material and craftsmanship.  The 
warranty is non-transferable.  Under no circumstances will Coan Engineering extend its warranty to 
products, new or repaired, which have been abused, misused, or incorrectly installed.  Disassembly of 
any product by means other than a Coan Engineering technician will void any potential warranty.  All 
warranty claims must be accompanied by the original invoice and are subject to the approval of Coan 
Engineering. 
 
The above stated warranty 

does not include

 any shipping charges or labor charges for installation or 

removal of any Coan Racing product. 
 

Liability 

 
In no manner, neither written nor implied, does Coan Engineering accept liability for consequential or 
incidental damages to person or property resulting from the use or misuse of its products.  Product failure 
occurring within the stipulations of the warranty policy will be dealt with explicitly under those particular 
guidelines.