TH400 whining

Discussion in 'Transmission & Driveline Topics' started by Coadster32, Apr 23, 2021.

  1. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    Lately my TH400 has been whining. It sounds like I have a blower on the car. It started last year when I redid the heads on the car. At that time, I fixed a crack in the tranny filler tube. I used to keep the fluid level on the lower side, as to not make a mess every time I park. Since then, I had brought the fluid level where it needed to be. I have tried adding more fluid, and then having less fluid, but no change. I confirmed it to be the tranny, when I had all the belts off over the winter and fired it up...the noise was still there. It happens in P, N, and all drive gears. The noise subsides as the car gets up to temperature and I drive it a bit, but is still there. Also, the car is slow to shift into the next gear when cold, but works fine when it warms up. This is a manual valve body transmission, so the shift should be pretty instant. I just had the front end aligned, and had them listen as well, and they think that it may be the pump making the noise.

    After "researching" this on internet, a common issue is that the pickup filter may be clogged, and cavitating, or starving the pump. Some say to swap the paper type filter to a screen type filter. Another might be the O-ring at the top of the pickup tube. One more might be the bearings on the input shaft. I feel that I can rule out the converter, as it's been in the car for about 2-3 seasons now, and hasn't given me a problem yet. I ordered up a new pan gasket, pickup O'ring, and bought both types of filters. It should all be here tomorrow, and plan on doing this on Sunday. I will be reusing the fluid, as it is garage kept, still looks good, and 2-3 season old with about 1500 miles on it, Obliviously will be filtering it a few times before returning it to the tranny. This is an easy, non expensive thing to go after first, so that's where I'm heading.

    Any other insights on this would be great. Is there something else I should check out while I'm in there? My concern is about any other damage that may occur if the problem persists, or that may have already happened.
     
  2. camaro71/holland

    camaro71/holland Veteran Member

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    Check/change the two obvious things like you're already planning and report. My first thought was/is the pump is going south, because it happens in all shifter stands. But hopefully it's the filter that's causing the pump to caviate.
     
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  3. Coadster32

    Coadster32 Veteran Member Lifetime Gold Member

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    Got to swapping out the filter and pickup tube O-ring this weekend. The filter media is only supposed to be visible in the pickup area, and not in the oval port where the fluid flows into. You can see the differences between the screen, and the paper type filter in this first picture.
    20210424_192619.jpg

    The filter I pulled out must have been stopped up somehow. I let the fluid drain for quite some time, and when I pulled off the filter, the tube spewed out alot more fluid. You can see the filter shifted to the oval port in this picture here.

    20210425_184626.jpg

    I filtered the fluid coming out initially, filtered it again from the catch bucket into pouring containers, and filtered it again going into the funnel back into the tranny. Fluid looked good. Cleaned the pan real good with our shops parts washer. O'ring was intact, but put the new one in anyhow. Whining noise didn't return, and cold shifting was back to being perfect. I went with the screen type filter this time, just to try something different. I'm pretty certain the other filter would have worked fine as well.

    I am glad I did this first...and relieved because I feel that you have to win sometime. It also backs up the "do the easy things first" approach. Thank you for chiming in Camaro71
     
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  4. mallard

    mallard Veteran Member

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    Congrats on the fix.
     
  5. camaro71/holland

    camaro71/holland Veteran Member

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    100x on start with the easy fix. Good job :bowtie:
     
  6. cadillac_al

    cadillac_al Veteran Member

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    TH400 filters actually catch and trap sediment. TH350's do not. TH400's do need a filter change once in a while. TH350's just let sludge accumulate in the pan. Easy fix this time.
     

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