A twister for thinking . ISX 650 Comes with a Jacobs Brake

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A twister for thinking . ISX 650 Comes with a Jacobs Brake

December 06, 2015, 12:33:16 pm

Cummins told me that my engine , ISX-650 comes equipped with a Jacobs brake . All that needs to be done is have it hooked up etc , etc . Now , where does this leave you with the transmission ? Could you use it along with the retarder at the same time ? If-- well maybe-- wow . Got to admit that would be neat . Brad Metzger

Re: A twister for thinking .

Reply #1 – December 06, 2015, 01:32:20 pm

A Jake / Retarder combination. The way most people tailgate this might be too much. Of course the way some people drive it may not be enough.

Go for it!

Re: A twister for thinking .

Reply #2 – December 06, 2015, 01:47:57 pm

Quote from: Brad Metzger – December 06, 2015, 12:33:16 pm

If-- well maybe-- wow . Got to admit that would be neat . Brad Metzger

Oh Yeah! Do it, just think how it'll sound with that resonator.

Re: A twister for thinking .

Reply #3 – December 06, 2015, 02:08:21 pm

Quote from: Brad Metzger – December 06, 2015, 12:33:16 pm

Cummins told me that my engine , a ISX-650 comes equipped with a Jacobs brake . All that needs to be done is have it hooked up etc , etc . Now , where does this leave you with the transmission ? Could you use it along with the retarder at the same time ? If-- well maybe-- wow . Got to admit that would be neat . Brad Metzger

Wondered the same thing. If I added a Jake how would/could everything work?

Re: A twister for thinking .

Reply #4 – December 06, 2015, 02:24:55 pm

I'd take a compression brake over a retarder any day. I would only use the retarder to suppliment on steep hills or anywhere with engine brake restrictions if it is too loud.

Re: A twister for thinking .

Reply #5 – December 06, 2015, 02:56:51 pm

Hook up the Jake's Brad you will love them on that motor.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #6 – December 06, 2015, 04:13:03 pm

Quote from: Dave Larsen – December 06, 2015, 02:24:55 pm

I'd take a compression brake over a retarder any day. I would only use the retarder to suppliment on steep hills or anywhere with engine brake restrictions if it is too loud.

This is an honest question (and I'm not being "snippy"): If a compression brake works so well then why would one want to supplement it with an Allison retarder on steep hills?

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #7 – December 06, 2015, 04:46:30 pm

Some driver's.of motor homes may not have the experience needed to handle the coach they pilot.others may..now not meaning anything by that statement it can be a benefit to have two systems. Just a thought.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #8 – December 06, 2015, 04:54:37 pm

Guys-- this sounds like the beginning of a "Ford vs Chevy" debate.

An engine compression brake (aka Jake brake) and a transmission retarder can both generate a LOT of braking HP. More control with the joy stick on the retarder, but most engine compression brakes are two or 3 stage brakes.

And, particularly the PRXB from PacBrake can also be extremely effective in the lighter coaches.

The secret is to learn how to used what you have effectively-- basic rule on descent is to choose a gear and supplementary brake (exhaust, engine or transmission) THAT WILL HOLD YOUR SPEED OF DESCENT IN EQUILIBRIUM. Said another way, you want a speed where you are neither speeding up nor slowing down without using your service brakes. If speeding up too much, firmly use the service brakes to slow down enough to drop another gear, etc.

Caution with a retarder-- keep an eye on transmission fluid temperature. If rising, drop a gear (down arrow) and lighten up on the retarder.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #9 – December 06, 2015, 05:06:50 pm

I would love to have the option of either a Jake or a Retarder. From what I hear from the Retarder Brigade, I would use the retarder most of the time to supplement mechanical braking but use the Jake on steep, long hills. to insure that I stayed at a reasonable speed without creating heat in the Trans fluid. Sounds like a win/win situation to me.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #10 – December 06, 2015, 05:34:38 pm

I drove a couple of provost conversions that had both, only one at at a time, if I remember correctly.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #11 – December 06, 2015, 05:39:25 pm

The 15 liter displacement would give better results in the Jake versus an 11 liter engine i would think.

Probably why Foretravel used the retarder versus the Jake on the 8.3,8.9 and 11 liter motors

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #12 – December 06, 2015, 05:43:09 pm

I will throw in my experience here if I may

On our off hiway logging trucks (google Kenworth 850) we run Allison 6061 powershift transmissions. Engines can be what ever you want but usually 550 to 600+ HP range.

The Allison transmission is not an automatic in that you have to move the shift lever to chose your gear, it has a torque converter and retarder much like the transmissions in your motor homes.

These transmissions only have an off or on position for the retarder, controlled with a foot pedal where the clutch would normally be positioned in a regular truck.

These trucks were built to move 100 ton plus loads over some incredibly rough and steep country, I have seen grades of up to 30%, that's right, 30% not a typo.

To help with keeping the speed in check while these monsters are descending these steep grades the driver uses a combination of the retarder the jake brake and the brakes (We spray water on the brake drums to keep them cool but that is another story)

The trucks are set up so that they CAN NOT run both jake and retarder at the same time. There are a few reasons for it but the main 2 are
- Danger of uncontrolled drive wheel lockup on a slippery surface. You people already know this
-The other reason is it is REALLY HARD on the drive to have that much braking horsepower going through it

Before I had both activated on a motor-home, I would want to contact the manufacturer of the rear end and see what they had to say, but I would not be surprised if they said it was not a good idea.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #13 – December 06, 2015, 05:56:23 pm

The one thing that stands out is , the Jacobs brake does not generate heat in the transmission like the retarder . But , my guess is the transmission would have to generate some . but probably not much , compared to . Got to admit , I am intrigued about this thing . I would also like to be able to take that big particulate muffler system off . Can't do it . All computer , A to Z . Cummins said the engine will not run if that is tinkered with even a little bit . Sensors --- . Yep ---EPA all over the thing . Have heard there is an outfit in Pittsburg Pa. that does this type of thing , but--- ? Would have to talk with someone that had that type stuff done there before I would give it much thought . The thing about my muffler system is there is a really fine screen that the exhaust has to go thru and it will fill up and shut you down when it reaches a certain point .There are two switches under the dash that allow you to burn it clean by injecting diesel into that chamber and it is ignited . This Pa. outfit can also boost the engine to 850 HP simply by adjusting the computer . Sounds really good , right? The fly in that pie is , the transmission can't take that much HP . Couple of darn's about now . Not unhappy with anything , but ----my wheels are turning . Brad Metzger

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #14 – December 06, 2015, 06:04:13 pm

The use of an exhaust or engine compression brake does not generate any extra heat in the transmission.

On both the Allison 3000 and 4000 series transmissions, the torque converter is locked up in "high 2nd" (feels like a a mini-shift as you go through the gears). It is ALWAYS locked in all higher gears. With the torque converter locked, very extra heat is generated in the transmission.

Allison temperatures rise for three (or a combination of three) reasons:

Stop and go traffic with transmission in gear at stop, first and lower speeds in second gear-- with the torque converter NOT locked in any of these conditions.

High coolant temperatures because that means the transmission cooler in the bottom of the radiator is exposed to hotter temps.

Retarder use.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #15 – December 06, 2015, 06:19:43 pm

Great reply and information from you both I really enjoy learning about things I don't quite understand. Thanks a lot.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #16 – December 06, 2015, 06:20:52 pm

Quote from: Rusty Socket – December 06, 2015, 05:43:09 pm

...
-The other reason is it is REALLY HARD on the drive to have that much braking horsepower going through it
...

Because of a failure of a bolt in the "throttle position sensor" on our C8.3/Allison system, I found myself at Inland Truck Parts in Fargo, ND. While talking the the technician, the subject of the transmission retarder surfaced. He said the local transportation authority tried retarders in city busses in Fargo. His report was that they consistently caused failure of the differential gears. That seems to be evidence of the requirement that the drive system must be capable of handling braking forces from the engine/transmission system.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #17 – December 06, 2015, 06:22:42 pm

Quote from: D.J. Osborn – December 06, 2015, 04:13:03 pm

This is an honest question (and I'm not being "snippy"): If a compression brake works so well then why would one want to supplement it with an Allison retarder on steep hills?

The ISX engine brake is very effective and may not need supplimenting. I personally wouldn't want to heat up the transmission fluid if I had a choice.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #18 – December 06, 2015, 06:29:03 pm

Yup, drive trains (including U joints) are designed to handle a given HP.

The use of BOTH retarder and engine compression brake would be well over the "motive" HP of any engine in that vehicle.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #19 – December 06, 2015, 06:55:11 pm

Quote from: J. D. Stevens – December 06, 2015, 06:20:52 pm

Because of a failure of a bolt in the "throttle position sensor" on our C8.3/Allison system, I found myself at Inland Truck Parts in Fargo, ND. While talking the the technician, the subject of the transmission retarder surfaced. He said the local transportation authority tried retarders in city busses in Fargo. His report was that they consistently caused failure of the differential gears. That seems to be evidence of the requirement that the drive system must be capable of handling braking forces from the engine/transmission system.

Most rear end gear sets in Rvs were not designed to be in a pusher position. Add in that most bidders would not specify the highly polished gear setup that you could see your face in. $100 option from Rockwell long ago.

Std rear ends needed to have the "pumpkin" removed at 40k miles after the wear pattern was set and the machining marks worn down. Then you could reset the backlash and reduce the rear ends noise.

Probably why the retarders killed their differentials. Backwards load on looser teeth. One or the other was ok but not both.

ORED 300 cats had a power on howl when new and as it cost me profit and was annoying I wanted to find out why and fix it.

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #20 – December 06, 2015, 07:04:43 pm

Sure do not see a need to use both at the same time . But , you got to admit it would be nice to say , use the retarder until the temperature in transmission got up a bit , then use the Jake . I could enjoy that . I don't have high temp in my transmission as an issue . I do not allow that to happen . Have heard stories about super high temps etc , Expect bad things will eventually show up . Brad Metzger

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #21 – December 06, 2015, 07:41:17 pm

I always thought a retarder was the cats meow. Sounds like something like a Jacob compression brake would be even better?

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #22 – December 06, 2015, 07:45:04 pm

Quote from: Mike Brez – December 06, 2015, 07:41:17 pm

I always thought a retarder was the cats meow. Sounds like something like a Jacob compression brake would be even better?

In a non 15 liter engine coach the retarder in its stronger positions has more hold back than the Jake as far as my info says

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #23 – December 06, 2015, 08:05:44 pm

Quote from: Mike Brez – December 06, 2015, 07:47:07 pm

I always thought a retarder was the cats meow. Sounds like something like a Jacob compression brake would be even better?

They both do a good job as long as you don't forget your main way to stop is next to the fuel pedal. How fast do you really need to get to the bottom of the hill?

Retarder can add quite a bit to a tranny overhaul cost should it become necessary. Not a factor for some, a big deal for others.

Pierce

Re: A twister for thinking . ISX 650 Comes with a Jacobs Brake

Reply #24 – December 06, 2015, 08:46:47 pm

I just looked up the specs on the ISX 650
There are 600 HP available for braking.

The way we operate our trucks is when descending a hill the jake switch is in full (position 3), the transmission is in lockup (there is a switch to keep it locked up manually).
The driver will start down the hill in the gear selected and will apply the retarder via the foot pedal. While he is descending he keeps an eye on the trans temp and when the temp starts to get up into the crispy zone, he will release the retarder and the jake will automatically cut in. Once the trans temp drops back down he will engage the retarder again with the foot pedal and the jake cuts out.

Now these are big trucks designed for long steep slopes. The trans coolers used to be cooled with engine coolant, much the same as your MH's, but most have been converted to different system to avoid the dreaded glycol in trans problem.

The retarder put the heat into your transmission and the jake puts it into your engine, either way you are going down hill so your not putting heat into your engine from fuel.

By swapping back and forth between retarder and jake the driver is able to keep his trans temp in the operating zone. The retarder in these trucks is a little different. They are designed to hold back way more than the ones on a motor home but the idea is still the same.

I don't really see any reason why a motor home that has both jake and retarder could not be hitched up the same way.

I would think that with 600 braking horse in a motor home on jake, that you would not even need the retarder.
Just my opinion

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