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Unread 09-26-2009, 02:42 PM   #1
flyerfan27
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Lower Rear Gear Ratio???

Hello everyone,

I hope everyone is doing well. I want to thank you all for all the past help. I thought I was done with my questions, but I was wrong.

I bought my 1996 Jeep Grand Cherokee Laredo with the 4.0L about a year ago. I just found out that the rear gear ratio was lowered from stock. To what it was lowered to.... I do not know. I just know it was lowered. Since I do not know technical things about vehicles I was hoping some of you could explain to me why the rear gear ration would be lowered. Like:

1. What is the advantage to having lower rear gear ratio?
2. Will it help or hurt me on the street?
3. Will having a lower rear gear ratio in my Jeep hurt the mpg?
4. Anything else that would be helpful to know.

I have no desire to drive my Jeep off road. I live everyday in pain from back and neck injures so bouncing around driving off road would only hurt me more. I only bought my Jeep because I love Jeeps and for the room in the back for my Service Assistant Dog. The only bad roads I will be on is wet ones and snow covered.

I guess what I want to know; should I have the gear ratio put back to stock or leave it? Or should I even go the other way and have the rear ratio raised. What I need out of my Jeep is the smoothest ride I can get with the best mpg. Is changing the rear ratio expensive to have done by a Jeep Dealer? I am no mechanic and I do not have a trusted person that I can take my Jeep to.

Any help would be more then appreciated!

Thanks,
James

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Unread 09-26-2009, 02:46 PM   #2
RedlineRyan
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stock gear ratio with stock tires would defiantly better mpg but if the rear was changed the front probably was changed or else your 4wd might not work
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Unread 09-26-2009, 02:59 PM   #3
flyerfan27
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Hello Ryan,

Thank you for replying to my question. I never gave the front a thought. I bet you do have to change both. Do you have any idea the cost of changing both the front and back gear ratios? Also; is there any advantage to having lower ratios?

Thanks,
James
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Unread 09-26-2009, 03:01 PM   #4
RedlineRyan
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the only advantage is lower speeds in four low offroad or bigger tires and stock speeds so you go bigger tires you usually change your gears to compensate all its really doing is making your jeep have more acceleration while you lose your overall speed it depends how low the gears actually are do you know what rpm you cruise at like 60 mph?
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Unread 09-26-2009, 03:08 PM   #5
flyerfan27
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Hello Ryan,

Thank you for the help I really appreciate it. I think I am starting to learn something here. I am not sure the RPM at 60, but I just noticed yesterday the RPMs at 65. It was around the 2250 mark at 65 mph. Does this information help? If not later I can take a ride and get the RPMs at 60.

Thanks again,
James
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Unread 09-26-2009, 03:14 PM   #6
RedlineRyan
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2250 is kinda on the high side i run that with 31s and 4.11s with my 5 speed your gas mileage defiantly suffers on the highway how much i cant say i lost about 1 to 2 mpg in my wrangler it might not be worth the cost of a regear which can cost $1500+
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Unread 09-26-2009, 04:08 PM   #7
flyerfan27
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Ryan; thank you so much for all the information you have given me. It is very kind of you to take this time out to help me. I really appreciate it.

I know my tires are 30s. I took the 31s off and sold them. I am just going to have to accept the gas mileage I am getting. Even if a gear change could give me mpg to make it worth the gear change I cannot afford the $1,500.00 to get it done. I had no idea it would be that expensive. That cost for a gear change is shocking! I had no idea.

Thanks again,
James
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Unread 09-26-2009, 04:10 PM   #8
xJoshxx
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Quote:
Originally Posted by flyerfan27 View Post
Ryan; thank you so much for all the information you have given me. It is very kind of you to take this time out to help me. I really appreciate it.

I know my tires are 30s. I took the 31s off and sold them. I am just going to have to accept the gas mileage I am getting. Even if a gear change could give me mpg to make it worth the gear change I cannot afford the $1,500.00 to get it done. I had no idea it would be that expensive. That cost for a gear change is shocking! I had no idea.

Thanks again,
James
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Unread 09-26-2009, 04:17 PM   #9
iluvtruenos
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I think your honestly best bet would be to borrow/use a GPS and find out your real speed.

When messing with regears, you don't know for sure how fast/slow you're going.

If they simply regeared but didn't regear the tranny, you'll be reading 55 while really driving at 45.

Or the other way around.

Lastly, draw a line on your tire, and count how many times your driveshaft turns for one 360* rotation of the wheel.
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Unread 09-26-2009, 04:36 PM   #10
flyerfan27
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Quote:
Originally Posted by iluvtruenos View Post
I think your honestly best bet would be to borrow/use a GPS and find out your real speed.

When messing with regears, you don't know for sure how fast/slow you're going.

If they simply regeared but didn't regear the tranny, you'll be reading 55 while really driving at 45.

Or the other way around.

Lastly, draw a line on your tire, and count how many times your driveshaft turns for one 360* rotation of the wheel.
I do know the last owner added a device to adjust the mph when making changes to the truck. He told me it was adjusted for the changes he made. With that said I did remove the 31 tires and replace with 30s so it is probably off now. Thank you for the idea with the GPS. I do have one that gives the speed. I just never compared them. I will do it tomorrow along with the driveshaft to tire revolution check. Then I will report both tomorrow night.

Thanks for the help,
James

Last edited by flyerfan27; 09-26-2009 at 05:00 PM..
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