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1964 RIviera and TH400 leak


first64riv

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Hey Guys,

 

This is the first time I've dealt with transmission leaks.  The oil spots are coming from the passenger side, looks like the front of the transmission near the bellhousing.  I see two spots and I believe one is the pan and the other may be the front seal.

 

Currently the car is resting in my garage.  It is leaking slow right now.  When I take it for a drive and get the fluid hot, it definitely leaks more at rest until it cools down again.  I attribute this to thickening of the oil as it cools hence less leaking.  Does this behavior help pin point the location of the leak?  I mean, if it were the front seal, wouldn't it stop since the oil has trickled all the way down to the pan?

 

My plan of attack is going to be to replace the pan (bigger leak) and gasket with another set that has a drain plug.  If that stops big leak, I may just live with the other leak.  I will be removing the inspection plate to try to see if I could see if the seal is leaking.

 

Any other advice, other things to check, or try?

 

Thank you for reading.

Chris

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Good plan, much easier and cheaper than pulling the trans. We get spoiled by high tech newer cars not leaking , almost all old cars leak something. As long as the trans shifts correctly and the leak isn't major puddles living with it is a reasonable option for a driver vehicle.

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I have a similar leak on my '67 Riviera and I suspect that it is coming from the o-ring seal where the dipstick tube seals against the transmission case.  That's on the passenger side and may well be your problem.  It doesn't leak right away, but as the car sits parked, gravity causes oil to drain out of the torque converter, eventually exceeding the height of the dipstick tube seal.  Normally, the oil gets sucked back into the torque converter as soon as the engine is started.  The dipstick will read over full with the engine off; which is why the transmission level is checked with the engine idling in PARK.

 

That said, a fluid & filter change with new pan gasket isn't a bad idea either...   ;)

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I took a closer look last night and I think one of the transmission cooler lines is the source of the leak.  I do believe the pan is also leaky so I'll tackle both at the same time.

 

Are the 1964 and 1965 Riviera transmission cooling lines the same?  One of the two sources for the lines says 64/65 are the same, the other only lists the 65.

 

Thank you for all the replies so far.

Chris

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  • 1 month later...

I thought I should respond and update the status of this issue.

I replaced the pan and used new bolts and new gasket.  The pan leak went away but now I've found that the trans cooling lines leak and my vacuum modulator leaks.  The modulator will be replaced this weekend.  I'll likely buy the cooling lines after the new year and replace those too.

 

I'm happy with the progress so far.  I'm also replacing the carb this weekend as long as my baffle gets here tomorrow.

Stay tuned!

Chris

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I worked in a transmission shop back in the mid 70's, and got pretty good at finding those pesky leaks. 

 

First, in MY experience, I almost never found a pan gasket to be the source of the problem UNLESS some overzealous person had over-tightened pan bolts to the point that they crushed pan gaskets to pieces. 

Second, the most important thing about fixing a leak was to accurately FIND the leak for absolute certain. Our best tool was the old style chlorinated BraKleen spray product. We would spray generous amounts of it directly on all the potential leak points on any particular transmission. This stuff dries right in front of your eyes in just a few seconds, taking any oil/grease/dirt along with it. You suddenly have super-dry and super clean surfaces, where before you had dirty, oily messes. Next we would put someone in the car and raise it back up on the hoist, and start the engine. We would put it in and out of gear a few times, while someone underneath shined a light from one potential leak point to another, moving quickly and watching for oil to start oozing through. This worked flawlessly for us, almost every time. The super-dry potential-leak areas would remain that way, EXCEPT for the guilty leak source. Even the tiniest seepage was easy to spot. 

 

400 turbos were very popular and common transmissions in those days. The dipstick tube o-ring was a common leak point, as were the shift-lever seal and the front and rear main seals. Keep in mind that for the front pump seal and the tail shaft seal, it is usually the bushing which the torque converter shaft rides on which wears out, allowing the torque converter (or driveshaft yoke in the rear) to move around too much, damaging the seal. So if you replace just the seal in such cases, the leak will return in a few weeks or months. If your front or rear main seals are leaking, be sure to replace those bushings first. You'll need special tools to replace the bushings. It is nearly impossible to pull the old bushings out otherwise. 

 

In my experience, cooling lines were not often the source of leaks UNLESS someone had removed them recently. And when I did find the lines leaking, all too often someone would have distorted them or twisted them to the point that a tiny hole had been created in the line.

 

So first, make sure you have definitely FOUND your exact leak point. Then if you need further advice, it will be easy to assist. 

 

Good luck! 

 

 

 

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  • 2 weeks later...

THINGS ABOUT THOSE O-RINGS, from experience . . .

 

The o-ring for the trans dipstick tube is NOT generic!  We had a parts guy that, when a tech asked for that o-ring, went to the universal o-ring box and got one of those of the same size and dimension.  Two weeks later, the car would be BACK with a trans leak in that area.  I looked in the Chevy parts book and found the GM-part number o-ring, after hearing the disgruntled tech's story, and we had them in stock.  I got him one of those . . . end of problem!  And he started asking for that "GM one" after that.

 

The "generic" O-rings might look to be the same, but the rubber has to be tolerant of the fluid it seals against.  Get the GM part number o-ring, period.  The vac modulator should come with its own o-ring package.  Hopefully, you can get one of the larger "can" modulators, but it might be a much smaller one.  If a modulator fails, it's a direct vacuum leak, not fluid leak.  But the o-ring seals seal atf from the inside of the case.  There might be an internal seal/diaphragm for the modulator's rod, though.

 

The cork gaskets can "wick" fluid through them, with time.  Once they start, no stopping it without a gasket replacement.  What I started doing with all cork-style gaskets is to put a thin coat of black silicone sealer (RTV) on them, on all sides, with my fingers.  Let it cure overnight, or so, prior to installation.  This flexible seal will stop all wicking, so no later smudges of fluid will appear later.  That's how I now do ALL of the gaskets I replace . . . carb base gasket, valve cover, and others.  MUCH easier to clean up when removed, especially compared to the old "yellow stuff"!  I got tired of trying to scrape valve cover gaskets where that yellow stuff had been used to hold things in place!!

 

Fastener torque is important, as noted!  "just enough", not too much!

 

Newer brake cleaners work ok, but not as quickly as the earlier ones.  Still a good tool!

 

Comments on the seals/bushings are VERY ACCURATE!

 

NTX5467

 

 

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12 hours ago, NTX5467 said:

Get the GM part number o-ring, period.

 

NTX - those are good words!  Do you happen to have the GM P/N handy for that dipstick O-ring?  I'd like to replace mine and eliminate that mess...

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  • 1 month later...

Alright, it's been about a month and I've done everything I set out to do and voila, no more major puddles.  There is still one leak and that is coming from the upper fitting on the cooling line.  That's the last TH400 leak and I think all i have to do is "phanagle" the fitting line as I tighten it.  It's no big deal to me, the cardboard soaks it up.  I'm just happy that I don't walk out to a big puddle of ATF anymore.

 

If anyone has questions, feel free to ask!

Chris

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  • 1 year later...
On 12/16/2016 at 9:45 PM, first64riv said:

I thought I should respond and update the status of this issue.

I replaced the pan and used new bolts and new gasket.  The pan leak went away but now I've found that the trans cooling lines leak and my vacuum modulator leaks.  The modulator will be replaced this weekend.  I'll likely buy the cooling lines after the new year and replace those too.

 

I'm happy with the progress so far.  I'm also replacing the carb this weekend as long as my baffle gets here tomorrow.

Stay tuned!

Chris

 

On 2/2/2017 at 4:00 PM, first64riv said:

Alright, it's been about a month and I've done everything I set out to do and voila, no more major puddles.  There is still one leak and that is coming from the upper fitting on the cooling line.  That's the last TH400 leak and I think all i have to do is "phanagle" the fitting line as I tighten it.  It's no big deal to me, the cardboard soaks it up.  I'm just happy that I don't walk out to a big puddle of ATF anymore.

 

If anyone has questions, feel free to ask!

Chris

 

I wanted to update everyone on this in case anyone else was dealing with little leaks here and there.

 

So after installing the pan with a rubber gasket in Dec 2016, it started to leak when parked again.  I had puddles but they weren't large enough to be of concern.  Besides, I had access to plenty of cardboard.

 

Fast forward to July 2018 and I finally decided to change the rubber gasket on the pan to a Fel-pro gasket.  Well, it's held up well overnight and no drips anywhere.  At this point, I will say rubber gaskets are garbage when used with stamped aluminum pans.  The pan that i am using has the raised ribs along the flange and I purchased it at Summit Racing.  It's the generic black one, not the fancy chrome one.  I'm now waiting to see what else will start to drip now that the pan is sealed.

 

Thank you and hope this helps others.

Chris 

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  • 1 year later...
On 12/19/2016 at 5:05 AM, lump said:

I worked in a transmission shop back in the mid 70's, and got pretty good at finding those pesky leaks. 

 

First, in MY experience, I almost never found a pan gasket to be the source of the problem UNLESS some overzealous person had over-tightened pan bolts to the point that they crushed pan gaskets to pieces. 

Second, the most important thing about fixing a leak was to accurately FIND the leak for absolute certain. Our best tool was the old style chlorinated BraKleen spray product. We would spray generous amounts of it directly on all the potential leak points on any particular transmission. This stuff dries right in front of your eyes in just a few seconds, taking any oil/grease/dirt along with it. You suddenly have super-dry and super clean surfaces, where before you had dirty, oily messes. Next we would put someone in the car and raise it back up on the hoist, and start the engine. We would put it in and out of gear a few times, while someone underneath shined a light from one potential leak point to another, moving quickly and watching for oil to start oozing through. This worked flawlessly for us, almost every time. The super-dry potential-leak areas would remain that way, EXCEPT for the guilty leak source. Even the tiniest seepage was easy to spot. 

 

400 turbos were very popular and common transmissions in those days. The dipstick tube o-ring was a common leak point, as were the shift-lever seal and the front and rear main seals. Keep in mind that for the front pump seal and the tail shaft seal, it is usually the bushing which the torque converter shaft rides on which wears out, allowing the torque converter (or driveshaft yoke in the rear) to move around too much, damaging the seal. So if you replace just the seal in such cases, the leak will return in a few weeks or months. If your front or rear main seals are leaking, be sure to replace those bushings first. You'll need special tools to replace the bushings. It is nearly impossible to pull the old bushings out otherwise. 

 

In my experience, cooling lines were not often the source of leaks UNLESS someone had removed them recently. And when I did find the lines leaking, all too often someone would have distorted them or twisted them to the point that a tiny hole had been created in the line.

 

So first, make sure you have definitely FOUND your exact leak point. Then if you need further advice, it will be easy to assist. 

 

Good luck! 

 

 

 

That's one of the most sensible post replies I've ever read very good advice and it's helped me hugely with my current trans dilemma on my '67 Riviera much appreciated cheers! 

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  • 4 months later...

Hello all,

 

So I'm back with what I hope to be my last update on this situation.  I recently rediscovered a couple of rubber/cork gaskets on a high shelf in my garage.  After another year passing and the ytansmission still leaking, I figured today would be a good day to tackle the leak once and for all.  I took off the old all rubber gasket, cleaned both surfaces, and placed the cork/rubber gasket on with no sealants.  Well it's been about 4 hours and no leaks.

 

My takeaway is, even a four year old cork/rubber gasket is better than a rubber gasket when used on one of those cheap Summit/Jegs all black steel pans.

 

Hope everyone is enjoying football Sunday!

Chris

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