VALVE GP-RELIEF 6E6283 - Caterpillar

To prevent personal injury when checks are made while the machine is in operation, make sure only approved personnel are on the machine. Keep other personnel off the machine and in view of the operator. Make sure checks are done in an open area.
Note: The parking brakes and the service brakes must be ON, until you are instructed differently.Take note of all "S" and "S" in these checks. Never start the next check until the warnings are read and understood completely.The checks that follow can be used to find many of the problems that are found during the operation of the machine. These checks can also assist in locating the system that has the problem.Check 1
This check will determine the following three items.
The scraper selection spools may be manually moved through all of the positions.
The scraper selection spools may move when the electrical system operates correctly.
The scraper selection spools may move when the hydraulic system operates correctly.
Illustration 1 g00788564
Scraper transmission selection shaftProcedure
Install 8H-8501 Open End Wrench on the scraper transmission selection shaft on the back side of scraper transmission.
As you look at the back side of the transmission, rotate the wrench counterclockwise until the shaft will not rotate. The spools are now in the REVERSE position.
Rotate the wrench clockwise through one detent position (10 degrees). The spools are now in the NEUTRAL position.
Continue to rotate the wrench clockwise. This will shift the scraper transmission through FIRST, SECOND, THIRD, and FOURTH speed positions.
Move the selection shaft back to NEUTRAL after this check is completed.Problem 1
Selection spools will not move.Probable Cause
Foreign material or a defect will not permit movement of selection spools.Check 2
This will show if the scraper retarder will engage and if the retarder will release. This check will also show if the scraper retarder air and oil pressures are good.Procedure
Make sure that air pressure is at normal pressure for operation. Keep the tractor engine OFF for this check. Turn the disconnect switch key for the tractor and the key start switch to the ON position. Do not start the engine.
With the tractor transmission in the NEUTRAL position, start and run the scraper engine at HIGH IDLE rpm.
Move the retarder control lever to the FULLY ACTIVATED position (pull toward the operator). The scraper engine rpm must decrease.Note: Be sure that the transmission oil does not get too hot.
Push the retarder control lever back to the RELEASED position. The scraper engine rpm must increase again.
Decrease scraper engine rpm to LOW IDLE. Stop the scraper engine.Problem 1
Engine rpm does not decrease with the retarder control lever in the FULLY ACTIVATED position.Probable Cause
The scraper retarder does not engage. Refer to "Testing and Adjusting" section of Systems Operation, Testing and Adjusting, "Retarder Operation - Test".Problem 2
Engine rpm does not increase when the retarder control lever is moved from FULLY ACTIVATED to RELEASED position.Probable Cause
The scraper retarder does not release. Refer to "Testing and Adjusting" section of Systems Operation, Testing and Adjusting, "Retarder Operation - Test".Note: The drive axles on the scraper must be removed