Interesting convo with local transmission shop

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badtlc

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I just called a local transmission shop to get a price for a full fluid exchange. Without saying it at first, all he does is drain the pan and refill with same amount. I asked if ever did full fluid exchanges and he said that isn't possible. He said Honda was the only one who had transmissions you could connect the input/output cooling lines and actually exchange all the fluid. He said for everything else, you can run as much fluid through the lines as you want but it won't replace anymore existing fluid with fresh fluid than if you drained/refill.

Has anyone ever heard this before? He said he was due to the design of the torque converter transmissions but I wasn't able to keep up with some of the technical details he was explaining.

He is definitely a no frills, no upsales kind of guy. He said anything but an OEM fluid was complete [censored]. We all know better than that but I can respect a guy who won't needlessly push the envelope.
 
When I did a pan drop on my ZF6HP the fluid out was significantly less than the published capacity of the transmission.

Capacity : 9.4 liters (10Q)

Fluid change kit: ~6 liters.
 
Mechanics belong to one of three different "camps" when it comes to transmission service.

The ones that tend to be dishonest or inexperienced and lazy advocate machine flushing.

The rest are split between drain/pan-drop/change-filter and full line exchange.

Good luck changing a mechanic from one camp to another, all will have their passionate reasons for the way they do it.

By the way, I belong to the drain/pan-drop/change-filter camp just like the guy that did your estimate for you.
 
Sounds like someone I'd want working on my tranny though.

Wonder if he used a 3rd party fluid and had to eat the warranty himself and got burned.
 
You don't exchange fluid with Honda.

You drain and fill it done. They last a long time if you perform this bit that easier then changing oil. Its a drain bolt affair. My Subie indy charges me $20 labor with an oil change on my MDX. I buy the fluid (3qts) from Honda dealer.
 
Originally Posted By: eljefino
Sounds like someone I'd want working on my tranny though.

Wonder if he used a 3rd party fluid and had to eat the warranty himself and got burned.


Good question. I swear I called him for a price quote about 5 years ago and he said he put Mobil 1 in everything, regardless. Either way, I had never heard that even a line flush can't get more fluid replaced than a drain/refill.
 
I'm 100% on board with him on the OEM fluid, so I wouldn't say we all know better, especially on this forum. Some aftermarket fluid is maximum junk.

Originally Posted By: badtlc
He said anything but an OEM fluid was complete [censored]. We all know better than that....
 
Originally Posted By: badtlc
I just called a local transmission shop to get a price for a full fluid exchange. Without saying it at first, all he does is drain the pan and refill with same amount. I asked if ever did full fluid exchanges and he said that isn't possible. He said Honda was the only one who had transmissions you could connect the input/output cooling lines and actually exchange all the fluid. He said for everything else, you can run as much fluid through the lines as you want but it won't replace anymore existing fluid with fresh fluid than if you drained/refill.

Has anyone ever heard this before? He said he was due to the design of the torque converter transmissions but I wasn't able to keep up with some of the technical details he was explaining.

Haven't heard it before. I have a Honda Pilot, and it has the same 2 in/out transmission lines that run to the radiator that everything else has. It does make a convenient place to do a high volume ATF change. Perhaps he's talking about those lines relative to the fluid exchange rate of the torque converter, something only a rebuilder might know about.
Originally Posted By: badtlc

He is definitely a no frills, no upsales kind of guy. He said anything but an OEM fluid was complete [censored]. We all know better than that but I can respect a guy who won't needlessly push the envelope.

Sounds like a good guy. Leave pushing the envelope to us BITOG types.
smile.gif
 
Originally Posted By: Oil Changer
I'm 100% on board with him on the OEM fluid, so I wouldn't say we all know better, especially on this forum. Some aftermarket fluid is maximum junk.

Originally Posted By: badtlc
He said anything but an OEM fluid was complete [censored]. We all know better than that....


I agree there are a lot of aftermarket fluids that are terrible. But Mobil 1, Amsoil, Red Line, etc. all make some very good fluids, too.
 
Not sure if this is relative to the Honda, but my Chrysler transmission, the pump (at the torque converter) does not engage in Park; you have to shift to Neutral to do a full fluid exchange. Wonder if that's the basis for this mechanic's conclusions?
 
Last edited:
OP, completely platform dependent.

For the majority of slushboxes a pan drop is about 1/3 the capacity.

Fluid exchange through the lines is the only way to even hope of swapping the majority of the fluid...
 
I have a Gen 4 Camry with 300K on the clock, all the automatic has ever received is 15K pan drains through the drain plug which Toyota thoughtfully includes on that model. According to the manual it's less than three quarts and that's what I replace it with. FOr about the past 100K it's received The Warren Oil product which Wally sells.
 
Probably wasn't ideal way to do it, but on my Taurus I disconnected a cooler line and started it up. Then filled through the dipstick tube while the engine ran and put it in different positions.

I put almost the entire capacity through the transmission. To the point that every time I checked , it looked brand new.
 
Originally Posted By: SteveSRT8
OP, completely platform dependent.

For the majority of slushboxes a pan drop is about 1/3 the capacity.

Fluid exchange through the lines is the only way to even hope of swapping the majority of the fluid...


That is the point of the thread. According to him, unless it is a Honda, the fluid exchange through the lines only replaces the same amount as a pan drop/drain/refill which is nowhere near all the fluid.
 
Originally Posted By: badtlc
I just called a local transmission shop to get a price for a full fluid exchange. Without saying it at first, all he does is drain the pan and refill with same amount. I asked if ever did full fluid exchanges and he said that isn't possible. He said Honda was the only one who had transmissions you could connect the input/output cooling lines and actually exchange all the fluid. He said for everything else, you can run as much fluid through the lines as you want but it won't replace anymore existing fluid with fresh fluid than if you drained/refill.

Has anyone ever heard this before? He said he was due to the design of the torque converter transmissions but I wasn't able to keep up with some of the technical details he was explaining.

He is definitely a no frills, no upsales kind of guy. He said anything but an OEM fluid was complete [censored]. We all know better than that but I can respect a guy who won't needlessly push the envelope.


He is flat out wrong with respect to most vehicles. Some may have to be put in N to do the complete fluid exchange.

But if your fluid is dirty, you can easily see how much old ATF you get out before the fluid changes color and its a whole lot more than whats in the pan.

I would agree you cannot do a total fluid exchange, but you are way above 90%.
 
Don't deal with this yahoo. Find a BG service center near you and get them to do a flush and fill with BG ATF using their own machinery that gets all the old fluid out and all the new fluid in. Anything other than OEM is junk? This guy is a real space cadet.
 
Originally Posted By: SteveSRT8
OP, completely platform dependent.

For the majority of slushboxes a pan drop is about 1/3 the capacity.

Fluid exchange through the lines is the only way to even hope of swapping the majority of the fluid...


Agree, but I can see where this guy is coming from.

As for the OEM only fluid, he was probably burned on a warranty claim at some point so he is taking the safe approach. We sell a ton of ATF to shops that have been screwed over using a universal fluid on a customer's vehicle.
 
Originally Posted By: badtlc
Originally Posted By: SteveSRT8
OP, completely platform dependent.

For the majority of slushboxes a pan drop is about 1/3 the capacity.

Fluid exchange through the lines is the only way to even hope of swapping the majority of the fluid...


That is the point of the thread. According to him, unless it is a Honda, the fluid exchange through the lines only replaces the same amount as a pan drop/drain/refill which is nowhere near all the fluid.


Thank you for your comment. At what point did I lose you?
 
I don't see how he can be right. All of the fluid is going to pass through the cooler lines. If you're constantly filling the pan with fresh fluid, it's going to circulate with the old and be run out through the cooler line until all that remains is the fresh fluid you're feeding it.

For instance, I did this type of fluid change on my Toyota. Per the service manual, a pan drop and fill is slightly less than three quarts, while a full fill is almost seven quarts. True to form, using the cooler line method to do the flush, I didn't start seeing relatively clean, clear fluid until around quart (get ready for it) seven or eight. If I had seen three dirty quarts come out of the cooler line and then it ran clear, I'd be more apt to believe him, but my evidence seems to say otherwise. I put three extra quarts through it for good measure for a total of eleven, and those last three quarts were clear as a bell and dark red.

I then hooked everything back together and drove the truck for 15 minutes or so to warm the fluid for the infamous Toyota "no dipstick" level check. During this time, if there were still four quarts of dirty fluid left in the converter, it should have mixed pretty well with the fresh fluid. Yet, when I pulled the drain plug and removed the roughly 1/2 quart overage, it was still deep red and clear as a bell.

In a nutshell, he may be right about *some* car out there, but not all of them.
 
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