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Proud Canadian
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96 Posts
Discussion Starter · #1 ·
anyone know who makes a good 3.73 gear? I have 4.56's (motive) right now and I need to go to a higher gear. 3.92's wouldn't be a big enough change, and I am not sure I should go to a 3.55, so I figure split the difference and go with 3.73

I see that Motive makes a 3.73 for these trucks, listed as an 8.25". I have heard that our diffs are all the same but sometimes are referred to as a 9.25" and sometimes as an 8.25". I just don't want to order the wrong gear set.
 

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if You have a 1500 model it came with a 9.25”rear end,target your search towards that. 373s are 3/4 , 1 ton gears .
 

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Proud Canadian
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96 Posts
Discussion Starter · #3 ·
if You have a 1500 model it came with a 9.25”rear end,target your search towards that. 373s are 3/4 , 1 ton gears .

Motive doesn't even list a 9.25" Chrysler, thats the thing. I am pretty sure when I picked up the 4.56's that Motive referred to them as an 8.25", but it was so long ago and I just don't remember.
 

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C9-25-373F1 is Motive's # for the set , I don't know why Motive doesn't list the 9.25 in their catalog any more.

but you are going to have some issues , that set is Reverse rotation for the front Diff for the 9.25 in the 2500 series trucks. NO ONE makes a 3.73 standard rotation for your rear axle.
 

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Proud Canadian
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96 Posts
Discussion Starter · #5 ·
C9-25-373F1 is Motive's # for the set , I don't know why Motive doesn't list the 9.25 in their catalog any more.

but you are going to have some issues , that set is Reverse rotation for the front Diff for the 9.25 in the 2500 series trucks. NO ONE makes a 3.73 standard rotation for your rear axle.

yeah I definitely couldn't find a set of 3.73's. I ended up buying 3.55's.
 

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Proud Canadian
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96 Posts
Discussion Starter · #7 ·
Weren't you the one who told me 4.56's weren't too much for this trans lol?

View attachment 50094

What changed your mind?

they are and they aren't. 7K rpm in 1st is pretty much right at 30mph (with a 305/35/24 tire), but I have the wot 1-2 set down at 5500 just because of how quickly the motor spins up. I couldn't imagine it on a boosted motor. the trans hits the shifts exactly where it is set to, but 1st is just too deep to go wot high up without excessive tire spin. my redline is 7K and I have the shifts set to about 6700, with the exception of 1-2. I could probably set it to 6900 and never touch the limiter, but 6700 is plenty. if I set the wot 1-2 shifts too high, there is too much tire spin into 2nd, and setting it in the mid 5K range does help with that. but i almost always launch in 2nd anyways.

but the main reason I went with a ratio change is to slow the driveshaft down. 2840rpm at 60mph with 4.56's compared to 2210rpm with 3.55's.

also with 3.55's my overall ratio in 1st will (obviously) be deeper than 2nd with 4.56's but not by a ton, so it will be quicker off the line than launching in 2nd like I usually do now with 4.56's.

it is great to drive with the 4.56's, and I think it will be as good or better with the taller gears out back. I didn't want to go to a 3.92 because it just isn't enough of a difference, and 3.21 would have been too much. I wanted to go with 3.73's but as we all know, that isn't a possibility. I am getting them installed on Wednesday and then I will know for sure.
 

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Red Trucker
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247 Posts
they are and they aren't. 7K rpm in 1st is pretty much right at 30mph (with a 305/35/24 tire), but I have the wot 1-2 set down at 5500 just because of how quickly the motor spins up. I couldn't imagine it on a boosted motor. the trans hits the shifts exactly where it is set to, but 1st is just too deep to go wot high up without excessive tire spin. my redline is 7K and I have the shifts set to about 6700, with the exception of 1-2. I could probably set it to 6900 and never touch the limiter, but 6700 is plenty. if I set the wot 1-2 shifts too high, there is too much tire spin into 2nd, and setting it in the mid 5K range does help with that. but i almost always launch in 2nd anyways.

but the main reason I went with a ratio change is to slow the driveshaft down. 2840rpm at 60mph with 4.56's compared to 2210rpm with 3.55's.

also with 3.55's my overall ratio in 1st will (obviously) be deeper than 2nd with 4.56's but not by a ton, so it will be quicker off the line than launching in 2nd like I usually do now with 4.56's.

it is great to drive with the 4.56's, and I think it will be as good or better with the taller gears out back. I didn't want to go to a 3.92 because it just isn't enough of a difference, and 3.21 would have been too much. I wanted to go with 3.73's but as we all know, that isn't a possibility. I am getting them installed on Wednesday and then I will know for sure.
That's why I was thinking of investigating if a 3.54 set would fit the 248RBI; The SRT-10 rear is a Dana 60 but it's different than normal Dana 60's. Not sure if a regular Dana 60 gear set will work.
 

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Proud Canadian
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96 Posts
Discussion Starter · #9 ·
That's why I was thinking of investigating if a 3.54 set would fit the 248RBI; The SRT-10 rear is a Dana 60 but it's different than normal Dana 60's. Not sure if a regular Dana 60 gear set will work.

I didn't know that. how does it differ from a standard Dana 60?
 

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Red Trucker
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247 Posts
I didn't know that. how does it differ from a standard Dana 60?
Every Dana 60 I've ever seen (granted, this is somewhat limited) doesn't have C clips. This one does. All things being equal that shouldn't matter with the R&P but I haven't looked yet. 3.54 was the normal gearset for muscle era Mopars with stick shift 440 6bbls and 426 hemis, as they came with the Dana 60.
 
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