In an earlier thread we discussed the merits of a preselect of 5th gear rather than 4th. I had mine changed and liked the results. After getting that done I had my single speed (all six cylinders) changed to a two speed. Now I have the choice of using three or six cylinders. With the 5th preselect and the two speed the Jake is much more usable. Still not as good as a retarder but getting close. Using the low setting (3 cylinders) on long easy grades at high speed (55 to 60) works great. If it's not enough, either drop down to 4th or change to high (6 cylinders) in 5th. I've only got about 300 miles using this setup but I had lots of hills so I think I have a pretty good handle on how to use it. Anyhow, I would recommend that anyone with a Jake change to 5th pre and make it a two speed.
In order to make the change, Cummins used one of the extra wires that runs from the dash to the rear of the coach.
Here's the switch we used. The middle is off. I switch on the rocker labeled "retarder" and leave it on. This turns on the Jake system but does not activate it. Then I use the new switch to select either low or high.
jor
John,
Since you've had both, what is your preference retarder or jake? I'm assuming you have an actual Jake brake and not an exhaust brake.
Chuck
Chuck,
It's a Jake, not and exhaust brake. Comparing the two, the retarder takes the prize. Just so easy to use. Also, it's no contest when it comes to an emergency stop. I still can't believe how that 320 would halt. That combination of discs, ABS and retarder is something else.
jor
You got the part number on that switch?
So you turn it on with the other switch, then go low or high?
John, I'll say this, the retarder on your ex 320 with the 4 series trans is much more powerful than in my coach with the 3 Allison. Thanks for the comparison, I was wondering about it, seems like an advantage to the Jake is no heat management, right?
Chuck
Dave, I could have predicted you would be asking for the part number.... :-)
Chuck, yes, no issue with heat using the Jake. The retarder heats up that fluid but in my experience I never approached the 4060's upper heat limit. Pretty much a non issue.
Dave, I'll get you the part number(s). It's actually a combo of two switches with the one you see slipped into the frame of one that would fit perfectly into the factory cutout. The visible one was $46 and the other, $13.
jor
It may just be my inexperience regarding driving these rigs, but I have
yet to feel the need for more braking power from the retarder on our 3 series tranny. In fact, putting back to the furthest position while on the highway would likely clear your countertops, if you neglected to do it before leaving :o
Don
That's why you don't use it when the roads are wet or slippery :o
On my 36 u320 the full retarder felt like the service brakes coming from my 270. Still they both work well.
I don't have experience with a Jake, but I can say I'm really thankful for the retarder in our U320. It is quiet, it works extremely well, it really saves the service brakes and I need to pay attention to the transmission temperature only on extremely long, extremely steep grades. I would definitely not want to be without it!
Dave,
Here are the three part numbers. Cummins had the first two in stock. The third one is the red switch; they got that one from Monaco.
jor
Awesome - Monaco switch ordered through Veurinks RV center in Michigan - Monaco Direct Parts Warehouse | VeurinksRV.com in Grand Rapids, Michigan (http://www.veurinksrv.com/monaco-factory-direct-parts)
Posted to them online - they called me in less than 10 minutes.