Automatic Transmission Fluid change or NOT
Burning Brakes
Joined: Jul 2007
Posts: 751
Likes: 0
From: Eau Claire Wisconsin
Transmission fluid wears out, filters get clogged, get it changed. Alot of the problems arise from people using the wrong type of fluid and/or not installing the filter the correct way. A valve body is a very sensitive
thing, you want that as clean as possible and the only way to do that is to drop the pan and do a fluid/filter change.
thing, you want that as clean as possible and the only way to do that is to drop the pan and do a fluid/filter change.
Melting Slicks
Joined: Jul 2007
Posts: 3,200
Likes: 34
From: Kingsville Ontario Canada
I have a 90 Auto L98 Vert with 45,000 miles on it. I am the third owner and have no idea if the fluid has ever been changed.
The Verts have the " X Brace" under the car.
Can I remove the pan with this in the way?
Any tricks or ideas would be greatly appreciated.
Thanks. Mark
The Verts have the " X Brace" under the car.
Can I remove the pan with this in the way?
Any tricks or ideas would be greatly appreciated.
Thanks. Mark
Burning Brakes
Joined: Dec 2000
Posts: 1,161
Likes: 0
From: Orangeburg, NY
From my experience, the best results are dropping the pan and replacing the filter. It is important to note that not all the fluid is changed with this procedure. There is still a subatantial amount of fluid in the tranny, torque converter and in the radiator/radiator lines.
I have also found it useful to remove the tranny lines tothe radiator and blow them out.
I have also found it useful to remove the tranny lines tothe radiator and blow them out.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
I've heard people say that you should not change fluid on high-mileage trannies, at least those with 100K+ or more. The idea is that there is enough abrasive material in the fluid that the clutches need that material to have enough friction so that the tranny shifts smoothly.
Remove the fluid with the abrasives in it and the clutch packs could burn up. This assumes that the clutches are worn to the point where excessive heat from slippage with the new fluid will kill the tranny in short order.
Is it true? Hard to say but in the OP's case with 78K on the tranny, it would be a good idea to have the tranny serviced. Not just drop the pan and replace the fluid that is in th epan, but do a complete fluid change using a flushing machine hooked to the cooler lines. This way, you get all of theold fluid out and new fluid in. Takes about 15 minutes doing it this way.
Remove the fluid with the abrasives in it and the clutch packs could burn up. This assumes that the clutches are worn to the point where excessive heat from slippage with the new fluid will kill the tranny in short order.
Is it true? Hard to say but in the OP's case with 78K on the tranny, it would be a good idea to have the tranny serviced. Not just drop the pan and replace the fluid that is in th epan, but do a complete fluid change using a flushing machine hooked to the cooler lines. This way, you get all of theold fluid out and new fluid in. Takes about 15 minutes doing it this way.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Old clutch material, metal shavings that eventually comes off the components, material from the bushings and bearings.
As the filter fills up with that stuff, the fluid eventually just forces its way through and the finer material can pass thru the filter as it gets clogged, then small holes are created from the fluid pressure. Some filters dont even have the same type of filtering media as you would see in oil filters.
As the filter fills up with that stuff, the fluid eventually just forces its way through and the finer material can pass thru the filter as it gets clogged, then small holes are created from the fluid pressure. Some filters dont even have the same type of filtering media as you would see in oil filters.
Pro
Joined: May 2005
Posts: 525
Likes: 0
From: San Antonio TX
I have heard that doing a tranny flush is not recommened for a tranny with lots of miles. But honestly I don't know why this is so or if it is really true.
However, a tranny flush is different than just dropping the pan and changing the filter. When you drop the pan you still have a good portion of your original fluid left in your torque converter.
IMO, I would still atleast drop the pan, change the filter, then replace the fluid lost and skip the flush.
PeteK is the right guy to ask about this. Hopfully, he will come across this post and chime in.
However, a tranny flush is different than just dropping the pan and changing the filter. When you drop the pan you still have a good portion of your original fluid left in your torque converter.
IMO, I would still atleast drop the pan, change the filter, then replace the fluid lost and skip the flush.
PeteK is the right guy to ask about this. Hopfully, he will come across this post and chime in.
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Melting Slicks
Joined: Jul 2004
Posts: 2,018
Likes: 1
From: OR
I'd generally follow what your owners manual says. I think mine says change it at 100k. Having said that, I changed mine at 30k. When I bought the car @ 25k, it looked like the previous owner had been doing burn outs with it...rear tires pretty shot, fronts looked like new. The transmission fluid smelled a little burned and had turned a little darker. I flushed it and it still looks and smells like new 50k miles later. Depends on how you use the car I guess.
From my shop days, if a customer came in with a high miler car with badly burned fluid, I'd tell them there was a chance that it wouldn't function the same or for long if we flushed the transmission. Theory being that as the material sloughed off the friction discs making them thinner, the friction material makes the fluid thicker, somewhat compensating the thinner discs. Replacing the thick old oil with thin clean oil could result those discs slipping after that. The transmission is considered to be needing rebuilt at that point either way, it just might go a little farther if left alone is all. That's what the transmission guys I learned from told me 30+ years ago anyway. I'm sure the fluid the poster is talking about is not in that bad of shape.
From my shop days, if a customer came in with a high miler car with badly burned fluid, I'd tell them there was a chance that it wouldn't function the same or for long if we flushed the transmission. Theory being that as the material sloughed off the friction discs making them thinner, the friction material makes the fluid thicker, somewhat compensating the thinner discs. Replacing the thick old oil with thin clean oil could result those discs slipping after that. The transmission is considered to be needing rebuilt at that point either way, it just might go a little farther if left alone is all. That's what the transmission guys I learned from told me 30+ years ago anyway. I'm sure the fluid the poster is talking about is not in that bad of shape.
Racer
Joined: Jul 2007
Posts: 281
Likes: 2
From: Mount Vernon Indiana
Just for information, if the transmission is already damaged, changing the fluid will most likely make it worse. If your transmission is in decent shape, then you won't have any added problem by changing the fluid.
The trans in my vette wouldn't shift at WOT, I changed the fluid and now it slips almost immediately. I knew going in, I'd probably need to rebuild it. That being said, I've changed the fluid in every trans I've had, some after 100k and had no issue what so ever.
**EDIT**
Actually, I just now read the post above me. I'd say this is accurate. The cleaner fluid will make it slip more if it already is worn out.
The trans in my vette wouldn't shift at WOT, I changed the fluid and now it slips almost immediately. I knew going in, I'd probably need to rebuild it. That being said, I've changed the fluid in every trans I've had, some after 100k and had no issue what so ever.
**EDIT**
Actually, I just now read the post above me. I'd say this is accurate. The cleaner fluid will make it slip more if it already is worn out.
Last edited by black_771; Jan 21, 2008 at 10:29 AM.
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
Jesus christ. Unless some of you back yard mechanics are going to fix it for him, why don't you lay off on the bad advice? If you don't know, which obviously most of you do not, than don't post.
The dealership told him the same thing every certified mechanic would.
To the OP: Why don't you call a few tranny shops if you don't like the answer the dealership gave you. If you find someone willing to flush it, and guarantee it will shift the same way it did when it leaves as when it arrived, then go for it.
-- Joe
The dealership told him the same thing every certified mechanic would.
To the OP: Why don't you call a few tranny shops if you don't like the answer the dealership gave you. If you find someone willing to flush it, and guarantee it will shift the same way it did when it leaves as when it arrived, then go for it.
-- Joe
Moderator Emeritus
Joined: Jun 2002
Posts: 46,133
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From: Maryville Tn
CI 5 thru 12 Veteran
St. Jude Donor '09 thru '23
NCM Sinkhole Donor
I've changed the transmission fluid in every vehicle I've purchased and never had any problems. I'd drop the pan, put a new filter in it, and fill it back up. Cheap insurance.
Drifting
Joined: Sep 2004
Posts: 1,638
Likes: 3
Jesus christ. Unless some of you back yard mechanics are going to fix it for him, why don't you lay off on the bad advice? If you don't know, which obviously most of you do not, than don't post.
The dealership told him the same thing every certified mechanic would.
To the OP: Why don't you call a few tranny shops if you don't like the answer the dealership gave you. If you find someone willing to flush it, and guarantee it will shift the same way it did when it leaves as when it arrived, then go for it.
-- Joe
The dealership told him the same thing every certified mechanic would.
To the OP: Why don't you call a few tranny shops if you don't like the answer the dealership gave you. If you find someone willing to flush it, and guarantee it will shift the same way it did when it leaves as when it arrived, then go for it.
-- Joe
And he makes money by doing changes - of course he makes more money on failures - soi by that token I guess he would recomend changes - but he says he gets alot of crap from customers after their change -- having a meltdown inside the tranny. I don;t know 3whats going on inside those things - they are magic to me - but if the pro and the dealer both say leave it alone - thats good enough for me!
Carl Johansson
Team Owner
Joined: Sep 2003
Posts: 88,393
Likes: 2
From: eville in
I agree with Joe. I have been told by my mechanic that his buddy that owns a tranny shop says once you get to 100K - the tranny is living on borrowed time - he says way to many times a fluid change is followed by serious problems.
And he makes money by doing changes - of course he makes more money on failures - soi by that token I guess he would recomend changes - but he says he gets alot of crap from customers after their change -- having a meltdown inside the tranny. I don;t know 3whats going on inside those things - they are magic to me - but if the pro and the dealer both say leave it alone - thats good enough for me!
Carl Johansson
And he makes money by doing changes - of course he makes more money on failures - soi by that token I guess he would recomend changes - but he says he gets alot of crap from customers after their change -- having a meltdown inside the tranny. I don;t know 3whats going on inside those things - they are magic to me - but if the pro and the dealer both say leave it alone - thats good enough for me!
Carl Johansson
Drifting
Joined: Feb 2003
Posts: 1,614
Likes: 163
From: Davis CA
Let me see if I've got this straight.
Don't service it for 100K miles and when it reaches 100K miles, whatever you do, don't service it then unless it has had regular prior maintenance.
I certainly appreciate that a transmission shop wouldn't want to touch a car that hasn't been serviced for over 100K miles because if anything goes wrong, they will be blamed. Heck, the owner is probably trying the fluid and filter change because it has started to act up. Even more reason to not touch it.
Don't service it for 100K miles and when it reaches 100K miles, whatever you do, don't service it then unless it has had regular prior maintenance.
I certainly appreciate that a transmission shop wouldn't want to touch a car that hasn't been serviced for over 100K miles because if anything goes wrong, they will be blamed. Heck, the owner is probably trying the fluid and filter change because it has started to act up. Even more reason to not touch it.