Spindifferent
Gold Member
This resolved my issue and I thought I would write this up for the community.
I have a model year 2005 JD 3520 that was displaying an Err 06 when moving in either forward or reverse.
The 3520 Operator's Manual says that this is a "MFWD Speed error caused by "No signal at MFWD speed input and that this would cause "No cruise function; Loss of performance".
After some internet searching on that error code, I found that the likely issue was a bad "MFWD Speed Sensor". It appears that this speed sensor part has gone through several part number changes over the years:
On my tractor, the part number noted on the speed sensor cable is 728086-01. I suspect that this is the original part from 2005.
Other part numbers for the speed sensor are LVA17409, LVA11184, and TA11587. TA11587 is the current part number as of September 2020.
You can purchase a new speed sensor at many places like eBay, Amazon, Greenpartstore, and directly from Deere.
On my 2005 JD 3520, the MFWD Speed Sensor is located on the upper right hand side of the transmission while sitting in the seat. Look under the right foot platform under the forward/reverse pedals and you will see a 6"-8 3-wire cable with a 3 pin connector on one end and the actual speed sensor bolted into the sensor port of the transmission by one bolt.
To remove the speed sensor, unclip the connector at one end of the cable and then use a 10mm socket to remove the bolt from the sensor port on the transmission. Note that hydro fluid will spill out of the sensor port, so be prepared to use a finger to plug the port while you quickly remove the old sensor and then insert the new one.
Once the bolt is tightened down, clip the speed sensor cable connector into the existing connector and then test to see if this resolves the Err 06.
In my opinion, this cable is connected to the transmission in a really bad location because the cable is exposed to whatever may scrape along the bottom of the tractor that could catch the cable and break it. The only way to secure that cable is to zip-tie it to another cable, but this still leaves a lot of the cable exposed. This may be different on more recent JD 3520 units and hopefully so on the current 3 Series.
Attached is a photo of the new part number next to the old part itself and a photo of the location of the speed sensor port with a new speed sensor installed.
I have a model year 2005 JD 3520 that was displaying an Err 06 when moving in either forward or reverse.
The 3520 Operator's Manual says that this is a "MFWD Speed error caused by "No signal at MFWD speed input and that this would cause "No cruise function; Loss of performance".
After some internet searching on that error code, I found that the likely issue was a bad "MFWD Speed Sensor". It appears that this speed sensor part has gone through several part number changes over the years:
On my tractor, the part number noted on the speed sensor cable is 728086-01. I suspect that this is the original part from 2005.
Other part numbers for the speed sensor are LVA17409, LVA11184, and TA11587. TA11587 is the current part number as of September 2020.
You can purchase a new speed sensor at many places like eBay, Amazon, Greenpartstore, and directly from Deere.
On my 2005 JD 3520, the MFWD Speed Sensor is located on the upper right hand side of the transmission while sitting in the seat. Look under the right foot platform under the forward/reverse pedals and you will see a 6"-8 3-wire cable with a 3 pin connector on one end and the actual speed sensor bolted into the sensor port of the transmission by one bolt.
To remove the speed sensor, unclip the connector at one end of the cable and then use a 10mm socket to remove the bolt from the sensor port on the transmission. Note that hydro fluid will spill out of the sensor port, so be prepared to use a finger to plug the port while you quickly remove the old sensor and then insert the new one.
Once the bolt is tightened down, clip the speed sensor cable connector into the existing connector and then test to see if this resolves the Err 06.
In my opinion, this cable is connected to the transmission in a really bad location because the cable is exposed to whatever may scrape along the bottom of the tractor that could catch the cable and break it. The only way to secure that cable is to zip-tie it to another cable, but this still leaves a lot of the cable exposed. This may be different on more recent JD 3520 units and hopefully so on the current 3 Series.
Attached is a photo of the new part number next to the old part itself and a photo of the location of the speed sensor port with a new speed sensor installed.
