Gear size for 40s

T&ERun

LOSER
Moving up to 40s from 37s. Right now I'm using 5.13s with manual trans. I'm changing axles and I'm trying to decide to order with 4.88 or 5.38. Comparing the two gear sizes with what i have now i would shave about 100rpm at 70mph and around 300-400 with the 4.88s. I loke the idea of the lower rpm on the highway, but don't want to sacrifice offroad. It is not a daily driver. I'm planning on switching to a rubi t-case soon also.

With all that said, any advice from you guys running 40s and manual trans (and 3.8 :( ) would be much appreciated.





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wayoflife

Administrator
Staff member
5.38 is the ratio I prefer to run with 40's but then, I also run a ProRock 60 up front and ProRock 80 in the rear. 5.38 will leave you with a pinion that is pretty small in a Dana 44.
 
I would say go with the 5.38's because it will give you more off road performance.

Here is a gear chart that might help.

gears.jpg

Edit: here is a trip to the Dusy when Moby blew a D44 5.38 ring and pinion.

 
Last edited:

OverlanderJK

Resident Smartass
So, i should get 60 front 80 back with 4.88 on 37"?

If there is ever a chance of you going 40's do 5.38's. You will be unhappy with 4.88's. And it'll be like $2500 to change your gears in the 60/80 if not a little more. A friend of mine had to do this.
 

ERAUGrad04

New member
Just had my 44s regeared to 5.13s and paired with the 37" Nittos, it's a perfect combo. FWIW, my Jeep has the 3.6 w/auto trans.
 

T&ERun

LOSER
I'm doing full float 60s. Sounds like 5.38 is the way to go. I would rather have a little lower rpm running highway speeds, but don't want to hurt performance off road. My thinking was changing to a rubi tcase I would be fine off road. Thoughts?

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wayoflife

Administrator
Staff member
I'm doing full float 60s. Sounds like 5.38 is the way to go. I would rather have a little lower rpm running highway speeds, but don't want to hurt performance off road. My thinking was changing to a rubi tcase I would be fine off road. Thoughts?

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With 60's, 5.38's are definitely the way to go. A rubi t-case would be a nice addition for sure.
 
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