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1964 Thunderbird, 390 FE
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Discussion Starter · #1 ·
Hi everybody, some background for you:

64 Thunderbird, Cruise-O-Matic MX transmission, 81,000 miles all city driving, sat in storage from 1994 until spring 2020. Transmission has never been rebuilt.

It did not drive much in 2020 due to various other issues, but after working out the kinks I've driven it about 500 miles this summer and fall with no issues (except leaks) until recently. It has leaked about 2.5 qt in the 500 miles, but only seems to leak after sitting in the garage for a while. It doesn't leak when sitting on the driveway for several hours if I wash or work on the bird.

Previous work:
2020:
Upon getting it running, it went into gear and drove ok with the old fluid, so I changed the fluid. Still worked good.
Developed rough shifts.
Found vacuum modulator had bad diaphragm
Replaced modulator
All good.

2021:
Worked out other problems and then drove the thing. Added fluid as necessary.

Currently:

It is slow shifting into high gear intermittently upon acceleration to highway speeds. By "slow" I mean slow to decide it wants to shift. When it does shift, it shifts normally, just at a higher speed than normal. It has done this 3 times in the last 75 or so miles. Other times completely normal.

Still leaks like a sieve.

The current plan:

  • Change filter and fluid.
  • See how bad it looks in the pan.
Main question:
Is there anything else I should do while the pan is dropped?

Options:

Now we enter a bit into speculation for now. I will post more when I get to work on it.

  • If it looks good enough as far as shavings and friction material, I put it back together with new filter and forget it.
  • If it's bad I may still slap it back together for now, but know its days are numbered...

I know for sure I can get a seal kit through a reliable source if I decide to go that route.

This place appears to have a rebuild kit:
https://www.rigidaxle.com/products/...um-automatic-transmission-master-overhaul-kit

A C6 swap has been done on 64 Tbirds before. From what I read on Thunderbird forums, it requires modification to shift linkage, crossmember, and a driveshaft. Doable, but I'd rather not mess around with that for at least another 2-3 years when I'm out of college and want to build the 390.

Any other options?
Other initial thoughts?

Thoughts on whether or not a guy who's never been into a transmission before could rebuild it right the first time by himself?

I'm more of an if it ain't broke don't fix it guy (but still believe preventative maintenance has its place) so even if it looks bad when I drop the pan, I will likely just not beat on it and drive it until it drops. I don't have a lot of time on my hands with school (read: almost no time), so I'll probably take my chances.

Again, I will be sure to post details later when I drop the pan so we can address the situation more directly.

Thanks for your responses as always.
 

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Burnt out transmission tech.
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For starters it is 57 years old. Seals will have hardened and shrunk. Leakage is probably from the shift and throttle shaft seals. Convertor drain back raises fluid level in the pan and leaks out those places. Start by dropping the pan for an inspection. Chances are there will only be a bit of sludge. Fliters are wire mesh and can be washed. You can try adding a can of TransX to the fluid. It softens old seals. Not a cure all or instant fix but may get you by. As for your ability? There is only one way to find out.
 

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1964 Thunderbird, 390 FE
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263 Posts
Discussion Starter · #4 ·
Hey Blue64. Where are the leaks originating from ?
Hello seven up, I can't directly answer your question at this time. I'll have to take a closer look.

It is dripping to the floor from everywhere, crossmember, bottom of the pan, and the bellhousing. The last time I was under the car to replace the vacuum modulator it had been sitting for several months due to getting the brake booster rebuilt, so it had already leaked all it was going to. I started to troubleshoot this, but my grandpa was starting to get impatient, so I buttoned it up, topped it off, and just watched the fluid level while driving it in the summer.
 

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Oh.

If your changing fluid and cleaning filter, there is a drain plug on the torque converter if I remember correctly. You will be able to turn the torque converter by the teeth to locate the drain plug(s). The cooler lines and tranny cooler at the radiator may also retain some of the old fluid. Type F tranny fluid is recommended by Ford.
 

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1964 Thunderbird, 390 FE
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263 Posts
Discussion Starter · #6 ·
Oh.

If your changing fluid and cleaning filter, there is a drain plug on the torque converter if I remember correctly. You will be able to turn the torque converter by the teeth to locate the drain plug(s). The cooler lines and tranny cooler at the radiator may also retain some of the old fluid. Type F tranny fluid is recommended by Ford.
Ok. Thank you. I did get Type F fluid. I am just waiting on a new pan gasket to arrive.
 

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I can remove the fill tube on the pan, so it shouldn't be too bad.
Right. There are few locations that may be the source of your leak, the fill tube connection at the pan may be one of them.
Front seal would be alot of work but you will get an idea when the inspection plate is removed if you drain the torque converter. Lots of might be. Cooler line connections. Rear seal replacement might cost you a front universal joint and the tranny fluid will pour out when the yoke is removed. Looking forward to your prognosis. :coffee: :coffee:
 

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Common issue with that transmission is the front seal and the bushing behind it. The bushing locates the the converter hub inside the transmission. Putting a new seal in will last about three days (or 100 miles) before leaking again. The shift arm seal will also leak but not at the rate you are talking about.
 

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1964 Thunderbird, 390 FE
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263 Posts
Discussion Starter · #11 ·
Common issue with that transmission is the front seal and the bushing behind it. The bushing locates the the converter hub inside the transmission. Putting a new seal in will last about three days (or 100 miles) before leaking again. The shift arm seal will also leak but not at the rate you are talking about.
Thank you for the information. The bellhousing drip is a combination of engine oil and ATF. I'm not sure what percentage of each. I will try to find a day this week to take a look-see.
 

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1964 Thunderbird, 390 FE
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263 Posts
Discussion Starter · #12 ·
Wow it's hard to believe I started this thread 3 months ago. Life has gotten in the way. After some inspection and discussion with my dad and a trusted friend we've decided to pull the transmission and get it rebuilt so that it's fixed right the first time. The goal is to be driving with the rebuilt transmission by May 15th, my last day of classes.

Ford blue blood, I will pay special attention to the front bushing you mentioned in post #10.

Thanks
 
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