Autos vs Manual transmissions

The autos that have been "tweaked" are kinda fun.

 

How much braking power do you need? Here is cummins graph of braking hp vs rpm. I suspect all new engines are similar. Do you really need to use 600+? I do just fine with often maximum gross weights even running all the grades on 80 or 90 and the coq in bc and the back woods of pa and I get along just fine in the 1500 range when using the jake brake. It works very well, even if it gets slightly steeper and you pick up to 16 or 1700 you can hear it whistle louder and can feel the increased resistance. And it brings you back to about 14-15. I have a hard time believing any engine maker today designed it to be repeatedly used at such high rpm when the trend has been reducing the rpm while cruising...same theory should apply when using compression brake, effective at lower rpm range. You company seat warmers do whatever though. Seems very unnecessary to me.

 

The Detroit engine brake works in different way, depending on whether you are in auto or manual mode, and even if you're in cruise control or not.
The engine brake is in its most "agressive" mode when the cruise control is engaged. Mine automatically engages all three banks when applied, regardless of whether I put the stick in 1, 2 or 3. It's in its least aggressive mode when you are in manual operation. It operates more like a standard engine brake.
And yes, the aggressive mode is in fact designed to run up to about 2,200 RPM, even for extended times. I've used it on the 10 mile downgrade on I-90 eastbound from the Ryegrass rest area towards Vantage in Washington state. I disengage my cruise control, however, so that I can change how much braking force I'm using, depending on grade percentage.

 

That's exactly what I said. I can't get the RPM's up high enough to drop it into a lower gear to get compression braking that I can get with the auto.

But when you say it its fine. When I say it "I must not be a veteran trucker." To the person that said that. no. it doesn't sound strange at all. Have you ever driven a truck with an auto? I doubt it. I know how jakes work. YOU HAVE TO REV THE ENGINE TO GET IT INTO A HIGHER GEAR TO GET THE HIGHER BRAKING. With STANDARD TRANNIES YOU CAN'T GO PAST 1700RPM. I can only downshift so far with a manual. The DD 12 speed in high braking can drop the thing down into 8th gear at 60mph just about sending you through the windshield. Try that with a standard, won't happen.

No, I'm an intelligent person who knows what the #### he's talking about. The auto tranny can get the tranny into a lower gear and rev the engine higher for more braking. To the floor I'm limited to 1700 rpm.

 

That’s crazy they make trucks now that limit rpm to 1800

 

Relax. I was just doin some trash talking. Youre ok

 

Can you inform us what truck and what brand of auto transmission this is?

So much vagueness in this thread. Saying autos are bad is almost like saying I don't like laptops because one froze up on me.

 

I never run my engine brake at 2200 rpm , I believe cummins suggests 2100 max rpm on engine brake , I limit to 2000 rpm then use service brake , after you run certain hills a few times , you know what gear to be in that will hold with only the engine brake at suggested rpm .
When it's your parts your attempting to scatter across the road you have more respect for the machine

 

??? I can rev up the engine on every truck I have driven and it far exceeds 1800 rpm.
The manufacturer of the engine sets up the red line limit to match the engine. The transmission has nothing to do with it.