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2001 Seville STS
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34 Posts
Discussion Starter #1
My understanding is that these 4T80-E's are "dry sump" transmissions. I went to do a fluid change today and I checked the level before draining. IT was almost at the bottom of the stick (hot). When I bought the car I checked the level an it was just right (this was about 2 months ago).

So I dropped the pan and about 10 quarts came out. Then I pulled the side cover drain plug and another quart came out. I've read that most of the fluid is supposed to come out of the side cover drain plug, and not the pan.

My car also exhibits a problem during the first shift into drive for the day. I start the car and put it into drive and the car will not move easily. If I wait for 30 seconds to a minute and then shift into drive, it engages drive fine.

I suspect that for some reason the transmission fluid is all draining into the pan instead of staying in the side cover. This would explain the large amount of fluid in the pan, and the delayed engagement of drive in the morning.

I've still got the bottom pan off, and I'm checking my Mitchell On-Demand for transmissions for a "check valve" or something similar, but I'm not turning up much. Any ideas?
 

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1997 Eldorado, 2003 Audi RS6
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1,320 Posts
This problem is interesting.

You may be onto something with this drainback thing.

The fluid is low while the car is running, yet you got a lot out of the pan. I'm not so sure about the 10 quarts thing... I've changed the fluid on these cars before. Usually you get the better part of ONE quart out of the pan when you drop it about an hour after the car was last run. You will get about 7 quarts out of the side tank. I actually do have a graduated sightglass on my drain pan, and these numbers check out on two cars so far since I've had this pan, and seems right for others prior.

Now this could all be caused in the morning by a leaking scavenging pump (the part that pulls the fluid out of the pan and into the side tank). This could allow fluid to leak around the actual pumping mechanism (I suspect a vane pump but have no idea what kind of pump the machine actually has in it) and then drain back to the pan. The reason I suspect a vane pump is that they require an anti-backflow valve to actually seal. If it were a gear pump it would naturally seal and a leak would not be so noticable.

An easy and stupid test is to check the fluid level with the car running when you put it away after driving. Then check it with the car off after driving immediately. Continue checking it every hour or so and watch to see the rate of draining into the pan, if any. Also, check before driving. Preferably do itevery hour until your next drive, say over the course of 12 hours. This of course may not be practical, so just check it regularly, then before bed, then when you get up for that midnight snack. Do NOT forget to check before starting in the morning.

Check for blocked screens on the pickup. They can be had for very little money if replacement is needed, though I've never even seen one blocked at all. Remember, fluid doesn't drain into the side tank, it drains into the pan. There is a scavenging pump that pulls the fluid out of the pan and into the tank. From this tank it is sent through the transmission.
 

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2001 Seville STS
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34 Posts
Discussion Starter #3
Well, I waited about 2 hours before changing it. I replaced the screens (2), the gasket, and the fluid with Dexron-IV. I have to say...that fluid is NICE! It smoothed out the slight reverse bang I would get, and shifting is smooth as can be. I dont have a history of the car or the fluid that was in it, but it was a brownish / red. It didn't smell burnt at all though. The original screens weren't plugged, but there were a few small specs of metal (aside from the usual particles). Nothing major.

Accordingto my Mitchell, the scavenging pump is a 3 gear type.

I checked it shortly after driving, which was about 2 hours before changing it...but the car wasn't running (I know, I know). So my readings are obviously off. Now while idling after the change the fluid is right.

In the morning, right after start-up I can almost hear what sounds like a fan slowing getting up to speed. I suspect I am hearing the scavenging pump filling up the side pan. If I wait until I hear this "fan" get up to speed and then shift into drive, all is well. If I dont wait, the I get the delayed engagement issue. I doubt the fluid change will resolve that problem though...

Sooo, there must be some sort of anti-drainback valve or mechanism in the scavenging pump that keeps the fluid in the side pan. I'll bet the fluid is supposed to remain in the side pan regardless of the time the car has been sitting...otherwise there would be no need for the drain plug.

My delayed engagement problem is probably directly related to all of my fluid being in the bottom pan less than 2 hours after driving. Many others probably have the exact same issue, but they probably dont jump in, throw it into gear, and go like I sometimes do.
 

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Premium Member
2006 STS V8 AWD, '95 Ford Ranger
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28,974 Posts
One of the most common transmission anomalys reported here is delayed engagement after sitting overnight. Maybe we just encountered a major breakthrough.
 

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2001 Seville STS
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34 Posts
Discussion Starter #6
Man, I searched and searched before my original post and didn't find much regarding the delayed engagement...like 3 posts. But I'm kind of glad to hear that this is a "common" problem. I'm going to look into this further, but I doubt any fix will be in-car.
 

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2001 Seville STS
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34 Posts
Discussion Starter #8
True. But I imagine that this is not normal, and while I doubt it will wreck anything I'd still like to know if there is anything I can do to fix it (while in the car). I'll bet though that any repairs for this type of problem require R&R of the transmission.

And if the fix is easy enough, it may benefit others that have similar (or worse) problems like this.
 

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Premium Member
2006 STS V8 AWD, '95 Ford Ranger
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28,974 Posts
There must be a transmission specialist somewhere that can tell us what the anti-drainback provisions are. In a dry sump aircraft engine it's a simple check valve.
 

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White Diamond '03 DHS (with DTS floor shift)
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86,990 Posts
I do know that you are correct in that the fluid is supposed to be in the side cover. I encountered that same thing when I changed the fluid on my '97. Got almost All of the fluid out of the pan, but never had any shifting problems that I can recall. I believe Ewill3rd is a trans guy.
 
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