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Retarder Fluid Temperature

I would appreciate any thoughts or opinions on the various temperature ranges for VMSpc caution settings.  I have yellow and red upper limit settings for the retarder, but they are totally arbitrary.  I have found no information as to what would be reasonable settings.  My retarder temp normally runs between 190 and 200 degrees and can easily spike up to 240 or above on steep downgrades. 

Thanks,

Richard
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Retarder Fluid Temperature

Reply #1 –
Quote from: Jan & Richard –
I would appreciate any thoughts or opinions on the various temperature ranges for VMSpc caution settings.  I have yellow and red upper limit settings for the retarder, but they are totally arbitrary.  I have found no information as to what would be reasonable settings.  My retarder temp normally runs between 190 and 200 degrees and can easily spike up to 240 or above on steep downgrades. 

Thanks,

Richard
Richard
This is a good question. Inquiring minds want to know. I have not done a lot of mountain driving, just Arkansas hills.
My retarder temps run close to what transmission is until it is used then goes up pretty fast. I try and not let retarder temp get over 220-230. I think I read that somewhere on here.
There is fine line between using gears, retarder, and brakes on downhills. I think that you need to set them up before you have started down hill and your speed is to fast to start with.
I have also heard and I try to do this on long and steep downhills use the same gear down as you came up the hill.
Anyone that has better info please make corrections to what I have said. I want to do it the best way also.
This is just my two cents
Ron Clark
Sherwood,Arkansas
1999 U 295 40 foot Build # 5550
2020 Jeep Gladiator
Motorcade # 18173
FMCA # F485593

Re: Retarder Fluid Temperature

Reply #2 –
Retarder temps run about 10° warmer than the transmission temps.  I set the warning light to turn yellow at 235° and red at 250°. If you are using synthetic oil in the transmission then it is more tolerant of higher temps than organic fluids.

The yellow indicator lets you know you have reached a temp where you should be paying attention to it. Stepping on the service brakes will make this temp go up fast.  If you get to this temp on a down grade maybe it is time to slow down a bit, downshift and reduce retarder a notch.  Increased RPMs will increase cooling of everything. 

If you get warm enough to make the red indicator come on do something now to reduce load and increase cooloun.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Retarder Fluid Temperature

Reply #3 –
Does anyone now what the stock Foretravel temp alarm is set at?  I've seen 250 degrees and never heard a peep.
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: Retarder Fluid Temperature

Reply #4 –
Don't know if any information here would apply. Page 46 uses 300 deg as max for stall test.

http://www.waghornswood.net.nz/Manuals_01_18/Vehicles/Allison_Automatic/Mechanics_tips_md_hd_b_series_Allison_on_highway_transmissions.pdf
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Retarder Fluid Temperature

Reply #5 –
Quote from: Chuck Pearson –
Does anyone now what the stock Foretravel temp alarm is set at?  I've seen 250 degrees and never heard a peep.

The FT alarm is activated via the retarder temp sensor directly.
Depending on the software of your trans, it is 281-285 F
I have the repair manual
See chart from book
Here is my post on the faulty retarder sensor

Allison Transmission Fault Codes, Retarder not working
Chris and Tammy White  CDA Idaho
Previous owners 1997 U295 36' 3126 Cat 300 HP Build # 4998
Former Foretravel tech & RVIA certified tech
Former owner Custom Satellite home/RV satellites 
Former owner Vans LTD  van conversions
Unemployed, panhandler, drag racer NHRA #6348

Re: Retarder Fluid Temperature

Reply #6 –
That sounds correct.

Yellow at 235, pay attention, slow down, and downshift

Red at 250, entering the danger zone, hit the brakes enough to use the actual brakes, slow more, consider another downshift. Really watch the rpms too.

I occasionally hit 260, but just for an instant.

Alarm at 280 and change. Time to hit the brakes hard. But not for long.

I have heard the alarm a few times, back before my VmsPC was installed.

Keep it under 300 and probably no damage done

And at some temperature, the retarder shuts itself off.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: Retarder Fluid Temperature

Reply #7 –
At 300 deg. retarder starts shedding.
Post from 12 years ago seems to explain a lot.

Retarder...this time from the manual
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Retarder Fluid Temperature

Reply #8 –
Quote
The FT alarm is activated via the retarder temp sensor directly.
Depending on the software of your trans, it is 281-285 F

Are we talking retarder temperature or transmission sump temperature as shown on the bottom of the chart? Silverleaf can show both. Doesn't the alarm on our FTs alarm at sump temperature?

Re: Retarder Fluid Temperature

Reply #9 –
Quote from: rclark –

There is fine line between using gears, retarder, and brakes on downhills. I think that you need to set them up before you have started down hill and your speed is to fast to start with.
I have also heard and I try to do this on long and steep downhills use the same gear down as you came up the hill.

This is just my two cents

You're correct on all 3 points.  The retarder gives you an extra layer of safety but at the end of the day you're managing a heat energy equation that is unforgiving if you get the wrong answer.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Retarder Fluid Temperature

Reply #10 –
When going down steep grades, I always select a gear lower, two if necessary. When the retarder temp starts to rise , push the joy stick forward, that  turn off the retarder.When off it will dump the hot oil and replace it. In one minute I reapply the retarder.. Retarders were not made to hold the whole load continuously....
it works for me on my motor home as well a commercial 650 HP Cummins with 62000 kg or about 135,000lbs of load.
Safe travels,
Dave
Dave
2001 U320 40ft
Build #5867
2003 Tracker
VE7DOD