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4L70E Leak if Overfilled?

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Old 12-30-2009, 02:43 PM
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Default 4L70E Leak if Overfilled?

Hey like the title states... could a silverados 4L70E tranny leak if it was overfilled? It is registering on the stick about a half to a quart over filled... thats a guess. Its about a 1/4-1/3 of an inch higher than it should be on the stick. So could it leak if I overfilled it? I did a converter change and its leaking now a little bit so i assumed that it was the front seal... but it looks to be overfilled to a bit, so i was just curious. Thanks for the help!
Old 12-30-2009, 08:53 PM
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Yes, it can come out of the vent tube when it's overfilled like that.

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Old 12-30-2009, 10:35 PM
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thanks for the reply... where is the vent tube located at? thanks
Old 12-30-2009, 10:36 PM
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oh wait.. isnt it right on top of the transmission?
Old 12-31-2009, 07:07 AM
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I normally fill a 4l60e to the full hot on the stick when it is cold. With that being said I do not believe that your trans is over filled. I would suspect that when you installed it if you prefilled it, that some might have got in the bell when you installed it. Brake clean the out of it and see if it continues to leak. The other thing to consider is if possibly you cut the pump to converter seal or if the converter has a pin hole in it. Chasing a leak can be a PITA but do a thourow a job and you will find it. Vince
Old 12-31-2009, 09:29 AM
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why do you fill the tranny when cool? does it need the extra capacity? not sure if this just applies to the overdrives or not, but a 3 or a 2 spd can spit it out if you are making any type of power.
Old 01-01-2010, 09:29 AM
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Originally Posted by TJ
why do you fill the tranny when cool? does it need the extra capacity? not sure if this just applies to the overdrives or not, but a 3 or a 2 spd can spit it out if you are making any type of power.
My comment is specific to the 4l60e. You are correct on the 3 speed transmissions especially the th400. I have always found that the 4l60e is not fussy with a little extra in there. Unless it is way over filled I have not seen this issue in a 4l60e. If you do see oil blowing out in the vent on a 60 there are other internal issues or an issue with the converter building pressure and releasing it into the transmission. Good question. Vince
Old 01-01-2010, 09:45 AM
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Originally Posted by Vince @ FLT
My comment is specific to the 4l60e. You are correct on the 3 speed transmissions especially the th400. I have always found that the 4l60e is not fussy with a little extra in there. Unless it is way over filled I have not seen this issue in a 4l60e. If you do see oil blowing out in the vent on a 60 there are other internal issues or an issue with the converter building pressure and releasing it into the transmission. Good question. Vince
i know exactly what you mean about a 60 spitting fluid when there is an issue.
buddy of mines lt1 car spit 3 of them out, but he was super hard on it.
i was with him twice when it went.
both times had to limp home, only 3nd gear left in the trans with a small cloud of "blown headgasket syndrome" behind us.
Old 01-01-2010, 09:59 PM
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Originally Posted by Vince @ FLT
My comment is specific to the 4l60e. You are correct on the 3 speed transmissions especially the th400. I have always found that the 4l60e is not fussy with a little extra in there. Unless it is way over filled I have not seen this issue in a 4l60e. If you do see oil blowing out in the vent on a 60 there are other internal issues or an issue with the converter building pressure and releasing it into the transmission. Good question. Vince
Thanks a lot for helping... and yes I will spray some brake clean up in there and see if that does anything... i just doubt it because everytime i wipe up the two drops under there and then drive again... there will be a couple more. Its not leaking fast at all... but it is a few drops every now and then. I did the change a while ago, so it seems like if I got any in there that it would have all gotten out by now... Am i going to hurt the transmission if it leaks like this for a little while? Some guy on another forum said that he kept filling his back up and then now he needs clutches because he let it leak. Is there any truth to that? I havent noticed a difference in fluid height so thats why I am wondering... Also do you think the seal could ever just completely blow out and then start pouring a bunch of fluid out while driving or would it continue to leak slow untill i changed it? thanks!
Old 01-01-2010, 10:21 PM
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im sure there have been cases where a seal will get ripped by a rough hub, or a pan gasket that has had enough, but its very uncommon, IMO.
you can leak fluid from florida to california. as long as its at the proper level, you arent going to hurt the tranny.
if it gets low and not filled, then youre going to have an issue.
do you have an aluminum pan on it?
what pan gasket do you use?
Old 01-02-2010, 12:39 AM
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Hey thanks for the reply and yes I have a gasket on the tranny... it is the one that came with the filter when i changed it. It came from autozone... nothing fancy. Why do you ask? you think i should of ran something different or sealed it with RTV or something?
Old 01-02-2010, 08:56 AM
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I personally do not like silicone on a pan with a gasket. I would definitely keep an eye on the fluid level until you get it figured out.

I was thinking this morning about your leak. It is possible that your pump to case seal might be leaking. On the later model units there is a metal clad type seal that do leak from time to time. If you have the front of this unit resealed make sure that this seal is replaced. To replace this seal the bell housing has to be removed.
Old 01-02-2010, 10:10 AM
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Originally Posted by BadBowtie03
it is the one that came with the filter when i changed it. It came from autozone... nothing fancy. Why do you ask? you think i should of ran something different or sealed it with RTV or something?
do you have a drain plug on your pan?
if so, i would capture the fluid and change out that gasket.
i have had nothing but trouble out of those cheap parts store kits.
i prefer to buy a filter and gasket separate. its more cash, but worth every penny.
most of the time, you get a cheap rubber gasket that will stretch like a rubber band just hand tightening the bolts.
dont have the part # offhand, but felpro has a nice gasket thats fiber, no stretch there.

i will smear a very thin layer of rtv on the pan side(and i mean thin) just to keep the gasket in place till i can get the bolts started.
much easier to clean off the pan than it is the transmission rail the next time you change the fluid/filter.
Old 01-03-2010, 01:43 PM
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thanks a lot for the help guys. right now im talkin to some guys near jax florida about replacing the seal for me. i might get them to do some upgrades to the tranny while there at it. i was thinkin an hd2 shiftkit and someone reccommended a shell or something? whats some good stuff to do to make it stronger while their in there? they are efi alchemy btw.



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