# Changing gears and gear boxes for better gas mileage? **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [October 13, 2008, 6:24pm UTC](https://community.cartalk.com/t/changing-gears-and-gear-boxes-for-better-gas-mileage/20680 "2008-10-13T18:24:04Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![denise\_w](https://avatars.discourse-cdn.com/v4/letter/d/87869e/32.png) [@denise\_w](https://community.cartalk.com/u/denise_w)\ **Post date:** [October 13, 2008, 6:24pm UTC](https://community.cartalk.com/t/changing-gears-and-gear-boxes-for-better-gas-mileage/20680/1 "2008-10-13T18:24:04Z")
i have a '93 gmc yukon,automatic, 4X4 on the floor can’t afford to buy a newer car at this time. i was told by a diesel mechanic grad. that i could change my gears,gear boxes and axals to get up tp 30mpg. he said the cost would be about $500.00 is this possible,can it be done and if so who does this? ---
**Author:** ![mcparadise](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mcparadise/32/32_2.png) [@mcparadise](https://community.cartalk.com/u/mcparadise)\ **Post date:** [October 13, 2008, 6:32pm UTC](https://community.cartalk.com/t/changing-gears-and-gear-boxes-for-better-gas-mileage/20680/2 "2008-10-13T18:32:08Z")
A change in rear axle ratio might make a slight difference, but don’t think you’ll ever see 30 mpg in this vehicle. Since you have 4 wheel drive, you’d have to change the gears in both differentials. I don’t think it’s worth it on a vehicle of this age. ---
**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\ **Post date:** [October 13, 2008, 6:34pm UTC](https://community.cartalk.com/t/changing-gears-and-gear-boxes-for-better-gas-mileage/20680/3 "2008-10-13T18:34:51Z")
It will cost much more than $500, you will NOT get 30mpg, and your '93 Yukon is not worth what this gear change would cost… ---
**Author:** ![FoDaddy](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/fodaddy/32/717_2.png) [@FoDaddy](https://community.cartalk.com/u/FoDaddy)\ **Post date:** [October 13, 2008, 6:56pm UTC](https://community.cartalk.com/t/changing-gears-and-gear-boxes-for-better-gas-mileage/20680/4 "2008-10-13T18:56:48Z")
That is laughable. 1st off what is being implied is that you could change out rear/front end ring & pinion. Seeing how this is a 4x4 expect to pay around $1000-$1200 to have this done. There are quite a few gearsets to chose from. If you’re intrested in better mileage you’ll probably be leaning towards a 3.08 or 2.76 rato. I believe the stock ratio for your vehicle is 3.73. Of course there is a downside. your in town mileage will likely go _down_ due to less mechanical advantage being involved in getting the beast moving. Accerleration will suffer, and towing ability will be compromised. Highway mileage will probably go up by maybe 2 or 3 MPG, but nowhere near 30 MPG. In short you’ll never recoup the money you put into it in gas savings. It’s a bad idea. ---
**Author:** ![Joseph\_E\_Meehan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joseph_e_meehan/32/21_2.png) [@Joseph\_E\_Meehan](https://community.cartalk.com/u/Joseph_E_Meehan)\ **Post date:** [October 13, 2008, 7:09pm UTC](https://community.cartalk.com/t/changing-gears-and-gear-boxes-for-better-gas-mileage/20680/5 "2008-10-13T19:09:24Z")
i was told … that i could change my gears,gear boxes and axals to get up tp 30mpg. In your dreams. If it was that simple, don’t you think GM would have done it? ---
**Author:** ![silvergc1](https://avatars.discourse-cdn.com/v4/letter/s/6f9a4e/32.png) [@silvergc1](https://community.cartalk.com/u/silvergc1)\ **Post date:** [October 14, 2008, 3:20pm UTC](https://community.cartalk.com/t/changing-gears-and-gear-boxes-for-better-gas-mileage/20680/6 "2008-10-14T15:20:34Z")
It’s even worse. The price is more like $1000 per axle to have somebody who knows what they are doing work on the vehicle. And, as Joe says below, there is no way you are going to get anywhere near 30mpg out of this vehicle. The laws of physics can’t be violated. This is a heavy vehicle with poor aerodynamics. ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [October 14, 2008, 3:54pm UTC](https://community.cartalk.com/t/changing-gears-and-gear-boxes-for-better-gas-mileage/20680/7 "2008-10-14T15:54:31Z")
This ranks up there with the guy who told me he’d be getting 35 mpg out of his dually Dodge Ram diesel as soon as he put in that chip he’d ordered… ---
**Author:** ![denise\_w](https://avatars.discourse-cdn.com/v4/letter/d/87869e/32.png) [@denise\_w](https://community.cartalk.com/u/denise_w)\ **Post date:** [October 15, 2008, 1:27am UTC](https://community.cartalk.com/t/changing-gears-and-gear-boxes-for-better-gas-mileage/20680/8 "2008-10-15T01:27:06Z")
thanx for the input much appreciated ---
**Author:** ![denise\_w](https://avatars.discourse-cdn.com/v4/letter/d/87869e/32.png) [@denise\_w](https://community.cartalk.com/u/denise_w)\ **Post date:** [October 15, 2008, 1:29am UTC](https://community.cartalk.com/t/changing-gears-and-gear-boxes-for-better-gas-mileage/20680/9 "2008-10-15T01:29:47Z")
thanx for the input,much appreciated ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [October 15, 2008, 5:04am UTC](https://community.cartalk.com/t/changing-gears-and-gear-boxes-for-better-gas-mileage/20680/10 "2008-10-15T05:04:23Z")
The guy who told you this is either misguided or erroneously over-optimistic. You’ll never see 30 MPG and 500 dollars won’t even touch the cost of the parts involved.