Retarder 101

Topic: Retarder 101 (Read 3053 times) previous topic - next topic

Re: Retarder 101

Reply #50 – August 28, 2012, 12:18:55 pm

Quote from: Tom Lang – August 28, 2012, 11:42:45 am

The retarder was about two notches engaged, but I always pull it all the way back when hitting the brakes (maybe improving the response time).

Hmmm, It would be interesting to know if manual joystick application really does improve the response time and stopping distance....

Dean

Re: Retarder 101

Reply #51 – August 28, 2012, 12:26:56 pm

Quote

> The retarder was about two notches engaged, but I always pull it all the way back when hitting the brakes (maybe improving the response time).

Hmmm, It would be interesting to know if manual joystick application really does improve the response time and stopping distance....

Going downhill I always have my left hand on the joy stick. So I think it does reduce response time in that case.

best, paul

Re: Retarder 101

Reply #52 – August 28, 2012, 01:19:00 pm

Quote from: Tom Lang – August 28, 2012, 11:42:45 am

I have a couple of comments.

One time, while going north on the Grapevine out of Los Angeles, a long downgrade with trucks limited to 35mph, I was cruising down the #2 lane with the retarder keeping my speed at 60-65. All of a sudden some idiot dives right in front of my front bumper and slams on the brakes. I have no choice but to do the same. The retarder was about two notches engaged, but I always pull it all the way back when hitting the brakes (maybe improving the response time). When all was said and done, I was doing 45 or so and the transmission had downshifted all on it's own. The idiot then took off, and I had to push the retarder all the way forward and tap the accelerator to allow gravity bring my speed back up. The automatic downshift did appear to multiply the retarder braking effect.

Another time, I had the misfortune of having a traffic light turn red at exactly the wrong moment while doing 60 on a should-have-been freeway-like highway with this lone traffic light out of nowhere. I simultaneously hit the retarder and brakes and came to a very fast stop. Good thing my wife was belted in, but everything I "thought" was put away ended up-front, and I managed to put a crack in the shower wall. I suspect this coach could out-stop some cars.

Did a lot of demo drives with customers when the retarder trans came out. Told the customer to get on the brakes. They normally tried them out some. Then I yelled at them to "GET ON THE BRAKES". They would almost stand up in the front seats. The look on their faces was priceless. Yes I warned them about looking in the camera as unaware cars behind might be in trouble.

My lever is set so forward is on. Are yours opposite?

Re: Retarder 101

Reply #53 – August 28, 2012, 01:22:09 pm

Quote from: Caflashbob – August 28, 2012, 01:19:00 pm

My lever is set so forward is on. Are yours opposite?

Fully forward only retards when the brakes are applied, pulling back 1-6 notches applies varying degrees of retarding whenever my foot off the accelerator pedal.

Re: Retarder 101

Reply #54 – August 28, 2012, 02:48:02 pm

Quote from: Tom Lang – August 28, 2012, 01:22:09 pm

Fully forward only retards when the brakes are applied, pulling back 1-6 notches applies varying degrees of retarding whenever my foot off the accelerator pedal.

Yep, mine works this way as well.

Re: Retarder 101

Reply #55 – August 28, 2012, 03:41:01 pm

Quote from: Dean & Dee – August 28, 2012, 02:48:02 pm

Yep, mine works this way as well.

Wonder why mine is setup reversed? Only 97's or mine or customer preference?

Re: Retarder 101

Reply #56 – August 28, 2012, 05:55:46 pm

Quote from: Caflashbob – August 28, 2012, 03:41:01 pm

Wonder why mine is setup reversed? Only 97's or mine or customer preference?

The joystick in our '97 turns retarder "off" (activated by brakes if "Retarder" switch is on) in forward position. It turns the retarder "on" (activated when accelerator is released) when pulled back to positions 1-6.

The joystick was added by MOT after we bought the coach. We did not express a preference for direction of operation, so they would have made a "normal" installation. I drove another FT with a joystick and it operated by pulling back to engage.

Re: Retarder 101

Reply #57 – August 28, 2012, 10:14:49 pm

Quote from: J. D. Stevens – August 28, 2012, 05:55:46 pm

The joystick in our '97 turns retarder "off" (activated by brakes if "Retarder" switch is on) in forward position. It turns the retarder "on" (activated when accelerator is released) when pulled back to positions 1-6.

The joystick was added by MOT after we bought the coach. We did not express a preference for direction of operation, so they would have made a "normal" installation. I drove another FT with a joystick and it operated by pulling back to engage.

Thanks mine is the other way. ? Wonder why MOT did it one way and either FOT or the customer did it the other way?

Re: Retarder 101

Reply #58 – August 28, 2012, 11:14:37 pm

Since my VMS 240 CL claims my retarder temp is never higher than the transmission temp (contrary to the experience of others, here), and the VMS reading of retarder temp jumps as soon as I engage the retarder, I'm beginning to wonder of my VMS is reporting retarder temp in Centigrade not Fahrenheit.

best, paul

Re: Retarder 101

Reply #59 – August 28, 2012, 11:30:09 pm

Paul.... One of the problems with the VMSpc retarder temp early on was the PID was not calibrated properly. Thus the readings were too low. They fixed this problem with a new version software (cited previously) which I am now using. Could you have the same problem with your setup? One way to tell is to look at the temp of the trans and retarder when you are driving down the road without the retarder engaged...both temps should be the same.

We drove from Wall, SD to an RV park outside of Custer City, SD today. It was a very hilly route. I kept an eye on the retarder temp and trans temp. The retarder temp jumps as soon as the retarder is applied and at one point was over 250 degrees F. However, the trans temp showed little change and remained around 185 or so. I try to keep the retarder temp below 250 degrees by slowing down and downshifting to improve cooling. When the engine goes from about 1400 rpm to about 1700 rpm in a lower gear the impact on the retarder temp is immediate and it drops into an acceptable range. Going slower means there is less heat generated in the retarder and with higher rpms there is better cooling. Maybe I am being too cautious with the 250 degree max, but I like being on the safe side when I can be. The trans fluid is Transyn.

Re: Retarder 101

Reply #60 – August 29, 2012, 12:03:31 am

RE: " Wonder why mine is setup reversed? Only 97's or mine or customer preference?

I think all 97's were manufactured without a joystick. Three levels of retard was activated only with brake pedal.

When joy sticks are mounted by a coach owner or mechanic it can be mounted with zero position toward the front or rear. Installer makes the choice either on purpose or by chance. Both ways work.

Most have zero position forward. If you would like to change the way your joy stick is mounted, you can easily re-mount it the other way around.

Re: Retarder 101

Reply #61 – August 29, 2012, 09:20:18 am

I must be the only one here that has a factory installed decal (or so it would appear, to the left of the drivers seat) that says to not run to long at 300 degrees.

Re: Retarder 101

Reply #62 – August 29, 2012, 10:49:14 am

Interesting decal, since everyone is aware that 250 degree is the max. So wonder what "too Long means"? Think if you hit 300, you are too late unless the location of the temp sender was mounted somewhere else insteadof in the sump pan.
Dave M

Re: Retarder 101

Reply #63 – August 29, 2012, 12:36:49 pm

I was paraphrasing the "too long", it said more like, ease up, if that doesn't help, pull over until it cools down, again I'm paraphrasing. I've never gotten it over 215 going down the I90 passes in western Montana and Idaho with an ambient temp of 90. Once over the pass the temp drops right back to normal.

Re: Retarder 101

Reply #64 – August 29, 2012, 01:35:24 pm

Quote from: Dave M – August 29, 2012, 10:49:14 am

Interesting decal, since everyone is aware that 250 degree is the max. So wonder what "too Long means"? Think if you hit 300, you are too late unless the location of the temp sender was mounted somewhere else insteadof in the sump pan.
Dave M

I was told long ago by my trash truck guys and the Allison guys that one hour at 300 would burn the trans fluid. If you pull the dip stick and it was orange and smelled burned it was.

Continuous 250 no issues ever heard of.

Bob

Re: Retarder 101

Reply #65 – August 29, 2012, 10:47:12 pm

Today I was coming down a a very long 7% grade into Deadwood SD. The signage said that trucks were limited to 25 mph which seemed to slow for the road. I tried to hold it down to 40 mph by down shifting to 5th and moving the retarder to 3 clickes back to be cautious. I had to apply some brake. At the bottom of the long grade my trans had downshifted to 4th and I got a warning bell (first time!). A check of the trans temp (dash gauge) showed 250 which was also a first. I don't know how to check retarder temp. Bell rang for about 30 secs and stopped when the trans temp fell to about 230. The warning bell was disconserting. I'm not sure why I got such a high temp in this instance.

Re: Retarder 101

Reply #66 – August 29, 2012, 11:07:29 pm

I did that grade a week ago. It was in the upper 90s. I was in third gear and hit only 235 or so. I was running 25 mph.

Re: Retarder 101

Reply #67 – August 29, 2012, 11:36:17 pm

Quote from: LBoyd – August 29, 2012, 10:47:12 pm

The signage said that trucks were limited to 25 mph which seemed to slow for the road. I tried to hold it down to 40 mph by down shifting to 5th and moving the retarder to 3 clickes back to be cautious. I had to apply some brake.

Trust the speed limit for the trucks. The low speed limit is based on the grade. Holding steady at a higher speed on a steep grade in a vehicle as heavy as yours can make a BIG difference in the amount of energy that must be dissipated. The grade is not such a big deal in a car. It is a big deal in a vehicle that weighs over 20,000#.

Re: Retarder 101

Reply #68 – August 29, 2012, 11:53:57 pm

Quote

Today I was coming down a a very long 7% grade into Deadwood SD. The signage said that trucks were limited to 25 mph which seemed to slow for the road. I tried to hold it down to 40 mph by down shifting to 5th and moving the retarder to 3 clickes back to be cautious. I had to apply some brake. At the bottom of the long grade my trans had downshifted to 4th and I got a warning bell (first time!). A check of the trans temp (dash gauge) showed 250 which was also a first. I don't know how to check retarder temp. Bell rang for about 30 secs and stopped when the trans temp fell to about 230. The warning bell was disconserting. I'm not sure why I got such a high temp in this instance.

For 7% in my 1999 40ft U320 I think I would have been in 4th early on.

Then use the retarder/service brakes to keep from red lining.

best, paul

Re: Retarder 101

Reply #69 – August 30, 2012, 02:56:48 pm

Quote

Today I was coming down a a very long 7% grade into Deadwood SD. The signage said that trucks were limited to 25 mph which seemed to slow for the road. I tried to hold it down to 40 mph by down shifting to 5th and moving the retarder to 3 clickes back to be cautious. I had to apply some brake. At the bottom of the long grade my trans had downshifted to 4th and I got a warning bell (first time!). A check of the trans temp (dash gauge) showed 250 which was also a first. I don't know how to check retarder temp. Bell rang for about 30 secs and stopped when the trans temp fell to about 230. The warning bell was disconserting. I'm not sure why I got such a high temp in this instance.

I came down that same Deadwood grade on last Sunday ( just in time to be tail end charlie in the Old Car parade , one hour to get thru Deadwood, good car show ). I never exceeded 200 tranny temp but I used truck speed as Max and geared down, If I recall I was in third at the light at the bottom.
Grades are easy, gear down, slow down, use retarder, when speed and/or RPM picks up bleed speed off until down to posted then, repeat.
Gary B

Re: Retarder 101

Reply #70 – August 30, 2012, 03:08:56 pm

Yes, maintaining a lower speed of descent ALWAYS takes less braking HP (and therefore less heat) than going faster. A reasonable gauge is that you are faster than the loaded 18 wheelers BUT, slower than the empty ones.

Said another way, you can produce sufficient braking HP to maintain that speed WITHOUT OVERHEATING THE TRANSMISSION/RETARDER. Overheating-- slow down and gear down to where the amount of heat produced by the Allison retarder does not exceed your cooling system's ability to dissipate the heat.

Re: Retarder 101

Reply #71 – August 30, 2012, 04:08:28 pm

I confess to charging up mountains hard, passing all RVs, Trucks empty or loaded, some cars, but when it comes to going down, I am one of the slowest, save brakes, keep temps well under control etc. Such a nice thing to have a hot rod for a coach.

We all have seen and smelled the effects of idiots running too fast down with brakes smoking etc. They also are the ones who need brake repairs, drums, rotors, shoes, pads, etc. Very costly redoing some brakes.

They must have small engines trying to keep up with the folks with normal engines or something or are clueless to what is going on.

We all do what feels best for us. Don't we ?
Dave M

Re: Retarder 101

Reply #72 – August 30, 2012, 11:22:20 pm

Dave,

Everyone does what feels best. Trouble is some don't make the mental transition from their daily driver to a big, heavy motorhome. Perhaps a little overconfidence from driving in familiar areas can lead to not realizing how close to the edge of the operating envelope they are. Trips out to the National Parks in the west are a real reality check with the two lane roads having potential to be far more dangerous than the fairly mild downgrades on the interstates. Adding to the strain of steep roads are the string of cars behind just adding more pressure to make a faster decent.

The smoking brakes with a nasty smell are only a very small percent from totally loosing the brakes with another mile downhill ahead. Just have to turn off the radio and plan ahead.

I totally lost brakes following the lead vehicle at one of the big fires in the Malibu Mountains. I was already in first gear when the brake pedal didn't slow us down any longer. Terrible feeling and even worse when you push the parking/anchorlok button and nothing really happens. Had to put the right side of the rig into the ditch next to the road and drag the front I beam in the dirt to get it stopped. Not much time from when the brakes first start to fade until they are totally gone. Not really much smoke either. Five minutes later, we headed down again, still in first but slower. Auto rear slack adjusters were not working so front had to do all the work. We all had our seat belts unfastened after the first time.

Pierce

Re: Retarder 101

Reply #73 – August 31, 2012, 08:59:21 am

Quote from: Pierce & Gaylie Stewart – August 30, 2012, 11:22:20 pm

Dave,
Adding to the strain of steep roads are the string of cars behind just adding more pressure to make a faster decent.
.

Pierce

One thing I keep telling my DW, "Don't worry about anything behind you. If they would have gotten up earlier this morning they'd be in front".

Roland

Re: Retarder 101

Reply #74 – August 31, 2012, 11:24:21 am

On the downhill side, I always run a bit slower then the up hill side. I can stop without a problem going up hill. Going down hill s much harder so, I downshift and learned to stab te brakes and I go usually 10
mph under my speed if the target is above 25. At 25 moh I use 2 gear or third gear and the retarder depending on the length of the hill. Two miles or so third longer and i am in 2nd.

Affiliate Notice