How do you determine rear gear ratio?

[Turbo Trucker]

How can you tell if you have 3. 55 or 4. 10s? I have a 5 speed dually and I'm running 70mph at 2100 rpm in 5th gear. Anyone know what gear this is?



Thanks

 

[LSMITH]

Wes, open the hood and look on the underside near the grill for a white tag. It should list the gear ratio as well as other options on the truck. I would guess that you have the 3. 5 gears if you still have the 215 tires on it, but I don't have any experience with the 3500 and 215 tires. Hope this helps.

 

[Turbo Trucker]

Looks like the tag is gone, there's a couple fragments of one attached to the hood liner but that's all I could find.

 

[LSMITH]

OK Wes. Try the tag on the door frame, it will list tire size and all of that, not sure if it will list the gear ratio though. You can also look inside the glove box for a tag that lists all the information that is on the underhood tag as well. Hope this helps.



Forgot, there also might be a sheetmetal tag attached to one of the diff cover bolts that list ratio. If all else fails jack up the rear, and turn the tires one revolution counting driveshaft turns. Three and a half turns versus a little over four turns is easily seen. Good luck.

 

[chuck3]

3.55.

I would bet it has the 3. 55 at that rpm and speed mentioned above.

 

[chuck3]

My auto runs 75 at 2k rpm with the 3. 55 and 265 tires.

 

[klenger]

There should be a tag on the rear diff. cover also.

 

[KPancake]

i'm not sure, but look inside the glove box and there should be a sticker with a bunch of info on it. not sure if it has the ratio or not.



Chris

 

[MikeR]

You have a 3. 54 rear. The 4. 10's would be turning about 2300-2350 at 70mph.



You can always go down to the Dodge dealer and give them your VIN and they can print you out a copy of the build sheet for your truck.



-Mike

 

[GMcLean]

MikeR is right,, the rpms and speed sound about right. .

If you ever require any info of this sort you can go to your nearest dealer and they can punch your VIN into the computer and give you any info about the truck you could ever use. .