thinking about Jakes

[Iceni John]

I recently rebuilt my Jakes using the Pacbrake tune-up kit  -  new oil connector tubes (one of the old ones was completely snapped in two!), new O-rings for the solenoids, new spool valves, then I adjusted them to the recommended 0.064" clearance.   Wow, what a difference!   They don't have Throw-You-Through-The Windshield deceleration, but they will hold speed down 6% grades in 3rd gear with no problem.   In 2nd gear the Half setting is usually enough, but I normally only use them on Full.   Jakes won't do much if the transmission is not in lock-up.   Curiously, even though there's little difference in cubic inches between a 6V92 and a 8V71, the eight-cylinder engine has more advertised Jake braking power,  because my bus is less than 30,000 lbs and has lower gearing than most, its Jakes work well.

John

[luvrbus]

Low gearing is the key to Jakes on a 2 stroke IMO

[Geom]

Thanks guys for those great answers and explanations!
I understand jakes much better now, and their importance in a diesel; and in a 2-stroke in particular.

So any slow-down I'd been getting thus far, has been predominately the work of the trans. And the engine had little to nothing to do with it. Good to know

I suppose jakes are now on "the list".
Aye, the list grows long, LOL.
But I suppose that's one of those fun things you get when you own a bus -an ever increasing list of must'ves, should'ves, and wouldlike'ves 

[luvrbus]

Keep in mine that Jakes on a automatic transmission only work when the transmission is in lockup example the 700 series Allison do not lock up in 1st the 600 series do not lock up in 1 or 2nd gear unless a torque converter lockup has been installed.David's bus has a Voith and I do not know anything about how it works when it comes to lockup    

[muldoonman]

All I know about 2 stage jakes in my 1991 8V92TA with 755CR trans is they work and good. Don't really need the brakes if you watch a head when stopping. Don't have any steep hills around where i live but use them all the time in every day driving.

[bevans6]

I'm kind of with Muldoonman.  I actually leave the Jakes off for the majority of my highway driving because I try to maximize coasting with throttle off to the greatest extent possible.  I flip them on only when a hill requires braking to the extent that I am willing to give up the coast.  Where I use them a lot and really appreciate them is in country road driving, to set up my speed going down a little short hill with a corner at the bottom, and in stop and go traffic to keep from getting on and off the throttle/brake dance.

[luvrbus]

If you have a 60 series then know how good Jakes can be   I change the one on my series 60 to a 3 stage the 1st and 2nd stage were just to much, you won't have that problem on a 2 stroke DD 

[lostagain]

The Jakes feel about the same in my 6V92 as they do in a loaded semi (80000lbs) with DD15. With the HT740, I don't remember using them in 1st gear. In 2nd gear, they are very powerful and will hold us back on any hill. 3rd gear is good for 8% grades, and 4th for 6%. Nice for off ramps. Once down in 2nd at the right speed, I turn them off before the yield sign. As nice as they are, we never had them on buses until the 1980s. We were trained to downshift to a gear low enough to hold us back going down the hill. Yes it was slow...

As has been mentioned, a simple way to wire them is with a momentary switch on the floor for your left foot. Pacbrake sells a nice one. So the power goes through a on/off switch on the dash, then to the floor, then directly to the Jakes. So when you need the Jakes, you rest your foot on the switch. I have driven buses set up this way and it works quite well. My Pete dump truck is also that way.

JC

[David Anderson]

Clifford's correct. I have a Voith.  It is in lockup in 2-4th.  It has a retarder, but I'm beginning to have ECU problems with the retarder brakes only.  If I don't use the retarder, I have 3 ECU's that can get me home.  However, we have done a lot of mountain driving and I used the retarder extensively.  Not sure how to do it without it.  The Voith service guy has been very helpful with me troubleshooting my issues.  He is the last guy left that was there when my bus was running with Houston Metro.  When he is gone there is no one left.  (Kind of like Norris retiring )

If ECU repairs are available it will probably be in the $2k plus range.  Jakes would be a less expensive choice and I believe less wear and tear on the tranny.

Clifford, I don't know if I have tall covers.  I can measure.  What measurement am I looking for?

David

[RJ]

Clifford, I don't know if I have tall covers.  I can measure.  What measurement am I looking for?

David -

Pretty simple, actually.  Do you have stamped steel valve covers about 2.5" high, or cast aluminum covers about 4" high?

HTH. . .

[Geoff]

I just gave away a set of 92 Jakes for $500 that had EVERYTHING FOR AN 8V92 TA.  If you wanted them or a 6V92TA you just needed the correct valve covers.

Fast idle was included with hi and low switch at the dash.

Sorry David.

--Geoff

[TomC]

Jakes work very well on my 8V-71 (Don Fairchild adjusted them). My V730 will lockup in 1st gear if you pull the gearshift lever down to first and keep your foot at least an inch up from flooring the gas pedal. Very nice for slow driving in the mountains. Good Luck, TomC

[David Anderson]

Here is a pic of my cover.  I had to turn myself into a pretzel to get this pic

[luvrbus]

You will need valve covers those are the low model

[David Anderson]

You will need valve covers those are the low model

What do you think those might run?  $$$