High & Low For Jakes or High Only?

[mikelutestanski]

Hello:
   The buffer switch idea is good one however I have discussed this with several detroit mechanics and the final disposition on the switch (for my experience)  is as follows: 
          The  micro switch is difficult to get right and stay adjusted for this application .  One mechanic was an allison dealer.
   Now is this true   dont know   is the right mechanic available and can he/she set this up in 30 minutes and have it work perfectly.   dont know.   
     Is this a bunch of BS  dont know.  However the mechanic that Installed the jakes on the motor gave me the micro and said have a ball..
    Another reason which I believe is correct is the same spot for the micro is occupied by the fast idle solenoid and that would require a different spot and type of soleniod for the fast idle soleniod. The parts may or may not be available anymore.   
   Is my memory correct   dont know   this discussion happened ten years ago..
     In any case I elected to install a foot switch and the electrical switches necessary to replace the other switch to do the job. THe pressure switch insures that a casual press on the foot switch wont activate the jakes because the throttle pressure switch would prevent that from occurring. THe reasoning is that I could activate the jake brake enable switch (I used the old reverse switch) and I would not have to reach over and turn the switch when I wanted the jakes on.
   In my case it was easier to install and calibrate  pressure switches then mess around in that governor box on my newly rebuilt engine.
     
     THe days of the savy detroit two stroke mechanic are drawing to a close.  most of the younger mechanics cut their teeth on 60 series type engines. The shop forman or senior mechanic may have plenty experience of he has not retired.
     FWIW.    This has been my experience as much as I can recall...
      REgards and happy bussin   mike

[Diesel_Gypsy]

       THe days of the savy detroit two stroke mechanic are drawing to a close.  most of the younger mechanics cut their teeth on 60 series type engines. The shop forman or senior mechanic may have plenty experience of he has not retired.
     FWIW.    This has been my experience as much as I can recall...
      REgards and happy bussin   mike

Mike

You are right about these young mechanics. They mostly just replace the parts that their computer diagnostic program tells them to replace. When you show up with something more than 20 years old, and no diagnostic port, they just scratch their heads.   There are still some older "mechanical" guys around though, but you have to look for them. Even when these 2-stroke's were new, there weren't many guys who could set them properly. They could get them to sound all right but they wouldn't,t pull or get decent fuel mileage. I used to have a few of them in various trucks and have been very unhappy, at times, with the service on them. I finally found a mechanic who knew what he was doing and got him to show me some tricks to setting them up. It was mostly just paying really close attention to adjustments with a few little things thrown in. Injectors, and especially modified injectors, are extremely important to power and economy in these 2-stroke's.

On your Jake switch, if you have a high idle unit replacing the buffer screw, it should still have a place for a Jake switch on it (although I think that is a different switch if I remember right). However, if you are happy with it the way it is, then that is all that matters.

Later. . .
Jim

[mikelutestanski]

Hello:    Yes I am very happy.     I dont remember about the buffer switch  sorry;   senior moment;  after all I will be 65 in may  so  I have a new excuse..   in retrospect however:
     My 72 MCI 7  came with a 4 speed spicer .  When my wife leaned over and said grind me a pound I decided a 740 auto was in order.
  So out came the engine and tranny.  I cleaned up the engine compartment including 40 hours of repairing the subframes and generally made everything whole that was holy.
    The 8v71 was modified from the stock 275 hp to a 318 with advanced timing set up with 65 injectors and jakes. Complete out of frame rebuild with a 740 bolted to it completely rebuilt also.  I put 45K miles on the bus with this powerplant. We moved to florida with this and a 24 foot carhauler. The engine has never let me down.
  But  I got bit with a bug to change things again so after much soul searching I decided to repower with another later engine and transmission.
  The new plant is an 89 Cummins L10 mechanical with an Allison B400R computer tranny. I bought a couple of transit buses and moved the powerplant to my bus.  There should be a couple of threads with pictures floating around in the archives.
     After much work the new plant is running and runs fine.  I changed the rear ratio to 4.625 to help out the OD gears and keep the rs down at cruise speed.  The engine is at 275 hp once more but If I need it I will bring it up to 300. SO far I dont seem to need the extra hp.  most of my driving is flatland.  It will climb in 4th or third if needed and the retarder works well  so life is good.
     The 8v71 has a new life and is presently being christined in another bus and ready to roll again.
  SO life is good and after painting the bus we will get it moving...
     Alaska in 2010...     and points west..
      Regards and happy bussin.   mike 

[JackConrad]

Hello:    Yes I am very happy.
       The 8v71 was modified from the stock 275 hp to a 318 with advanced timing set up with 65 injectors and jakes. Complete out of frame rebuild with a 740 bolted to it completely rebuilt also.  I put 45K miles on the bus with this powerplant. We moved to florida with this and a 24 foot carhauler. The engine has never let me down.
      The 8v71 has a new life and is presently being christined in another bus and ready to roll again.
        Regards and happy bussin.   mike 

For those that do not know, this is the new (to us) engine that is now in Orange Blossom Special II.  We have had our granddaughter the last few days, during her Spring Break, so I haven't quite got the bus ready for it's first test drive yet. I hope to finish the Jake Brake wiring tomorrow and re-calibrate our Tachometer, then take it for a test drive. Results will be posted

[JackConrad]

    After installing the pressure switches on the air throttle and the transmission lock up test port, I installed an LED indicator in the dash that is connected to Jake Brake wire at the cylinder head. I did not have Jakes installed yet on our old engine but I had installed all the wiring (which is now being modified slighlty, changing from High only to High/Low). I took the bus for a drive and turned on the Jake Brake switch (wired for High only) to the left of the Driver's seat. Jake would only activate when throttle is a idle position (no air pressure on air throttle) and transmission is in lock up mode. When transmission shifts out of lock up (at about 12-15 MPH), Jakes shut down. A slight throttle application (3 PSI) also shuts down the Jakes. It takes 5 PSI on air throttle actuator to increase engine RPM from idle position.  Jack

[buswarrior]

Excellent report!

Sounds good to me!

Oh to have the time to have fun....

slave to the man for another 7....

happy coaching!
buswarrior

[Tom Y]

Jack, Why not use a single switch with a off and two on positions? A double pole, double throw will work.  Tom Y

[bobofthenorth]

That's the way mine is setup & I have a toggle extension on it so I can reach down without looking at it and flip it off or on.

[Barn Owl]

I have added a "momentary on" foot switch to my system that works better than I would have thought. I can still use the panel switch if I want to but sometimes I only need a little bump and the foot switch saves me from having to slightly feather the throttle the whole time the panel switch is on. To much unintentional Jake activation causes lower fuel mileage.

About locking the Allsion Transmission; Several weeks ago I called Allsion to talk about oils and while I had the Tech on the phone I asked about the forced first gear lockup. The short story is: don't do it.

[belfert]

I have a Series 60 with B500 tranny and I do have a Jake Brake.  I have low, medium, and high for settings.  I have rarely ever used anything but high when I do use the Jake.  Low and medium don't seem to do much.  I actually think I should be getting more from the Jake, but I have not driven anything else to know for sure.  The Jake was adjusted when I had my Series 60 tuned up a while back.

If your engine and tranny are computer controlled like mine you might run into an issue when you use cruise.  With the Jake and cruise both turned on, the tranny will start downshifting and upshifting every few seconds if the bus gets more than maybe 1 MPH above the set speed.  I don't think the Jake is coming on, but it will come if the speed gets more than about 5 MPH above the set speed.  I just turn off the Jake when using cruise.  If the terrain is hilly enough to need the Jake I probably wouldn't use the cruise anyhow.

[buswarrior]

belfert, those thresholds are all programable. You can add a few mph to the gap between jake intervention and cruise set speed. You can program the jakes to intervene whether the jake switch is on or off, lots of combinations available, whether the transmission downshifts with the jakes or stays with the regular program, such that you can really screw your driver around.....

On a long downgrade, having the flexibility of multi stages of jakes, and the flexibility of gear choices, especially with a B500, the driver may shuffle the deck and find a combo or "hold the speed" that works under quite a range of road speed and degree of slope, without having to fool around turning things on and off with more limited options of too strong or too weak.

We don't always have the freedom to cruise down the hill at our preferred speed due to other traffic.

happy coaching!
buswarrior

[belfert]

belfert, those thresholds are all programable. You can add a few mph to the gap between jake intervention and cruise set speed. You can program the jakes to intervene whether the jake switch is on or off, lots of combinations available, whether the transmission downshifts with the jakes or stays with the regular program, such that you can really screw your driver around.....

Interesting.  I have a DDEC III.  The local Detroit dealer says that is just the way it works.  They never mentioned changing any parameters.  I'm not sure I will change it now as myself and the other drivers just know to turn off the Jake when using cruise.  The Jake isn't really ever needed until we hit Western Nebraska or Wyoming anyhow. 

There probably aren't too many here that have electronic engines and trannies where this might affect them.

[JackConrad]

Jack, Why not use a single switch with a off and two on positions? A double pole, double throw will work.  Tom Y

By having 2 separate switches at the Driver's panel, I can select which cylinder bank I want to use for the low setting. This may come in handy in the future for diagnostic purposes, should the need arise (and I had the space for 2 switches).  Jack

[Jerry32]

I had an oldtime detroit trained mechanic install my jake brake and he installed the buffer switch in the governor. He also found three bad rockers while doing the install and changed them. I am going to install the wiring to have high and low jakes which means three wire system. The book says that high idle was on front 46 but did not come out on rear 22 or I would have had the DPDT switch hooked up now.
anyway there are still some old and properly trained mechanics around to work on these detroits. Jerry

[Diesel_Gypsy]

Jerry

I'm glad to hear you found a good mechanic. They are too few and too far between these days.

I'm also glad to hear that you got your Jake set up properly. I'm sure you'll be happy with it, especially with your 8V92TA 

Enjoy. . .
Jim