Synthetic Transmission fluid: pro's and con's ?

[RickB]

Hi folks,

I was talking to a transmission specialist friend the other day and he said "without a doubt the single most preventative maintenance thing you can do for your allison is use synthetic fluid".

Is that the consensus of the blog as well??

I am imagining it is going to be expensive, (isn't everything on these buses??)any ideas on price for my 754 to switch over?? I know I should have asked him but it slipped my mind.

Thanks in advance,

Rick

[Sean]

Rick,

I switched to Transynd years ago.  It is very expensive, $35-$50 per gallon, but it improved my tranny performance greatly.  Specifically, it lowered my temperatures allowing the retarder to be used more extensively.

It takes two complete fluid changes to go to the "extended drain interval," but you will get the other benefits of the synthetic on the first change.

Your tranny is probably 7-8 gallons, depending on cooler and how far away it is, so figure $300-$400 to refill with Transynd.

-Sean
http://ourodyssey.blogspot.com

[luvrbus]

Rick, most of the Allisons hold from 39 to 48 quarts x 10 buck and you need to do it twice.FWIW they will shift smooth and wear good with 15/30 oil. I  use Cat transmission fluid in mine with good results never had any wear according to the samples tested      good luck

[Sean]

Sorry, I must have been off on the fluid quantity.  I believe the 39-48 quart (10-12 gallons) number to be correct.  I think the 7-8 gallon number I mentioned is the sump size.

-Sean
http://ourodyssey.blogspot.com

[edroelle]

Transynd is the best.   It can live longer at higher temperatures.  I know of no downside except cost.  But, do you need it?  

I asked this same question of the Allison engineeer of Transynd.  He suggested -

Allison World Transmissions should use it because they are weaker than the 7XX Series
Not as necessary on lower torque and lighter coaches driving few miles.
Synthetic would be beneficial if you do significant mountain driving or like Sean, use a retarder.

I also changed to Transynd

Ed Roelle

[c-coop]

I used Mobil delvac synthetic atf which is the same as transend and also recomended by allison. I paid $21 per gallon in 5 gallon cans

[johns4104s]

Rick,

My Allison 754 has a very low ist gear, when it changes up from 1st to 2nd or down from 2nd to 1st it changes with a thud. Allison did the last change and used engine oil. I have been recomended and have bought Hydrotech synthetic oil out of Dallas Texas. They supply school bus fleets truck fleets etc, they recomend a test annualy, Some fleets are running 300,00 miles between changes. I will be changing to Hydrotsch and report.
During the oil change without starting the engine do I get rid of most of the oil? If the bus sits will the oil eventually drain out of the torque converter?

Thanks

John

[Ed Hackenbruch]

When i had a service done on my tranny  it cost me only $200 more to get the transynd put in. The major benefit besides smoother shifting is the service interval is 4-5 times longer now so it more than pays for itself by the time i need to do it again.

[scanzel]

I have a Spicer 6 speed standard, is there any advantage to using Synthetic in it also?

[johns4104s]

On my 4104 I changed my 4 speed spicer  to synthetic you would not believe the difference in changing gears, it was so much better. BEWARE if you have any leaks it will find them..

John

[junkman42]

I had a conversation with the shop manager at Stewart and Stevenson about the proper fluid to use  in My HT70.  I was told to not use synthetic fluids as the clutch or friction materials in My transmission were not compatible with many synthetic fluids.  I presently use type A fluid which was recommended by the aforementioned person.  I was also told that if I wanted I could use straight 30 weight engine oil providing temps did not drop below freezing.  Maybe good advice or not.  I still am not sure about the proper fluid.  Regards, John

[luvrbus]

Synthetics are a personal choice in the 700 series transmissions there is no need spend 1000 bucks for oil.
I looked into changing over to synthetic and VP of Stewart and Stevenson ask me why, the 740 been using different oils for year with no problems so why pay 500 for a oil change instead of 80 bucks.   

How many of you guys are going to drive 10,000 miles a year and it is my understanding the synthetic oil has to be changed do to age also.   

He did tell me synthetic was the best to use in the B500 Allisions. 

FWIW my 740 never has a temperature higher than the engine temp around 180 degrees and a little work on the trimmer springs it shifts as smooth as any transmission on the market. Just my way  good luck

[Sean]

... why pay 500 for a oil change instead of 80 bucks.   

How many of you guys are going to drive 10,000 miles a year and it is my understanding the synthetic oil has to be changed do to age also.   

In the HT series, Transynd doubles the service mileage limit from 50,000 to 100,000 and quadruples the service time limit from 12 months to 48 months.  It also doubles the filter change interval from 6 mo/25,000 miles to 12 mo/50,000 miles.  (Source: http://www.allisontransmission.com/documents/product/1099B.pdf)

If you shop around you can find the stuff for $35.  So say $400 for 48 quarts of synthetic, versus perhaps $80 for the same quantity of bulk ATF.

If you don't drive more than 25,000 miles per year, you are thus looking at around $100 per year in Transynd, vs. $80 per year in regular ATF, and that's assuming it costs you nothing to change it (I don't have the facilities, so I have to pay a shop to do the change every time).  I would say that the cost factor ends up being pretty close to a wash for most of us.  (There is a slightly higher penalty the first couple of years, since it takes two fluid changes to get to the extended intervals, by the book.)

At these numbers, I'd rather have the advantage of the synthetic fluid.  As I wrote earlier, I see considerably lower temperatures and better performance in the mountains.

BTW, I am trying to get to 10,000 miles a year -- really I am.  But right now, I'm still closer to 20,000.  Still not enough to force me to change tranny fluid by mileage, though.

-Sean
http://ourodyssey.blogspot.com

[johns4104s]

Cliff,

Who does the work on your trimmer springs? Are you able to do your own adjustments,

Thanks

John

[MCI-RICK]

Sean,

You drive your bus 20,000 miles per year?