I hope I'm doing this right. Another new user. Have had good response to previous questions so thanks to all. In reading some posts/threads, it seems that sometimes the positive battery terminal is disconnected and then shorted against the frame and sometimes the negative terminal is disconnected. Do these have the same result? Or do you do them under certain circumstances?

 

If you think about this logically, it should all make sense. The entire automobile is powered by the battery when the engine is off. There are some circuits that are off completely when the ignition key is OFF (actually, most of them) and then there are a few components like the radio and the computer that have an "always hot" connection (this is one that bypasses the key and is still connected to the B+ (positive) terminal) to keep certain things alive. In the case of the computer, this connection keeps the temporary memory alive & it's this memory that holds the volatile diagnostic codes. Once the power is off, the memory is cleared & in a DC circuit, whether you disconnect the positive or negative terminal, you disconnect the power. There are some capacitors associated with the computer that retain power for a short period of time, but if you keep the battery disconnected for a while, these capacitors will drain there charge and you end up with no power whatsoever in the computer & the memory is cleared. The idea of disconnecting the positive terminal and grounding it comes from the idea that the capacitors will drain quicker. As long as you take one terminal off and leave it off for a while (it doesn't need to be long, the capacitors associated with the ECU aren't large and they'll discharge fairly quickly once the power is disconnected), the memory will be cleared. If you feel comfortable with removing the "positive" terminal, and grounding it, go ahead and do that.

 

Thanks for the confirmation. I thought this would give the same result. With your comment about the capacitors I understand why to leave it disconnected for a while.
Some threads have discussed having a 4.10 r&p in a 3.7. How do I know which one I have now? Is it able to be found in the VIN? I think I read somewhere that there's a tag on the body--maybe on the bottom of the hood? Thanks again to everyone for your help.

 

if you mean a 4.10 geared rear end, that is aftermarket only. Our trucks come with 3.55 or 3.92. You can request a build sheet here https://dodgeforum.com/forum/3rd-gen...ild-sheet.html and that will tell you what rear end gears you have along with all the other things your truck came from the factory with.

 

Would the change to 4.10 be worth the expenditure? I'm guessing it would cost $500 or more. If all I want to do is increase mpg, that seems like a lot of miles to recoup the cost. This is a 3.7 auto slt quad cab 2wd with 65k we just bought. If you think so, any preference for manufacturer/rebuilt. Whatever info you could give would be appreciated. Thanks.

 

I think want 3.55 gears, higher gears, higher torque, higher mpg. That's how I understand it

 

The gear ratio works this way - let's say you have 3.55 to 1 gearing ratio, then your pinion would rotate 3.55 times for every 1 turn of the axle. If you increased the ratio to 3.92:1 and left everything else the same, your engine would need to turn faster to give you the same road speed, but you'd get more torque at the rear axle - the faster rpm per mph means more fuel used. Essentially, you need to match the differential ratio to what you're doing with the vehicle. If you're doing more pulling or pushing, you may need more torque, if you put larger wheels on, you most likely would need more torque. On my jeep, for example, with 35" wheels, I use 4.11:1 differential gear ratios so that I can use all 5 transmission speeds (even this is on the low side for off-roading). If you do a lot of highway driving without heavy hauling or pulling, you'll probably want to stay with the lower ratios (like the 3.55). Drive the truck for a while in the environment you want to use it in and see how it reacts and then you can make a decision.

If you choose to change the gearing to after-market ratios, you'll find that the gears alone will be a LOT more than $500 and this is not just a quick "bolt on" project & if you have a 4x4, you need to spend this amount for each differential. You'll find that many people that change to higher ratios than OEM axles give them, use axles from other vehicles and modify the suspension points etc (including drive shafts) to fit these axles to their truck.