My '92 is in midst of a transmission rebuild. When I asked the shop to ensure they used synthetic fluid, I was informed they don't believe in it and will only put in normal petroleum based product. This floored me! Am I missing something here? My impression from all you folks and various other sites is that this is the only way to go! The shop claims synthetics don't clear contaminants as well and allow the transmission to run hotter thereby damaging components. Even claims his fluid supplier, which carries synthetic product, does not recommend them! Also claims Subaru does not recommend them! Can anyone give me or point me to good, sound, technical material that can educate both me and the shop either way? I'm worried they won't warranty there work if I push for synthetic! Actually, some of you have probably been running synthetic for a long time - what's your experience? Thanks to you all for any help!

BTW - this new site is terrific! At last you can follow a thread!

It can be kind of tough to get a good, clear answer to that question. People who don't believe in synthetics will tell you not to use them, and tell you things like what the transmission place told you. They are very convinced that they are correct. However, I don't think any of them can provide documentation that will support their claims.

People that believe in synthetics, like myself, can point you to charts, and graphs, and tell you stories as well. We are very convinced that we are correct. If the fluid meets the recommended fluid type (Dexron II, III, Type F, whatever), then it is okay to use it. I don't think I've seen any owners manual that specifically states "do not use synthetics, or you will void your warranty". If you ask a dealer, they may tell you it will void your warranty, but tell them to give it to you in writing, and I can guaranty they won't, because it's not true. As far as Subaru not recommending them goes, I don't think they recommend anything they haven't specifically tested. I have, in the past, installed an ATF temp guage, and saw for myself that the temperature spikes were lower. The synthetics run cooler, and can withstand extreme temperatures 3 times longer than petroleum ATF's. Everybody doesn't have to use synthetics. That is completely up to the individual. I know lots of enthusiasts that use it and like it, but can't say that I've ever talked to anybody that actually used it and had a bad experience with it.

I can e-mail you a Spec Data Sheet for Amsoil ATF if you'd like. It's in Adobe .pdf format. I use, and sell Amsoil. That's why I have their Spec Sheets, because I use them. I think you can probably also get similar information from Redline's website, and Mobil's, and anybody else you might want to look up.

Good luck with your transmission. I'm not sure what to tell you about how to handle it. It seems kind of odd that they won't follow the wishes of the customer. I suppose you could let them do the work, then after a short period (to make sure nothing is wrong), get it flushed and refilled with synthetic. Unless they get it analyzed, they'll never know the difference.

Rich

Excellent post, Rich. I saw tjpops post on yoohoo and about blew a breaker.
I felt like telling him to run away from there as fast as he can, but it's kind of hard when they have your tranny apart.
Your solution was the best alternative I could think of - let them go ahead and finish the rebuild and then flush & fill with a goood synthetic ATF on down the road.

Synthetics
 

Its actually a good thing to allow them to NOT put in synthetic fluid into a rebuilt transmission. The reason being synth fluid is not good for breaking in parts, it allows almost no contact at all and things dont break in correctly. If i were you, id run the tranny nice and easy for 5-6k miles wiht the fluid they put in it(and a filter kit) and then change over to synth.

tjpops- what you are missing is the fact that even among supposedly knowledgeable car folks a lot of "wisdom" is based on old wive's tale. Much as any transmission is better of with synthetic, our overheating-prone transmission needs it even more. As far as I know resistance to heat breakdown is the biggest advantage of synthetic.

phast - are there parts in a transmission that "run in" through sliding contact or whatever? I know in your engine the valves need to form a metal on metal seal and the rings need to seal to the cylinder bore. Are there transmission parts that have a running fit like this?I know there are friction surfaces (which we don't _want_ broken in) and gears (rolling contact & they better be ground to fit together right from the start).

Also, no matter how slick an oil is it can't prevent contact... the "high spots" on the metal which need to rub and wear, if they were going to rub with dino juice, they will rub with synth. If anything the run in process might be a little bit slower on synthetic, but I feel like this might give better, tighter fits.

Just my $0.02

cheers
mbs

This is another one of those subjects that I would like to see a "definitive" answer or some kind of documentive evidence on - either way.
Synthetics have been blamed for leakage, poor break-in, stirring up old deposits, etc.
I think a lot of those things can be traced back to "old wive's tales", but who knows?
I tend to agree with Micah's opinion on this, but it's really no more than my two cents.

Thanks for the thoughts
 

Thanks for everyone's input - regardless of opinion it's nice to know how others think. I agree it is difficult to get definitive information but tend to believe that proper maintenance with either petroleum base or synthetic will provide similar results. I guess I just like to think the properties of synthetic provide some advantages that are hard to pass up on given the problems with these transmissions.

Micah - In any system, energy is neither created or destroyed. Merely converted. Thats gen Physics right there. Heat is a bi-product in this case. Wether you want to think your tranny is rubbing in gear selection or not, it is. If it wasnt, then heat would be of no major factor in the detonation of our tranny's. but it is the sole reason

I understand that heat is generated in the transmission, what I was wondering about is, are there parts that need to run in.

I gave the gear example because a gear is a precision rolled or ground part. Gear to gear contact is primarily rolling contact, yes there is a small sliding element and this generates heat. However there is no "running in" going on; the gear should be finished to spec at the factory. IE, just because there is rubbing doesn't mean there is break in. Likewise, bearing surfaces better be microfinished from the factory.

So my question was: You say that there are parts in your transmission that need to break in, and that synthetic oil will hinder this. Can you tell me which parts inside a 4EAT need to break in?

cheers
mbs

Doesn't most of the heat generated in an automatic tranny come from the torque converter?
I don't think that the heat generated from gear contact would be significant, at least not a danger to the tranny.

Another thought on conventional ATF: I'm not ragging them, they're probably fine for 90% of the vehicles out there. For a "cooling-challenged" car like the SVX, it seems silly not to use a fluid that can handle temp spikes better.

tjpops-

After having followed the synthetic ATF debate for some while now, it is my plan to replace with synthetic. I do want to collect a little bit of data, however. I have a B&N ATF temp. gauge kit that I can hopefully get around to installing in about two weeks. I plan to run the petroleum based fluid long enough to make some temp. measurements. Then, probably in early summer, I'll flush and replace with synthetic, and collect some more data. When I get these data, I'll be glad to share them, of course. But, the bottom line is that I feel that the arguments for switching to synthetic outweigh the ones for not switching. Hopefully, this will be borne out.

The bottom line is that I'll switch, FWIW.

I have a B&M tranny cooler on the shelf waiting to be installed, but what I'm more interested in now is getting a tranny temp gage.
Bill, when you do your gage installation, be sure to post some notes on it here - I figure I may need to use them.

Sure, Jerry, I'll be glad to do that. I'll even try to take some photos and put them somewhere. I don't have a scanner, but I know someone who just bought a digital camera. Maybe I can borrow that.

I've got the gauge, and the cooler all ready to go. But I thought I'd do the gauge first, and see what happens. Then I'll put in the cooler as sort of Phase III.

I bought B&M's outboard filter kit, also. It uses a standard Fram filter, which is sort of large, and I haven't quite figured out where to mount it. But, it has a nice little tapped hole for screwing the temperature sensor into, so you don't have to have it brazed into the tranny pan or anything. I'm sort of reluctant to do that.

Like I said, two weeks - that's spring break, so I'll have a couple of days that I devote to it.

I have noticed that a change in ambient temp has a huge effect on tranny temp - keep that in mind when recording your data, maybe include that in the data. I have 2 tranny coolers, one with an electric fan on it and a temp gauge and remote filter. I mounted the filter in the drivers side fenderwell in front of the front tire. There is plenty of room in there - pictures are in my yahoo briefcase.

Yes, I had thought of about needing to record ambient temp. Isn't it great that the SVX conveniently provides a thermometer useful for that very purpose? :)