[Peter]

We’ve had two previous Marathon that had been changed to run Mobil Delvac 1300, 15W40 motor oil in the transmission.

We have been told, the change to motor oil serves several purposes, although not recommended by Allison

1.) Helps in smoother shifting, less “snap/slam/jerking

2.) Allows owner to carry single fluid for coach drivetrain.

Bill Jensen, now retired from Prevost, told us once a coach has run motor oil thru the transmission, you can’t go back to Dexron, or Trans Synd for that matter

Our current coach had a catastrophic transmission failure before we bought it last summer, and in the new transmission we verified it had Tran Synd synthetic in it not motor oil. Made sure it was tagged, and took off awarding tag pertaining to Mobil Delvac

During a routine transmission service, in 2003″with our 2002 Marathon XLII, a tech, yes at Prevost, didn’t pay attention to sticker warning about Mobil Delvac. He put in Dexron III at the time. Shifting on test drive was so abrupt, upon return to the shop, pulled dipstick to see red on it. We saw red, too in another way. Delaying our evening departure, Prevost had to drain

out of Dexron, change filters yet again, and re-introduced Mobil Delvac. Upon returning to the service center 3″months later, and 2500 miles, they drained it again.

[Archived]

My Allison Manual says Dextron or any C4 equivalent and that would include certain motor oils.

I have had buses that have had both and been switched with no adverse effect.

[Gerald]

Allison now lists “recommended” fluids as being those meeting TES295 specification.

If we review the maintenance schedule it shows fluids other than those that meet the specification above have a very short maintenance interval. Apart from the cost of more frequent required fluid changes, my concern would be if a retarder is used the high temps generated would damage the fluids if other than TES295 fluids are used.

To the best of my knowledge clutch wear could be an issue prompting an early need to either replace clutches or rebuild the transmission. My guess is Allison started pushing very hard for the use of the synthetic fluids as a result of long term experience with the transmissions. There is a huge difference in cost of the two types of fluids, however $300 or $400 cost of fluids per fluid change might be cheap if the transmission life is compromised. I had to replace a transmission on my second coach due to excessive clutch wear. I always used Transynd, but did not know what fluids were used previous to my purchase of the coach.

[Archived]

C-Bus…..have you noticed any increase or decrease temps with oil selection ?

When I had the CC Affinity switching from Dextron to TransSyd trans temp dropped 12 degs running at highway speed.

[Archived]

B/A

0593 had Trand Synd in it after transmission over haul last June. It had just arrived at Marathon from Pacific Truck Center down the road from Marathon when we first saw it. Apparently, previous owner was driving it to Marathon for consignment from Bend when failure occurred.

So we don’t have a reference. But, we replaced Dexron III in the 1992 Beaver XL 40 Prevost with Allison HT-755 and did notice Trans temp climb much slower and never topped 200 degrees

[Bill]

Although expensive I’d go with what Allison recommends (TES295). It lasts 4 years and should be changed same time as transmission filters.

It is not a bad job if you do it yourself. Just be very careful of not stripping the threads of the bolts in the aluminum oil pan for the filter access panels. This would be my biggest concern in having the transmission filters changed in a shop.

[AL]

Gerald has brought up somthing every owner should know and keep in mind when it is time to service the transmission.

Allison has a specification for the torque values for the fluid filter housing bolts. Failure for the mechanic to observe those values (which are on an instruction sheet with the filters) can result in a very expensive repair bill. There is a good fix but it requires a special tool and kit. Jeff at ETLC has one, and I am sure other shops do also. This is something I just do not trust to anyone so I do my own because too many of us have spent serious money fixing someone’s mistake.

I believe the later model transmissions may have a thread insert and be less susceptible to thread damage compared to earlier coaches.

[Chip & Pam]

A very good point Jon.

I had transmission filter and fluid change done to both Marathon’s. One at Marathon Texas, other at Jeff’s.

I do not want any air tools near my Allison Trans. I’ve watched the service to confirm outbound and inbound bolts are not striped.

Second thing if shop does not have a torque wrench…skip the service.

IMHO…..If a tech uses an air ratchet on a Allison Trans….Idiot comes to mind.

PC members you have to really pay attention getting transmission service . Shops that make a mistake will usually play the blame game….Oh, we found the bolt stripped.

I believe the Allison filter housing bolt repair kit is north of $300.

[Archived]

If any shop changes your transmission fluid, and after the fact you find the wet spot on the bottom at one of the bolts on the filter housing is because one of the bolts has been stripped you will hear the excuse Al mentioned above.

As soon as the shop that changed transmission fluid tells you they found the bolt stripped, advise them that excuse is only valid when they bring you the bolt, with aluminum still stuck in the threads BEFORE they begin to change the filter or fluid. If they insist, advise them they are morons and liars because nobody would be so stupid as to try to thread a bolt back in a hole they already knew was stripped.

This covers the “World” six speed transmission.

However, those with the 5 speed transmission used on coaches up to around the mid nineties are also potential victims. The service requirement for that transmission calls for occasionally dropping the oil pan to service an internal filter. The exact same potential for damage exists with the bolts around the perimeter of the transmission oil pan because the oil pan bolts are being threaded into the aluminum transmission case flange.

[Dorel]

Glad to see the informative discussion on transmission fluid change, etc. I’ve been reading about this, it’s completely different from my old bus that had a Donaldson spin-on filter for the Allison automatic transmission.

But, getting back to the fluid vs. oil question… I guess what I’m really wondering about is, what does Allison think about this? Are they okay with people using oil in their transmissions? Is the change from fluid to oil actually done by an official transmission service facility, or do owners make this change on their own in their personal garage or driveway? If Allison is not okay with using oil, what are the ramifications or repercussions in the event of a problem? If it were your bus, would you change it back to the fluid recommended by the manufacturer?

Kirby

[Mike & Brigitte]

I looked for a simple way to ask Allison a technical question on their web site, but found none. Allison does now call for Transynd or its equivalent even though the transmissions of today are the same as those that allowed the use of motor oil.

I do know the synthetic fluids have a much longer service interval which tells me they remain in good shape much longer than engine oil or Dextron. The Allison service intervals reflect this.

Transynd or equivalent is not cheap, but neither is a transmission.

[Jim/Chris]

Mine had engine oil (Mobil) when I bought it. I communicated with a former Allison engineer (on another site). Per his recomendations did a “double flush”…..I drained the oil and let the filters sit overnight to drain. I reinstalled the filters then filled with Transcend and drove it approx 1000 miles and changed it again and installed new filters. That was four years ago and so far all is good.

[tom]

We use synthetic in the pumpkin and hubs and Transcend in the transmission. We think it runs cooler and doesn’t break down as fast.

[Fred F.]

I ran across this while trying to find something definitive regarding TES 295 spec fluids compared to motor oil or Dextron.

It is relatively short and appears to be specific to Foretravel coaches, but it is directly applicable to our coaches also. The service intervals really do tell the story because they are so much longer if Transynd or equivalent is used. There is a greater expense using the synthetic fluids, but if it prevents the loss of a transmission it is well worth the expense.

http://beamalarm.com/Documents/transynd-fluid-change-interval.html

[Archived]

Thanks to all for their input and especially thanks to Jon for the above post with link to the Foretravel information. After reading that article, I believe I will switch from the 15W40 to TransSynd. I just queried the previous owner who had the coach for 15 years and he says he never changed the transmission fluid.

Kirby