Hello everyone,

Has anyone of you ever opened the transmission filter and can tell me whether there is filter fabric in there or a metal screen, that can be washed out? The number on the transmission nameplate shows: "C-63 14337"

I purchased my 1963 Fleetwood 60 Special with the original 390cui two years go and have driven about 3.000km since then without any issues. Still smooth, non recognizable shifting from 1-2 and 3-4, but up from the begining this slight jerk when shifting from 2-3. 

I know it´s by design (double clutch) and should be lived with as long as it doesn´t get worse.

But I´m thinking about removing the oil pan and checking the abrasion and the filter. The pan looks like it hasn´t been off for a very long time. The oil is fresh, bright red and the transmission is not leaking anywhere.

I am therefore faced with the question of whether to open it or follow the golden rule: "never touch a running system"

I would really appreciate some recommendations.

Many thanks in advance and greetings from Germany


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if the trans fluid is not to the full line the Th- 400 trans does not shift as it should ( a quart down ) 

The dip stick is marked in pints 

The trans should be shifting  very smoothly in all gears when correct 

A filter and fluid change would be the first thing to be doing to see if that corrects the issue 

The filters gets replaced in our cars and not washed out as some might 

The trans is known to be one of the most bullet proof tans there is so good chance that might correct the shifting problem 

If that does not work just drive the car until the trans  gets worse and may have to be rebuilt or replaced with a used unit at some time in the future 

Good luck with the fluid change 

Jason Edge the web master and parts supplier here has replacement transmissions removed from our year Cadillacs if that need arises 

I have a feeling that the fluid change might get the shifting to improve 

How many miles on your trans now ? 


Hello Tony,

thank you for your input. My 1963 has no TH400 but the 4-Speed Hydramatic/Jetaway (shift pattern PNDLR)
My Cadillac was delivered in Switzerland, has got a Km-Speedo with 5 digits and shows 87.000km (54.000miles)

Due to the low level of wear and tear in the engine compartment, interior and on the chassis, it is at its maximum 187.000km (117.000miles).

Unfortunately, it is currently difficult to get the right filter at a reasonable price here in germany. e.g. Rockauto is out of stock. So I asked about the possibility of washing out the filter.

Attached is a picture of the filter housing.



We have Rock auto — Kanter auto and eBay  —-here that might have the part but not sure if  they ship to Germany 

I would get a new replacement filter as I do not know of anyone who cleans our cars trans filters but I do understand your problem with finding one 



Try Fasco - they specialize in trans parts 


Correction  that’s —- Fatsco 
Mark and I did the posting  about the same time 

It has been a loooong day on my end 


Thank you all for your help!

luckily I found another set of filter & gasket in stock at a Cadillac specialist here in Germany:  Andreas Winterwerber

The set costs 120€ (126 US $) . That would be even cheaper than importing from the US.

Soon I will then remove the oil pan and replace the filter & ATF when  I change the engine oil.

Just for info: a german company (LiquiMoly) offers an oil that matches perfect the specifications for our engines: 10W40 with addition of MoS2 (solid lubricant like graphite) including the higher concentration of ZDDP designed for our old cars.

LiquiMoly 10W40 MoS2

My engine runs very smooth with it and I can highly recommend it.

have you checked the throttle rod adjustment? 

Hi Mark,
the throttle response can be dosed very well, so I didn't check it so far.

To avoid that jerk from 2-3, so far the usual approach has been to accelerate 1-2 normally. Then lift the gas pedal slightly while engaging 3rd gear and then continue to accelerate again normally.

This procedure enables relatively normal acceleration.

Due to a well-running but not original Edelbrock 1806S, the Kick Down is not hooked in yet, but is fixed in normal position. 

The previous owner gave me a mountain of bills for parts and repairs, but it wasn't a bill for a transmission oil filter or gasket in it. So I think more and more that it could still be the first filter, or at least a 20-30 years old one that should be changed soon.

If the filter is clogged and preventing the trans from generating enough oil pressure to change from 2-3, this could solve the problem.

A clogged filter will delay shifts first and foremost, then cause slippage, and then pump burnout.  It won't usually cause a harsh shift unless it leads to starved clutches, at which point the transmission will have to be disassembled.

An inoperable throttle valve will cause harsh shifts.  Its function is to control the pressure in the shift valves and the accumulators, which act as shock absorbers for the clutch application.   If the valve is in low throttle position, there will be low pressure in your accumulator and therefore no hydraulic cushion for the shift, which is what you described.  

Running a hydramatic without a working throttle valve will lead to early failure.  This is an unavoidable truth. It may already be too late.  

Hello everybody,

I opened the transmission to see the filter: it was a very old, clogged one, >15-20 years old.
Attached you will find some pictures.

So I installed a new filter and gasket, filled up the transmission with new ATF III and did a testdrive.
I was so impressed: even before that, the shifts were very smooth, except for the shift between 2-3.

After replacing the clogged filter, the shifts were even smoother and the shifting process from 2-3 now takes only half as long and has also become softer.


Good to hear.



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