synthetic fluids

[GirsMJ86]

ok so i thought i had synthetic transmission fluid in my transmission but eagle brought up in another topic that i was the only person he heard of with that in a jeep. so i checked it out and the guy only charged me for the syns but used regular old dexron 3.

 

so this brings me to the question of this, what synthetics work best in jeeps. 4.0L HO, aw-4, stock axles is mine.

 

wanting to go all synthetics but if i can't then i need to know what i can't use, can use, and what would be best for the jeep.

 

Thanks,

Alex

[carnuck]

Buddy of mine swears by Amsoil. (he became a supplier to save himself a few bucks)

[Eagle]

I strongly advise you NOT to use synthetic in the transmission.

 

Why? Not from my own experience, because I'm a 5-speed kind of guy. But I've been a member of NAXJA since it was founded, and ALL reports from the NAXJA tech forums are that synthetic tranny juice is death to the AW4 transmission. Nobody knows exactly why, there are several theories, but my view is ... why argue against the collective wisdom of several thousand serious owners? Enough people have reported problems that I do not wish to tempt fate. I run my wife's XJ on Castrol full syhthetic in the engine, but the AW4 (which is due for a change) gets conventional.

[GirsMJ86]

I strongly advise you NOT to use synthetic in the transmission.

 

Why? Not from my own experience, because I'm a 5-speed kind of guy. But I've been a member of NAXJA since it was founded, and ALL reports from the NAXJA tech forums are that synthetic tranny juice is death to the AW4 transmission. Nobody knows exactly why, there are several theories, but my view is ... why argue against the collective wisdom of several thousand serious owners? Enough people have reported problems that I do not wish to tempt fate. I run my wife's XJ on Castrol full syhthetic in the engine, but the AW4 (which is due for a change) gets conventional.

 

alright tranny is out of the picture for synths.

 

what do you all think about valvolines synthetics? the "dura blend" and "syn power".

 

Alex

[Duner]

Comments from Duner's Dad:

 

We would have to know all of the circumstances involving each and every failure but I will lay down the basics about synthetic lubricants and a bit of insight that may cause the failures.

 

FYI - US Military uses synthetic lubricants in almost everything they have that rotates or has metal to metal contact. If someone shoots a hole in the engine pan, radiator, trans pan, diff, etc. and all the fluids leak out the military wants that vehicle to continue moving to get the occupants to safety.

 

The reason for synthetics working better than conventional are as follows superior molecular adhesion and film strength this keeps the lubricant on the part and the oil then resists the compression and does not allow the two metal parts to contact each other. (current penzoil commercials are good illustration) the other advantage of synthetics is extreme temperature resistance to break down. sludge is formed in conventional oils when the organic hydrocarbons (dinosaurs and plants)and parafin waxs (substance that makes oil slippery) are cooked out of the oil this is the nasty black crud caked on to every portion of the internal surface of your engine that does not have metal to metal contact.

This crud build up will not occur in synthetic lubricated engines.

 

Thats the basics in a nutshell.

 

Now why do our automatic transmissions fail when we switch from conventional to synthetic?

 

Your automatic tranny has a number of friction clutches which wear depositing their fibers into the fluid where we are all hoping that the filter will remove them (high hopes). The only thing that will kill an automatic transmission faster than dirty fluid is lack of fluid flow so the filters let most of the particles circulate. The particulates then hook up with the parafins and organic compounds in your conventional fluid. The plus is that this new thicker homogenized crud fills the increasing tolerances between the friction clutches and your tranny keeps on going although gettin a little more sluggish as time goes on.

 

Failure happens when transmissions are not serviced regularly and we are not talking about mfg's intervals if you do your oil every 3k your trans should be every 9k and 7k if you sit in traffic or idle for long periods.

Most owner's manuals spec 30k or 15k for severe duty and towing.

 

So the happy truck owner decides at 90k miles that he will switch over to synthetic lubricants in everything engine, trans, tranfercase and diffs no problem.

 

Diffs and tranfer case and manual trans could careless they are happy as long as they are not filled with sand and water in most cases.

 

Engine begins to really clean itself up like cleaning a barbecue pit with easy-off oven cleaner as long as you change your filter every 1k and synthetic oil again at 3k it generally during the initial switch over it will adapt with no problems.

 

Auto Trans is another animal first and biggest issue is changing the oil all of the oil including the torque converter. This means installing a drain plug in the converter if not factory fitted. I'm not familar enough with this sucking and changing fluid machine that most lube shops use now. Nothing like actually watching it come out and filling it up yourself besides the filter needs changing anyway.

This conversion is also expensive as most trans will need 10 to 14 quarts of new synthetic.

 

So new synthetic fluid goes in removes all crud and deposits them into the filter which it then clogs while opening all friction clutch tolerances and pump seals thus creating an expensive rebuild for the vehicle owner. (who then swears synthetics are worthless)

(This same problem can occur with convential fluid if it has not been changed or changed regularly when a complete and thorough change is peformed)

 

 

So if you changed your auto trans fluid more often than the factory suggested you can probably survive the switch problem free.

 

If you have never serviced your trans and your thinking I'm going to drive it to colorado for the jeep jamboree next month don't change the fluid before you go.

 

If you are one of the people who at least did filters with 3 quarts of fluid once in while I would reccomend that you continue to do just that but you can add a quart or two of synthetic or blended synthetic and derive some of the benefits.

 

If you were fortunate enough to have bought your MJ or XJ new and switched it over to synthetic fluids right away you probably don't read the tech column except to muse yourself with our sufferings.

 

I have used Royal Purple long before it showed up on the tv programs or the auto stores started selling it (I do like the quarts compared to the 5 gal jugs I was buying) I switched from Mobil One after I watched it fail in a film strength test. Also most Nascar engines run this oil as opposed to what the large sponsor decal on the car may say.

 

Just remember that no matter which you choose they are all superior to convential oils and fluids this goes for brake and power steering as well.

All high end automobiles and all german cars (even vw's) use synthetics from the factory - check out a corvette at the local chevy dealer and read the lubricant recommendations.

[CEThomas]

Kind of what I was told many many years ago, buy a guy that worked on cars from the time autos were put into autos :D He told me that when it came to the trans never switch the type of fluid and never never change the fluid if you did not do regular fluid changes from the start. If you did it would kill the auto for the same reason you listed.

 

Back about 10 years ago I had a 5-speed Ranger that the PO had put the wrong fluid in. During the winter it was hard to shift till it got warm, I thought well it's not an auto so I will switch back to the right fluid. Well all the bearings got used to the wrong stuff and every bearing in it went out in about 10K after I put the right fluid back in :cry:

 

Charles

[87manche]

I like valvoline oil, and it's what the 4.0 gets.

The wife's camry get's mobil 1.

The diffs get the cheapest oil I can stuff in them, because they get changed frequently. If you wheel it hard it's not worth putting the syntheting in the diffs, because eventually you'll be popping the cover for something.

For a street machine I'd put valvoline or mobil one 85-140 in the rear diff, and 75-90 in the front.

If you don't tow or romp on it hard 75-90 is fine in the rear, I run the heavier oil because it settles the detroit.

[Eagle]

Comments from Duner's Dad:

 

We would have to know all of the circumstances involving each and every failure but I will lay down the basics about synthetic lubricants and a bit of insight that may cause the failures.

 

...

 

Just remember that no matter which you choose they are all superior to convential oils and fluids this goes for brake and power steering as well.

All high end automobiles and all german cars (even vw's) use synthetics from the factory - check out a corvette at the local chevy dealer and read the lubricant recommendations.

I am well aware that the US military uses synthetics in all vehicles. I am also aware that the US military isn't running a whole lot of XJs and MJs with the AW4 transmission, and any they have either came from the factory with synthetic or were converted upon delivery.

 

You are free to do as you wish, Sir, but the kind of people on NAXJA who have encountered this problem are not the typical "drive it 'til it drops" kind of owner who would ignore normal maintenance. As I wrote, enough people have noted that converting the AW4 to synthetic kills the transmission that I am not willing to risk it. These people, generally, made the attempt because they had not encountered this problem with other automatic transmissions. They did encounter it with the AW4.

 

Take it for what it's worth.