6420 problem

[Hilltopper]

My nephew has a 6420 that the transmission warning light comes on. He changed the oil and the filters it made no difference It has maybe 1500 hours on the unit It is a quad tranny. All wire are in place. It has no visible or audible problems. Do the warning senders on these give trouble ocassionaly? I was wondering if this could be the solution. Where is the place to check trans pressure located? Is it a metric fitting? I have not been able to check on it. He is using the 4255 to plant with to busy to go to the 6420 it is parked.

 

[Tx Jim]

I would think it has a test port to check trans psi. If you can't find a test port remove sender and install a gauge in that port. I suppose it shows no "codes"?

 

[ryan3020]

It has test ports that have a quick coupler style fitting. The first thing you need to do is find out what codes its throwing. I believe the owners manual will tell you how to retrive them. With that low of hrs on it im betting its an electrical problem, maybe a bad sensor or loose/corroded connector.

 

[MightyReek]

Ok, you may have one of two problems.

The "good" problem is the sensor damaged. Some older types used to malfunction. The sensor is located above the transmission filter (there are two sensors, this is the one that is above the other. Ref. RE212876).

The "bad" problem is if you actually have low pressure in the system...

There's a test port near the engine-transmission shaft, it's labelled SYSTEM.
You should have 12-14BAR there at 1500 RPM.
Remember to measure the pressure when the light bulb is flashing, and warm the transmission oil.

If the pressure is low, you may try to figure where's the leak.
If it's always low, you'll probably have problem in the transmission pump itself, or in the transmission front cover.

If it's not always low, you may try a few clutches and brakes to see when the pressure falls:
PowrQuad's 1, 2, 3, 4
Forward
Reverse
FWD
PTO
Diff lock

When you find the one that makes the pressure fall, you have your problem found...