Now that I have my engine running well and the engine oil leaks fixed... I'm moving on to the transmission fluid leak. As best as I can tell, the leak is just from the pan gasket. Instead of just resealing the pan, I'm considering replacing the pan with an aftermarket pan with a drain plug. Obviously I'll need to add new fluid afterwards. The PO had the trans (TH400) rebuilt when he did the motor, about 10K miles ago, but I don't know for sure what ATF was used. I've been adding Dextron III when it gets low... I assume no one uses type A anymore? My plan was to replace the trans filter while the pan is off, install the new pan w/ drain, and do 2 or 3 fluid changes to get all or most of the fluid replaced. Is Dextron III the best choice?

 

I use Valvoline "Dex/Merc Long Life" for transmissions with over 75,000 miles. Works great.

I too need to change my pan and gasket and filter. I have a bad leak (I hope its just the pan leaking). I got a great price on an aluminum pan and filter from JEGS. I also got a steel re-inforced gasket online. I can't remember the name of the company. It was highly recommended by someone on this site. Its been a couple of months since I bought everything. Its finally cool enough outside to install everything. I just hope the hell that the new pan and gasket stop the leak.

 

I changed the transmission fluid on my '67 Delta using whatever inexpensive transmission fluid was available at Autozone. I used it all up, so I don't have any containers left, but I think it was their house brand. I did not change the filter, just the fluid, and I put on a new gasket at the same time.

Anyway, I did it only because it hadn't been changed since I bought the car two years ago, so I had no idea how long ago or how many miles ago the last change was.

I was experiencing no issues, and I haven't had any since as well. The transmission currently does and always has shifted smoothly. The old fluid was clean and red like it should be and probably didn't need to be changed. The pan itself, which is original as far as I can tell, is undamaged and in very good shape.

To be honest, if you're not experiencing any problems, I think what you're proposing is a bit of overkill. Change your fluid and filter and drive the car. A year from now, do it again if you think it will help anything.

If the pan on the car is in good shape, I would consider not bothering with the aftermarket, drain-plug kind. That's just another place where a leak can occur. Yes, dropping the pan is a bit of a pain. But it's not that bad if you do it carefully and lower it in one corner first to let most of the fluid out. If you do it only every 30,000 miles or whatever the service interval is, enough time elapses between fluid changes that you forget what a pain it was the last time!

Just my 2 cents.

 

Im on the synthetic band wagon now due to the fact that modern ATF is geared towards the modern lock up converter transmissions. That means the ATF people are able to back off on some of the friction modifiers because the modern transmission runs cooler verse the old school trans. Call or email TCI and ask the question they will give you a similar answer.
Thats what I use is TCIs racing trans fluid. I believe you can mix it with standard fluid again call and ask. Worse case silmpy drain as much of the ATF out as possible. You can get 95-98% of it out with pulling a plug in the side of it. Screw in the necessary fitting and run a hose into a bucket. Start the car and let the trans pump its self out doesnt take long. Then drop the pan and R&R the filter and fill er back up with the TCI juice. That takes the guess work out of choosing what right wrong. No dont use "A" or "F" Ford type fluid in your 400. Only old school DEX or what I mentioned here.
If you know the shop that did the rebuild you could ask them?
Yes the pan with the plug makes life easier to service the filter.

 

I hear ya. The trans shifts great... just the the leak needs to be fixed. My reasoning is since a good portion of fluid will be in the t/q, if I dumped it a few times I'd get most of it replaced. Plus, I'd have no problem with replacing the fluid every 30k and leaving the filter alone for 90-100k... a drain plug would make the fluid changes a breeze.

 

I understand.

In my case, I put about 1000 miles on my '67 every year. It will take me 30 years to reach the next fluid change interval, and I'll be in my 80s! At that time, I'll take it to a shop and have them do it.

 

Yeah... me too!

 

Aw, hell... that takes all the fun (and mess) out of it.

 

So, is Dex III old school enough? I really wouldn't be concerned if I knew what fluid was already in it... I just hate the idea of mixing two different fluids together.

 

All specified ATF is required to be intermixable.

If what they put in there is what's supposed to be in there, then you can add in any other thing that's supposed to be in there.

So anything from the Dextron specified in 1968 to Dextron VI, or even Dextron / F should be good.

Also, and someone else may have more info on this, as far as I know, all modern ATF is "synthetic."

- Eric

 

Great! That's good to know. The fluid that's in it looks to be in real good condition... still red, no burnt smell. I'll just fill 'er back up w/ Dex III & not worry about it then.
Thanks for the info.

 

MAK is that a miss type...90-100K on a filter. Any trans mechanic would strongly advise not letting the filter go out that long. 25-30K Max. That is unless they are slow and are looking for work to rebuild a trans...A $10 filter is good insurance for $1000 trans. This is just a former trans mechanics oponion.

 

No typo. I'll replace the filter when I have the pan off. If I end up putting on a pan with a drain plug, I won't change that filter again for a 90k or so... I'll just dump & the refill fluid every 30k.

 

I scored a new Summit aluminum pan on eBay: http://www.ebay.com/itm/290619761598...84.m1439.l2648
I've got a new filter & a Farpak rigid gasket ready to go with it. I've got my fingers crossed that it's just the pan gasket leaking.

 

If you are going to dump the oil every 30k why not spend another $ and change the filter?, the oil will cost more than than a quality filter and the pan will be off anyway.
Cheap insurance IMO, and if you find particles lodged in the filter you have advance warning that all might not be well.

I hope you don't find anything in the filter, just belt and braces for an expensive part of your car. You wouldn't change the engine oil without replacing the filter at the same time.

Roger.

 

What's wrong with running type F?

 

It's for F_rds.

Not designed or intended for GM transmissions.

- Eric.

 

You say that the PO had the trans done about 10K miles ago. Did you try re-torquing the pan bolts to stop the leak? That may be all it needs. Be careful if you install the new pan. A friend of mine did that on his '65 Buick Wildcat and ended up having "Park" messed up. He thought he had broken the dog and took it to a trans shop for repairs. They found the corner of the new pan was blocking some part of the operation. They ground out the corner to solve the problem.

 

Now THAT is useful information I will remember for the future!

Thank you.

- Eric