Just picked up two gallons of Amsoil transmission fluid along with a bottle of Amsoil Engine/Transmission flush. I've been thinking about doing a complete transmission flush but I've read mixed reviews about doing this exact procedure. Some say that it's bad to flush the transmission as supposedly there are certain particles in the old fluid that help the transmission and flushing it would just knock the particles loose.

There is 138k miles on the car and I would assume that it has the original transmission. (Bought the car with 101k miles)

Anyone recommend on just a regular drain and refill? Or would a complete drain of the pan and torque converter be alright? Amsoil instructions say to completely drain all old fluid out but I wouldn't want to do that obviously if it'll do more harm than good.

If anyone has any insight on this, it'd be appreciated. Thank you!

 

Opinions and experiences vary. Not sure what the Amsoil "flush" product is.

In rare cases flushing can cause problems due to muck be circulated thru the trans rather than sitting harmlessly in the bottom of the pan. Most typically a problem would occurr if the trans is already on its last legs to begin with. The "power flushing" equipment used by many professional shops can exacerbate the muck stirring.

I would pull the pan to check for (and clean) any sediment in the pan the proceed with exchanging the fluid. Might as well replace the filter although in actuality they very seldom are clogged.

If your torque converter has a drain plug (many don't) then by all means drain it. Most of the fluid is held in the converter.

If you don't have a converter drain then one alternative is to drain the pan, refill with your new oil, drive a couple miles, then repeat 3-4 times. Obviously, each time you repeat the process the proportion of new oil versus mixed oil increases

Another idea is to pump out all the old oil by disconnecting one of the cooler lines and attaching a hose to dump the output in a 5 gallon pail. With the hose attached run the engine for a few seconds and replace however much has been pumped out with fresh oil. Repeat the process several times. The oil gets pumped out very fast. I only pump out 2-3 quarts at a time.

The layout/configuration/accessibility of the cooler pipes on some cars....not sure about yours....can make this technique impractical. It's just too difficult to get a hose attached.

Cheers
DD

 

My take.....are you having transmission problems? If not why would one go through the trouble of flushing it with an AMSOIL flush product which is not what Jaguar put in it or intended it to have. If preventive maintenance is desired I'd just do a pan drop, filter and fluid service and as Doug said clean the pan of sediment. If it isn't broke I wouldn't recommend fixing it, 50% of ones maintenance is usually caused by 50% of ones maintenance. Not a big fan of "flush" products as they are not always easy to ensure they are completely gone and auto trans relies on very small passages which have been known to get trapped "flushed" byproducts in.

 

As doug said, a flush can cause more problems. What car do you have? Do you know if it's the getrag box or the big GM? If you're going to replace fluid, which is never a bad thing, especially if you don't know when it was last done, drain everything, and replace the filter. I don't know if i'd personally use a flushing product, but would 100% recommend replacing the fluid.

 

I agree with Doug, drain the fluid then drop the pan and take a gander. If all looks good, clean the inside of the pan, change the filter (may as well) and then do a series of fluid drain and refills.

It's very straightforward and although a bit expensive, your tranny will thank you

 

A drain plug in the transmission pan naturally makes the process much easier. My 4L80E trans has one but my understanding is that only *some* of the ZFs do. If you don't have one it's no big deal to install one.

I do the drain-n-fill every 12k miles or so. A bit of overkill, no doubt, but it's irresistably easy. I can do it without even raising the car. I reckon the perpetual fluid sweetening can't hurt and might help.

Cheers
DD

 

My ZF has a drain plug

 

Last time I did this, I removed the fuel injection fuse and just cranked. Still came out so fast I had to weight down the end of the hose in the bucket with vice grips to keep it from flailing about spraying everything.

 

I've got a 1996 XJ6 with the 4HP24 transmission and as far as I know, I don't have a drain plug in the torque converter or the pan.

Since I have 2 gallons of transmission fluid what I think I'm going to do this weekend is just a drain and refill with no flush then drive for a week then the next coming weekend, do another drain and refill. I'd rather not risk hurting my transmission with the flush.


Thanks for all the input everyone! The reason for wanting to do a transmission flush is I'm at about 138k with the same fluid but only did a drain and refill so it's a mix of new fluid at 101k and old fluid that I have no idea how long it's been in the transmission.

 

I've used Amsoil's Engine flush for many vehicles over many years with good results. Every used vehicle I've bought has been flushed with this product; that is the engine has been flushed. Only recently did Amsoil change to a combined engine/trans flush, and I've never used any chemical flush in a transmission.

Auto trans flushes can fry transmissions on poorly maintained units that are full of sludge. They can dislodge larger particles that then circulate and occlude the small passageways within every auto trans. But, this occurs in the setting of not changing the filter, just doing the flush, refilling with new fluid, and leaving the old filter which can't remove the circulating particles.

If you're going to change the ATF I would also definitely change the trans filter. Synthetic engine oil and ATF have much stronger solvent properties than regular petroleum fluids, so they will gradually remove sludge and varnish without a dedicated flushing chemical, just a lot more slowly. Where does the solubilized debris go? Into the filter, hopefully!

Here's one recipe for a thorough fluid renew:

1. Drop the pan, drain as much ATF as will come out, install a new filter.
2. Replace the pan, refill with new fluid. Drive for a few km to ensure all the new fluid has mixed with the old.
3. Drain the pan again, refill, drive. Do this 6-8 times in total.
4. Start driving the vehicle as usual.
5. After a few thousand km/miles replace the filter again.
6. Now do a fluid/filter change at whatever change interval makes you happy.

For my XJR's GM auto trans, a pan drop alone allows ~4 qts to drain. So, I calculated the percent change in ATF per 4 qt replacement in my 13.5 qt capacity trans:

change 1--30%
change 2--51%
change 3--66%
change 4--76%
change 5--83%
change 6--88%
change 7--92%
change 8--96%

OK, mea culpa, I've got OCD traits. Anyway, I'd change the fluid as many times as you wish to get to the percentage new fluid that makes you comfortable.

 

I always change out the filter for oil and trans fluid changes. I'm going to go with the "safest" way I think for now which is just dropping the pan, changing the filter then gradually replacing the fluid once every few weeks and each with a new filter.

 

Your plan works too. But I don't think you need to change the filter that often. You need to give the fluid time to solublilize any sludge which the filter will capture.

One benefit to your plan though is that removing the filter allows more fluid to drain. At least it did in my XJR's GM transmission. When I was having all the initial work done on my car, I had the mechanic change the fluid and filter. I used regular petroleum Dexron III oil. By removing the pan and filter he was able to drain out almost 8 qts. When I did a pain drain only (my trans has a drain plug) to start installing synthetic fluid, I got 4 qts to drain.

So, using my transmission's volumes (not sure about the ZF trans), changing 8 qts at a time in a 13.5 qt trans would give this sequence:

change 1--57%
change 2--83%
change 3--93%
change 4--97%

So, 4 changes could essentially completely refresh the trans fluid. When you do you first pan drop and filter change, let it drain for as long anything drips and see how much comes out. Then you can calculate how many changes it will take to refresh the fluid to the percentage that you want. Let us know how it goes.

Which ATF do you plan on using?

 

I think what I'll do is replace the filter after the first pan drop, drive the car around for a little bit, maybe wait until the next day to drop it again to replace fluid again but not change the filter until maybe the 4th fluid change. I'm not sure right now how many changes it would take to get close to 100% fresh fluid but I'll go with your calculations so at least the second filter will be flowing with almost all new fluids.

I'll be using the OE Amsoil transmission fluid all the time.

 

According to a few posts I found, your ZF transmission may only have a capacity of 7 or 10 litres. Not much available on the 'net for this unit. If so, you'll need less changes to refresh the fluid than I calculated for my 4L80E trans.

Good choice on the Amsoil ATF. I've used "ATF" not "OTF" but Amsoil products are excellent. Once you refresh all the fluid you can go back to the recommended factory fluid change interval.

 

According to the ZF manual, the capacity is 8 litres. You can expect to get about 3-4 litres out by dropping the pan and filter.

 

AllanG, many thanks for the correct capacity. I've recalculated the percentages based on your information, per oil change:

A. If 3 litres can drain, out of 8 litres total:

1--38%
2--62%
3--76%
4--85%
5--94%

B. If 4 litres can drain, out of 8 litres total:

1--50%
2--75%
3--88%
4--94%