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Discussion Starter · #1 ·
I HAVE A PROBLEM WHEN IN OVERDRIVE CLIMBING ANY INCLINE THE TRUCK FEELS LIKE IT MISSES OR THE TRANNY IS JERKING AROUND. IT NORMALLY HAPPENS AT ABOUT 1200 RPM'S AND 50MPH. OCCASIONALLY THE HEATER OR AIR CONDITIONER WILL SWITCH FROM THE VENT TO DEFROST UNTIL I LEAVE OFF THE THROTTLE OR ACCELERATE. I'M LEANING TOWARDS VACCUUM LEAKS BUT DON'T KNOW WHERE TO START. ANY HELP WOULD BE APPRECIATED
 

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I have a similar problem, mine downshifts from 3-4 too much when cruisin at 45-50mph, or when there is a little incline in the road when in OD. I dont know if thats the same problem or not but I am curious too.
 

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When I am in cruise control mine switches from vent to defrost all the time. When this happens the cruise usually goes off about 3 or 4 MPH. This happens at highway speed. I don't think it is the tranny as It has happened threw two of them.
 

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if your air/ac switch is anywhere but off, the ac compressor is gonna be kicking on and off. thats more than likely what you all are feeling. next time, try turning the air off and see if you still have the problem.
 

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Mine will switch to defrost when I'm on the throttle too.
 

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look at teh hoses in the engine area and cab that control your vacuum for the vents first..i.e. easy to find problems like cracked hose, or connector or old hose dried out etc.. you may get lucky..

vacuum leaks are not easy to find...
it could take you all day to find it..
people used to used propain (though I would not suggest it unless you know what you're doing)...
your local garage should have a smoke machine... and that can find a vacuum leak in about 20 minutes.
 

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look for a vaccum pot. there should be a line to it and a line out. it helps keep vaccum to the climate controls. i think its in the fender well but i dont remember off hand. just follow vaccum lines and one will lead to it. it probly broken
 

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If I remember right, when I first got my truck I had the same problem. I bought my truck in MT and drove it back to VA. So I had plenty of time of my hands so I had my wife read the "Owners Manual". Now if I remember right our A/C system is designed that away for less strain on the engine. I just tried finding it in the owners manual with no luck. Maybe it was a dealer in VA that told me that? I don't remember now.. Sorry..
 

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I have had the privilege of owning two Dodge Rams, a 96' model and the current 00' model. I have had the problem in both of them. It is a simple matter of vacuum, it takes less vacuum to go to the "defrost" setting than to stay in the "vent forward" setting. Not really much you can do about it, maybe add another vacuum can inline, to hold a bit more vacuum in the line. It is just a small inconvenience, most vehicles I have driven have this same problem. As long as the setting goes back to where it was before, then I would imagine you will be okay. Now, it was suggested to check all the vacuum lines in the engine compartment, and this is a good idea, you should do so anyway periodically to make sure that everything is tip-top for everyday life. You should especially check it more often if you use your particular ride for offroad adventure (like I do), there is a bit more maintenance involved, but it is worth it to make sure things are going to be functioning when I need them. Cracked hoses are pretty difficult to find, but some of the things to look for are dry-rotted hoses, rips around the neck, and if the hose is particularly stiff, hard, or brittle. The hoses should be nice and flexible, but do break down over time. Also, make sure that the hoses are seated as far as they can be on the neck of the fitting, and that they are not loose. Small leaks attribute to small problems, but get bigger over time. Anyway, hope this helps...
 

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Discussion Starter · #12 ·
ITS NOT THE VENT TO DEFROST PROBLEM THAT BOTHERS ME SO MUCH, BUT IT'S THE WAY THE TRUCK MISSES OR JERKS AROUND WHEN UNDER A LOAD. I'VE BEEN TOLD TO CHECK FOR VACCUUM LEAKS WITH STARTING FLUID. IT WILL MAKE THE ENGINE REV UP WHEN TAKEN INTO THE VACCUUM SYSTEM. I HAVE TRIED THIS ON THE LINES UNDER THE HOOD WITH NO LUCK. DOES ANYONE HAVE ANY OTHER SUGGESTIONS WHERE TO LOOK.
 

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Mine had the same problem and there was a vacume canister under the drivers side of the cab and the vacume lines where almost off and I put them back on and it runs fine now. Hope this helps.
Chris
 

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The reason your truck changes vent settings is due to the vacumn drop in the engine when it accelerates. Theres not enuff vacumn in the system to hold the dash vents open, do your ducts return to the defrost setting, which BTW is a government mandated safety setting. A vacumn canister with a one way inlet should alleviate this. Or its broken hoses.
I dont know all the details of your truck, but if your running like 3:55 or even 3:92 gears with tall (35 inch and up) tires, its quite likely that your bogging the govenor either electricly or mechanicly and trannys brain cant decide whether you should be in od or not. I know my ram hates my 285s when on the highway for long stretches because it will kick out of OD on the slightest hillclimb or headwind and want to stay out till i hit the brakes. But running without the OD keeps the rpms too high for my tastes, even tho Im only about 2500 rpm, whhich is what a non OD truck would run with 3;55S and 33 inch tires. Try running your truck without the OD and see where it Tachs. If its under 2500 rpm, your bogging the motor too much in OD and the brain/tranny is trying to compinsate by constantly kicking the OD out. You'll need lower gears or shorter tires. Its VERY noticeable when towing, and can damage the tranny. If youre gonna run 35 inch tires on the highway, youll need 4:10s, but dont plan on towing much, and i mean that. Most guys find 4:56 gears are the optimum size for power, speed, and towing max gvw with 35 thru 38 tires. Good Luck!
Dd

I just reread your post and noticed that you said you were turning only 1200 rpm at 50 mph. THATS WAY TOO LOW !!!! You should be taching about 1750 maybe even 2000 rpm. I wouldnt run any OD at 50 mph. In fact i dont run the OD myself until I need to run over 60 mph for a long stretch In OD at 50 mph Im running at least 1500 rpm and thats a BIG difference as far as your computer and tranny are concerned. Be aware your creating lots of heat in your tranny by doing that too> . Good Luck!
Dd
 
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