do i need to replace the rearend??

I recently swapped tires on my 1992 s-15 jimmy- until this point i had never towed anything- well it seems like i have no power when towing- a friend of mine says when you step up in tire size( i put 30" on ) you have to change the rearend to keep your power- if this is true what size rearend do i need to install???

I recently swapped tires on my 1992 s-15 jimmy- until this point i had never towed anything- well it seems like i have no power when towing- a friend of mine says when you step up in tire size( i put 30" on ) you have to change the rearend to keep your power- if this is true what size rearend do i need to install???

Is it 4x4?

Did you replace all the tires, or just the back ones?

yes it is 4x4 and yes i replaced all 4 tires-

You just can't replace the rear gears, you will have to change the front as well.

Change the ring and pinion gears in the front and rear ends. That will give you back some "power".

What are you towing? If your towing another vehicle with a Jimmy, don't expect to have much power.

You need to select the proper gear ratio, called the "effective Gear Ratio" Follow these to steps to determine what you need.

1) Effective Gear Ratio:
The effective gear ratio illustrates the changes that occur when larger tires are installed. For example, by replacing 29 inch tires with 33 inch tires, your 3.54:1 axle ratio will perform like a 3.11:1.
Divide the old tire diameter by the new tire diameter, then multiply by the original ratio. This will equal the effective ratio of the new combination.

2) Equivalent Ratio:
This formula is used to find the axle ratio needed to bring the overall tire/axle ratio gearing back to an approximation of stock after you have installed larger tires.
divide new tire diameter by the old tire diameter then multiply by the old ratio. This will equal the new gear ratio.

Hope this helps.

TDSG :sly: