Transmission flush - good or bad idea?

Transmission flushes are usually high priced gimmicks. Unless you're having some transmission problems (and some Hondas do) don't waste your money.

My mechanic (friend) told me that whenever places tell you that you need an "anything" flush, what they are really going to be performing is a wallet flush on you.

I'm interested in this too.

Does this mean you never need to have anything done with the transmission, except for keeping the fluid topped up?

mebert wrote:

Unless you're having some transmission problems (and some Hondas do)

Correct. A filter and fluid change with the CORRECT HONDA FLUID should be all that is needed.

If this is a CVT (some Civic HX's, GX's and Hybrids as well as the Insight hybrid), transmission use the CVT fluid, if not use ATF-Z1. Check the manual for the correct application. I would pay the difference for the Honda brand.

I've seen incorrect fluid cause a lag in shifting and poor drivability.

For a 10 year old vehicle I wouldn't recommend a flush. A flush is a pressurized fluid push through the transmission, and although a good machine can exchange around 98% of the old fluid for new, there is the possibilty of damage. At our shop we don't do them on vehicles with more than 60,000 miles. The reason for this is that there is an internal liability once the transmission has some wear/aging on it. The internal seals may not handle that much force on them, and if they break, that vehicle won't be driving out of that shop, or if it does, look for big problems down the road. The unit will basically have to be rebuilt. I would recommend a fluid and filter change. With this service, you will not get all the fluid out of the transmission. There will be fluid trapped in the torque converter (4-6 quarts) and as much as 4 quarts trapped in other places like the cooler and cooler lines etc. You may only get 4-6 quarts of old fluid drain out. This is why you want to stay ahead of the fluid curve and change your fluid every 25,000-30,000 miles.

Transmission flushes can help clear out carbon deposits and other junk that's built up in the tranny. The only problem is that as carbon builds up, your tranny adjusts for the increasing pressure, so when you flush all that stuff out your tranny isn't adjusted and could crap out and now you gotta get a new tranny. It's pretty risky and not really worth it.

Just change the fluid and filter.

not a tranny wrote:

Transmission flushes can help clear out carbon deposits and other junk that's built up in the tranny. The only problem is that as carbon builds up, your tranny adjusts for the increasing pressure, so when you flush all that stuff out your tranny isn't adjusted and could crap out and now you gotta get a new tranny. It's pretty risky and not really worth it.

Just change the fluid and filter.

This IS NOT correct.

Carbon buildup is a by-product of combustion of the engine and is no way related to the transmission.

Click or Clack wrote:

not a tranny wrote:

Transmission flushes can help clear out carbon deposits and other junk that's built up in the tranny. The only problem is that as carbon builds up, your tranny adjusts for the increasing pressure, so when you flush all that stuff out your tranny isn't adjusted and could crap out and now you gotta get a new tranny. It's pretty risky and not really worth it.

Just change the fluid and filter.

This IS NOT correct.

Carbon buildup is a by-product of combustion of the engine and is no way related to the transmission.

I was going to say the same thing. The gunk, for lack of a better term is likely caused by varnishing of the fluid. This is what happens when the fluid ages and it loses it's detergent qualities(see above post about staying ahead of the fluid curve). It will lose it's original color and become brown and sludge like. There may also be friction material in the pan from the surface of the clutch packs.

How often should the fluid and filter be replaced?

I have a chevy, and don't recall ever having it changed.

Three weeks ago my 1999 Infinity I30 with 125,000 miles on it had it's FIRST transmission fluid changed ("flush") at a Grease Monkey shop. They have a special machine to do that.After 10% discount cost is $109.24. Big difference: acceleration is very much smoother,gears shifting is practically imperceptible. I will repeat that at 200,000 miles.

All American Automotive Tech wrote:

The gunk, for lack of a better term is likely caused by varnishing of the fluid. This is what happens when the fluid ages and it loses it's detergent qualities(see above post about staying ahead of the fluid curve). It will lose it's original color and become brown and sludge like. There may also be friction material in the pan from the surface of the clutch packs.

My '89 chevy with 85k miles started jerking every few seconds early in the year and scared the heck out of me. The mechanic said it was probably the clutch not shifting right in the transmission and recommended a couple of changes of the fluid. He said about 65 percent of the fluid would be replaced with each change.

The first change was early in the year and the car drove better after that, at least it wasn't grabbing every 100 meters. Usually it would grab, a lot less than previously, every 10th of a mile or so when cold but not after being driven for 20 to 25 minutes. After that it would be fine and no grabbing.

The second change was a couple of months ago. The car has been pretty good since then but still grabs slighty sometimes, less than before, especially the first 15 minutes of driving. After that it is fine.

Is the grabbing due to the friction material?

Is there anything else that can be done, for example some additives?

By the way, the fluid and filter changes were $100 each.

Obviously depends on who does it. But the only time I had it done, it worked wonders for my transmission.

All American Automotive Tech wrote:

There will be fluid trapped in the torque converter (4-6 quarts) and as much as 4 quarts trapped in other places like the cooler and cooler lines etc. You may only get 4-6 quarts of old fluid drain out. This is why you want to stay ahead of the fluid curve and change your fluid every 25,000-30,000 miles.

So there are 3 to 4 gallons of fluid in there? Wow.

Actually the mechanic said the torque converter was probably sticking.

Is there any additive that might help, now that it's been flushed a couple of times?

fluid and filter x 2 wrote:

Actually the mechanic said the torque converter was probably sticking.

Is there any additive that might help, now that it's been flushed a couple of times?

At what speed does this occur? Is it when first starting to accelerate or after your are up to speed?

Does it only happen when cold and/or is it worse when the weather is cold?