I just bought a Dodge Ram 1500 4X4 this weekend and It is my first Dodge. I want to do some mods to make it a little better off-road. I really want to put lockers in it. I am unsure as to what axils are in it and what the gear ratio is. Where can I find this? Also, I have 285 75-16 on it and I was wondering how far off the speedo is.

 

I have a '99, and my axle info is written on a tag on the axle tube. In the rear, it is on the passenger side, on the front of the axle (i.e forward facing). The gear ratio will be the same in the front since it is a 4x4. I think the gear ratio is also on the tag on the inside of one of the doors. Since it is a 1500, you probably have a Dana 44 in the front, and a Chrysler 9.25 in the rear with 3.55 gears.

With 285/75-16 tires, your speedo is off by about 4 mph. Stock tire for you should have been a 245/75-16, but you can check that on the tags on the inside of the door, or look at your spare.

 

285's would be more than 4mph off I have 265's and I am off by 5 at 50 i would guess 8 or 9 best bet would be ask a tire store or find one of those portable radar machines.

Steve

 

Oops, you right, it is about 7.78 mph off. I plugged in the wrong tire size (I used a 265/75/16, which is just a little over 4 mphoff, instead of a 245).

 

So is that % at like 100 mph? so at 100 it is really 107.78
Also, do they come stock with duel exhaust or is that aftermarket? I think that it is a sport cause it is higher off the ground then my friends and it has a lift block on the back axle. Not really sure though. I guess that I will have to crawl underneath and take another look. Thanks allot for the help!

 

At 65 mph, you would be going 7.78 mph faster.
Dual exhaust is aftermarket.
Stock trucks have a block in the rear. You just need to measure yours to see if it is bigger then the stock block. You could also have an add-a-leaf in the rear if the block is stock size, but it looks lifted.

Post some pics, I bet we could all tell you more if we saw it.

 

I think the speedo error is a percentage. I have 4.11's, and used to have 285's and my speedo was off by 8.7%. I figured this by using the mile markers on a road trip. 50 miles of markers and my speedo was off by 4.3~4.4 miles so I just split the difference and came up with the 8.7%.

Now that I have the 295's I was un-sure of the new error. last weekend coming out of Yosemite NP my little woman and her truck helped me figure the new error (more or less depending on her speedo error) and over 131 miles with 2 data points, 1 being in the middle, the new error is 9.3%

if you go with the assumption that the speedo is a "mph" off, then you can say that at 65 you might be going 72 but at 85, your not going 92, it would be faster than that.

you would think that with me going to 4.11's and 295's that my speedo error would be minimal but it's not. My hypertech programmer does not correct for the tires even though your programming it in. Ive tried stock to 40" tires and the speedo error does not change.

 

I just opened a cardomain.com account but i don't know how to link it to here yet. You can look me up, I am leinad78.
Thanks for all the help

 

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Swing by your local stealership and have the guys at the parts counter print you out a build sheet. This will have all of the specs on your truck. including axle and gearing info. If you have access to a GPS, you can use it to see how far off your speedo is as you drive. Or, if you have cool cops in your area, you might be able to get them to clock you with radar. I've done that before, after putting big meats on my Jeeps.

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Yeah, I have a friend that has a GPS so I will have to stop by there and pick it up from him. I really wanna know how fast/far i am really going. I am going to stop by the dealership this weekend and get a build sheet.
Thanks for all the help!