Gears & RPM - highway driving
#21
JK Super Freak
Join Date: May 2008
Location: Grand Junction, CO
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Not to throw another wrench into the equation, but what about pinion strength? I'm going to regear my 6 speed probably at the end of the summer. 4.56s on 35s would put me almost exactly to the same place I was with 4.10s and the stock 32s. 4.88s would give me a little more oomph. But I saw a comparison of pinion strength somewhere a long time ago and if memory serves me right a 4.56 pinion is stronger than a 4.88 pinion. By the time you start talking 5.38s there was a pretty considerable difference.
I don't have the original article to reference so if someone has some real data on it, please post it up.
I don't have the original article to reference so if someone has some real data on it, please post it up.
#22
JK Super Freak
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You don't say that you have a Rubi so I'll assume you have 3.73's. So the answer to your question is yes. With 5,13's or 5.38's you will do much better than you do now.
#23
JK Newbie
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Thank you for reponding Chuck 45. My Jeep is not a Rubicon it's the Unlimited and I put 37 inch tires on a year ago and lost all my power. I put a Max Energy programmer in it that helped but I still bog down on the uphill grades. One other question, if I go 5.38 gears will they be ok in the front end Dana 30? I don't do extreme rock crawling. Thanks
#25
JK Super Freak
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Thank you for reponding Chuck 45. My Jeep is not a Rubicon it's the Unlimited and I put 37 inch tires on a year ago and lost all my power. I put a Max Energy programmer in it that helped but I still bog down on the uphill grades. One other question, if I go 5.38 gears will they be ok in the front end Dana 30? I don't do extreme rock crawling. Thanks
#26
JK Newbie
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To be honest I don't know if 5.38's are even available for the D30. I think if I had a D30 up front, with it's smaller pinion, I'd go with 5.13's. You will see a huge difference with the 5.13's over the 3.73's; enough to make the expenditure very worthwhile. If you had a D44 up front I would definetly recommend the 5.38's over the 5.13's with 37's. Heck I've got 35's and wish I had 5.38's! If I recall my calcs correctly you'll be at 2410 rpm at 75 with your 5.13's and 37's. With your 3.73's the calcs show 1759 at 75 mph. I'd rather see you at a bit higher rpm than 2400 but that will be a huge improvement over 1759. If your tires are not a true 37" diameter but a little smaller your rpm's would be a little higher which would be a good thing. Hope that helps.
#28
JK Super Freak
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BTW, after you get your gears installed let us know what you think.
#29
JK Newbie
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I had a major problem with the auto down shifting, sometimes 2 gears when hitting small hills while pulling my enclosed motorcycle trailer with the stock 411 gears. Went to the 513, it doesn't hesitate a bit, and my towing gas mileage went up almost 2 mpg since there is no lugging anymore. I'll never make up the money the gears cost but I'm a much happier camper.
#30
JK Newbie
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I just called Absolute Offroad here in Phoenix, AZ and setup an appointment for June 8th to get gears installed. The owner Joe is pushing me towards the 5.38's because I have a 1700 lbs tent trailer that I want to tow on occasion. His shop uses exclusively Yukon gears he said Superior Gears make noise (I don't now). Anyway, the whole job out the down for $1300.00. Does this sound about write? Again thanks for your assistance.