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Discussion Starter · #1 ·
I always drive with my Exhaust Break on, and as most I like the added stopping power.

I drive maybe 7-8 miles a day one way with most of the drive being a 6 mile stretch of Freeway.

When approaching the off-ramp I tap my shifter 3 clicks to the left which drops it 4th gear and the Turbo spools and the combination of the Exhaust and Transmission Break kicks in real hard and slows down the truck really fast, than I tap the shifter one more time to the left and 3rd gear kicks in and the hard stopping kicks in again.



Now the million dollar question, or at least around $4,500, is this hard on the Transmission?


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Well I believe the exhaust brake has something like 250 brake horse power and your truck has 350 that's one thing to consider.

If I were you though I wouldnt be using my exhaust brake if you have only driven 6 miles your truck is most likely not up to operating temp, and the exhaust brake creates alot of back pressure rather quickly.
 

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Discussion Starter · #3 · (Edited)
I drive around 75 mph on the Freeway and with the Max Tow (i.e. 410s) the truck warms up quick and it just gets its 1st or 2nd coolant cycle close to the end of my Freeway run.

The truck is up to operating temperature and I have ARP Studs. Also I've read somewhere on this Forum where someone stated the back pressure from the Exhaust Brake is not the same as Drive Pressure when your Turbo spools over 35 psi and your timing is way advanced. I don't know the difference myself but maybe someone can chime in.

At the end of the off-ramp there is always a stop-light and I usually hit it every time. So I'm approaching the stop-light at around 60 mph and the light goes yellow, my hand is already on the shifter so I click it left 3 times to downshift 4th. The RPMs jump up, the Turbo spools up quick, the Exhaust Break gets really loud, (almost sounds like a big-rig) and the truck slows down fast. Once I'm down to around 2,000 rpm, I'll tap the shifter again to the left to 3rd, and again hard Exhaust/Trans Breaking kicks in. I slow to a 5-10 mph roll where I just have to tap the service breaks to stop completely.

It's kind of fun and I like the sound, but not that much if it's damaging my truck. Service brakes are a lot less expensive to replace.

I do the same thing with my BMW, (front-to-back instead of side-to-side on the shifter) but it's a lease...


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No -- to answer your question. This is what it's built to do. The transmission locks up in the gears, the vanes close in the vgturbo and then you get braking. If it gives you joy (not mocking you), do it. I do the same. You can get great breaking power by keeping the RPM's over 1500. As soon as a gear gets down to 1500, bounce down to the next lower. You can do this and get it to lockup all the way through 2nd. Enjoy.
 

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And for your other question no you don't have to worry about drive pressure while decelerating, the cylinder pressures are very low and will not be a problem. Drive pressure with high cylinder pressure is a recipe to replace a head gasket though.
 

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Yup. People even use the exhaust brake to help speed warm up. Thats why the exhaust brake comes on at idle when its cold out and the thermostat is below 170 degrees. So it's safe to use when its cold. The first time it did that I freaked. Then I learned it was by design.

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The sales guy I bought my truck from showed / mentioned that you should turn it on at startup as it brings it up to temp quicker... Whether or not there's truth to that? Dunno.. :) I don't have the manual yet to read.
 

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Try it. you'll see in cold weather at a stoplight when idleing the exhaust brake kicks on. This creates back pressure which creates heat and this helps the engine warm up. One the engine gets to 170 degrees the EB stops coming on at idle.
 

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As far as the cold thing goes I was meaning using it heavily when then engine is cold. Like engaging it at high rpms the drive pressure can easily hit 80psi+
 

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The exhaust brake will come on at idle till the trucks gets to 168F. It's by design and it'll help with the warm up process..... Exhaust brake in tow haul mode with a nice load behind the truck equals full on Semi effect during decel.... :)
 

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As far as the cold thing goes I was meaning using it heavily when then engine is cold. Like engaging it at high rpms the drive pressure can easily hit 80psi+
I never knew this. It never occurred to me to worry about it -- I just used it.

I defer to you on this one.
 

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Discussion Starter · #13 · (Edited)
I found this video on YouTube and he hits the EB fairly hard and DP jumps to 56 psi and that is a lot higher than I previously thought. There is one comment at the end that states cylinder pressure from timing and boost isn't the same as DP from the EB and should be safe for the Head Gasket?

So this got me thinking and I'm the last one to claim I know anything about this stuff. Do you think the DP created by the VGT has as much impact on the actual cylinder pressure as a large mix of fuel, 35+ psi boost, at 20 degrees BTDC?

In my mind I can see a large mix of fuel an air pressure igniting in a tiny little space with nowhere to go except up by the force of the piston into an even tinier little space and all the cylinder pressure that it would create from an exponentially expanding explosion. Next I can see the Head Bolts stretching and the Head lifting, and the excessive pressure blowing by and damaging the very fragile HG at that point with no support from the structure around it, (i.e. Engine Block and Head).

Now cylinder pressure just from creating back-pressure at the Turbo, I just can't see them being even close to the same thing? DP is one thing, but cylinder pressure with a combustible mix of excessive fuel and pressure at TDC with enough force to stretch Head Bolts, lift the Head, and blow an HG is something else.


I couldn't get the YouTube video to work but if you want to see it search on; "6.7 Cummins Exhaust Brake Back Pressure", you should find it.

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You just said a lot of words that hurt my head. LOL!
 
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