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The "towing" 3.73 ratio versus the 3.55

M

Mopar500

NAXJA Forum User
Location
Colorado
I am trying to determine if the difference in gear ratios is noticable.
Has anybody felt both? Is there a seat-of-the pants difference?
I would think the difference would be slight with a .18 change.
The deal is, I recently drove cross country in my 92 4.0, HO. I had the cruise set at 80mph. When I would take a long hill on I-80 the engine wouldn't hold overdrive. (Maybe I am expecting too much?) In the past I drove a 96' XJ that seemed to have more off the line than mine. It is impossible to locate that vehicle again so I don't know what it had.
I am wondering if a simple gear ratio change might give noticable low end grunt while helping hold overdrive better.
I don't want to go too crazy (4.10 or something) and screw up my fuel economy. I also don't want to have to keep my foot planted to the floor to cruise at 80mph.
So I wonder if the 3.73 is the ticket.

Whatduyathink?
 
I'm running 4.10's on 30" tires and love the performance, but I think I will go 31" because with 4.5" lift, my 30's look too small. If you are planning on keeping the 235's, go with the 4.10's and you will love the kick in the *** you get when you get on it! Fuel mileage will be better in town and slightly worse on the highway.
 
Yea, higher rpm but since the gear swap mine will stay in OD down to 30 mph and shifts alot less and a light foot on the gas is all it wants to get going now.

Immediatly after the swap with no other mods my in-town mileage jumped by 1-2 mpg, highway dropped by 1 mpg.
 
Remember that when you re-gear and change tire size your speedo is no longer accurate. Increasing tire size will cause your speedo to read low, while increasing gear ratio will cause your speedo to read high. It is easiest to work in percentages to figure out how far off they will be.

example: the jump from 30" to 33" is +10% and the jump from 3.73 ito 4.10 is +9.9%. Since they affect the speedometer in an opposite direction from each other the net speedometer difference is .1%.

Going from 3.55 to 4.10 is a difference of 15.5% so with stock tires your speedo would report a speed of 81mph when you are going 70mph. increase your tire size to 235/75 and you can knock a few percentage points off of that( I have to leave you SOME math to do). I hope this has helped.


Oh and remember that when computing diameter of metric tires (if you should choose to do it yourself) multiply the height by 2, then add your rim size.
i.e. 235/75-15 diameter is 2(235mm X 75%) / 25.4(mm/in) + 15 = 28.9".
 
i drive a stick with 3.07s and i tested out a stick with 3.73s and it was a damn big difference to me. but 3.07 is alot lower than 3.55 as well. i think you'll be able to notice the difference but not too much.
 
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