This will be a bit of a long post, so please bear with me.
I have a frustrating auto trans fluid leak in my 1969 GTO. This is a driver-quality, numbers matching car with a factory turbo 400 trans. I bought it earlier this year (see pictures below). The transmission shifts perfectly.
About a month after I bought it, I noticed trans fluid leaking on the garage floor – not a lot, but probably a couple of cups. So I took it in to a shop I’ve been using for a few other things.
First, some info on the shop. It’s not primarily a classic car shop, but they do promote on their web site that they work on classic cars, and in fact each time I’ve been in they’ve had one or two classics in their shop being worked on. They are AAA approved, won the AAA best shop in Washington State for 8 years, have Consumer Checkbook’s highest rating for quality and customer satisfaction, and a 4 ½ star rating on all the online review sites. I’m not a mechanic and so really did my research before choosing this shop. All indications are that they know what they’re doing. However, read on.
It looked like an oil pan leak, so they replaced the pan gasket. The trans has been rebuilt once and had a non-factory chrome replacement pan installed, which they said in their experience had more problems than an OEM part.
Drove it home (about 10 miles, 8 of which were freeway speeds), so the car was nice and warmed up. No leaks later that day. No leaks the next morning or the next night, but the second day home it was leaking again. About a cup the first day, and then maybe another cup a day after that.
So, took it back to the shop, where they were surprised, since it didn’t leak there after the repair. But they only had it for a day after and it didn’t leak for me until the second day home. They said they now suspected one of two things. First, when the trans was rebuilt they put an after market trans fill tube and dipstick and that may have been giving an inaccurate reading, causing the fluid to be filled higher than it should be and thus leak out.
The other possibility was something bad internally in the transmission, causing it to overheat and boil the fluid, making it leak out. I’m not a mechanic but said this didn’t make sense to me, since no fluid was leaking when I got it home and the trans had time to get plenty hot driving on the freeway, plus it shifts great. So I said to go ahead and put an OEM fill tube and dipstick in, which they did. It turns out that there was too much fluid in the trans, as indicated by the new dipstick. With the correct level in, they drove it, checked it that day and the next and no leaks.
I picked it up, drove it home, with the same result: no leaks after driving or the next day, but the second day once again about a cup leaked out and I’m pretty sure that will continue.
I suspect they will now lean towards the transmission being the problem, but in another post on the forum it was mentioned other possibilities: the modulator O ring, front seal, rear seal, or speedo cable.
The odd thing in all this is that it’s two days later before it leaks again. Has anyone else experienced this problem and if so can you recommend a fix? I’m no longer confident the shop I’ve been using is up the task.
Sorry for the long-winded post and I appreciate any observations/advice you may have before I go back to the shop.
Tom
I have a frustrating auto trans fluid leak in my 1969 GTO. This is a driver-quality, numbers matching car with a factory turbo 400 trans. I bought it earlier this year (see pictures below). The transmission shifts perfectly.
About a month after I bought it, I noticed trans fluid leaking on the garage floor – not a lot, but probably a couple of cups. So I took it in to a shop I’ve been using for a few other things.
First, some info on the shop. It’s not primarily a classic car shop, but they do promote on their web site that they work on classic cars, and in fact each time I’ve been in they’ve had one or two classics in their shop being worked on. They are AAA approved, won the AAA best shop in Washington State for 8 years, have Consumer Checkbook’s highest rating for quality and customer satisfaction, and a 4 ½ star rating on all the online review sites. I’m not a mechanic and so really did my research before choosing this shop. All indications are that they know what they’re doing. However, read on.
It looked like an oil pan leak, so they replaced the pan gasket. The trans has been rebuilt once and had a non-factory chrome replacement pan installed, which they said in their experience had more problems than an OEM part.
Drove it home (about 10 miles, 8 of which were freeway speeds), so the car was nice and warmed up. No leaks later that day. No leaks the next morning or the next night, but the second day home it was leaking again. About a cup the first day, and then maybe another cup a day after that.
So, took it back to the shop, where they were surprised, since it didn’t leak there after the repair. But they only had it for a day after and it didn’t leak for me until the second day home. They said they now suspected one of two things. First, when the trans was rebuilt they put an after market trans fill tube and dipstick and that may have been giving an inaccurate reading, causing the fluid to be filled higher than it should be and thus leak out.
The other possibility was something bad internally in the transmission, causing it to overheat and boil the fluid, making it leak out. I’m not a mechanic but said this didn’t make sense to me, since no fluid was leaking when I got it home and the trans had time to get plenty hot driving on the freeway, plus it shifts great. So I said to go ahead and put an OEM fill tube and dipstick in, which they did. It turns out that there was too much fluid in the trans, as indicated by the new dipstick. With the correct level in, they drove it, checked it that day and the next and no leaks.
I picked it up, drove it home, with the same result: no leaks after driving or the next day, but the second day once again about a cup leaked out and I’m pretty sure that will continue.
I suspect they will now lean towards the transmission being the problem, but in another post on the forum it was mentioned other possibilities: the modulator O ring, front seal, rear seal, or speedo cable.
The odd thing in all this is that it’s two days later before it leaks again. Has anyone else experienced this problem and if so can you recommend a fix? I’m no longer confident the shop I’ve been using is up the task.
Sorry for the long-winded post and I appreciate any observations/advice you may have before I go back to the shop.
Tom