C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Possible Transmission Leak (Automatic)

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Old Jun 7, 2018 | 01:34 PM
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Default Possible Transmission Leak (Automatic)

Hello, I'm having an issue with my car that I just can't figure out where to start without just trowing money at it. The other day when I drove home from work, I noticed some smoke coming from underneath the car towards the passenger side. So naturally I look under so see my exhaust (by the transmission pan) has a fluid on it that was causing it to burn off. and upon further inspections I was able to see Trans fluid on the passenger side of the pan and some that was on the side of the transmission. If anyone that has had an issue like this, any help would be appreciated.
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Old Jun 7, 2018 | 03:06 PM
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Quite often it is the pan gasket that can cause a leak. Might try snugging down the bolts a little bit. If you are lucky, that might fix the leak. If not, it's the gasket or a seal.
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Old Jun 7, 2018 | 04:05 PM
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I recently put my 85 up on a outdoor rack and coated the underside with simple green and pressure washed it all...In that process I noticed the built up tranny oil and was amazed at how many of those bolts needed snugging up.....didn't even need a new gsk......

Last edited by playsdixie; Jun 7, 2018 at 04:06 PM.
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Old Jun 7, 2018 | 05:39 PM
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When I had my transmission rebuilt. I had a leak on the passenger side of the car. It turned out to be the throttle valve cable that goes into the transmission on the passenger side. The dealer replaced the whole cable and that took care of the leak.


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Old Jun 8, 2018 | 11:10 AM
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Thanks for all the advise and the info on the cable, will be able to get back under the car Monday. Will let you guys know how that goes.
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Old Jun 12, 2018 | 12:25 AM
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So when I was going to tighten the bolts on the transmission pan (was surprised how many I was able to snug down) I noticed that a metal line was coated in transmission fluid that may be another culprit. All help is greatly appreciated. I'm also doing as much as possible DIY so any tips are also welcome.
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Old Jun 12, 2018 | 01:45 AM
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Originally Posted by 84Cross-Fire
Hello, I'm having an issue with my car that I just can't figure out where to start without just trowing money at it. The other day when I drove home from work, I noticed some smoke coming from underneath the car towards the passenger side. So naturally I look under so see my exhaust (by the transmission pan) has a fluid on it that was causing it to burn off. and upon further inspections I was able to see Trans fluid on the passenger side of the pan and some that was on the side of the transmission. If anyone that has had an issue like this, any help would be appreciated.
The usual culprits are the dipstick seal, the TV cable attachment to the top of passenger side. Or over filled with trans fluid and coming out of the vent on top of transmission.

Even professionals can get it wrong........ when my trans was last rebuilt the so called new TV cable plastic was cracked.
would only leak when turned off ... leaving trans fluid on my garage floor.

Took some time to find it, the new TV cable plastic housing that bolts onto the trans was cracked... and guess what ... red hi temp silicone was smeared all over it.

Needless to say when I replaced it and took the old TV cable assembly to the transmission rebuilder, they were shocked and would not believe one of their guys would try to fix it with silicone ....
Well after some stern words the at least refunded the cost of the TV cable, needles to say I will not do business with that mob again...
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Old Jun 12, 2018 | 12:46 PM
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Originally Posted by gerardvg
The usual culprits are the dipstick seal, the TV cable attachment to the top of passenger side. Or over filled with trans fluid and coming out of the vent on top of transmission.

Even professionals can get it wrong........ when my trans was last rebuilt the so called new TV cable plastic was cracked.
would only leak when turned off ... leaving trans fluid on my garage floor.

Took some time to find it, the new TV cable plastic housing that bolts onto the trans was cracked... and guess what ... red hi temp silicone was smeared all over it.

Needless to say when I replaced it and took the old TV cable assembly to the transmission rebuilder, they were shocked and would not believe one of their guys would try to fix it with silicone ....
Well after some stern words the at least refunded the cost of the TV cable, needles to say I will not do business with that mob again...
So the build up on the lower transmission cooler line normal? or could that be another issue. the pan isn't leaking anymore but I'm still having fluid drip onto my exhaust. If you look at the picture I posted you can see a wet spot on my exhaust.
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Old Jun 12, 2018 | 10:35 PM
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Originally Posted by 84Cross-Fire
So the build up on the lower transmission cooler line normal? or could that be another issue. the pan isn't leaking anymore but I'm still having fluid drip onto my exhaust. If you look at the picture I posted you can see a wet spot on my exhaust.
Hi

Yes it can be a loose cooler line, overflowing out the top vent hole or TV fitment....

You really need to pressure clean the area at a car wash, you can get a pressure cleaner nozzle down from the engine bay and have a good go at it. Only then after a short drive can you pinpoint it , even engine oil and any trans fluid will spray up from air turbulence when driving.

It does look like the TV cable area where the leak is coming from, make sure you clean the trans before tackling the TV cable.
If its that..
Is a small bolt and the TV cable can be removed, then unhook the cable from the small rod.
There is a round rubber seal, it can easily fall into the transmission so be careful.

I ended up removing the pan to retrieve my seal and make hooking up the TV cable easier, it helps to have someone put tension on the TV cable when you have hooked it on to the rod CAREFULLY Refitting the TV cable into and onto trans taking care not to force the seal out... its a bitch of a job when in the car

Good Luck
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Old Jun 14, 2018 | 01:14 AM
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After cleaning it and driving the car around, I see fluid from the tv cable and the dip stick tube. unfortunately I don't have the tools to get to these ports so I'll be contacting a local transmission shop near me to get a quote. Thank you for all the advise and solutions to my issue
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Old Jun 14, 2018 | 02:06 AM
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Originally Posted by 84Cross-Fire
After cleaning it and driving the car around, I see fluid from the tv cable and the dip stick tube. unfortunately I don't have the tools to get to these ports so I'll be contacting a local transmission shop near me to get a quote. Thank you for all the advise and solutions to my issue
Hi

Yeah you have to remove the front exhaust to get to the 10mm bolt that holds the TV valve to transmission, its not a hard job but if you don't have a decent trolley jack stands and tools best get it done.
That small TV cable to trans seal is a bitch, can easily fall in if you are not careful inserting the TV cable body end into trans.
Plus you need an extra pair of hands to pull on the cable gently, as you place it into position after hooking it onto the trans rod.

I've done it while in the car........ cursed plenty I tell you as that rod can pop out the end of the TV cable. When its in place it cannot pop off, just takes a lot of care and patience.

The dipstick has a bolt on the back of the head from memory, once that is out the dipstick will come out. The seal should stay in the transmission and need to be pulled out with a finger, then replaced and dipstick refitted.

At least you have found the leak
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Old Mar 15, 2021 | 11:31 AM
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Originally Posted by gerardvg
Hi

Yeah you have to remove the front exhaust to get to the 10mm bolt that holds the TV valve to transmission, its not a hard job but if you don't have a decent trolley jack stands and tools best get it done.
That small TV cable to trans seal is a bitch, can easily fall in if you are not careful inserting the TV cable body end into trans.
Plus you need an extra pair of hands to pull on the cable gently, as you place it into position after hooking it onto the trans rod.

I've done it while in the car........ cursed plenty I tell you as that rod can pop out the end of the TV cable. When its in place it cannot pop off, just takes a lot of care and patience.

The dipstick has a bolt on the back of the head from memory, once that is out the dipstick will come out. The seal should stay in the transmission and need to be pulled out with a finger, then replaced and dipstick refitted.

At least you have found the leak
Do you know how to access the bolt holding the tranny dipstick? I have traced my leak to the dipstick seal. I can see the bolt holding the dipstick tube on top of the bellhousing (from underneath with car on lack stands). How the heck do I access the bolt to remove and replace the tube?

Last edited by 1985 Vette; Mar 15, 2021 at 11:31 AM.
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Old Mar 15, 2021 | 01:20 PM
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Originally Posted by 1985 Vette
Do you know how to access the bolt holding the tranny dipstick? I have traced my leak to the dipstick seal. I can see the bolt holding the dipstick tube on top of the bellhousing (from underneath with car on lack stands). How the heck do I access the bolt to remove and replace the tube?
From under the car you will need a 14mm socket a pivoting angle piece and a few lengths of half inch extension bars, to reach around the bellhousing and transmission to beside and towards the rear of the transmission to get the ratchet on and unscrew / remove the bolt.

I think you can reach the bolt front under the hood with a flat ring spanner too.

The only areas it can leak trans fluid are the dipstick seal the tv cable seal, cooler lines and don't forget a breather on top of bellhousing if trans fluid is overfilled will spit out fluid there when hot.

Good luck
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Old Apr 27, 2021 | 08:18 PM
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Thanks for the advice I did the job a few weeks ago and forgot to update.

I did not have to remove the stock exhaust system, though the pre-cats were a pain as they were right in the way.

I was able to get to the dipstick tube bolt from underneath using a long extension and a 9/16" universal socket with electrical tape to make it less floppy. Still very difficult to remove the bolt. After the tube was loose, I had my dad pull up on the tube from above just enough so I could pick the old seal out and install a new one. Then I guided the tube back in as he pushed it down. I thought installing the bolt would be harder than removing, but it wasn't. I guess I got lucky.
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