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Author Topic: Jakes on 6V92 w/ auto  (Read 1711 times)
gumpy
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« on: November 28, 2006, 03:31:18 PM »

How many have Jakes installed on a 6V92 with an automatic tranny, and are you happy with it?

I'm considering installing a set on mine, and my mechanic (whose opinion I trust very highly) keeps telling me I may be disappointed for the price. He says performance of Jakes on a 6V92 is not the best, and installation is going to run about $1500 just for labor.

I've become comfortable driving mountains in the bus without jakes, but there are times when I'd really like to be keeping the brakes cool on the down side.

Am I expecting more than Jakes can provide on this engine / tranny combination?

craig
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Craig Shepard
Located in Minnesquito

http://bus.gumpydog.com - "Some Assembly Required"
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« Reply #1 on: November 28, 2006, 04:46:30 PM »

Craig,

I have a Suburban Fishbowl with a 6v92 v730 with jake brakes. I love them. I don't use my service brakes very much. I can tell a large difference between jakes and no jakes.

HTH,
Dale
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skihor
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« Reply #2 on: November 28, 2006, 05:34:29 PM »

'67 Mc5A with 6V92 allison 5 speed auto. I LOVE jakes. Just smoke one set of brakes drums etc... and see what that costs.

Don & Sheila
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larryh
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« Reply #3 on: November 28, 2006, 05:43:03 PM »

I have installed over 500 sets of jacobs brakes on all kinds of rigs and never had anybody come back and say they wasn't happy with them if you are below lock up MPH or RPM they will not function much on this combination but above the lockup speed you will def feel a big difference. For instance coming down cabbage patch hill in OR 15-20 in lower gear and a lot of applications of service brakes a pucker raising trip to be sure. Coming down wit jakes approx two application of service brakes and this only on the 30mph turns rest of trip down approx 40-45 mph 7 miles of no problems.

But as they say do it your way if out West please use the jakes so i don't have to go out and recover your mess off the hillside.


LarryH
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« Reply #4 on: November 28, 2006, 06:16:16 PM »

Craig, I have a couple of extra cylinders, though smaller ones, and a V730 w/ Jakes... makes a huge difference coming down grades, esp. straight ones. I usually stay in second lockup and just hit the Jake switch to slow down when need be. I try to keep it between 1800-2000rpm for max effectiveness. And the service brakes rarely get touched.

Short of a Telma, they'll be the best investment you make for safer mountain driving. And I know you come out West a lot.

HTH,
Brian B.
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Brian Brown
4108-216 w/ V730
Longmont, CO
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« Reply #5 on: November 28, 2006, 06:39:35 PM »

This may not be exactly "Jake" brakes related, but my HT748 has a trans retarders that works quite well...although, I've heard that they'll heat up the trans  pretty quickly.  Don't know....I do know that the thing works well.   It works with brake application sorta like a Jake.   NJT was so proud of the brake saving capacity of these retarders that a light was located on the outside of the coach so that the super would know when the thing was turned off.  I suppose turning off the retarder may get the driver a negative attaboy.
Don't know if a trans retarder can be retrofitted, but NJT takeouts are all over the place...whole HT740Rs for less than you're describing, if you use new Jake parts.
There may be sundrous reasons for not doing this...or even using a trans retarder??  They were expensive add-ons.  
I've had my bus on both I 40 and I 26 coming out of Asheville, and the speed is quite easy to control.  Agreed, this ain't the western mountains..but they are 5 plus mile major downhill grades.   A bus doesn't seem to gain speed like a truck.
Didn't realize that Jakes were that expensive to install...I would guess that the wiring is probably already in the rear junction box in the form of unused leads...?  
JR




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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

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« Reply #6 on: November 28, 2006, 10:24:52 PM »

Maybe you need another mechanic if he is charging you $1500 just for the labor.  That should be the whole job.  If it takes much more than a day to install, he doesn't know what he is doing.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
gumpy
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« Reply #7 on: November 29, 2006, 05:10:26 AM »

Well, they definitely know what they're doing. They are one  of the best bus shops in the country.

However, their labor rates are up around $85-$90 now, so even at 8-10 hours, that's nearly a grand.

I'll be talking to them in more detail if I decide to do this, but right now, it looks like it won't happen
now as the guy I was going to buy them from sold them to somebody else.

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Craig Shepard
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« Reply #8 on: November 29, 2006, 05:15:57 AM »

I have a 85 Eagle with a 6V92TA and a HT740 transmission and would not be without the Jake's after heating the brakes on I-26.  It is real confronting when the Jake's kicks in and you very seldom have to use the service brakes.  The $1500.00 for installation is an outrageous price for labor.  Should take about four to six hours for installation and adjustments.
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RJ
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« Reply #9 on: November 29, 2006, 08:05:14 AM »

Craig -

Picture this:  I-80, WB from Reno, NV to Sacratomato, CA.  On that run, once you crest Donner Summit, you've got about 70 miles of 4, 5, and 6 percent downgrades.  Not exactly service-brake friendly, eh?

Back in my charter days, I used to regularly come off that grade with the jake brake on and never touch the service brakes the whole way, except if an idiotic four-wheeler did something stupid.  Quite often it was 44 passengers and three full baggage bins, too.  Didn't make any difference if it was a coach with the 8V71 or the 6V92, overall results were the same.  Transmissions were either the HT-740 or HT-754, depending on the MCI. 

Some of the older GMCs in the fleet at the time with manual gearboxes did not have Jakes on them.  If one of those was used on these Reno runs, it was climb the Donner Grade out of Truckee in 2nd, catch 3rd just after cresting the hill and keep it in third, occasionally tapping the service brakes, until you got to Auburn, where the grades begin to level out.  This meant 40 - 45 mph in the slow lane, with the rest of the traffic whizzing by you at 70 mph.  Also added about 20 minutes to the travel time.  The newer GMCs in the fleet, still with manual gearboxes but equipped with Jakes, could come off the hill in 4th, just like the MCIs.

There is a slight difference in the braking capability between the 6 and the 8, but unless you drive them back-to-back, you really don't notice - which would be your case. (Side note:  8V71 =  568 cu. in.  6V92 = 552 cu. in.  Not a huge difference in the overall scheme of things.)

Are you talking about JD at C&J?  Good shop, well-known and recommended.  For comparison, you might call Luke (1-888-262-2434) and ask for a ball-park labor rate at his shop to install Jakes on your MCI.  Be interesting to see how they compare. . .

Keep an eye on eBay, a set usually shows up about once a month/six weeks or so.

FWIW & HTH. . .

 Wink

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RJ Long
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Fresno CA
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« Reply #10 on: November 30, 2006, 09:08:41 AM »

Hi Craig ...I don't have a 6V92 but it's big brother with Jakes and living the the BC mountains, well you know what they're like, I would never "leave home with out them". The only time I have to use the brakes, is when I come to a stop. When I jump into my diesel pu and de'sel ...I keep waiting for the Jakes to come on ...then realize that I have to step on the brakes to slow down...LOL. You'll save that much money on brakes and drums
Ron
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Gary W
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« Reply #11 on: November 30, 2006, 09:33:43 AM »

Hi Craig
  I had jakes installed on my 6V-92 , like Ron says don't leave home without them here in BC. I bought a used set of jakes for $800 and paid $800 to have them installed at reputable shop.

Gary
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