Turbo 400 filter(s)

[Bright Idea]

Just to share my TH 400 filter and fluid change experience. TH 400 , 90 Suburban right at 200,000.
Drug it out of a barnyard in early JAN. Have been going thru all the usual stuff and when I got to the transmission fluid /filter change I learned a few things. Bought a NAPA filter and gasket. Drained and cleaned the pan replaced the o ring on the pickup tube and installed the new filter with a washer on the backside between the spacer and the new filter. This stabilizes the filter a bit as without it really flops around. Most information I found indicated the flopping around is normal. Buttoned up the pan and refilled with fluid. Approximatelty 5 1/2 quarts will get it to normal level. Upon startup i hear what sounds like a pump running dry, this went away in about 30 second to a minute. During the day intermittently driving this noise did not exist. After sitting overnight it would make the pump noise. After researching I decided that possibly the o ring on the pickup tube wasnt seated or the tube into the grommet on the filter for some reason was not tight. I bought a new filter and gasket and went thru the process again this time taking what I thought was a bit more care. Cold startup exact same noise form the pump. I remembered that there was an retired GM Service Mechanic that I know casually so I decided to see if he had any suggestions. The first thing he asked was what I was using for a filter ? I told him the standard NAPA filter /gasket kit. He asked if I knew if it was a screen or fabric filter and I knew it was fabric. He asked if I had the first replacement and I did, so I took it to him. Instantly he said the pump cant pull thru that material fast enough on cold startup and the noise is exactly what I had thought. He said that I need to find a filter with either a brass or stainless screen rather than the fabric. No one locally, could come up with anything but fabric or paper filter medium. I found filters with brass screen on ebay. I installed the filter a couple of days ago and the pump noise is gone. He said that prolonged use of the paper/fabric filters will eventually ruin the pump. He said that despite the claims that filters meet OEM Specs that is not always the case anymore. He said that the claim that the filter medium exceeds OEM spec can be very misleading and reduces the volume that is able to flow thru a system that needs a specific volume. He went on to say that there is no proof but he believes that with the advent of the drive up oil change places that usually use a house brand filter that is produced offshore at a very significant cost savings and the Specs were given little or no consideration in all likely hood have been the cause of many lack of lubrication failures in engines and transmissions. Normally caused by using a filter that is too restrictive for the application. Another case of " more not necessarily being better" Just a bit of information that may keep someone else from changing the fluid and filter 3 times. I do have very new looking red fluid.

 

[CorvairGeek]

Had an AutoZone filter do that on my T400 too. Had used NAPA fabric filters in the past with no problem. Most recent have been AC Delco. I understand as well they very sensitive to flow.

 

[HotRodPC]

It's likely not at the filter end. It's common to need 2 O rings up top where there tube goes into the case. It's very possible you only have 1 O Ring there and it's partially sucking air instead of fluid. When it warms up a bit and the O Ring swells then it's OK. See if you have 2 O Rings and maybe give it a try.

But in any case, if you want to go screen filter anyway and check the O Rings while you swap filters, here's the filter from the trans parts supplier I use most of the time.

http://www.transmissionpartsusa.com/TH400_Transmission_screen_filter_p/460-000046922.htm

 

[CorvairGeek]

It's likely not at the filter end. It's common to need 2 O rings up top where there tube goes into the case. It's very possible you only have 1 O Ring there and it's partially sucking air instead of fluid. When it warms up a bit and the O Ring swells then it's OK. See if you have 2 O Rings and maybe give it a try.

But in any case, if you want to go screen filter anyway and check the O Rings while you swap filters, here's the filter from the trans parts supplier I use most of the time.

http://www.transmissionpartsusa.com/TH400_Transmission_screen_filter_p/460-000046922.htm

That's good to know. I've only ever used a single O-ring from the kits, but only had one that seemed to be a problem, oddly the only cheap filter I purchased.

 

[Bright Idea]

I have used 2 o rings in all 3 changes and and was careful that the tube was well seated.
The only thing that changed the situation was the screened filter. I believe that sources of filters that the different retailers use change from time to time and that would cause something to work this time and possibly not the next time if the manufacturing source had changed.
Hot RocPC the filter that you have shown your source for is a brass screened filter. This is what changed my situation for the better.

 

[Matt69olds]

2 o-rings on the filter tube is a common practice. I don’t care for the fiber filters for exactly the reason you have discovered. I think the fiber filters do filter better, but at a cost of fluid flow. Make sure there is a magnet in the pan, put a brass filter in, chances are the noise will be gone.

 

[Bright Idea]

Agreed, they likely do filter better, but at the cost of transmission damage in the long term. I have put the screened filter in and the noise is gone. Pan is extremely clean with a good magnet. After 3 changes of about 5.5 quarts each time within 500 miles the fluid is very clean as well.

 

[Matt69olds]

Once the fluid is clean, if the trans doesn’t slip it should stay pretty clean. Unless something is slipping or wearing out, there shouldn’t be anything to cause debris in the pan. Normal clutch and bushing/thrust washer wear won’t amount to crud.