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Differential change for my 62 Dodge D100

Mtbase

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Joined
Jul 5, 2021
Messages
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Location
Huntington, Ma
Hi;
I'm looking for opinions for changing gearing on my D100

It arrived in my possession with a 225 6 cyl and a 4 speed trans. The issue is that the 1st gear is a "granny gear"....way to low to be of any use to me and with the gearing so low...60mph has the pedal to the floor.

I'm told that the differential has 3:92 gears, or something like that ( not really my field of expertise), in a 8-3/4" rear end. I'm told by some that 3:23 should make it so that the 1st gear will actually be needed and the truck could hit 70mph.

Anyone ever try this?

I'm not trying to make this anything other than a cool old ride.

Thanks
 
Yes you can change the ratio in the 8 3/4, it's going to be a trade off though. What you gain in speed, your going to lose is towing ability and acceleration
 
3.55 is a good compromise gear for that. I've had and been around several slant six trucks with geometric four speeds (NP435 Wide ratio) that were pretty happy. 1st is still mostly unusable but necessary if you haul or tow. It would be really good with an NP445 close ratio, as first in it is 4.56:1, as opposed to 6.68:1.
 
agree if you are NOT going to tow anything (or heavy loads)you could even go to the 3.23's, But the six shooter will not like pulling or hauling if you go below (smaller no.) then that.Do not know if changing it to 3.55's would be felt? My gamble if it were mine would be the 3.23's Only way to know is hind sight.
 
my 64 d100 had a tapper axle type 8 3/4 with3.91 legger . had drum issues , so i swap it out for a 9 1/4 out of a 74 d100 with 3.54's ls it holds up fine with my heated up hp 383 auto .
 

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