Allison 740 fluid leaking into air system

[jmanoske]

I have a Allison 740 electric shift In a mc8. the problem i have is there is a hose comming off the bottom of the torque converter housing to a cylinder on the side of the trans with a hose out of top of that. And that hose goes to the D2 unloader valve. This hose is putting trans fluid into the air systen that supply's the tag axle. What is that cylinder for and can i eliminate it. What can i do to stop the flow of trans fluid to the d2 valve. Any help Thanks Jeff

[busguy01]

Not home now - traveling - so no manuals at hand BUT --- I think the cylinder is a retarder on your 741. Sounds like you MAY have a hose hooked up wrong. Has there been any work done to it lately?? I may be way off target here.

[jmanoske]

I just bought this coach back east and ran it to west coast. Now we are going through some items and this is one of them. I dont think it has a retarder though it has jakes. This item has two hoses in at the bottom and one out at the top going to the D2 valve. What is the hose that goes to the bottom of the trans for?

[makemineatwostroke]

sounds like you have a hydraulic powered Stone Bennett shifter that needs rebuilding  


www.utxchange.com has the rebuild kits 



So I don't confuse you about the shifter the electric part is just a control the unit is powered by air or hydraulics off the transmission the bad part about a hydraulic powered unit is it takes all 3 items to work  have a good day

[jmanoske]

So your saying the cylinder has fluid in one side and air in the other?

[makemineatwostroke]

So your saying the cylinder has fluid in one side and air in the other?
[/quote] 


No the air to it is a safety device so it will not engage till the air pressure is built up   

[buswarrior]

Hello.

What is this "D2 unloader valve"?

Without more info, sounds like a cobble job to me.

We need some more info as to what this beast that is installed in your MC8 actually is.

Check the build plate on the side of the transmission and share all the details.

How do you know tranny oil is getting into the tag air system?

At the minimum, sounds like a check valve needs to be installed to prevent blow back when this thing fails...

happy coaching!
buswarrior

[jmanoske]

I just had a talk with Donnie @ United Trans. He is the Stone Bennett guy. He had said that the item in question is a pressure actuator to shift the trans back to neutral if it dies in gear. There is no need for two sources of pressure so we can just cap off the air side and leave the transmission side hooked up. Sooner or later Dennis said we will have to rebuild the accumulator. Thanks for all the advise

Jeff

[makemineatwostroke]

Better hope the rebuild is a lot later those parts and labor are expensive on the Stone Bennett glad Donnie solved it for you those are good people at United, now just make sure you don't stop the engine in gear if it doesn't have a netural kill switch       have a great day      

[jmanoske]

Yea, if we had to buy a replacement its around 600.00. But when you are dead in the water and sinking fast id pay twice as much for things to operate correctly.