Learning the the retarder useage

Topic: Learning the the retarder useage (Read 3157 times) previous topic - next topic

Re: Learning the the retarder useage

Reply #25 – March 26, 2020, 05:03:54 pm

And, for those just learning to use the retarder, on those long downgrades, ALWAYS keep the engine RPM at the higher end of their approved RPM range.

This uses 0 fuel (throttle closed) and turns the water pump faster which keeps transmission temperature lower.

And, a little more digression for those new to the "sport". Each engine has several RPM numbers that you need to commit to memory (determine from your engine manufacturer for your engine serial number):

Peak torque RPM-- do not operate the engine under anything but light load below this RPM

HP RPM-- RPM at which max HP is generated

Governed RPM-- highest rated engine speed UNDER LOAD

Max no-load RPM-- in most cases higher than governed RPM and is the max safe RPM with throttle closed-- like with retarder on.

In general, I try to keep max RPM with throttle closed with retarder on between HP RPM and governed RPM, but if very steep long grade, you will do no damage going up to max no-load RPM. Said another way, on those long steep grades over-temp on service brakes or transmission temperature from retarder is less desirable than operating the engine at higher RPM.

Re: Learning the the retarder useage

Reply #26 – March 26, 2020, 05:28:03 pm

Hi Brett,
Always love your posts!
How would we find out those rpm numbers?
Is there a way to look it up?
I have a 98 325 Cummins with 3060r Allison.

Re: Learning the the retarder useage

Reply #27 – March 26, 2020, 05:30:37 pm

Brett nailed it!!! Thanks Brett

Understand those numbers can be found on the Cummins website. All you need is your engine serial number.

Re: Learning the the retarder useage

Reply #28 – March 26, 2020, 07:40:56 pm

Interesting all the high temps I read on here with retarder use. Have towed my loaded race car trailer, and Jeep down big grades, hammering the retarded.
I have never seen temps past 205-210, on the gauge or the sileverleaf. The trans and silverleaf are pretty close to the same temps, up and down, and follow the engine temp. (not on down grades)
Am I missing something? Or maybe I am cycling it right, on and off, and using part brakes.
It all seems to work fine.
Chris

Re: Learning the the retarder useage

Reply #29 – March 26, 2020, 07:53:27 pm

Two different temp senders I understand. One in sump? The other in the retarder?

Re: Learning the the retarder useage

Reply #30 – March 26, 2020, 08:01:33 pm

Quote from: Caflashbob – March 26, 2020, 07:53:27 pm

Two different temp senders I understand. One in sump? The other in the retarder?

That is what I am thinking too. I believe there is some deal, where you can move sender at the trans.
My over tempt never goes off, except for back when I had the issue with it, where it went off periodically (even cold)
But I fixed that, by changing that sender in the trans.
Have transcend, not going to worry about it.
Chris

Re: Learning the the retarder useage

Reply #31 – March 26, 2020, 08:39:13 pm

Use PID 120 on your VMSpc for retarder temperature. It generally runs about 5 degree above transmission temperature and can go from 185 to 235 in seconds when the retarder is engaged.

Re: Learning the the retarder useage

Reply #32 – March 26, 2020, 09:22:56 pm

Quote from: Tom Lang – March 26, 2020, 05:30:37 pm

Understand those numbers can be found on the Cummins website. All you need is your engine serial number.

Tom, I was unable to find those numbers on the Cummins web site. I don't doubt that they are in there somewhere but I sure could not find them. I was, however, able to get three of the numbers off the engine data plate. The only one I am lacking is the max no load RPM.

Re: Learning the the retarder useage

Reply #33 – March 26, 2020, 09:47:44 pm

Sooooo, on the Cummins 300, 8.3 what rpm is max going downhill working range

Re: Learning the the retarder useage

Reply #34 – March 26, 2020, 09:52:10 pm

I understand our 97's does not report #120 out of data plug? Is that incorrect.

Re: Learning the the retarder useage

Reply #35 – March 27, 2020, 10:32:14 am

I found that I really had to pay attention to the transmission temperature on the Vms. So I go along depending on what the temperature is. As others had said on the highway bring the joystick all the way back. It will cause minimal drag when you come off the gas. And really heavy traffic though I bring it up towards the end. That way as soon as I come off the gas it starts braking me. That's some serious safety. We all know that as we get older our reaction times are much less. The retarder really helps with that. Invaluable in my opinion.

Re: Learning the the retarder useage

Reply #36 – March 27, 2020, 10:38:38 am

Quote from: Caflashbob – March 26, 2020, 09:52:10 pm

I understand our 97's does not report #120 out of data plug? Is that incorrect.

Correct, at least for my '97. It does not report Retarder temp on the data bus. I have to rely on Trans temp, which lags the Retarder temp a little bit, and may report a few degrees cooler but has been close enough.

Re: Learning the the retarder useage

Reply #37 – March 27, 2020, 10:59:50 am

Question,if you just have the rocker switch and add the joystick can you still use the rocker switch?

Re: Learning the the retarder useage

Reply #38 – March 27, 2020, 11:19:37 am

Re: Learning the the retarder useage

Reply #39 – March 27, 2020, 11:24:19 am

Quote from: Roger & Susan in Home2 – March 26, 2020, 08:39:13 pm

Use PID 120 on your VMSpc for retarder temperature. It generally runs about 5 degree above transmission temperature and can go from 185 to 235 in seconds when the retarder is engaged.

Thank you Rodger
Ours is the old dos look, black box, with Cat engine.
Chris

Re: Learning the the retarder useage

Reply #40 – March 27, 2020, 11:27:28 am

Quote from: Caflashbob – March 26, 2020, 07:53:27 pm

Two different temp senders I understand. One in sump? The other in the retarder?

Yes, the one in the retarder is the one I replaced. There is also one for the gauge in the sump line.Replaced that one 1st. The retarder one is the one that was setting off false alarm.

Pic inside retarder
Pic of gauge sender (crappy pic)

Re: Learning the the retarder useage

Reply #41 – March 27, 2020, 12:09:07 pm

I agree Phranko. 55mph is max downhill and still feeling comfy. I only drive 65 on the flat max.

Re: Learning the the retarder useage

Reply #42 – March 27, 2020, 01:18:26 pm

The more I read about this subject, the more I like the simple 3 position setup we have (no joy stick).
If the cruise is on (engaged), the retarder is disabled.
If the cruise if off (not engaged) and retard switch is on, retard begins as soon as you let off the throttle.

As to the above quote, definitely not the way ours works.

With the joystick in the "off" position, or "0" which is forward on mine, the stick has no bearing on the operation of the retarder. If the rocker switch is on the retarder works off of the service brake pressure switches and deactivates when speed is below 10 mph. The retarder will drop out the cruise control if activated and the cruse control can not disengage the retarder. If the joystick is in any position other than "off" then the retarder is activated when the accelerator is released. The joystick does not override the rocker switch operation, the rocker must be "on" for the joystick to work.

Maybe this will clear up what seems to me to be some confusion about retarder operation.

Re: Learning the the retarder useage

Reply #43 – March 27, 2020, 01:30:20 pm

Quote from: John44 – March 27, 2020, 10:59:50 am

Question,if you just have the rocker switch and add the joystick can you still use the rocker switch?

Yes. We added the joystick 15 years ago. When the rocker switch is off, all retarder functionality, including the joystick, is disabled. Rocker on = all retarder functions on.

Re: Learning the the retarder useage

Reply #44 – March 27, 2020, 02:01:25 pm

Be aware that retarder joy sticks can be mounted so that forward is off, back full retard, OR the reverse where forward is full retard. We all get used to our own setup and don't realize that others are reversed.

Relating to tranny temp dash gauge, our sensor is in a 1/8" NPT hole on the large diameter coolant lines that come from the forward side of transmission. If the sensor is on the return from tranny cooler, dash gauge will read slower and lower. We relocated our dash sensor to the line going to the cooler, so now we see realistic quick & higher temp readings. Also, after a long down-hill run where gauge got into 300 degrees, the cooler works so well, we see temps sink low very fast. So, the input to cooler line location is very responsive.

Re: Learning the the retarder useage

Reply #45 – March 27, 2020, 02:10:42 pm

Quote from: Barry & Cindy – March 27, 2020, 02:01:25 pm

Be aware that retarder joy sticks can be mounted so that forward is off, back full retard, OR the reverse where forward is full retard. We all get used to our own setup and don't realize that others are reversed.

Relating to tranny temp dash gauge, our sensor is in a 1/8" NPT hole on the large diameter coolant lines that come from the forward side of transmission. If the sensor is on the return from tranny cooler, dash gauge will read slower and lower. We relocated our dash sensor to the line going to the cooler, so now we see realistic quick & higher temp readings. Also, after a long down-hill run where gauge got into 300 degrees, the cooler works so well, we see temps sink low very fast. So, the input to cooler line location is very responsive.

I have heard of this, and want to do it. Can you post a picture please.

Thanks Chris

Re: Learning the the retarder useage

Reply #46 – March 27, 2020, 03:41:16 pm

A couple of photos, Chris

Our lower forward face of transmission has two large diameter elbow fittings that direct tranny fluid hoses up and back to large tranny cooler. One hose is transmission out and other is return to transmission.

Our return elbow was probably drilled by Foretravel factory for the factory 1/8" NPT sender.

Because the two elbows are next to each other, hose runs would bump into to each other so factory had one hose looped down so it was the lowest part of the drive train, vulnerable to damage.

During a transmission maintenance visit when fluid had been drained we eliminated the down loop and had a the other elbow drilled to relocate the temp sender.

Found these related postings, oldest first:

Erratic coolant temperature & transmission temp gauge change

Retarder - hose rerouted

Experience Wanted - Speedometer install

Retard feature pros and cons

Allison Transmission Temp Sensor

Retarder 101

Transmission temp gauge

Re: Learning the the retarder useage

Reply #47 – March 27, 2020, 08:35:50 pm

Jan and Richard,
A good rule of thumb is that max no-load rpm is usually 20% above governed rpm.

Re: Learning the the retarder useage

Reply #48 – March 27, 2020, 08:55:48 pm

Jake Brakes rule ..sorry alll....could not help myself lol

Re: Learning the the retarder useage

Reply #49 – March 27, 2020, 10:21:52 pm

Here's what I got out of this thread.

Disconnecting the brake light actuation when the retarder engages may stop the trans downshift command from being sent to the trans.

The auto downshift command adds the additional cooling and engine compression retardation to the retarders input

Can be done manually but I noticed the trans ocassionally would auto downshift under occasional heavy loads on the retarder Function.

So as I see it my personal choices choices are to not have the trans auto downshift when the retarder engages or not have the retarder kick off the cruise control.

So trans downshift or retarder with cruise on.

Anyone have a thought on how to build a work around? I there a way to make the trans think the brakes are applied so the trans downshifts but not kick off the cruise?

Am I wrong? Does those whose brake lights work have their trans downshift readily? This is a finesse observation I think.

You may have to drive a similar coach with the relay on and then off. Just to compare the trans downshift pattern.

I choose to manually downshift the trans to raise the engines rpms and to have the retarder work on cruise versus it kicks off the cruise versus auto downshift the trans?

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