Changing Transmission Fluid

Basic Repairs and Fixes.

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Rocketguy
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Changing Transmission Fluid

Post by Rocketguy » Thu Jan 13, 2005 4:54 pm

According to the service manual, the transmission in my TS holds 11.5 quarts. If you change the filter, it specifes 6 quarts to refill it. This is roughly half the fluid.

Would it be benneficial to replace all of the fluid?

Has anyone ever pulled the pan and run the car briefly to pump more or all of the old oil out of the trans before refilling it?

Is there any chance this would this damage the transmission?
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Post by Le-T-Type » Thu Jan 13, 2005 5:23 pm

I had my tranny serviced yesterday by the same mechanic that rebuiilt it a few years ago. He is a top notch mechanic and did mention that I need to fill the tranny up to the bend on the level stick verses the normal spot pattern section of the dip stick. He did not start the car to try and drain any extra tranny oil. The fluid was pretty clean for 50K miles since it was rebuilt. I probably would not take the chance and if I was concerned I would do a double flush by filling it up and running it for a few days and drain the tranny again and refill to be on the safe side to get rid of any dirty tranny fluid that may have stayed when you drained it the first time.
Last edited by Le-T-Type on Thu Jan 20, 2005 1:09 am, edited 1 time in total.
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BillyBoy
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Post by BillyBoy » Thu Jan 13, 2005 5:26 pm

A large portion of the fluid ends up in the torque converter.
I don't think it is possible to get the fluid out while it is in the car.

There are some fancy machines that are made to cycle out all of the
fluid through the cooler lines while the engine is running.

I don't see it being necessary as long as you have never overheated
the trans fluid.
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Rocketguy
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Thanks for the input dudes....

Post by Rocketguy » Thu Jan 13, 2005 5:42 pm

Thanks guys.

I considered running it for a few days a half hour too late.

The service manual says you should re-use the gasket as long as it is not damaged. I put the new one on in conjunction with silicone sealer. I should have reinstalled the old gasket, run it for a few days, drained it and reinstalled the pan with the new gasket. Doh! ! :twak: Now I don't want to take the pan off again cuz it will most likely destroy the gasket.

I guess since it was only $12 I should just do it all again in a few months or so.

It just seems like it would be best to change all of the fluid if you were going to change it, which is why I asked about pumping it out.

I did consider the tork converter holding the fluid. I think at least some of it would pump out if you ran the car though. The OEM converters used to have drain plugs on them, but I don't think they have used them for some time. I did not pull the inspection cover to check to see if it had one. I was pleased to see that the factory had put a magnet in the pan though.

Back in the early 80s I bought an old Cutlass engine from a junkyard. I wanted to hear it run before I left the yard with it. It started and ran fine, but the radiator was not in the car. It pumped all of the trans fluid out the coolant lines. I know it was empty because I could hear the vanes spinning inside the converter. The fluid was nasty, and had about 100K on it. I put the engine/trans in another car and about 5-10K miles later the trans went out. I don't know if it had anything to do with pumping out the fluid or not. It was an old 2 speed Super Turbine 300.
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Post by MICHAEL MEYER » Thu Jan 13, 2005 6:20 pm

you definately can start the car for a few seconds while the pan is off of the tranny - it will get a little more fluid out of the converter without harming anything

mechanic and did mention that I need to fill the tranny up to the bend on the level stick verses the normal spot pattern section of the dip stick.
that is sooooooooo WRONG!!! NEVER do this!! if the auto tranny has more fluid in it (past the full mark) it will start to foam the fluid and the air bubbles in the fluid will make the clutch holding power weaker and cause the tranny to start slipping!! definately dont want that!

The service manual says you should re-use the gasket as long as it is not damaged. I put the new one on in conjunction with silicone sealer.
first of all, never re-use the gasket. leaks just arent worth the troulbe!
secondly, NEVER NEVER NEVER use any kind of silicone on or near any part of the transmission!!!! that is death to auto trannies!! if one little tiny spec of silicone smaller than the width of a human hair gets loose and makes it through the filter you will destroy the tranny! it will make a valve stick and then toast the tranny. please dont use any silicone on the pan gaskets or anywhere else in a tranny!
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Post by Le-T-Type » Thu Jan 13, 2005 6:36 pm

MICHAEL MEYER wrote:
mechanic and did mention that I need to fill the tranny up to the bend on the level stick verses the normal spot pattern section of the dip stick.
that is sooooooooo WRONG!!! NEVER do this!! if the auto tranny has more fluid in it (past the full mark) it will start to foam the fluid and the air bubbles in the fluid will make the clutch holding power weaker and cause the tranny to start slipping!! definately dont want that!
I questioned this too but I also trust my mechanic. All he does is transmissions and has been doing it for 30 years. He has a major shop and services alot of commercial vehicles as well. I have kept the tranny fluid according to his instructions after he rebuilt it and when he drained it yesterday it looks very clean for 50K miles on it. I only fill it a little passed the full mark where the first bend in the dip stick is.
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Post by T » Thu Jan 13, 2005 7:24 pm

Here's what I do if the fluid hasn't been changed in a while. Drain the fluid and the cooler lines. Refill with fluid and run for several minutes. Drain the fluid and cooling lines again and change the filter. Replace fluid.

This gets most of the fluid out and a lot of particles which are often left in the cooler and lines. Buy your filter at the dealer(around $20 with gasket) they give you the correct one with a correct gasket unlike some places. I usually get around 6.5-7 quarts out of it this way. Some transmissions you can only get 20% out of(mostly Foreign), this is what some companies use to justify a flush machine.

Use the new DEXRON IIIH fluid it is much better then older variations. I use Chevron. Stay away from additives, most are snake oil or actually harmful. I have heard good things about Lube Guard's product and I used AutoRX on my 210,000 mile transmission with no problems.

-T

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Post by tony t-man » Fri Jan 14, 2005 3:00 am

Hey T, the Tranny fluid is called Dextron III H? If so that's good to know because I have to service mine in the spring.

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Post by T » Fri Jan 14, 2005 3:39 am

Yes it's the latest DEXRON III requirement. It should say "meets H spec" on the bottle somewhere.
-T

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Post by tony t-man » Sat Jan 15, 2005 12:13 am

Thanks for the info. :)

Tony
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Post by viper_cole » Sun Jan 16, 2005 4:18 am

i know i need to service my tranny any tips on the first time???
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Post by Mistascott » Sun Jan 16, 2005 8:54 am

Le-T-Type wrote:
MICHAEL MEYER wrote:
mechanic and did mention that I need to fill the tranny up to the bend on the level stick verses the normal spot pattern section of the dip stick.
that is sooooooooo WRONG!!! NEVER do this!! if the auto tranny has more fluid in it (past the full mark) it will start to foam the fluid and the air bubbles in the fluid will make the clutch holding power weaker and cause the tranny to start slipping!! definately dont want that!
I questioned this too but I also trust my mechanic. All he does is transmissions and has been doing it for 30 years. He has a major shop and services alot of commercial vehicles as well. I have kept the tranny fluid according to his instructions after he rebuilt it and when he drained it yesterday it looks very clean for 50K miles on it. I only fill it a little passed the full mark where the first bend in the dip stick is.

We are told to overfill our trannys by a quart in the GN community. The reason has to do with a rather shoddy pan design. Most GM trannys have a weep hole that will let out excess fluid. It shouldn't present a problem in my opinion.
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Post by Mistascott » Sun Jan 16, 2005 9:00 am

viper_cole wrote:i know i need to service my tranny any tips on the first time???
The filter is annoying because it has a metal bushing instead of an o-ring around the plastic filter neck. I ended up breaking mine off and I had to pry the metal bushing out.

Be very careful and patient with the new filter. I had to remove the bushing from the new filter, lightly hammer it into the tranny, then slide the plastic filter neck (and filter) into the bushing.

I used a no-name Advance Auto kit (filter and gasket). It worked fine and the cost was around $15. Hope that helps.

Finally, I wouldn't worry about not getting all the fluid. If you change it regularly (every 30K), you will generally do a good job of cycling new fluid through.
Scott
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Post by T » Sun Jan 16, 2005 5:15 pm

I have a fully write up on changing transmission fluid started. I never finished it because I didn't get a response to my other write ups, but I can finish it if people want.
-T

'87 Lesabre T-type
L67 swap, CAI, STB, 180deg stat, Walbro 307 fuel pump, tranny cooler, Michelin XGT H4s, ZZP 3.4 MPS, AC 41-601 plugs.
PB: 14.447@95.08 (2.299 60ft.)

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Rocketguy
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Transmission Transfustion

Post by Rocketguy » Sun Jan 16, 2005 5:25 pm

Mike Meyer, your expertise is an asset to this site, thank you. I will never use silicone on a trans pan again! Once used, I will have to be especially careful when I change it next time because that is when pieces of it will get broken loose.

Do you use any gasket sealer at all on the pan?

My filter was stubborn coming out and going back in too. The service manual says to use a screwdriver or similar to remove it, and I had to use a small dead blow hammer to carefully tap mine back in all the way.

After I refilled mine with the reccomended 6 quarts, it was still 2 quarts low. It must have been that way before I drained it (I didn't check it before). I just drove it 1200 miles in the last 2 days, when I checked it this AM the color was nice and red, so it is fine. In fact I accidentally over filled it about a half pint. I checked it a couple times on the trip when getting gas and there was not the slighest hint of bubling or foam in it.

The old fluid was nasty, it stunk up my whole garage.

When I do it again I will drain the coolant lines and run the car for a few seconds to extract as much of the old fluid as possible. If you do this guys, have a big drain pan or a lot of saw dust handy.
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