3.08 Rear End Options
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Junior User
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3.08 Rear End Options
Hey fellas, need some thoughts here.
Finally got my new motor in good shape. It's a 0.020 over 351w with a XE264HR, matching springs and roller rockers, heavily ported E7s, and port matched 5.0 intake.
Behind that is a T18, and 3.55s in the 10.25 sterling on 33's.
Now as it sits, I can take off in 2nd all day long pulling any load. She has gobs of low end torque.
But with 4th gear being direct, shes turning about 2500rpm at 70mph. I'd like to bring that down a good bit so I'm thinking 3.08s.
Being that 3.08s for the 10.25 are more rare then hen's teeth, what other rear end would be good to swap in that has 3.08s available?
I know there are 3.07s for the D61. What about the 10.5 though? Disc brakes would be pretty nice.
I do do a good bit of moderate to heavy towing, and am considering a 4wd swap in the future so obviously I would need to be able to match the front end ratio.
Finally got my new motor in good shape. It's a 0.020 over 351w with a XE264HR, matching springs and roller rockers, heavily ported E7s, and port matched 5.0 intake.
Behind that is a T18, and 3.55s in the 10.25 sterling on 33's.
Now as it sits, I can take off in 2nd all day long pulling any load. She has gobs of low end torque.
But with 4th gear being direct, shes turning about 2500rpm at 70mph. I'd like to bring that down a good bit so I'm thinking 3.08s.
Being that 3.08s for the 10.25 are more rare then hen's teeth, what other rear end would be good to swap in that has 3.08s available?
I know there are 3.07s for the D61. What about the 10.5 though? Disc brakes would be pretty nice.
I do do a good bit of moderate to heavy towing, and am considering a 4wd swap in the future so obviously I would need to be able to match the front end ratio.
Logistics Pro
Joined: Aug 2010
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From: Chillicothe
Well, with the mention of a 4wd swap, I'd wait. Since you will need to find a 4wd trans to do the swap just find a five speed trans. That way you can keep the current rear end and will only have to get a front end.
Effectively killing 2 birds with one stone.
Effectively killing 2 birds with one stone.
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Junior User
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I was actually thinking of going with a divorced NP205 for the swap. I'm a sucker for the T18 lol
Logistics Pro
Joined: Aug 2010
Posts: 3,716
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From: Chillicothe
The problem with going to 3.08s is finding gear sets for the sterling and d60. The bigger problem is now you can cruise at a decent rpm, but every gear under 4th is working the engine harder. In town mileage and performance will suffer more than you realize.
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I actually just discovered you can get 3.21s for a 14 bolt. Sounds like that would be a decent compromise, even if it is Chevy lol
Elder User
Joined: May 2013
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With such a little change in gearing you will barely feel a change let alone notice any gains if better mileage was a goal. The return on the investment is very very small. And i don't mean this in a negative way at all, just letting you know 
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Junior User
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I thought I had a plan to go 3.31 in the rear and then swap in a D44 in the front with 3.31s, but I cant seem to find a source for reverse cut 3.31s.
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I'm going to put another vote in for swapping the trans, 2500rpm is not high for a V8 and definitely not for one with the upgrades you have. A ZF 5-speed would retain the granny low you have and add a 0.75 OD ratio, that would put the 70mph cruise at 1900rpm which is as low as you want to go, any lower than that just makes gas milage worse. And if you plan to make this a 4x4 eventually there is a good chance larger ties will be part of that deal, and if you go much bigger your gearing will need to go in the opposite direction. 3.55s are good for 32-33" tires with that motor and trans but any bigger than that and you will really start to feel the loss of power. If you were to find a ZF with T-case you could swap both in and use the truck even without the front drive axle present, nothing wrong with that.
Elder User
Joined: May 2013
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I'm not too worried about the mileage, its going to suck no matter what lol my main issue is as it is now is I'm in 4th just putting around town at 40mph because its wound up higher than necessessry in 3rd. Also I built this motor with low end power in mind, so dropping 500 or so rpm at 70mph would be nice.
I thought I had a plan to go 3.31 in the rear and then swap in a D44 in the front with 3.31s, but I cant seem to find a source for reverse cut 3.31s.
I thought I had a plan to go 3.31 in the rear and then swap in a D44 in the front with 3.31s, but I cant seem to find a source for reverse cut 3.31s.
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