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How strong is your retarder?

March 14, 2015, 03:44:54 pm

My retarder is very weak compared to the one in the '05 U320 that I drove about a year ago. I expected mine to provide the same braking effect that I experienced in the '05 coach. What might be the reason for this? Are all retarders created equal?

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Re: How strong is your retarder?

Reply #1 – March 14, 2015, 04:24:00 pm

Need some more info.

Is the trans full?

 Does it act the same with the hand control compared to the retarding you get when you press the brake pedal? If you get more from the brake pedal then it could be the hand control may have a bad spot in the rheostat.

Have you checked the air valve at your accumulator tank to see if you have an air leak? If it leaks air or is stuck this can cause loss of retarder effectiveness.

 Make sure your wiring harness is good and plugged in at the hand control.

Just a few easy things to check

Pamela & Mike

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Re: How strong is your retarder?

Reply #2 – March 14, 2015, 04:33:29 pm

I took my FT into an Allison shop to have the driveshaft looked at and during the course of their testing, they came back and told me that the valve that controls the retarder pressure was malfunctioning.  They will be able to monitor the pressure through the  Allison computer harness up front.  I did end up with more transmission braking after the change.

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Re: How strong is your retarder?

Reply #3 – March 14, 2015, 06:30:14 pm

Possibly a leaking retarder valve, I think this is the one the previous posts are mentioning ... Replacing transmission retarder valve (split from What did you do to your coach)

Some pics of the general area:

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Re: How strong is your retarder?

Reply #4 – March 14, 2015, 06:52:48 pm

Steve,

Yes that is what I was looking for, you are the man.  I could only try to describe it.

Pamela & Mike

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Re: How strong is your retarder?

Reply #5 – March 14, 2015, 08:32:45 pm

I wonder if ANY 3-way 12-volt pneumatic valve could work for the Allison retarder accumulator?

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Re: How strong is your retarder?

Reply #6 – March 14, 2015, 10:52:45 pm

My retarder valve was not working. My retarder would still work, but it took about 5-10 seconds before it really became effective and provided braking.

I didn't hear the air release when adding throttle during retarding (something I'm used to hearing from driving city buses). I put a little grease on the vent of the retarder to be blown away when it released, but it never moved.

I bought a new valve off ebay, brand new, for a good price. Same electrical plug, but valve was newer design. I haven't drove it since install, though. I expect it to produce much quicker braking force than before (what I was used to in buses).

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Re: How strong is your retarder?

Reply #7 – March 15, 2015, 11:29:54 am

I haven't had any of the described problems, but I am sure that one could have these problems.  After purchase of my coach, I used the retarder almost all the time, but lately I haven't been using it as much except to check that it is working.  Brake application is a lot smoother without the retarder.  A panic stop would probably be shorter with the retarder though.  In the mountains I use it, but most of the time rarely more than 3 detents (straight up on the control stick).  I find this allows me to descend in one gear higher than without the retarder, and at the same time keep the transmission temperature from overheating.  Retarding force is determined by the amount of fluid in the retarder and road speed.  Full retarder and slow speed (5-10mph) results in very little retarding, while high speed (60-70mph) and a half full retarder will produce a lot of retarding force and overheat the fluid.  It's a balancing act that all us old owners know about.

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