Jacobs Exhaust brake operation with an Automatic
 

I just purchased this truck recently and am in the process of getting familiarized with it
1996 2500 ex cab 2wd Cummins automatic
The truck has what appears to be a factory installed Jacobs/Cummins exhaust brake. The truck was purchased new by cummins corp.
Up on the dash there is a button (same appearance as the driving lamps and O/D switch)...this button says EB
It lights up when I depress it.
I tried to activate the ebrake and it never really slows the truck down or makes that loud exhaust sound when activated. Sometimes when I have the truck in OD "off", and activate the EB,it makes a slightly louder exhaust noise,but still don't actually slow the rig down.
I don't see any toggle switch to lock-up the torque converter.
MY QUESTION IS THIS..... How can I tell if this EB is working properly?
Everything under the hood looks 100% professional. The Cummins part number on the Jacobs brake,the solenoid up on the firewall,etc etc everything looks right. I can't imagine someone going through all the trouble to install this EB and it not do anything. My guess is this is doing what it should be doing,and will only really work right if the TQ is locked up.
IDEAS anyone?

"My guess is this is doing what it should be doing,and will only really work right if the TQ is locked up."
I believe you're right, the TC must lock up for the brake to slow the truck. The lockup controllers I'm familiar with have a box of some sort with a switch to select desired function. I used a BD control on my '98. A "mystery switch" would also work but I preferred the smoother action of the controller.
Someone may have removed one from your truck before you bought it.

Dan

Most tranny shops advise against EB's on automatics! Not a good combo.

Locking switch for TC will work well and is good for long ups and downs in mountains.

RJ

I guess If i got the right $$ for it, I'll sell the Jake setup. I don't do any heavy hauling and certainly don't do any mountain driving here in the midwest.

I think youll be alright if you have a billet input shaft. Most good transmission builders sell their own version of the controller. DTT has one for sure.

Is a billet input shaft really really needed?
If I haul anything at all it would be 100% NO MORE than 10,000 lbs MAX
I am figuring my trailer which weighs 1500# and any car I could haul on it.....5K max

Talk to any builder - I would bet that most would recommend a billet input shaft.

Thanks for your "input" on the INPUT shaft.

an EB works good in an auto if you get a valve body thats able to lock up in all gears .I got one from Dave Goerend that locks in 234 and wish i would of got the 1234 lock up but for the most part it still works good , with out being set up right you might as well stick your hand out the window to slow down!

well I am no rocket scientist,but why cannot a guy wire in the torque converter to lock up with the same button that activates the engine brake?
I know there are guys out there who rig up a toggle switch to lock-up the TC.
So instead of monkeying around with two switches,why not incorporate them?
That way I don't even need a valve body.
Again,I am no rocket scientist...... I am just a real green newbie when it comes to these trucks and the automatic trannys.......

Correct,...if you want the two stage effect use both hands
[laugh]

you can you just need the right switch to do it, but with out a valve body it will kick out in 1-2 and if your RPMs are to low in 3-4 you dont have any holding power , thats why 1-2 makes a huge diff ...RPMs can be raise by pulling it in to a lower gear

I see....so a regular toggle will not do it the right way.
I need either a controller or a valve body.
who has these and how much do they cost?

a switch with 1 toggle but separate pole because the EB uses 12volts to activate and the TC needs to be grounded . a controller still wont lock up in 1-2 the valve body needs to be set up to allow lock up in 1-2 Dave goerend transmission will set you up with a good VB and BD sells controllers but all you need is a switch .I think most controllers use speed limiters of some kind ( I hate them) to automatically shut them off like mine ...off at 15 mph and not back on till 30mph. I want my brake on when I want it on!

If I had that setup I would just use a single toggle for the TCC lockup, then a momentary right below it for exhaust brake. If you wanted to get fancy, I think there is a switch that senses only when throttle is fully closed for the e-brake on 12V's, could run the momentary through that so the exhaust brake disengages on any throttle. I like being control of the vehicle, not the other way around...no controllers!

PS Don't think you'll sound like a peterbuilt hitting stage III jake's coming down a hill. The big guys have a different head on the motor that allows exhaust valves to open on the power stroke, making that all familiar noise. I don't know first hand what an exhaust brake sounds like.