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Engine Brake/Exhaust Brake Upgrade 1993 8.3L 6spd
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Supporting Member of 10/10
Picture of roman
Was an exhaust brake or engine brake a factory option on these motor homes? The one I'm looking at has only air brakes and every other motor home I have driven or looked at has had some other braking device be it exhaust or engine to lessen the wear on the brakes. I'm thinking an exhaust brake might be the way to go but being new at this motor home thing I'd like to get your views on the subject. Thanks in advance.


1993, 34', Regency, Widebody
300 HP Cummins
6 spd Allison, Spartan Chassis
Posts: 74 | Location: Alaska | Member Since: 03-08-2009Reply With QuoteReport This Post
Supporting Member of 10/08
Picture of MWrench
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In order to be effective, the transmission torque converter should be a lock up type otherwise the exhaust brake will not work well.

94 30' Breakaway #3864
30-BS-6B side entry
230 Cummins, Allison 6 speed
Spartan chassis
Posts: 2228 | Location: Los Gatos, CA | Member Since: 12-08-2005Reply With QuoteReport This Post
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In the mid-80's for only a couple of years Bluebird used genuine Jake brakes, then returned to transmission retarders because they were quieter and less expensive. They are prized (the Jake Brake years) today because they work better (even through the 4 and 5 speed Allison automatics of the period).
The transmission retarders can overheat on steep grades and Jake brakes don't. I don't think a lock up torque converter is required.
Posts: 70 | Location: Texas | Member Since: 11-26-2008Reply With QuoteReport This Post
"First Year of Inception" Membership Club
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A Cummins 8.3 does not have an engine brake. An engine brake works off the engine valves and requires a different head, which cummins never put on their 8.3. The ISL however did have it available, but was a later engine.

The larger, L10 cummins, and cat 3176 both had available engine brakes.

I think it requires a lockup converter or too much slippage occurs and the 'brake' doesn't work, whether an engine brake or exhaust brake. The engine brake has roughly twice the brake hp of an exhaust brake.
Posts: 87 | Location: Washington DC | Member Since: 03-11-2001Reply With QuoteReport This Post
Picture of dcarguy
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I have an exhaust brake switch on the dash and if it works I don't notice any effect on braking and i have driven trucks with this feature before with better results.Drove a truck once with the transmission retarder.They come with a temp gauge because if you over use them they get way scarry hot.
Will be taking the knowledge found here and get under the rig.Will post my findings.
Posts: 7 | Location: Oakhurst,ca | Member Since: 07-14-2014Reply With QuoteReport This Post
Supporting Member of 9/09
Picture of Lance Walton
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My 93 Regency has a PacBrake which is an after market addition. When the previous owner had it installed the valve springs had to be replaced per Cummins specifications. My Allison WTEC II ECU controller has an option for the PacBrake and the wiring was added to do so.

The ECU normally requires re-programming for it to work correctly. I went to Jacksonville to an Allison service center to have this done. After they contacted Allison with the model and serial number it was determined that my ECU was a very early model and that function did not require re-programming.

I did have to change the pinout at the output of the relay module since, in my ECU, it required a normally closed vs a normally open contact.

The only thing I don't like with the way mine works is that it works in first gear which is not normal. When engaged it definitely has an effect in deceleration. It only kicks in when the throttle position is in idle.

There is one item I have not been able to get done. That is to have the PacBrake exhaust valve properly set. The model that is intended for the 8.3 is a "generic" model and does not have a pre-set position. Allison's procedure calls for taking exhaust pressure readings while decelerating down a substantial grade. I live in Florida so good luck with that. What I did do was set it fully closed and backed it off a few turns.

Anyway, this is what I have in my Regency.

Lance & Sue Walton
Previous owner of a
1993 38ft Regency
Cummins 6CTA8.3 300HP
Allison MD3060 Transmission
Spartan Chassis
Loveland, CO
Posts: 253 | Location: Loveland, CO | Member Since: 06-21-2009Reply With QuoteReport This Post
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    Forums    Tech Talk    Engine Brake/Exhaust Brake Upgrade 1993 8.3L 6spd

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