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-   -   96 auto trans lack of power 49-60 mph (https://www.dieselbombers.com/12-valve-2nd-gen-dodge-cummins-94-98/102780-96-auto-trans-lack-power-49-60-mph.html)

lms1977 09-25-2012 11:06 AM

96 auto trans lack of power 49-60 mph
 
hello I have a 96 2wd truck and tow a 14ft trailer with 3 quads 55gal of water a few cans of gas and camping stuff "3000-4000lbs" the truck just seems to be a dog on hills when in that 49-60mph the converter locks and it does not accelerate.

motor and trans are stock and original 180k on them truck feels good empty I'm new to the truck only put a few thousand miles on it seems to lock up at 50mph is this normal? when I push the gas harder or floor it it wont down shift it does not smoke at all wot up hills.

when I pull out from a stop sign with the trailer it seems good tach goes to say 2000-2200 and kinda stays there thru the shifts then hits 50mph locks up tq converter and drops to 1500ish rpms which is fine except when on hills..

is this normal I tried to explain it the best I could I would like more power but I dont have money for a trans right now and am afraid I will be on borrowed time if I mod the power output am I correct?

thanks Mike

angelic0- 09-25-2012 11:21 AM

Pushing the O/D Off button has no effect ?

lms1977 09-25-2012 11:50 AM


Originally Posted by angelic0- (Post 941693)
Pushing the O/D Off button has no effect ?

yes it will shift out of overdrive but then screams and as soon as you put it back in O/D it locks up right away I guess I could rev it out more just figured I should not have to

JBearSVT 09-25-2012 12:05 PM

Mine does the same thing with a trailer, the auto is a dog on hills with a stock engine. I was actually going to start a topic about it myself, looking for more high MPH/low RPM boost. I can enter the highway pulling a trailer with 30psi of boost pulling good right until it shifts into lockup, where the RPMs drop to 1500 and it falls flat on it's face. I can't get more than 10psi of boost @1500 RPM, and that's just plain not enough to keep accelerating with a trailer.
Similarly, maintaining speed with a trailer on the highway below 80mph is impossible. If I'm going 70mph at the bottom of a hill with it matted to the floor, I'll be lucky to be doing 55mph at the top. At 75-80mph, the RPMs are up around 2000 and there's 25+ psi of boost available with a quick stab of the throttle, and 80mph is enough provides enough momentum to get me to the top of most hills without losing more than 10mph of speed, but if I ever want to pull any kind of load and actually maintain 65-70mph, forget about it.

I'm wondering if the issue is the lack of boost at low RPM in lockup, or not enough fuel. Based on my limited understanding of how these engines are set up, it makes sense to me that it's not enough fuel since changing the governor springs in the pump allows you to have enough fuel to spin more RPM, but I'd hate to go throwing more fuel at it and still be stuck under 10psi of boost @1500 RPM in lockup because it's something else.
Direction appreciated!

lms1977 09-25-2012 12:13 PM

that is my issue to the T on the way home I was going fast like 75 or so on a bigger hill and could accererate no problem passing everyone the issue is most of my driving is thru the mountains going riding 45-60 mph

JBearSVT 09-25-2012 12:23 PM

If you aren't going over 55-60mph, turning off the OD will definitely help; the main problem is that that's as fast as you can go with it off, which is more of an issue on the highway where the speed limit is 65mph or more. I pretty much leave the OD off with a trailer unless the speed limit is over 55mph.

The reason it's easier to maintain speed @75mph or more is like I said, more boost is available at the higher RPMs. What it's doing is more obvious if you have a boost gauge and can watch it slam from 30psi down to 10psi the instant the converter locks. So my question is, is low RPM boost limited by fuel, something else, or both?

lms1977 09-25-2012 12:56 PM

how high is it safe to rev the motor to for a 1 mile long hill thou?

JBearSVT 09-25-2012 01:19 PM

If the engine is stock and running right, to the floor all day long, more or less. It won't let it rev past 2500 without making changes, and redline is 3000 Ergo, it won't let you run it over like, 80% duty cycle, which is what these engines were designed to run at.

angelic0- 09-25-2012 01:27 PM


Originally Posted by JBearSVT (Post 941735)
If the engine is stock and running right, to the floor all day long, more or less.

This :rocking:

And with #60 or #120 valvesprings you can take it even further...

1mile trip with the pedal to the floor won't hurt anything...

i've only got #60 springs and i will do 4000rpm with the 4k all day long without worrying about any damage...

There's no timing chain or belt to worry about... these are ROUGH and TOUGH motors :tu:

lms1977 09-25-2012 01:49 PM

wow thanks I guess I'm just a pussy :argh: I start to get all worried over 2200 rpm or so


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