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Transmission overflowing even though fill level is normal


adarict's Avatar
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08-04-04, 06:03 AM   #1  
adarict
Transmission overflowing even though fill level is normal

I have a 1973 GMC pickup with a 350 V8 and automatic transmission. I have been having a problem where after I have been driving it for a while (15 to 20 minutes) it will start to spill transmission fluid out through the fill tube. This weekend I dropped the transmission pan, and replaced the filter. The old filter was definitely bad, it had tears along the edge of the screen. I then refilled the transmission per specs (it said 3 quarts, I added 2 then started the engine and warmed it up before continuing to add until it reached the fill line, which ended up being just under 3 quarts total). At first this seemed to fix the problem, as it went for 2 days without the problem reoccuring. However, it started it again today. I am definitely not a mechanic, just someone who is competant enough to follow directions for minor repair work. Does anyone have any ideas on what would cause this? When I replaced the filter, there were some metal shavings in the bottom of the pan, but everything appears to work, although there is some hesitation before going into reverse first thing in the morning.

 
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08-04-04, 06:37 AM   #2  
the rotation...

...of pasrt inside the trans causes pressure buildup...also the fluid expands and therefore takes up more space when hot than cold. the change in space and pressure is taken up by air so the transmission must have a working vent. on top of that transmission is a little plastic tube (supposed to be, at least) and it may be stopped up. start there...

ps...when filling an automatic, it's always best to drive the vehicle for about 15 minutes before verifying the correct fill level. just idling takes an incredibly long time for the trans to get to full operating temp.

 
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08-04-04, 06:42 AM   #3  
adarict
Where exactly would I find this vent/tube? Do I have to drop the transmission pan again to find it? The only other tube is the actual fill tube that goes all the way to the top. There aren't any other things between it and the transmission that I can see. Like I said, I am not much of a mechanic.

 
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08-04-04, 07:14 AM   #4  
you'll have to look and..

...and feel for it...so don't do this when it's hot. as i said in the previous post, it's on top of the trans case. going to the library and finding a picture of that transmission (most likely a THM-350...a manual will help with the ID also) will help you most.

 
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