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Topic: Is it a retarder or exhaust brake? (Read 781 times) previous topic - next topic

Is it a retarder or exhaust brake?

Quote from: PatC –
Craig,
Your Cummins "Retarder" exhaust brake is probably 3", so if it is working and you plan on retaining it, you might as well stay with the 3" all the way from the engine to the rear.  But if you plan on changing to a Pac PRXB exhaust brake (which is already  set up with  4") and do it at the same time, then it would be feasible to change to a larger diameter exhaust from engine back.  But I see no benefit of going larger than 4".  If you go larger behind the existing 3" Retarder exhaust brake, I really doubt you will see and power gain.

I had thought that the retarder was an Allison transmission thing... not an exhaust thing. So maybe someone can fill me in on that detail a little more fully. If it's an exhaust device then is it before the muffler or after?

Staying with 3" is not a problem as far as I'm concerned. The tail pipe is 5" but that's a chrome piece (with a curiously deformed bottom - almost like someone crunched it).

It's just like a big puzzle. :P

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: Is it a retarder or exhaust brake?

Reply #1 –
Quote from: wa_desert_rat –
I had thought that the retarder was an Allison transmission thing... not an exhaust thing. So maybe someone can fill me in on that detail a little more fully. If it's an exhaust device then is it before the muffler or after?

Staying with 3" is not a problem as far as I'm concerned. The tail pipe is 5" but that's a chrome piece (with a curiously deformed bottom - almost like someone crunched it).

It's just like a big puzzle. :P

Craig
Well, there are two types of "retarders" depending on brand.  Allison has the transmission retarder on their 6 speed transmission and Cummins put out a exhaust brake for the 5.9 engine and it was called a Cummins Retarder.  On the U225, it has a 4 speed Allison and no transmission retarder.  The Cummins 5.9 exhaust brake (Retarder) was a option.  Most that I've ran across have seized up because of lack of maintenance.  It is critical that they be used and lubricated with a special high temp lube oil.  The Cummins Retarder exhaust brake has pretty much been replaced by the Pac brake.  The new Pac PRXB is state of the art.  http://www.pacbrake.com/index.php?page=prxb-exhaust-brakes-2
1994 U225
build #4514

Re: Is it a retarder or exhaust brake?

Reply #2 –
So the switch labeled "retarder" is not an Allison transmission retarder but a Cummins exhaust retarder instead? I had thought that I had an Allison retarder. Nice to have confusing nomenclature. Where is the exhaust retarder located? I guess I need to do a better examination of the engine compartment before I try to upgrade anything.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: Is it a retarder or exhaust brake?

Reply #3 –
Raise your bed and look straight down into the engine compartment.  It is part of the exhaust piping.  Looks similiar to this:


You will probably only see the top part stuck onto the exhaust pipe.  The bottom round hole will be attached to exhaust pipe and the top parts just sticks out there like a sore thumb.  mine was right at the foot of the bed straight down.
1994 U225
build #4514

Re: Is it a retarder or exhaust brake?

Reply #4 –
Well it *is* an exhaust brake... and it's a PAC but I couldn't hold the bed up and simultaneously read which model of PAC brake it is. Have to wait for the DW; or a strong stick.

Looks like a fairly new installation, too. With flex headed down towards the muffler. Why they didn't pull that monstrous can out of there is beyond me. But that's on *my* list.

Thanks for all the info. :)

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: Is it a retarder or exhaust brake?

Reply #5 –
If it is a fairly recent (within last 2-3 years) installation, the chances are good that it is a PRXB by PAC. If so, that is good news. The PRXB is very good, probably the best for an exhaust brake. I had a BD exhaust brake; worthless in my coach. Installed the PRXB last June and traveled 6,000+ miles in the Rockies, Cascade Range, and Coastal Range and it exceeded all expectations.
Don Hay
'92 Grandvilla, U-280
The Hayfever Express
Build #4055
'97 GEO Tracker
Life is like licking honey off a thorn.

Re: Is it a retarder or exhaust brake?

Reply #7 –
Quote from: PatC –
Craig
Read this:  www.pacbrake.com/index.php?page=lube.  You want to keep it working!!

Thank you Pat. I see that they don't make it easy to buy their special lubricant. Dealers only, apparently. I'll have to call the one in Spokane tomorrow and see what a tube costs and whether or not they're willing to ship it.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: Is it a retarder or exhaust brake?

Reply #8 –
Quote from: wa_desert_rat –
Thank you Pat. I see that they don't make it easy to buy their special lubricant. Dealers only, apparently. I'll have to call the one in Spokane tomorrow and see what a tube costs and whether or not they're willing to ship it.

Craig
"Tri-Flow" will do the deed.  I'm told that is what they use and said to be better than their lube.  Any good hardware store.
1994 U225
build #4514

Re: Is it a retarder or exhaust brake?

Reply #9 –
Craig,

Regarding PAC Brake's Superlube, I also found it nearly impossible to find a dealer down here in south Texas, so I called the PAC company directly and ordered it from them. They're shipping it out today. Here is the phone number: 1-800-663-0096. Ask for Jim Foster. He is the one that arranged for my PRXB to be shipped directly to me (last June) and today said that he could ship the Superlube. Total Cost, including shipping, is $12.00. Not bad, IMHO.
Don Hay
'92 Grandvilla, U-280
The Hayfever Express
Build #4055
'97 GEO Tracker
Life is like licking honey off a thorn.

Re: Is it a retarder or exhaust brake?

Reply #10 –
Regarding PAC Brake's Superlube: I forgot to mention something important: Jim Foster said "don't bother unscrewing the access screw (B) to the cylinder airline port" They have found people have ended up "breaking things" by trying to open up that port. The most important point to lubricate, in his words, is the butterfly valve shaft. FYI.
Don Hay
'92 Grandvilla, U-280
The Hayfever Express
Build #4055
'97 GEO Tracker
Life is like licking honey off a thorn.

Re: Is it a retarder or exhaust brake?

Reply #11 –
Quote from: Don Hay –
Regarding PAC Brake's Superlube: I forgot to mention something important: Jim Foster said "don't bother unscrewing the access screw (B) to the cylinder airline port" They have found people have ended up "breaking things" by trying to open up that port. The most important point to lubricate, in his words, is the butterfly valve shaft. FYI.

Thanks Don. I think I'll try both options (Tri-Flow and the PAC brand). What surprised me was how conveniently located the PAC brake is on my U225. I lifted the bed up and was shining my LED flashlight all over and then suddenly it dawned on me that it was right there in front of me!!! But my back ran out of staying power and I didn't get the model number. It is nice to have something easy for a change. LOL

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: Is it a retarder or exhaust brake?

Reply #12 –
Just curious - is there any reason not to add this aforementioned pac brake to a vehicle that has the Allison retarder also???
1996 U270
Build #4846

Re: Is it a retarder or exhaust brake?

Reply #13 –
No such thing as a U225 with a transmission retarder-- please correct me if anyone has ever seen/owned one.

And, with the 4 speed Alllison, one has to be careful adding an exhaust brake unless the Allison has a lock up torque converter-- at least in higher gears.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Is it a retarder or exhaust brake?

Reply #14 –
Gayland inquired: "Just curious - is there any reason not to add this aforementioned pac brake to a vehicle that has the Allison retarder also??? "

Gayland,

IMHO, it would be waste of money. You would be disappointed in the effectiveness (lack thereof) of the exhaust brake compared to a transmission retarder. For the exhaust brake to be really effective you have to downshift big time to get the rpm's up high enough to produce the backpressure necessary to slow the engine appreciably. In the 8.3 you quickly approach redline (2400 rpm) in order to slow the coach down in steep grades. It's a constant interplay between braking and the PRXB. You get used to it, and the PRXB is very good for an exhaust brake, but it's not in the same "solar system" compared to the Allison transmission retarder. FWIW.
Don Hay
'92 Grandvilla, U-280
The Hayfever Express
Build #4055
'97 GEO Tracker
Life is like licking honey off a thorn.

Re: Is it a retarder or exhaust brake?

Reply #15 –
I've put over 250,000 miles on two pickups with Cummins exhaust brakes on 5.9 engines.  No lubrication or other maintenance has ever been required.  It's important that the stronger exhaust springs have been installed to get maximum braking.  I installed both of my exhaust brakes, but there can be peace of mind having Cummins do the installation using their product.
Regards,
Brett

'99 42' Foretravel Xtreme
'14 Brown Motorsports Stacker
'05 Chevy SSR
'02 BMW R1150R

Re: Is it a retarder or exhaust brake?

Reply #16 –
Monthly exercise is the biggest maintenance item
The selected media item is not currently available. Dave Head & Megan Westbrook
Titusville, FL - The Great Outdoors
'98 270 buying this month
Toad is a 2018 F150 XLT
 

Re: Is it a retarder or exhaust brake?

Reply #17 –
Quote from: wolfe10 –
No such thing as a U225 with a transmission retarder-- please correct me if anyone has ever seen/owned one.

And, with the 4 speed Alllison, one has to be careful adding an exhaust brake unless the Allison has a lock up torque converter-- at least in higher gears.

If I'm not mistaken, the 4 spd Allisons in U225s are MT643s (at least mine is), and the torque convertor locks up in the two higher gears, according to the documentation I have. My U225 did not come with a exhaust brake, but I found all the documentation and a receipt dated 1997 from a diesel service outlet in Florida for the installation of the Cummins/Jacobs exhaust brake called the "Extarder". Looks just like the PAC unit. The Extarder documentation mentions that the brake is not nearly as effective without a lockup torque convertor, but it still provides some braking assistance.

I was working on the system today, as it was inoperative. Didn't take long to find that the wires to the fuel pump switch had been disconnected/torn off. And judging by how dirty and corroded the wire terminals were, it had been that way for a very long time. The rest of the wiring install also left a lot to be desired, so I redid most of it, and reconnected everything properly. To my surprise the brake now works. Way cool.

Steve
1991 U225 Grand Villa