Transit Buses Equipped with Jake Brakes

[TransitGuru1981X]

I have a question about transit buses (not highway buses such as the MCI MC-9) equipped with Jacobs ("Jake") engine brakes: besides the GMC and Flxible New Looks and some GMC RTS II-01/03s and Grumman/Flxible 870s, which other buses had Jake Brakes on them (cf. Gillig Phantom, Orion I, Neoplan AN4xx)?

I reiterate: how many Orion I's (among other T-drive transit buses) throughout the U.S. and Canada, with 6V-92TA Detroit Diesel engines and Allison HT-740 series transmissions, had Jake Brakes?

~Ben

[WayneNYC]

While Jake brakes are common on big rigs and OTR coaches, I've never heard of a transit bus having them.   Not saying that it hasn't ever happended, but my thoughts was that retarders was the way to go for transit buses.

[WMAveteran]

With my very limited knowledge on this subject I think the major reason you don't see Jake brakes on US buses and coaches is because the majority of them have automatic transmissions.  Even most US OTR coaches seem to have automatic transmissions.  In Europe almost all of the OTR coaches (in my experience) have manual transmissions which allow drivers to downshift as a form of a Jake brake.

[TransitGuru1981X]

You can mate Jake Brakes to automatic transmissions, too. Some firetrucks with Allison automatics have Jakes.

~Ben

[WMAveteran]

Currently I am visiting New Orleans and yesterday I took a 3 hour Hurricane Katrina bus tour in an immaculate MCI 102A3 (45 footer) with automatic transmission that had a Jake brake.  The coach driver used it liberally throughout the tour.  This was a Grey Line Tour operated by the Hotard Company.

[79MetroExtraMD]

While Jake brakes are common on big rigs and OTR coaches, I've never heard of a transit bus having them.   Not saying that it hasn't ever happended, but my thoughts was that retarders was the way to go for transit buses.

I was thinking the same thing. Plus, with so much stop and go traffic on many different routes, Jakes wouldn't be really necessary.

[WayneNYC]

Currently I am visiting New Orleans and yesterday I took a 3 hour Hurricane Katrina bus tour in an immaculate MCI 102A3 (45 footer) with automatic transmission that had a Jake brake.  The coach driver used it liberally throughout the tour.  This was a Grey Line Tour operated by the Hotard Company.

Yes, I see plenty OTR coaches with Jake brakes and I have to assume it's likely that they're automatic as most buses are nowadays.  Also, I forgot to mention earlier that the huge fleet of NJTransit MCI D4000 and D4500 have Jake Brakes and all of them have auto trannys.

[Tristan]

I don't think any of the three tranny manufacturers even makes a manual for a motorcoach, unless you ask specifically...and even then ... ?

There is one transmission, the ZF AStronic, that is referred to as "automated" -- it's like a manual with an autonomous clutch.  It's actually relatively popular because it apparently weighs something like 1000lbs less than a standard tranny, I've heard.  It sounds like a manual because it pauses between shifts, but don't be fooled -- there's still a computer at work!

[79MetroExtraMD]

I don't think any of the three tranny manufacturers even makes a manual for a motorcoach, unless you ask specifically...and even then ... ?

There is one transmission, the ZF AStronic, that is referred to as "automated" -- it's like a manual with an autonomous clutch.  It's actually relatively popular because it apparently weighs something like 1000lbs less than a standard tranny, I've heard.  It sounds like a manual because it pauses between shifts, but don't be fooled -- there's still a computer at work!

The ZF AStronic. I remember being on a D4505 with it. Shifting 2 gears in one shift or something like that. The one thing I still can't get is why it revs up when it's downshifting.

[Tristan]

I'm a bit confused on transmission terminology -- I once was told that "downshift" means to go from 1 to 2 to 3 instead of the other way around as you'd expect, because of the gear ratios involved.  If you're talking about the jump in RPMs when that happens, it's the same as what happens with any manual vehicle when you depress the clutch -- since the engine is no longer engaged in turning the wheels, there's a momentary surge in RPMs until it re-engages when the clutch is released.  With the AStronic, that's happening automatically but it's still happening.

If you're talking about the other way around (3-2-1), then that's no different from any other vehicle with an automatic transmission.  Do you hear it here? http://transit.tecsbrain.org/recs/index.php?l=12&p=Eastern1115-071506.mp3

[WayneNYC]

Once time I posted on a message about hearing what I thought was a MCI J4500 with a manual tranny.  Someone replied and stated that it was very likely that I observed a bus with a ASTronic transmission.  Then I finally rode a bus with the Astronic (BoltBus X3-45).  I was amazed at how much this bus shifted like manual but was automatic.  I think it's what's referred to in the auto industry as a seqential manual or double-clutch manual.  They're basically automated manual transmissions.

Tristan - Downshifting (auto and manual) is just what the words imply.  When a vehicle starts moving, it is in it's lower gears and upshift to the higher gears as the speed increases.  Does just the opposite when the vehicle slows.  Now, there are some other shifting patterns depending on what is happening.  For instance and vehicle on an upgrade will downshift (for more power) when as it loses speed.  As you start to drive more you'll see exactly what I'm talking about.  If you're moving (in a higher gear) and you press hard on the accelerator, the vehicle will likely downshift (one gear and you'll feel it and hear the higher revving of the lower gear) and eventually upsift again.  Sometimes when a person moving at speed needs to slow down quickly, they'll downshift (even in an automatic) to a lower gear.