How important is the transmission retarder?

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How important is the transmission retarder?

November 30, 2015, 09:03:43 pm

Foretravel is the only make I have seen so far that uses a transmission retarder. (Maybe some other high-end coaches use one as well - but I'm not going there.) If you have experience driving a DP with and without one, how much difference do you feel they make? I know there are also Jacobs Engine brakes out there as well - so if you have used both retarder and Jake brake I'd like to know your sense of the differences there as well. The retarder is one of the features I feel I would value, but it's hard to know in advance...

As always, thanks very much for the benefit of your experience!

Re: How important is the transmission retarder?

Reply #1 – November 30, 2015, 09:23:35 pm

You will get a bunch on this. A retarder was a big part of what steered me to a FT. We went from no braking assist to the retarder. It is a great part of the driving experience.

It really helps going downhill. Speed and temps (coolant and transmission and retarder) are managed with gears, retarder and brakes. Sort of in that order for me. Safety and your sense of comfort is the most important.

Whatever you get will take some time for you to understand how these things are interdependent on each other on your particular coach.. What gear, what speed, how many RPMs, what boost, what temps are OK, how much retarder to use? All of this balanced with your own sense of comfort level comes with some experience. Folks who drive pretty much in the flat lands have to learn what to do in the mountains when they go there. It is different.

Some folks use the retarder all the time as a brake assist. It works well, takes some getting used to but some have had very long brake life.

The retarder is just one of the big parts that make a FT a great coach. Ride, suspension, body stiffness, fit and finish, quality components and the Forum all add up to a hard to get combination in any SOB.

Re: How important is the transmission retarder?

Reply #2 – November 30, 2015, 09:39:12 pm

Roger gave a very good idea of why the retarder is so valuable.

For me, it is a must have which is why we have been living and traveling full time for the last 8 years in our Foretravel. It not only helps going downhill, but on all braking as it is activated when you push on the service brakes. The harder you push, the more the retarder works also - which is great with our heavy coaches.

I like to use the retarder especially while in stop and go traffic as I can have it set on step 3 so when I let up off the accelerator, it starts slowing the coach before I can get my foot on the brake pedal. Nice to have when so 4 wheeler in a hurry decided he wants your lane while you are still in it.

Re: How important is the transmission retarder?

Reply #3 – November 30, 2015, 09:46:52 pm

As Roger said, you will probably get a lot of response re: your retarder question. Would we drive a diesel pusher without one? No.

Like Roger's decision concerning FT, the Allison transmission with retarder was a big part of our decision to purchase a Foretravel. We can "set" downhill speeds pretty much like trimming an airplane for a stable descent. The six steps on the retarder joystick provide different degrees of retard or speed control. Once the stick is properly set, the retarder holds the desired speed. Service brakes are saved for need to slow down rapidly or an emergency.

You asked about any comparable experience with engine brakes. Mine is very limited, so others on the Forum are certain to be more qualified to address your question. However, in research leading to the purchase of our coach, we drove a Newmar Ventana with what appeared to be a very simple engine brake (on or off). With only an on/off setting, it's hard to imagine it would perform the way the Foretravel retarder does on long descents.

The engine brake worked well in stop-and-go driving, which is where the salesperson told us to use it, mostly eliminating the need to touch the service brakes except for the final stop. I think [?] this is a technique somewhat like Roger was referring to as "brake assist." The transmission retarder in our Foretravel does the same thing as the engine brake, but is more useful (in my view) since you can dial-in more or less retard, adjusting for traffic, based on the stick setting. I use it in city traffic.

Hope this adds something to your research. It would be hard to overvalue the transmission retarder, although obviously a lot of coaches don't have one. You'll find this is a great Forum and you should get a lot of info/help. Best wishes in your search!

Re: How important is the transmission retarder?

Reply #4 – November 30, 2015, 09:49:54 pm

In a nutshell the retarder uses the transmission fluid to hydraulically slow you down. When you tap the brake pedal the retarder energizes. My old 91 uses the brake pedal to activate it. some have a joystick which I can imagine would be nice as you could toggle the retarder to slowdown. Keep in mind that Foretravel coaches also have Air Disc Brakes. These are very efficient in their own right, add a retarder and stopping shouldn't be a issue. I don't know of any other brand that puts Air Disc on as standard equipment. Heck my Peterbilt semi dosn't have air disc on it. The engines could also have a jake brake installed if you felt you wanted an option between a retarder or jake or use both, that would be at your expense but is also a option, I doubt you would need too especially after you drove one of these coaches.

Re: How important is the transmission retarder?

Reply #5 – November 30, 2015, 09:55:03 pm

One piece of advice. Learn to drive without it, then use it as a supplement to your service brakes. If your retader ever fails then you will know what you can and shouldn't do. That's something I learned in the military tractor-trailer course and it served me well in ten years of owning a small trucking company.

Re: How important is the transmission retarder?

Reply #6 – November 30, 2015, 10:08:19 pm

One extra benefit of the retarder vs an engine or Jake brake. A lot of towns, cities, etc, have signs saying no engine brakes allowed-usually due to the noise they produce. I just smile while I use my quiet retarder to slow my coach down.

Re: How important is the transmission retarder?

Reply #7 – November 30, 2015, 10:27:08 pm

Retarder: nice to have, but not essential. When we started looking at Foretravel coaches, I wanted a retarder. We ended up buying a model that does not have a retarder. We could not be any happier with our choice. Do I ever have "retarder envy"? Sure I do - the retarder is a big part of the Foretravel Mystique. However, I would not pass up a otherwise perfect-for-you coach just because this one feature was missing. We have driven all over the western half of the country, crossed the Rocky Mountains several times, and lived to talk about it. As Stump said, Foretravel coaches have excellent brakes. They will stop just fine without a retarder.

Re: How important is the transmission retarder?

Reply #8 – November 30, 2015, 10:41:38 pm

I've had both and did a post on my impression awhile back. In my opinion the retarder with a joystick is superior. I really like the incremental braking application with the six joystick positions. As long as you keep the revs up you shouldn't have any issue with transmission overheating. However, the Jake is a close second... it does an excellent job of keeping your speed down as you descend a steep grade. Of course, there is no heat issue with a Jake. Regarding noise, if you have the stock muffler you can just barely hear the Jake at work.

In stop and go town driving, if you like, you can use the retarder with little application of your service brakes. Not so with the Jake. Probably better to exercise the service brakes anyhow.

Finally, there is no comparison in emergency stopping situations. The retarder coupled with ABS is something else!

Bottom Line: They both work great but the retarder wins by a length.
jor

Re: How important is the transmission retarder?

Reply #9 – November 30, 2015, 11:04:04 pm

As Roger said you will get a lot of input!1
We live in the mountains and I would not like to be without it, but beware of LONG decents with it full on. When we first got the coach Texas told us very little about its use so we were coming down a long mountain deep in Nowhere, Montana with it full on when all of a sudden at the very bottom we got chimes and an absolute silence from the power department as it had shut down before it got too hot. No power steering, but good air brakes.
The answer came from FT, who in those days answered the 'phone, and the ruling is whatever gear you go up the mountain in, use coming down the other side, and use the retarder and brakes as well just as Roger says. A balancing act but well worth the trouble. Definatly a brake saver.
My only complaint is that if I let got of the joystick, and forget, the Red light is hidden under my armrest and I never see it!! Operator error I know but I could get the surgery!!
As for driving in traffic with it half on, not so sure that is a good idea, and I would say makes you prone to overheating the transmission?? I am sure I will be corrected, but that is my 2cts worth.
Brian.

Re: How important is the transmission retarder?

Reply #10 – November 30, 2015, 11:18:42 pm

Just to add my solution to the concern about heating up the transmission by using the retarder in traffic- I have full synthetic transmission fluid in my Allison. I know some will say to use Transyd, but I have Amsoil Torque Drive in my tranny and from day one it has run 25 degrees cooler. Synthetic transmission fluid dissipates heat much better than regular tranny fluid and heat is the enemy of our transmissions. This does not mean that the operator does not have to watch the temps, rather it is a better system for keeping the temps in line.

Re: How important is the transmission retarder?

Reply #11 – November 30, 2015, 11:31:34 pm

Thanks all for the insight! My driving experience has been mostly in cars, some farm tractors and smaller (gas) trucks, but never anything with the weight of a diesel pusher. Driving a manual transmission gas vehicle downhill I know I can rely on the engine to slow me down but I also learned that the same stopping power doesn't exist with a diesel engine unless there is a Jake brake. There happens to be a "no engine brake" sign about 100 yards as the crow flies from where I sit, and the signs are commonplace around here (Ted & Karen). When I learned about the transmission retarder I thought it would make a worthy slowing mechanism and one that can be used freely, but especially in the event the brakes get too hot or fail for some reason or better yet - to prevent that from happening altogether. Knowing you can just "dial it in" sounds (as LookingWest said), like trimming an aircraft for descent. (As Chuck & Jeannie said) the air disc brakes must be *very* nice to have as well. I think I would want something in addition to brakes alone though, like an exhaust brake or engine brake if a transmission retarder isn't available, at least if I'm driving a vehicle that could weigh up to 15 tons (GVWR 30,000+ !) and moving off the flat from time to time.
Thanks all - I'm keeping the retarder on my list. There's no telling where my travels will take me!

Re: How important is the transmission retarder?

Reply #12 – November 30, 2015, 11:31:40 pm

Having driven both, I am a big fan of the Jake. No heating the transmission fluid and when the warning light comes on, you can't use it any longer. Not good if you are still in mountains. Not everyone will have the sense to pull over and let it cool. High transmission temps shorten the life of the fluid and may cause transmission problems if maintenance is not done. Plenty of graphs online with trans fluid temps vs transmission life. A transmission overhaul will cost significantly more if retarder equipped.

A retarder like a Jake can be an aid but using the retarder to the point of the light coming on frequently is either poor driving technique or a fault with the service brakes. In an emergency stop, the Meritor disk brakes will lock up all six (or eight) tires all by themselves.

In snow, ice or even wet conditions, a retarder may cause the rear to lock up unless the operator is very knowledgable and even with ABS, a downhill grade can be tricky to descend.

Betting no member lives in steeper terrain than we do. Our Jake even with toad works great and never has given us a moment that we wish we had more braking ability.

So, while the retarder may provide a little more auxiliary breaking, I think the minuses outweigh the pluses and would chose the Jake every time if given a choice.

Pierce

Re: How important is the transmission retarder?

Reply #13 – December 01, 2015, 12:03:42 am

Hummm Jury is still out

Currently i have both, one with retarder 03 GV 295 & one without 94 GV 225. Last year I drove the one without a retarder from TX to OR and back (4500 mil) without any issues. I had all new and improved suspension with all brand new tires so I was even doing some spirited driving, especial during the WY to UT stretch. Not once I had a need for anything more than what the U225 had, regular brakes ... also I did not know any better. So within last several month's, i have driven few FT's with retarder and now i have one ... it is nice ... nice to have .... but now I am finding out, it is a bit of balancing act ... using it requires some finesse, especially if you are as anal as i am where i like to use the best fluids and use it in a way to prolong its life as much as possible. Now for what ever reason, I will say this I am hoping my wife will enjoy driving the one with retarder more.
Good luck.

Re: How important is the transmission retarder?

Reply #14 – December 01, 2015, 12:47:33 am

Unihome and unicoach air disk brakes are cold blooded. They were designed for more weight than we have.

Same problem with old beaver Marquis with gillig bus chassis's under them. Massive s cam brakes. Never got hot enough.

Glazed the shoes. Had to pull the 300 pound rear drums with a chain hoist and sand the shoes.

The 280 poster runs his regularly and they are not glazed it seems.

Now after a long rainy cold level ground drive followed by a panic stop may show some cold bloodedness.

In some fancy new cars if the wipers are on the brakes pads are pre tensioned against the rotors to displace the moisture and warm the pads and react quicker.

As long as you understand the conditions that might require pre warming the disk brakes then the retarder is not needed as much.

I have inquired about adding a Jake brake to my m11 as under severe use I can get the retarders 250 degree warning buzzer to come on. As I understand it it takes 300 degrees for the retarder to turn off the load.

I "ride herd" on the brakes and retarder knowing their use and operating limits.

As long as you have good condition brakes and keep them warmed up for the conditions present the retarder is not as necessary

Ah.... Long downhills....or a rolling road....on cruise......

My retarder works unlike some on cruise control.

Keeps the coaches downhill speed under control subject to the control arms position which is how much retardation is being applied versus how long.

Re: How important is the transmission retarder?

Reply #15 – December 01, 2015, 05:33:04 am

I have driven both in different applications and now I have a question about them. I have used a Jake brake in a Cummins powered Mack with a thirteen speed eaton trans with a four speed brownie. The Jake was awesome coming off mountain passes in Colorado loaded to the gills with prestress concrete. But that was standard transmission. It was going to stay in whatever gear I chose until the gear box melted down.

I love the retarder in our FT. But that is an automatic transmission that will ( to my understanding) always want to up-shift as the engine hits higher RPM's. Not having driven an Allison with a Jake, does it just pop up through the gears until it gets to top gear and then use the engine compression to slow down?

Seems to me, having both would be the ideal if you do a lot of high mountain cruising.

Thanks,
Len

Re: How important is the transmission retarder?

Reply #16 – December 01, 2015, 07:14:25 am

I think it's like your first computer. You weren't sure that you needed one but folks kept saying you'd like one so now after having that computer you can't imagine being without it. Same with the retarder. We're on our third coach and this is the first with a retarder. Would never be without one again. 160,000 plus miles and still on first brake pads and rotors.

Re: How important is the transmission retarder?

Reply #17 – December 01, 2015, 07:22:32 am

I drive the mountains and would not be without one. Liberty and vantre bbut conversions have them standard. Trash trucks use them too. I pull the lever back in stop and go traffic too. Works well as does the combination of reducing gears and retarder in the mountains. Pulled back three stops and third or second gear will keep you slow and not super heat the transmission for miles and miles.

Re: How important is the transmission retarder?

Reply #18 – December 01, 2015, 09:44:38 am

Not qualified for the pros/cons discussion of Retarder vs. Exhaust brake side by side comparison.

Retarders used most often in mining and garbage trucks applications to reduce wear on brakes and as a more effective secondary brake than exhaust. Rare in motorhomes due to cost considerations. FT made them standard in the mid nineties, in alignment with their philosophy to use the best available products and technology to build their coaches (vs. designing a coach for a specific market segment/price point).

Pros

With joystick, 6 position independent braking action from brake pedal (also coupled to brake application) - very nice for smooth stops in city traffic, or to help control speed on long down grades Excess stopping power - really amazing how quickly my coach and 2400 lb toad (w/o aux brakes) can stop No noise (vs. exhaust style brake) Expensive merit or disk brakes last forever....usually sticking pins and slack adjusters cause pad replacement, not actual wear Operation is automatic, retarder can be left on virtually full time. Some even drive with it engaged one or two clicks, since it is off under acceleration - I call this "garbage truck" mode - will cancel your cruise control - so I don't really see the use for that mode unless in city traffic

Cons -

Considered as a severe service addition by Allison, calling for more frequent transmission oil changes - Recommend every year w/o synthetic fluid - (I do not use synthetic and do mine about every 18 months Need to watch heat build up if in use on long grades - primary speed control should always be downshift vs. retarder/brakes on any long grade - heat quickly dissipates if you take retarder off for even a brief period - Retarders held on by a bracket - some coaches had bracket break and needed reinforced - easy fix Not recommended in HEAVY rain or slippery conditions - breaking action on rear wheels VERY effective, and if rear wheels break free and lose traction, the heavy end of the coach (rear) will come to the front and want to lead the parade.

Love mine, can't imagine life without one.

Re: How important is the transmission retarder?

Reply #19 – December 01, 2015, 09:53:48 am

This is what I LOVE about this Forum - it permits a free exchange of opinions, without anyone getting mad or starting a fight!

One more thought from the Minority side of the house - the OP mentioned a exhaust brake. We have one. IF one happened (for whatever reason) to purchase a coach without a retarder (or Jake), and then felt the need for some kind of add-on braking assist, a exhaust brake is the only practical (affordable) solution. This handy device can be added to almost any diesel powered vehicle, as long as space permits. The newer designs can be pretty effective, under the proper conditions.

In case anyone listening is curious, and because I don't have anything better to do, I will briefly describe the operation of our unit. Those of you with retarders can move on to the next post. Our exhaust brake control, mounted on the wall next to the driver seat, is pretty simple: it is ON or OFF. The control incorporates a pressure sensor on the "gas" pedal. When you turn the switch to ON (assuming the ignition switch is ON, you have sufficient air pressure, and your foot is off the "gas" pedal) the exhaust brake valve closes. Touch the "gas" pedal with your foot, and the brake valve opens. Like I said, pretty simple.

When the brake valve is closed, it blocks the free flow of waste gases in the exhaust pipe. This creates back pressure in the engine, which is translated into a "slowing" effect by the transmission. The degree of "slowing" is directly related to several factors. In my experience, the most important factor is RPM. The higher the RPM, the better. If I activate the exhaust brake while driving in town, I feel almost nothing. The sound of the exhaust changes - that's about it. BUT, "coasting" down a mountain road with 4th gear manually selected and the tach reading 2500 RPM, when I activate the control there is a STRONG braking effect. I have found this particular combination (4th gear, 2500 RPM) to be very effective, almost totally eliminating the need to use the service brakes, while allowing me to maintain a reasonable descent speed (40-50 MPH).

Note: Exhaust "braking" is also more effective when the transmission torque converter is "locked". Foretravel (Allison) transmissions are good in this respect, because they are programmed to "lock up" at fairly low RPM in the "highway" gears (4th, 5th and 6th).

There are limits to how much back pressure can be tolerated by a given engine. One important factor is the exhaust valve spring rating. Some engines have stronger springs than others. If the springs are relatively "weak", too much back pressure can cause the valves to "float", with unhappy consequences. On some engines, if desired or required, the exhaust valve springs can be up-graded, allowing higher back pressures.

The design of the exhaust brake itself is another factor. The simplest design is a single valve with a hole in the center. When closed, it creates "some" back pressure, but allows enough exhaust flow to prevent over-loading the engine. The newer designs incorporate two separate valves - a large primary valve (with no hole), and a secondary (smaller) "relief" valve. The big valve closes - back pressure rises to a pre-determined limit - the small valve opens and maintains this pressure. This design is much more effective, over a wider RPM range. Our coach has the up-graded exhaust brake design, and I find the performance is quite satisfactory.

In the end, each buyer must decide what features they require in a coach. Retarder, or no retarder - it's totally up to you (and your wallet)!

Photos of our setup below, and link to more info on the exhaust brake fitted to our coach (Super Duty D-Celerator):

D-Celerator Diesel Exhaust Brake

Re: How important is the transmission retarder?

Reply #20 – December 01, 2015, 10:49:46 am

Len,

I select the gear I want before heading downhill. Something steep might require second gear. The engine then increases RPM until I apply the service brakes and drop about three hundred RPM . The process is then repeated until the bottom of the grade is reached. The Jake either slows the increase or stops it altogether. It's up to the operator to limit the maximum RPM as allowing it to increase past the designed speed may cause engine failure. In my opinion, this was the cause of the bent pushrods and ultimately the engine failure in a Foreforum member's coach several years ago.

Chuck,

Yes, excellent implementation of the exhaust brake to your coach. You probably gross at about 33K lbs and it gives extra security, especially if you have a heavy toad without brakes. It's a freebie also with no heating load on the transmission.

I keep the Jake on at all times where we live in the Sierras but on flat ground, I like to keep it switched off part of the time to monitor how effectively the service brakes are working. Coming down the Malibu mountains on a campaign fire, I lost all brakes due to fade and had to put the truck half off the road and bump along with one wheel down in a ditch to finally stop it. This was a slow motion event all in first gear. The fade was traced to a bad slack adjuster plus we were in a hurry to get down the mountain before the fire burned more homes on it's way to the ocean. And for those interested, applying the parking brake/Anchorlok with faded brakes does nothing.

Understanding the operation and monitoring the service brakes effectiveness will keep what should be your primary means of slowing the coach in top condition. Again, using a retarder or Jake all the time can mask a problem in the service brakes. Used correctly, they can add an extra margin of safety to RV travel.

Chuck, yes we are all trying to get through life in one piece. No sense in adding a low self esteem put down and making an enemy out of someone with a different opinion. I don't think there is anything wrong with a little back and forth bantering as long as no one takes it too seriously. Sometime difficult to see the smile on one's face when reading a reply.

Pierce

Re: How important is the transmission retarder?

Reply #21 – December 01, 2015, 12:59:58 pm

You've already seen lots of opinions--but I'll also offer mine.

Having driven various heavy vehicles without a transmission retarder I am extremely happy to have on one our Foretravel. It's a real convenience under most driving conditions, but it's a huge safety factor in mountain driving. I would never again want to be without one.

I suppose that engine compression (Jake) brakes are just as effective, but I personally prefer the smoothness and multi-stage selection available with the transmission retarder. I understand that some exhaust brakes work well, but they appear to be significantly less effective than a transmission retarder or engine compression (Jake) brake.

Re: How important is the transmission retarder?

Reply #22 – December 01, 2015, 01:14:22 pm

You may care, or not, to verify, but I am very sure I was told by technical at FOT that the FT comes with both jake and retarder, they just do not hook up the jake. But a customer in Canada got both hooked up due to mountains he always in.

Someone can check if they care, but I was "shocked" and questioned the guy about what he said.

Very interesting if true....maybe too good to be true! But I think if both there, clear retarder can well handle usual mountains. Hope Dave Cobb posts on mountain experience.

mike

Re: How important is the transmission retarder?

Reply #23 – December 01, 2015, 01:26:56 pm

The Jake requires a taller valve cover on Detroits. The non-Jakes have the words "Detroit Diesel" cast in large letters on the top of the slightly lower covers. Don't know about ID differences on Cummins or CATs other than the Jake wiring loom.

Some confusion may be attributed to the "retarder" switch on the instrument panel of GVs. The same switch (labeled "retarder") was used on both retarder and Jake models. On a Detroit, the first position activates the Jake on the starboard side and the second position on both sides.

The Jake is also an expensive option so doubt very much if it was fitted but not used on some FT models.

Pierce

Re: How important is the transmission retarder?

Reply #24 – December 01, 2015, 01:47:26 pm

Quote from: lenspeiser – December 01, 2015, 05:33:04 am

I have driven both in different applications and now I have a question about them. I have used a Jake brake in a Cummins powered Mack with a thirteen speed eaton trans with a four speed brownie. The Jake was awesome coming off mountain passes in Colorado loaded to the gills with prestress concrete. But that was standard transmission. It was going to stay in whatever gear I chose until the gear box melted down.

I love the retarder in our FT. But that is an automatic transmission that will ( to my understanding) always want to up-shift as the engine hits higher RPM's. Not having driven an Allison with a Jake, does it just pop up through the gears until it gets to top gear and then use the engine compression to slow down?

Seems to me, having both would be the ideal if you do a lot of high mountain cruising.

Thanks,
Len

It is my understanding that you can "hold a gear" in the Allison by using the down arrow button on the shift pad.

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