Why don't transmission pans have drain plugs?

[satterfi]

It sure would make the job easier.

I changed the auto trans fluid in my wife's Explorer yesterday. This is the first auto transmission I've done work on. Even though I sucked out 2 quarts from the filler tube, when you drop the pan, fluid goes everywhere.

This is not job to be done without wearing safety glasses.

 

[lee]

I've got two Toyotas and a Subaru. These are all the automatics I've ever owned (wife's insistence). Anyway, didn't know autos didn't have a drain plug - all of mine do, usually get 5 qts from the Subaru and 4 from the Toyotas with a simple drain. The differentials also have drain and fill plugs. Been doing a drain and refill with oil change the last couple times - figure it can't hurt.

 

[digitaldrifter91]

my auto has a drain plug...

 

[Patman]

I think the idea behind it was to make sure people would put in a fresh trans filter as well as cleaning off the pan magnet. If they just put in a drain plug, people would neglect doing these things. Although with the advent of the full trans flush, people don't often drop the pan anymore anyways. My 75,000 mile Firebird has never had the pan off, since when I got the car I had the trans fully flushed, they didn't have my filter in stock for it. But I plan on getting a fluid and filter change done on my transmission this month.

 

[dkcase]

How much should one expect to pay for the full trans flush ?

 

[satterfi]

I've been paying $130 for the job at one garage. He changes the filter.

The Ford dealer charges $80 with no filter change.

I have my doubts about the flush procedure. They charge you for 10 quarts of oil but you can only get 4.5 quarts out when you drop the pan. The torque converter can't be drained without removing the transmission and then pulling the torque converter off the flywheel.

 

[SteveD2]

Some models of Ford transmissions have a torque converter drain plug that is accessible when the pan is off.

The usual way to flush is through the cooler hoses. A machine with a dual-chamber vessel is connected to the hoses, one chamber is filled with new ATF, and the engine is run. The pressure of the ATF being pumped from the transmission fills the empty chamber and forces the new ATF from the other chamber into the return hose and into the transmission. Cheapo shops just clamp the hose with vise-grips while they add new ATF down the filler tube.

I prefer to drain the pan and refill before the flush. Best, of course, is to remove the pan, clean it, and renew the filter, if fitted.

Shade tree mechanics can do the same job by connecting a short hose to the cooler hose from the transmission. After draining and refilling the pan (if feasible), idle the engine, pump two quarts of old ATF into a jug, stop the engine, add two quarts of new ATF down the filler tube, pump out two more quarts, etc., etc., until a full exchange is complete, 14 or 15 quarts on most transmissions.

I'd like to use 6 oz. of Auto-Rx in the transmission for 500 miles before the flush. If the transmission sump doesn't have a filter I'd add a filter in the cooler line.

Ken

 

[Frank]

Transmission Fluid never gets out of the torque converter by using conventinal flushing methods.
Unless the torque converter is clean (in my opinion) your wasting your money by putting clean transmission fluid in the top end only, because it will get contaminated again quickly.
visit www.auto-rx.net for some differen't ideas
on cleaning your entire transmission.

 

[OneQuartLow]

quote:

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Originally posted by Ken:
...I prefer to drain the pan and refill before the flush. Best, of course, is to remove the pan, clean it, and renew the filter, if fitted.

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Definitely. An old plugged filter doesn't help fluid movement, or valve operation should something come loose. I've heard of too many valve-body malfunctions the week after a flush. I'm not sure if these are reverse flushes or something unusual but it's too common to be comforting.

quote:

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Shade tree mechanics can do the same job by connecting a short hose to the cooler hose from the transmission. After draining and refilling the pan (if feasible), ...

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Yep. After changing the filter I use two identical buckets and a drill motor pump. Start the engine & match drill speed so I fill at the same speed it's dumping. When supply is spent, shut off, reconnect hoses, & ensure proper level. Not difficult once you get a procedure down.

-Use identical buckets.
-Use a new, white, trashbag/liner for the supply bucket. (helps keep out junk)
-Use plastic stir sticks to mark graduations. (Supply counting downward, dump counting upward.)
-Use an inline fuel filter between the pump & the line back to the trans. (Filters gremlins & acts as female/female adapter.)
-Make sure drill has a full charge. Flushus interuptus.

David

 

[Greg]

mine does.

in fact it has like 4. the main one which is magnetic, then 3 other little 10 or 12mm bolts that screw on at an angle on the bottom of the tranny.. if you unscrew those a few mL of fluid comes out. oh well, it adds up i guess.

91 honda civic btw.

 

[jason07-1zzfe]

That's a good question! Maybe they heard used ATF was good for you, so they thought they would be doing us a favor by giving us a shower of it?

And how about no drain plugs on GM's diffs?? Who's brainstorm was that?!?

 

[lee]

Please help - trying to learn...

I think the "full flush" method doesn't work well on my car - are others the same? Here's the way my tranny works...

Pump splits flow - part to torque converter (TC) - part to valves/clutches, etc. The part going to the TC then goes out to the cooler and then returns to the pan (this is the hotter path as I understand it). The part that went to the valves, etc, just goes back to the pan without ever seeing the cooler.

So if I flush, new fluid being added to the pan and mixing with the old - right?. This mix is then sucked up and part of that mix goes to the TC and out to be discarded. Part goes through the valves and back to the pan to remix yet again, etc. Seems to me that one would have to run considerably more new fluid (than the system dry would hold) to get a total replacement - maybe 3 or 4 times as much as dry capacity?

But if I drain, then drop the pan to change filter I get a straight-up half system fluid change. To get the same half replacement in a flush scenario I think I would have to double the amount used and I still have to worry about the filter change.

What am I missing here?

[ November 13, 2002, 10:09 PM: Message edited by: lee ]

 

[nick778]

quote:

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Originally posted by Jason Troxell:
That's a good question! Maybe they heard used ATF was good for you, so they thought they would be doing us a favor by giving us a shower of it?

And how about no drain plugs on GM's diffs?? Who's brainstorm was that?!?

---

I personally think that GM does not put drain plugs on some of their diffs, tansfer cases and transmission pans so the average joe is more motivated to make a visit to mr goodwrench. Given that fluid changes in all these area is a routine service item for GM vehicles(i.e., every 30K), it has to be something GM made a decision not to do.

 

[RobZ71LM7]

quote:

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Originally posted by nick778:

quote:

---

Originally posted by Jason Troxell:
That's a good question! Maybe they heard used ATF was good for you, so they thought they would be doing us a favor by giving us a shower of it?

And how about no drain plugs on GM's diffs?? Who's brainstorm was that?!?

---

I personally think that GM does not put drain plugs on some of their diffs, tansfer cases and transmission pans so the average joe is more motivated to make a visit to mr goodwrench. Given that fluid changes in all these area is a routine service item for GM vehicles(i.e., every 30K), it has to be something GM made a decision not to do.

---

It's really simple. When doing a ATF change on a GM vehicle you're supposed to remove the filter at the same time which require that you remove pan. This makes the plug unnecessary so GM eliminated it in order to cut costs. Lately they've started putting it back on the trucks b/c of consumer complaints.

 

[SteveD2]

quote:

---

Originally posted by lee:
Please help - trying to learn...

I think the "full flush" method doesn't work well on my car - are others the same? Here's the way my tranny works...

Pump splits flow - part to torque converter (TC) - part to valves/clutches, etc. The part going to the TC then goes out to the cooler and then returns to the pan (this is the hotter path as I understand it). The part that went to the valves, etc, just goes back to the pan without ever seeing the cooler.

So if I flush, new fluid being added to the pan and mixing with the old - right?. This mix is then sucked up and part of that mix goes to the TC and out to be discarded. Part goes through the valves and back to the pan to remix yet again, etc. Seems to me that one would have to run considerably more new fluid (than the system dry would hold) to get a total replacement - maybe 3 or 4 times as much as dry capacity?

But if I drain, then drop the pan to change filter I get a straight-up half system fluid change. To get the same half replacement in a flush scenario I think I would have to double the amount used and I still have to worry about the filter change.

What am I missing here?

---

You're right, but what's the best alternative? The flush isn't perfect, but is far superior to the alternative (doing nothing). If you just want to drain the pan and refill every other oil change, or some other regular schedule, OK...still far better than nothing.

Ken

 

[nick778]

quote:

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Originally posted by RobZ71LM7:

quote:

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Originally posted by nick778:

quote:

---

Originally posted by Jason Troxell:
That's a good question! Maybe they heard used ATF was good for you, so they thought they would be doing us a favor by giving us a shower of it?

And how about no drain plugs on GM's diffs?? Who's brainstorm was that?!?

---

I personally think that GM does not put drain plugs on some of their diffs, tansfer cases and transmission pans so the average joe is more motivated to make a visit to mr goodwrench. Given that fluid changes in all these area is a routine service item for GM vehicles(i.e., every 30K), it has to be something GM made a decision not to do.

---

It's really simple. When doing a ATF change on a GM vehicle you're supposed to remove the filter at the same time which require that you remove pan. This makes the plug unnecessary so GM eliminated it in order to cut costs. Lately they've started putting it back on the trucks b/c of consumer complaints.

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yes, but they still leave it out of the rear diff and the transfer cases of 4x4 vehicles....

 

[FowVay]

The fact that the domestic mfgr's want the filter changed at the same time as the fluid is certainly no reason to have such a absurd method of changing the fluid. It is completely ridiculous to have to try to balance a pan full of fluid which is going to spill on the entire shop floor. Just imagine the concept of draining the fluid BEFORE removing the pan. And if this were their primary reason for leaving off the drain plug then how are their new filters lasting the life of the vehicle? I think they're just too cheap to put a plug on the pan.

 

[OneQuartLow]

Many transmissions service schedules include band adjustment that coincides with filter replacement. The pan usually has to come off to get to at least one of them.

That, along with checking the magnet and removing wear material, means pulling the pan. (much like proper differential service)

The process isn't very difficult or even messy if you have one of those 5ft tall stand-up drain pans, and the lift to go along with it.

Seems like mfgrs make presumptions about shop equipment while bean counting. There probably aren't many shadetree mechanics on the design teams.

I agree though, it can be painful. To make it simpler use lots of cardboard and drop one corner to let the bulk out before the circus balancing act. If you know anyone with a welder, drain plugs cost
Personally, I don't mind the balancing part as much as the continual valve body drips while adjusting things.

David

 

[RobZ71LM7]

quote:

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Originally posted by nick778:
yes, but they still leave it out of the rear diff and the transfer cases of 4x4 vehicles....

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That's b/c it's regular to inspect the gars when you change the fluid-and the gasket usually has to be changed anyways. My rear end covers also have magnets on the inside too. Ultimately it all boils down to cost reduction.

 

[The Car Whisperer]

A way that I have found that eliminates taking a shower with the ATF is to transfer the fluid out of the transmission through the fill tube. It's easy and no mess. All you need is a vacuum pump and a large brake bleeder jar that you can make yourself from an old mason jar. It works best if the fluid is warm.