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ZUKIWORLD Discussion Forum => Suzuki 4x4 Forum => Topic started by: OHIO_ZUKI on June 10, 2008, 06:17:23 PM

Title: If I swap from a 4.625 to a 5.12....
Post by: OHIO_ZUKI on June 10, 2008, 06:17:23 PM: What will that do to my freeway speed? I ask because I do not trailer my rig. I drive it. Sometimes up to 250 miles. With lowering my overall gear ratio, will that be bad for freeway driving? My friends are telling me to just stick with the 4.625's and lock the rear, and I will be fine.
Title: Re: If I swap from a 4.625 to a 5.12....
Post by: Skyhiranger on June 10, 2008, 08:13:31 PM: You are running 33s right? If so, you should be fine with 5.12s.
Title: Re: If I swap from a 4.625 to a 5.12....
Post by: OHIO_ZUKI on June 11, 2008, 03:48:31 AM: No, I am running 31's. Will that make a difference?
Title: Re: If I swap from a 4.625 to a 5.12....
Post by: Jeremiah on June 11, 2008, 08:10:31 AM: http://www.izook.com/gearcalc.htm
Title: Re: If I swap from a 4.625 to a 5.12....
Post by: beercheck on June 11, 2008, 08:45:55 AM: You'll prefer the 5.125s.
Title: Re: If I swap from a 4.625 to a 5.12....
Post by: Drone637 on June 13, 2008, 01:01:53 AM: Well, your looking at about a 10% drop. So if you turn 3K at 60 now, you will be turning 3.3K instead.
Title: Re: If I swap from a 4.625 to a 5.12....
Post by: Luke on June 13, 2008, 05:49:50 AM: I've got 5.12's and 31" tires, if you drive on the freeway you'll want to use the right shoulder.
Title: Re: If I swap from a 4.625 to a 5.12....
Post by: Skyhiranger on June 13, 2008, 06:13:37 AM: According to my calculations, if you are running true 31s (which you are probably not....so your RPMs will be slightly higher at any given speed), and you have the 3 speed auto tranny (1:1 high gear), then your RPMs will be as follows.......

MPH RPM with 4.62s RPM with 5.12s
60 3008 3333
65 3258 3611
70 3509 3888

These numbers also do not take into account any slippage in the tranny (which with the torque converter locked up should be none or very minimal), but if you are getting any slippage, the RPMs will be slightly higher.
Title: Re: If I swap from a 4.625 to a 5.12....
Post by: OHIO_ZUKI on June 13, 2008, 07:59:18 PM: Err ha. So basically, I can run those gears, but i will have to add an additional 45 mins to my drive time to get anywhere. (ha)
Title: Re: If I swap from a 4.625 to a 5.12....
Post by: Drone637 on June 13, 2008, 11:50:58 PM: Your drive time will be the same, you will just run at higher RPM's. Of course, if you are already running larger then stock tires, this will just bring you back to where you where before. Or closer to it. :)
Title: Re: If I swap from a 4.625 to a 5.12....
Post by: Skyhiranger on June 14, 2008, 07:45:50 AM: Quote from: OHIO_ZUKI on June 13, 2008, 07:59:18 PM
Err ha. So basically, I can run those gears, but i will have to add an additional 45 mins to my drive time to get anywhere. (ha)

3900 RPM at 70 isn't that bad. You'll probably be a little higher than that, since, like I said, your tires probably don't measure an actual 31".
I was trying to think what one of my 4 door trackicks run for RPMs at 70.....I was thinking around 3600.....so you'll still be in the "ballpark" and you will probably want to run a little higher RPM than "stock" because those tires will be a little harder to keep turning (because of the additional weight) than the lighter stock sized tires.

Oh, and these engines don't redline until 6500 RPM.....so you should be ok running 4K-4500 RPM for extended periods. Just keep the maintenance up on the engine (like you should on any engine, no matter whether you are running it at higher than "normal" RPMs or not). Keep the valves adjusted, the oil changed, etc.