Rear gear question

[DBrown21]

I have the 3.7 v6 dodge ram, I'm currently on 285/70/17's and I use my truck to pull race-cars around on a weekly basis. The trailer is very light and the car only weighs 2300lbs. I don't really have a problem cruising around town or doing about 60mph but when I try to get going up past 70mph on the interstate I find my trucks struggling, it's a 5-speed tranny and I can run 4th gear but I'm turning like 3000-3500rpms and that seems like I'm just pouring gas through it and when I go to 5th gear it will barely keep speed and I have to be deep on the petal to keep it at a constant speed. So my question is would putting in a different rear gear help me any? My truck has whatever come stock in my truck, which I'm not sure what it is, or even how to find out what kind of ring and pinion I have. Any info is helpful thanks!

 

[Csanders1992]

A taller gear would be better for holding speeds on highway, but being a v6 you'd really struggle if you hit a hill or through town. If you got a shorter gear you'd be running an even higher rpm on highway


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[DBrown21]

Any idea of what gear ratio comes stock in my truck without me having to pull the cover to see. Doesn't seem like it would be a huge difference. What about bigger tires, would that help or hurt me?

 

[hemihustlin]

Using a gear ratio calculator you can see the difference a gear swap will make in rpms at say 60 mph. But first you need to know what gears you have. If you dont see the tag on your diff you can request a build sheet from chrysler. You can find the request form on their website.

Just for fun, how much mpgs do you get pulling a race trailer at 70 mph?
You probably already know but this sounds like a job for a v8 lol

 

[hemihustlin]

Bigger tires means more energy needed to move them. If you want to help get smaller and lighter tires.

 

[DBrown21]

Hmm

I'll have to look on the rear end to see if I can find what ring and pinion is in it, and I'll get back to you. I wish I had a v8 now, thought with a v6 is get better mpg and at the time I wasn't pulling trailers. Might have to upgrade soon... But I'm not totally sure but I'd say somewhere around 7mpg if my math is close. That was back roads on a trip that I didn't have to deal with highways.

 

[hemihustlin]

Contact Dodge

Fill out all the info, in the briefly describe section put " vehicle build sheet"
You should get an email pretty quickly, worked for me.