How important is the transmission retarder?

Topic: How important is the transmission retarder? (Read 4411 times) previous topic - next topic

Re: How important is the transmission retarder?

Reply #25 – December 01, 2015, 01:57:37 pm

Quote from: bigdog – December 01, 2015, 01:47:26 pm

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

True, UNLESS you will exceed the engines max safe speed in that gear. If that occurs, the Allison WILL UPSHIFT to protect the engine.

Said another way, if you manage your gear/speed/use of brakes to keep RPM toward the upper end of safe RPM, you are OK. Apply service brakes if RPM continues to climb. If need by, use the service brakes FIRMLY and long enough to allow you to drop to the next lower gear.

Re: How important is the transmission retarder?

Reply #26 – December 01, 2015, 02:26:03 pm

Ours has the PacBrake PRXB new-generation system installed in 04. Dropped into Phoenix down I-17 from Flagstaff and it worked great. I noticed it was lubed with PacBrake goop in 2014. Wonder how often to lube it?

Re: How important is the transmission retarder?

Reply #27 – December 01, 2015, 02:32:25 pm

Brett,

I have been wondering about that. I took it past the 2100 RPM limit and up to just over 2300 downhill and it still had not shifted. Does the upshift apply to all Allison transmissions? I think this is how the FF member bent his pushrods.

We don't have a "down arrow" and just punch in the gear we want.

Pierce

Re: How important is the transmission retarder?

Reply #28 – December 01, 2015, 02:33:46 pm

Quote from: mike leary – December 01, 2015, 02:26:03 pm

Ours has the PacBrake PRXB new-generation system. Wonder how often to lube it?

Mike,

Get one bottle of PacBrake lube from them or a dealer. Lube it a couple of days before you are you are going to let the coach sit for awhile.

Plan "B" is to lube it any time you raise the bed to access the engine for any reason. Takes less than 30 seconds.

Re: How important is the transmission retarder?

Reply #29 – December 01, 2015, 02:36:38 pm

Quote from: Pierce & Gaylie Stewart – December 01, 2015, 02:32:25 pm

Brett,

I have been wondering about that. I took it past the 2100 RPM limit and up to just over 2300 downhill and it still had not shifted. Does the upshift apply to all Allison transmissions? I think this is how the FF member bent his pushrods.

We don't have a "down arrow" and just punch in the gear we want.

Pierce

Pierce,

You know the numbers for the DD 2 strokes a lot better than I do. Suspect like most engines they have two different max RPM's:

Under load/governed RPM
Max permissible RPM no load/over-run

Often there is a 200 or so RPM difference.

For example on the 2003 Cummins ISL:

Peak HP 2100.
Governed RPM 2330.
Overspeed no load 2600.

Re: How important is the transmission retarder?

Reply #30 – December 01, 2015, 02:40:58 pm

Is 2100 our max for the CAT, as well?

Re: How important is the transmission retarder?

Reply #31 – December 01, 2015, 02:45:35 pm

No, being a smaller engine (shorter stroke) RPM is higher.

If you don't still have the Caterpillar book, call the Caterpillar RV hotline with your engine serial number which is # 2BK25862:

Caterpillar: 877-777-3126.

BTW, your engine is a 3116, not 3126. 250 HP and 650 lb-ft torque at 1,650 RPM.

Re: How important is the transmission retarder?

Reply #32 – December 01, 2015, 03:01:36 pm

Quote from: wolfe10 – December 01, 2015, 02:45:35 pm

No, being a smaller engine (shorter stroke) RPM is higher. BTW, your engine is a 3116, not 3126. 250 HP and 650 lb-ft torque at 1,650 RPM.

For such a relatively small engine, I'm amazed how (if I don't pay attention) fast she likes to go! Even with an after market o'drive the Airstream/Isuzu was done at 3200 rpm @ 65 mph. Climbing the Rockies, I could have walked faster!

Re: How important is the transmission retarder?

Reply #33 – December 01, 2015, 03:14:37 pm

Quote from: wolfe10 – December 01, 2015, 02:36:38 pm

Pierce,

You know the numbers for the DD 2 strokes a lot better than I do. Suspect like most engines they have two different max RPM's

Yes, they have different governed RPM depending on the application. I was wondering at what RPM the Allison is programmed to upshift over the governed RPM and where to find the info. Did Foretravel or Allison define the upshift point? Has anyone gone over the governed RPM and had it upshift while locked in a lower gear going downgrade? I have looked at several Allison publications but can't seem to find info. Perhaps not the best to trial and error.

While I have the Pro-Link cartridge for the engine, I don't have one for the Allison transmission computer so can't read the data or change parameters.

Pierce

Re: How important is the transmission retarder?

Reply #34 – December 01, 2015, 03:53:47 pm

Pierce,

Suspect a trip to an Allison dealer to have them download the programming criteria would be required to really know how it was programmed-- this on the Allison 3000 and 4000 series.

I don't have any hands-on experience with your 4 speed transmission.

The only "my Allison allowed the engine to over-sped and caused damage" I am aware of was with some Caterpillar 3176's a LONG time ago.

Re: How important is the transmission retarder?

Reply #35 – December 01, 2015, 06:13:50 pm

Wow! I had NO idea!

So it sounds as if FT has provided speed control mechanisms for most models, with transmission retarders in most Unicoaches, and exhaust brakes or Jake brakes in many Unihomes. And if you didn't get one or the other as OEM, you can add your own exhaust brake. It also sounds to me that it's probably a good idea to keep an open mind - and probably not let the absence of a transmission retarder stop me from considering a particular FT when the time comes.

Thank you all! And Brett - thank you for keeping us from wandering too far off the path. I know whatever I end up with I will be sure to get the manuals wherever they can be found - and *use* them!

Re: How important is the transmission retarder?

Reply #36 – December 01, 2015, 06:58:59 pm

We have had both an exhaust brake on our first U225, installed a week after it was taken home by the first owner. As the third owner, I was always less than impressed by the way it worked. A newer model of that PacBrake was available.

Our present 98 U295 has what I would call the best feature, the transmission retarder. I have driven some 17K miles thur 28 states, towed my Avalanche and lighter other flat tows. I am amazed how well it works to work as the down hill speed control as mentioned up this thread. We did long 7 mile descents in PA last May, without any issues. Last August we made a descent from Bobcat Pass, east of Red River to Questa NM, some 16 miles. The retarder was used along with the service brakes as needed and the temp gauge stayed in the recommended temp range.

On a trip rushing home in a tropical storm from Nacogdoches to Arlington to make a Dr. appointment, I was running maybe 50 in huge rains and major water on the roadway. The water blasting off the duals loosened the temp sender wire off the transmission and gave us a high temp warning. We had nice cool 70 degree morning, and the gauges had been showing normal ranges. I stopped and checked the transmission temps with the digital heat gauge, and remembered the same problem mentioned on a forum. I drove the coach home, without the retarder working. Oh how I have learned to like having it working. The Allison repair shop in Ft. Worth told me to drive in and they would read the codes. 20 minutes later, the high temp code was cleared and the wire was cleaned and reconnected. They would not even write a service ticket. The service manager that read the code and did the repair, explained the problem. He explained the computer protects the transmission from operator misuse. He said that his lot was full of misc trucks, most have retarders, and employees driving those trucks don't kill the Allisons. He suggested that RV owners are just so unlikely to ever have retarders issues.

It might just be that a Foretravel is the least expensive coach anyone can buy with the very expensive transmission retarder. And I will enjoy it's ability, and keep an eye on the temp gauge and fear no mountain.

Re: How important is the transmission retarder?

Reply #37 – December 02, 2015, 10:31:44 am

Back to driving in traffic with the retarder selected one or two notches. Does this not put your brake lights on?? If so you are driving like some others who have one foot on the brake, and with the other are giving it gas. Correct me if I am wrong.
And, the warning I was speaking of that hides under my arm is the one to show that you have the retarder selected, not a high temp' warning.
Brian.

Re: How important is the transmission retarder?

Reply #38 – December 02, 2015, 11:06:01 am

Read all the posts and have a couple of observations.We have only had our coach a few months,it has the rocker switch
retarder.
I would not make a coach choice based on no retarder or which extra braking system.
If you get a coach with out a retarder your only choice is an exhaust brake as retarder would be too costly to install.
The jake brake and/or exhaust brake however slight still ads some extra wear to the valve components,I would rather change
my trans oil and filters more often than have a worn engine.
Am in the process of changing over to synthetic trans fluid,2 main reasons,every person I have asked has noticed a 25 degree
heat reduction,this will translate into that much more retarder braking power.
Also the synthetic will never varnish up or burn like dino oil,all it would take is one circumstance or occurrence to coat the internals
with dark brown varnish that no flushing will remove.
Just my opinion.

Re: How important is the transmission retarder?

Reply #39 – December 02, 2015, 11:23:41 am

Speedbird1, pretty sure the brake lights only come on when you depress the brake pedal, and/or take your foot off accelerator with retarder lever in any selected position. Have seen some posts where an owner says their brake lights only come on when depressing brake pedal.

Re: How important is the transmission retarder?

Reply #40 – December 02, 2015, 11:26:54 am

Quote from: John44 – December 02, 2015, 11:06:01 am

The jake brake and/or exhaust brake however slight still ads some extra wear to the valve components,I would rather change
my trans oil and filters more often than have a worn engine.

I have never found any evidence that using a Jake will wear or shorten engine life even a little bit. Lots of rumors out there but perhaps this page will dispel them: Google

Pierce

Re: How important is the transmission retarder?

Reply #41 – December 02, 2015, 11:45:26 am

Quote from: John44 – December 02, 2015, 11:06:01 am

The jake brake and/or exhaust brake however slight still ads some extra wear to the valve components,I would rather change
my trans oil and filters more often than have a worn engine.

I have never heard of extra wear do Jacob engine brakes.

Having owned Detroit, Cummins, Caterpillar all equipped with compression brakes approaching a million miles each have never encountered any wear problems.

Re: How important is the transmission retarder?

Reply #42 – December 02, 2015, 12:30:35 pm

I knew I was going to get some replies,the jake brake mechanism itself adds extra components to the valve train,the more moving parts the more to break.The heavier valve springs themselves add more stress than non heavier springs,I know what your saying
about not hearing about any problems,if I myself had to pick one or the other with my knowledge I would choose a retarder.

Re: How important is the transmission retarder?

Reply #43 – December 02, 2015, 01:07:54 pm

We drive the first 50 miles of any trip or outing with the retarder off to keep the service brakes active, all parts moving freely and such. Only turning it on for a down grade before the 50.

We only have the pedal activated retarder and seems as though it's safer with two hands on the wheel and all that. But, having said that. How much is the joy stick upgrade and how hard to install. Anyone been there done that?

Re: How important is the transmission retarder?

Reply #44 – December 02, 2015, 02:55:47 pm

Quote from: Bob & Sue – December 02, 2015, 01:07:54 pm

How much is the joy stick upgrade and how hard to install. Anyone been there done that?

Results from using the "search" function of the Forum (a very useful tool):

Installing Joy Stick Retarder Control

Allison retarder

Re: How important is the transmission retarder?

Reply #45 – December 02, 2015, 08:52:38 pm

rbark,
Thanks for that. Just going on what FT told is when we bought it. I must put DW in the TOAD and give her the walkie talkie and see what it shows???
Brian.

Re: How important is the transmission retarder?

Reply #46 – December 03, 2015, 12:38:31 am

On mine, the brake lights come on whenever the coach is braking, either from the service brakes or the retarder. Coasting with the retarder off or joystick full forward does not activate the brake lights, coasting with the retarder on and the joystick not full forward does light up the brake lights (and disengage the cruise).

Re: How important is the transmission retarder?

Reply #47 – December 03, 2015, 12:43:26 am

Quote from: Tom Lang – December 03, 2015, 12:38:31 am

On mine, the brake lights come on whenever the coach is braking, either from the service brakes or the retarder. Coasting with the retarder off or joystick full forward does not activate the brake lights, coasting with the retarder on and the joystick not full forward does light up the brake lights (and disengage the cruise).

My cruise stays on.

Re: How important is the transmission retarder?

Reply #48 – December 03, 2015, 06:54:05 am

Jake Brakes DO NOT use heavier valve springs,
ONLY the exhaust brakes, the type that close the exhaust from the turbo, those DO require the heavier springs.
FWIW

Re: How important is the transmission retarder?

Reply #49 – December 03, 2015, 07:03:51 am

Quote from: Bob & Sue – December 02, 2015, 01:07:54 pm

We only have the pedal activated retarder and seems as though it's safer with two hands on the wheel and all that. But, having said that. How much is the joy stick upgrade and how hard to install. Anyone been there done that?

While I can't provide any cost information I highly recommend you get a joystick installed. I really enjoy having that control over the retarder, and using it becomes quite natural very quickly. It is especially useful in mountain driving.

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