66 TH400 trans fluid coming out of dipstick tube

[Chuck Swanson]

I proactively changed the pan and filter on my '66 transmission.  Drove OK after the filter change, but now it starts pouring out fluid from the dipstick.  Researching online, saw that this could be caused by air getting in the trans.  The fluid coming out is foamy, and it pours out when I take the dipstick out (like 1/2 quart).  I believe I took out the old O-ring when changing filter, but research shows maybe an old o-ring is stuck, and it's sucking air.    I don't see any leaks coming from the pan, but did have to replace one of the bolts that was striped when replacing pan, and installed a longer bolt (but don't see any cracks).  When warmed up, shows low on dipstick, and I need to add fluid to move the car as it won't drive of course when fluid too low.  I also saw in research the vent may be clogged.  Any ideas?  Trans was fine before I did the filter change (and line replacement)

Thanks, Chuck

[TJ Hopland]

Slightly low should not cause foam or no go at all.   If its sucking air that would cause the foam which would cause the no go so I would go after that filter and O ring thing.   I don't remember if its the 400 or not but I think the filter can also be damaged by the O ring issue like it may get crushed by the pan?   So maybe pick up another kit so you know you will be covered.    Do you still have the old filter to compare to make sure the new one is the same height and such?

[bcroe]

Certainly the TH400 is vented by a small tube at the top.  I could
imagine a problem with the old style filter, do check that all out. 

I have never had such a problem with the common 68 up style
filter.  These can be retro fitted with a pickup tube and 68 up pan,
the problem is the bolt holding the filter in place.  The original
valve body can be drilled and tapped for this, a bit tricky in a
car to keep filings out.  Another way is swap the valve body to
68-mid 70s. 

If a filter can not cure it, I think the trans must come out.  If it
has never been refreshed, it is WAY OVERDUE for at least the
soft seals, though the hard parts might be fine with lower mileage. 
Do take care to keep the trans an original 66 switch pitch, which
most shops do not understand.  Bruce Roe

[Poncholover]

It is also a classic sign of overfilling.

[Chuck Swanson]

Thank you all!   Yes, initially overfilled, then had to use suction pump to remove after overfill.  Then it wouldn't move as it was too low.   I may not be letting it warm up all the way before checking and filling.  Before swapping the filter again, should I just let the car get warm idling after starting, up to temp maybe 10 mins, then fill to dipstick full, or drive a short distance while warming up and then fill?  Since the filter change, car has only been drive .5 miles on my long driveway only.  Thanks, Chuck

[wheikkila]

Good Evening
If it worked before the filter and fluid change. I would thing something is wrong with the filter. There should be a plastic tube that the filter slides on. There is a oring on the top and make sure the tube is not cracked.
Good Luck   

[2manycars]

Since everything was ok before the change, something must be up with that filter. I agree with the others who have suggested purchasing another filter kit, drain the unit, and pull the pan and filter. Check very carefully, o ring placement, and feed tube. Make sure the bottom of the pan has not been pushed in.

Hope it goes well.

[savemy67]

Hello Chuck,

You would be surprised at how sensitive a transmission is to correct fluid level.

By all means, let the car warm up - 10 minutes should be OK.  Be sure the car is on level ground - no more than an inch of incline over the length of the wheelbase.  I would also shift the selector through each position and hold each position for three seconds.  Do this twice through the full range of the selector.  You are trying to get the fluid to flow through as many hydraulic circuits as possible,  Check the dipstick and adjust as needed.

The replacement filters do not fit as well as the originals.  Check that the pick-up is close to the pan when the pan is installed.  Some replacement filters do not align the pick-up correctly.

Respectfully submitted,

Christopher Winter

[fishnjim]

Sounds like Chuck is learning or messed up depending on your view.   Just joking.   a fixbroke job?
I won't go into my favorite saying as some others are picking up on it.   
If the vent is blocked, it has no other place to go.   Normally, it should escape the vent before the fill tube.
I never had any trouble out of a t400, a very robust trans as witnessed by it working before maintenance.  Wish I had a few spares.   There's a few schools on trans, some say don't touch it, others 50-75K between fluid/filter changes.   I use the higher value, if subject to load, like towing/hauling.  I get it flushed by the machine.   Not even concerned til 100K under highway use.  Of course, earlier preceding trans aren't as robust.   Best is to look at the fluid and if it's discolored or cloudy then change.   It'll get darker, lose lubricity,  if it's overheated.
I'd never put a longer bolt in a stripped hole.   The threads are only so deep and you risk cracking the casting.   All you're doing is wedging the longer bolt into non-threaded part of hole.   Always chase the threads first and use new bolts.   If it's loose after, then you have some options, like leave out, helicoil, or oversizing or a dab of epoxy thread sealant.   Other surgical techniques left for the more skilled and daring.   
ps: Could be an issue with the torque convertor if this continues.   

[bcroe]

My school is similar to that on the timing chain.  A trans has
rubber seals to seal and conduct pressure to things like the
pistons that engage the clutches.  The seals are on a time clock,
as well as mileage used.  I have removed seals from 4 decade
old transmissions, that were so hard they broken when bent. 
Others were shredding.  Refresh those seals with an inexpensive
kit after a couple decades, and avoid serious damage later
when clutches burn up. 

Most of the hard parts I see in a used TH400 are suitable for
reuse, and just maybe are better quality than the available
replacements.  I put them back and run the trans another
200K miles/2 decades.  Bruce Roe

[Chuck Swanson]

Update:
Brought to a Trans shop I have been using since 2000.
Good news is that I replaced the filter correctly, no issues
Bad news, transmission is shot.    Needs a rebuild.  This one has been sitting since 1986, so Bruce was correct above   I kinda figured may be the case as my level was good eventually, and it was getting worse each time I pulled out of garage...longer delays going into gear.  Driven less than 2 miles in driveway after since sitting for decades.  First .25 mi driveway run was great, but started to go downhill from there.

I'll update again when back from shop.  I gave them a new rebuild kit that I had, but they will check if good to use, or old from sitting around (Not sure of age) as I said lean towards a new one if any doubt at all. 

Thanks, Chuck

[bcroe]

OK, VERY IMPORTANT.  Your 66 is a SWITCH PITCH TH400, which
has advantages over 68 and up.  So much so, that I have converted
my 5 cars 77 and later, ALL to 65-67 switch pitch.  MOST trans
shops have no idea about this, and will tend to THROW AWAY your
special switch pitch torque converter and pump assembly, because
they do not have a replacement converter on the shelf.  They put
in a 68-79 instead. 

My advice, under 100,000 miles (I go higher than that) just keep
your original torque converter, these can be checked (see manual)
for wear.  They can also be replaced, I have a stack of rebuilt
converters.  Make sure the shop gets this.  good luck,
Bruce (does not trust anyone to rebuild his trans) Roe

[Chuck Swanson]

Bruce thank you!!  I will check with them in morning.  Thanks, Chuck

[fishnjim]

They usually sit for a reason.   Not many good running cars go unattended for so long if they were in good working condition at the time.   That happens but rare, owner health, death, etc. reasons.
At least it's being corrected and a good vehicle will return to service.   Solid cars.   Best trans of their time and much later.   For the other owners, if your T400 trans is spitting back at you, it's not a good sign...   I've have them overheat, spew fluid, slip, let cool, add fluid, and be OK.   Most others are toast if that happens.   They can also be "beefed up" quite a bit.  Roe knows - he has a stash.

[Chuck Swanson]

Update:
Transmission rebuilt by a seasoned transmission rebuilder (doing for 40+ years).  They used old torque converter as they said in good shape.  Rebuilt the existing switch pitch pump.  No hard parts needed.  Didn't look too bad they said.   Runs and drives great now (just short test outside shop.)  Thanks all for the tips!
Chuck

[bcroe]

Thanks for the follow up report, cheers my day too.  Let other owners
note, driving an automatic trans past half a century without even a soft
part refresh is inviting trouble.  Bruce Roe

[71 Fleetwood]

Thanks for keeping the updates going everybody.  I'm on my first TH400 with a car that sat for lots of years - about 4 decades. 
I had some slipping, the fluid was low so I added a cup of ATF and didn't notice any more problems.  It's at the Caddy dealership for a complete fluid/filters/hoses/belts job.  The brake master cylinder had gunk mud so my fingers are crossed that the transmission is in better shape.

[wheikkila]

Just a little thought on changing the transmission filter. If your transmission has a paper filter. TH400, some 350 it should be changed as reamended. Screens are more forgiving. But the paper will glug.
Thanks Wayne