First "Partial" Transmission Oil Change On A 2007 E350 Chassis

We have a 2007 Ford E350 chassis with the 6.8L-V10 engine and the Torqshift transmission of that time.  Our transmission has a secondary fluid filtration system, a bell jar design which I understand was installed for a 2 year period, 2006 and 2007.  Our PC has 38,000 miles and so I thought it would be a good time to change the oil and filters.  I bought everything, 9 quarts of Mercon SP fluid, primary transmission filter, and secondary filter that resembles a roll of toilet paper.

Well I chickened out changing the primary filter in the trans pan after draining the near perfectly clean trans fluid and change only the secondary toilet paper roll filter this first time.  The secondary filter was dark & dirty but not alarming.  It's condition indicated it was doing it's job well.  I will change the main filter and everything else again in 22,000 more miles when the odometer hits 60,000.

I found it interesting how the external secondary filter works.  It is not in-line with the trans oil system but rather taps off the system so some oil gets filtered through it and returned to the transmission while most oil gets cooled through the two external oil coolers.  The paperwork that came with the secondary filter stated that running the vehicle without this filter will greatly increase transmission operational temperatures, damaging the transmission.  It is fine to drive the vehicle with a 100% plugged-up filter, but do NOT use the vehicle with the filter removed.  With a plugged-up dirty secondary filter, the trans fluid would naturally get dirty more quickly.

This is the secondary filter cartridge.


The bell jar is very similar to this, if not identical.  It is mounted on the driver side of the transmission, hanging down in logical fashion.  I wonder why this secondary filter was removed in the years that followed.

Wow!  I have added bypass oil filtration to vehicles, I did NOT know they were on the transmission. Will have to check on mine... neat find Ron! 

https://www.amsoil.com/bypass/how-it-works.aspx

From link:

How Bypass Filtration Works
Bypass oil filtration features a secondary filter with the purpose of eliminating nearly all contaminants from motor oil. Bypass filters have high capacities and eliminate much smaller particles than full-flow filters, including soot. Bypass filters reduce engine wear and increase oil volume, but their high efficiencies mean they also have higher restriction and must be used in conjunction with a full-flow filter.

Bypass filters operate by filtering oil on a "partial-flow" basis. They draw approximately 10 percent of the oil pump's capacity at any one time and trap the extremely small, wear-causing contaminants that full-flow filters can't remove. Bypass filters have a high pressure differential, causing the oil to flow through them very slowly and allowing for the removal of smaller contaminants. It is called bypass filtration because the oil flows from the bypass filter back to the sump, bypassing the engine. This continual process eventually makes all the oil analytically clean, reduces long-term wear and can dramatically extend oil drain intervals.

Several other good tabs to open at the link with more detailed info.

 The paperwork that came with the secondary filter stated that running the vehicle without this filter will greatly increase transmission operational temperatures, damaging the transmission.  It is fine to drive the vehicle with a 100% plugged-up filter, but do NOT use the vehicle with the filter removed.  With a plugged-up dirty secondary filter, the trans fluid would naturally get dirty more quickly.

The reason you cannot omit the second filter is that it is flow limited by design. Being a 'bypass' filter, the flow through it does not go through the cooler(s). If you remove the element, thereby removing the designed flow restriction, too much oil will bypass the coolers. The tranny fluid will go the path of least resistance. Hope that makes sense.

Volkemon,

Your detailed description covers the function of this secondary filter very well.  I find comfort in knowing I have this extra fine particle by-pass filter on my transmission.  Based on it's dirty color, I wonder if I should be changing it more frequently.  Our first 38000 miles of accumulated dirt was not horrible, but maybe it would be better to change that filter every 25,000 miles, just the filter, not the fluid.

BTW, I found Mercon SP fluid sold on-line HERE FOR $11.99 PER QUART but watch carefully of the pop-up menu to get 20% off your on-line order and free shipping to your house.

My 2350 is registered as a 2008, but I believe it is a 2007 chassis.  I will have to check this morning to see if I have one on mine.  Thanks.

The alloy bell jar for the filter is located on the driver side of the transmission, but seen only when crawling under the rig and looking higher up.  There is an unrelated metal bracket preventing you from seeing it unless doing so.  The hex on the bottom is 22mm.  Mine was exceptionally tight, very hard to break loose even though my rig has no corrosion.  If your alloy bell jar is corroded, I imagine you run the risk of bending it's mounting bracket.  If so, using an impact wrench "gently" may break it loose without bending anything.