Tranny Fluid

I want to change my tranny fluid but put in the Mobil 1 synthetic tranny fluid. I know I won't get out all of the old stuff and the bottle, if I remember right, says that it is compatable with non synthetic fluid. How true is this,? I know some companies claim lots of things that might not be true. Also if I am just changing the filter and fluid, anyone remember how many quarts? I have done it before but can't seem to remember. this is on a 98 auto XJ.

Most synthetics will mix with dino oil - as I recall. Aren't there a couple 50/50 premix synthetic blends on the shelf at the local? I know Valvoline did it, and I think Castrol and Pennzoil did as well. I've mixed Castrol Syntec with dino Castrol and dino Valvoline with no ill effects as well.

You probably don't need to change the filter - if you don't get any little nasties in the fluid and it looks good, I'd not drop the pan. Whether you change the filter or not, you will need four quarts of fluid for a drain and fill.

5-90

In the industrial products line, Snap-On tools has a machine that changes the fluid completely. You place the machine in series with the trans cooler and start the engine. Fluid flowing to the machine goes into a waste oil storage tank and the machine pumps clean atf into the system via the cooler. The machine works great but uses about 2qts. more than a complete refill as the extra 2 qts act like a flush. At a shop where the labor rate was $95 per hour, this procedure cost me $150 including ATF. The machine costs ~$8K.

That said, I have seen posts on this board stating not to use synthetics in the auto tranny, to slippery for the vicous coupling. I did use synthetic ATF in my CJ7 that had a GM THM 400 without ill effects, but stayed with dino for the XJs AW4.

Good Luck,
Tom

I don't have an auto.. but I recall hearing something about it running funky with synth stuff (no... it's not the AX15 issue I am talking about...). You might want to go to the old style (archive) forums for the OEM and search through them: you might get luck and come across a post about it...

Kejtar

i spoke/asked on this topic extensively a few months ago b4 i did my tranny flush/fill, and the result ( i believe was this
(and i use synth everything in my XJ)

do not use synth ATF in the tranny. period. DO NOT.
especially Mobil 1....because its apparently not rated for it, and its too slippery for the AW4.
i used regular Valvoline with great results so far.
CAM II is cheap, so instead I'd go with a good brand of regular ATF and simply change it frequently (regularly).

feel free to ask me any more questions about this, i read up a lot on it awhile ago ;-)

CaptTrev

Thanks for all the help. I am glad that I checked back here because I was at the parts store earlier and almost just bought the stuff . I was talking to one of the other mechanics at work who only fixes the company cars and trucks and he mentioned the same thing. He said that the synthetic doesnt seem to agree with some chrysler/jeep trannies but seems to work fairly good in GM applications like the turbo 350. Too bad they can't make a fluid that can withstand the temps that the synthetic can but, isn't too slippery.

The results of Syn in the auto tranny run from 'good' to 'no change' to 'toasted it'. I'd stick with either OEM fluid or normal tranny fluid.

Hummmmm

If a trans fluid has the rating Dexron II or III it will work just fine in the AX4, reguardless if synthetic or not. Cannot be too 'slipery'. That is an old wives tale. Yes, is an improved lubricant in many ways and may exaserbate a serious problem in the trans that is presently existing. This is the thing that one runs into- if damage has been done to clutch packs at some point, and a lube change, especially one with really good ATF might cause things to go ahead and go completely bad. So, if you are worried your trans has been really damaged at some point in the past to where you notice occasional slippage in a gear, you might not want to use synth ATF, or even do a service at all. I have seen many times where a marginal trans has had a service then went totally bad.

I have noticed the same thing on several occasions. Anyone have an idea as to why this is? It would seem to me that fresh fluid would help things not make problems worse. And also is there really any difference from the oem fluid, and say a good quality dextron fliud? I doubt that chrysler makes it own fluid so it must buy it from somewhere, which means there is probably some cheaper brand which makes Identical fluid.

Generally, when clutches start to slip, the fluid is "broken in" to the point where it isn't as slippery. When you put in the new fluid, it's really slippery and will finally break the friction of the clutches. Going to a synthetic fluid exacerbates this.

Despite reports, synthetic fuild is "slicker" than dino oil - that's the way it's designed to be! Generally, when you see specifications like SG/CD or the old Dexron ticks, they are referring to the additives, detergent levels, heat resistance, viscosity consistency, and the like. The base fluid doesn't change. If you were to break down 10W oil and transmission fluid, the oils would be the same (the additives will be entirely different!)

5-90

But isn't it the additives which determine how slippery the fluid will be? I thought that was why traditionally Type F fluid won't work in applications that call for dextron?

The additives have something to do with it, but the base oil is exactly the same - ATF, Power Steering Fluid, and industrial hydraulic fluid use the same base oil family - and even motor oil, gear oil, and the like are all similar. The principal difference is the base viscosity of the oil - which carries from lighter oils than the 10W base in transmission and hydraulic fluids all the way out to axle grease!

Additives are primarily viscosity improvers, heat-resistance packages, detergents, and the like. Detergents can be antagonistic to some seal materials and to various elastomers, and are usually downright nasty to latex and natural rubber (Buna-N and Viton are common sealing materials because they are cheaper than Nitrile and Butyl, but are still resistant to petroleum and detergents.) Transmission fluids carry a nastier additive package than engine oil, which is why you can (sometimes) run some ATF into your engine to clean out the gallerys and crankcase. Problem with that is that the ATF detergents are generally antagonistic to the materials used in engine seals - notable the valve guide seals and front and rear mains. These materials are typically more tolerant of Diesel fuel than ATF!

If memory serves, the endurance package is better in the Dexron line, and the additives aren't as nasty. I do seem to recall TypeF making a better hand cleaner than Dexron...

Here's another little note - rerefined oil. It is interesting to note that there is not enough head in an engine to actually break down the base oil - it is the additives that break down and need to be replaced. Rerefined oil is simply used motor oil and other auto/industrial lubricants that have had the additives "flashed" off and new packages added. If you have ever seen an oil refinery, you will note that there is a tower that is about 1/3 the size of the rest - this is the rerefining station. The larger towers handls all oil "fractions" from natural gas to asphalts and tars, while the shorter tower is designed to split from 5W to about 300W (light grease...)

5-90

Guys,

In Feb 1990 Chrysler sent out a Technical Service Bulliten on "Choosing your Automatic Transmission Fluid", BULLETIN: # 9002006.

They instructed the dealers to have their suppliers prove (certify) that the fluid meets the OEM specificaitons. They say in the TSB the supplier "will do that by supplying you with the license (certification) number issued to him by the O.E.M. A DEXRON-II license number (sometimes referred to as a "D" number) will always start D-2." I am sure at Dextron III cert number would start with D-3.

I used Mobil 1 in my 88 XJ. The bottle said it meet and exceed Dextron requirements but DID NOT have the cert number on the bottle. I used it trusting the Mobil 1 brand name.

I lost 3-4 mpg after installing the Mobil 1 ATF. I changed lots of sensors and nothing. Finally I looked at the Mobil 1 site for find the cert number required by the TSB, figured Mobil just left it off the bottle. The Material Data Sheet on the Mobil 1 site does not list the cert number, that set off a flare when the cert number was conspiciously abscent. When I saw that I took my XJ to the dealer, had the AFT transfusion done. I regained my lost MPG.

I am just trying to say ONLY use Dextron AFT that has the certification number on the bottle. If the number is not on the bottle then don't use it. I don't care if it is synthetic or not, just make sure General Motors approved the fluid you plan on using.

I used Mobil 1 without a cert number on the bottle and lost 3 mpg. So in the future only ATF with the cert number on the bottle going into the AW4 in my 88 XJ.

I work in engineer where we have suppliers certify the steel meets specs, the plating was done to a spec, etc. We as consumers think if it says Dextron on the lable it "Dextron" but what I learned that hard way is make sure the cert number is on the bottle.

HTH

Martin