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Ask Dan Your Own Question
Dan, Technician
Category: Construction and Road Equipment
Satisfied Customers: 5408
Experience:  17+ yrs. shop and field experience with all major brands of heavy equipment and trucks - 1995 WyoTech graduate.
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I have a Cat 420D backhoe with automatic shift transmission

Customer Question

I have a Cat 420D backhoe with automatic shift transmission that has plenty of pushing power into piles but won't pull a grade on road. It has boost pressure and fuel pressure. Leaning towards a torque converter or trans issue. Any ideas
JA: What is the complete model and serial number of your machine?
Customer: serial number 420DITBLN13139
JA: Anything else you want the equipment mechanic to know before I connect you?
Customer: Operator says once in a while it is fine but for most part it is dead on hills and it rpms to 2000
Submitted: 4 months ago.
Category: Construction and Road Equipment
Expert:  Dan replied 4 months ago.

Hi my name is***** will be glad to try to help. Let me know what you have for full RPM no load. Then do a hydraulic stall ( HIGH RPM one function deadheaded) Record the RPM... Do the same with just the transmission in 4th gear, forward neutralizer disabled High RPM against the brake and record RPM. Then do both hydraulic and transmission stall at the same time. Record RPM. Let me know the values

Expert:  Dan replied 4 months ago.

Remove and inspect the transmission filter for metal/debris indicating an internal failure occurring. Also check the transmission suction screen for debris indicating a problem. Look for discoloration and burnt smell in the oil. Let me know

Customer: replied 4 months ago.
Hi Dan and thanks for attempting to help me diagnose this thing. Did no load full RPM 2100. Hydraulic stall with lift cylinders full extended 2100. As for a stall test the lever is in 4th but with it being full automatic it is in low gear but runs to 2000. oil smells good haven't pulled filters yet. But as a note it doesn't feel like a slipping clutch or anything like that it rpms but has no power going up small grade on highway and seems to be in 4th gear at that point. Thanks, Paul
Expert:  Dan replied 4 months ago.

Thanks for the update Paul. Id cut open the filters and have a look at a sample once the excess oil is squeezed out in a vise. If clean the next step is to get some test gauges on this and verify if your pressures are in specs per the shop manual.

Expert:  Dan replied 4 months ago.

Hi, Did you get this resolved?

Customer: replied 4 months ago.
no just spent $1000 for manual which we didn't have and reason I tried this site
Expert:  Dan replied 4 months ago.

Where are you with this now? Are the pressures in specs? Find any debris in the filter and oil?