How to control speed with a manual trans

rotfl rotfl rotfl Thanks...... now I know how a simple exhaust brake functions....rotfl

 

There could be a way that we ALL are RIGHT. Now here me out here....

We have to remember what kind of load we are talking about!

A link that was posted talks about motorhome people being not used to a different feeling of a diesel vs. gas going down hill. Well.....motorhomes are heavy.

I am refering to the average trailer pulled behind the average diesel 3/4 pickup (like my case) which would be in the 6-9K range or so. Thats only a max rig weight of around 16K. I think Cummins rates the ISB in medium duty applications, say like a huge motorhome, up to 35-40K IIRC.

So.... getting to how we could all be correct... in theory my ISB should feel like it's a Sunday afternoon walk through the park with a measly 16K rig weight, so when I yank that succer down into 2nd gear and spin it up to 3,200rpms, its no wonder that it about throws me through the windshield. If I owned a huge rich person motorhome I might feel completely different and think the thing is running down the hill like a rock falling from the sky, since it weighs double of my semi loaded Dodge.

Take a typical gas powered (454 trucks is what I have) 454 3/4-1 ton, load it to what you can max out a 454, say 25K or so, and it would probably feel like it has more holding power than the same 35K loaded Cummins above. Take my 454 powered C3500 with my 16K weight, next to my DD Cummins loaded at the same total 16K, and the Cummins would probably feel like it holds back better ( 100% results in my many times using multiple pickups) simply because it is loaded down a much smaller percentage than the 454.

Ok, thats what I think then, and how we are all basically right.... opcorn: Technically, I'm wrong that a diesel could hold back more weight, but after further thought about it, i say only under similar load percentage placed on the same engines, gas or diesel.

 

i guess then you have no experience with the origonal posters question at hand...

where as i drive one EVERY day, with or without a load... my exhaust brake is on.

when i drove I-5 from san diego to Eugene oregon, i didnt have an exhaust brake. with my 10k trailer, going down the back side of grapevine i had a very hard time keeping the truck at a safe speed.

when i drove back on the return trip, 8 months later with now an 18k trailer and exhaust brake, i had NO problem keeping the truck at a safe speed. like i said, ANY time you want to drive one, if ya come out this way, you are more than welcome... till then, i guess you dont have any room to talk about a MANUAL DIESEL SETUP!

the auto plays a HUGE factor in helping the engine slow the truck down. its more the trans than the engine, and even more both of them working together...

 

if this theory were true then my 8k empty truck going down a hill would slow down a LOT faster when i down shift with the exhaust brake OFF... guess what, unless i try to go over red line, it wont...

 

Oh wait... did I mention we have an '02 HO 6spd..... oh and did I mention it has a Jacobs EB on it? Barely even need to use the exhaust brake going down hill with the manual, just stuff it in 5th gear and ride down the hill, occasionally hitting the exhaust brake for a couple of seconds.

Did I also mention I've got two Chevys with 454s?? One with an auto.... and you guessed it... one with an NV4500. I've got all the trucks with different drivetrains to compare with, I'm a farmer and drag around boats to snowmobiles, to 15K disks and plows. Did I also mention I farm in hilly terrain????

 

Just for fun.... I pull ~14k pounds about 500-800 miles a month. Without my exhaust brake my truck runs away. I can shift into 3rd if I want the rpm's will shoot through the roof and truck just gains speed. Put on the exhast brake and 4th gear holds me at 55 on any descent, even the grapevine which is a notorious hill around here.

Saying a diesel has more compression braking due to compression ratio is rediculous. Yes it is all in the throttle butterfly valve and since a diesel doesn't have one, guess what?

You may have no problems slowing your truck down when it's just your truck, but slap a load on the back and try it out, on a big hill.

And yeah I drive with mine on 100% of the time because it saves a ton of life on my service brakes. On a typical red light I only have to use the brakes from 13mph to 0.

 

I said I have no problems holding speed loaded, with say 7K or so.

If I had an exhaust brake, I would use it all the time to, to help save brakes also.


I give in. I don't think it's worth pushing the disscussion any further. It was a fun debate though!

 

Ohhhh, THAT's why it works for you; "hilly" as opposed to "mountains."waytogo I pull my 10k trailer on I80 over the Sierra's 5-6% grades.

You're right, good discussion. I think bottom line is: look at the terrain you drive. If your rig seems to hold on hills you're ok. But if it wants to run away, add an EB.