3.42 to 3.73

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Hammer_95

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Has anyone went from a 3.42 to 3.73 with the TBI engine and 4l60 transmission? I’m wanting to get it to stop unlocking when passing at highway speeds so with the deeper rear end I’m wanting to keep it in the sweet spot for the engine. Fuel mileage doesn’t matter to me just drive ability
 

L31MaxExpress

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Has anyone went from a 3.42 to 3.73 with the TBI engine and 4l60 transmission? I’m wanting to get it to stop unlocking when passing at highway speeds so with the deeper rear end I’m wanting to keep it in the sweet spot for the engine. Fuel mileage doesn’t matter to me just drive ability
That change is not even noticeable. 4.10s are noticeable.
 

someotherguy

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That change is not even noticeable. 4.10s are noticeable.
3.73's are decent if your truck already came with them. If you're going to go to the expense and labor of 3.42 -> then yes, go ahead to 4.10's. Looks like you might be running slightly larger than stock tires, too, so that's even more reason.

Richard
 

kennythewelder

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I went from 342s to 373s. I am running 275/60/15 tires, on the OE 15 inch rims, on a 2WD. since it looks like you have bigger tires, I agree with the above. Go with 410s. Change all of your bearings, and I did the crush sleeve eliminator kit. Once you set the pinion depth, your done. It can not change. I was very glad I used it, when my pinion seal was leaking. It made it easy to pull off the yoke, and replace the seal, with no worries about changing the pinion depth. I also installed an Eaton truetrac to replace the OE open diff carrier. If you don't have a G80, you may want to look at a locker. The Eaton, is good on the street, but there are better choices for off road use.
 

WV_Dave

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I think the parameters for locking and unlocking of your torque converter can be altered via a tune. It might be cheaper and more effective in your case. Worth checking into.
 

Pro439

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I went from 342s to 373s. I am running 275/60/15 tires, on the OE 15 inch rims, on a 2WD. since it looks like you have bigger tires, I agree with the above. Go with 410s. Change all of your bearings, and I did the crush sleeve eliminator kit. Once you set the pinion depth, your done. It can not change. I was very glad I used it, when my pinion seal was leaking. It made it easy to pull off the yoke, and replace the seal, with no worries about changing the pinion depth. I also installed an Eaton truetrac to replace the OE open diff carrier. If you don't have a G80, you may want to look at a locker. The Eaton, is good on the street, but there are better choices for off road use.
Hey Kenny
I’m looking at diff’s and am not happy with the posi replacement from Eaton. I was looking at the grizzly cone style but I don’t find much information on how good they work. Do you know anything about them and this is for 400hp bbc in a 8’ box crew cab. I personally don’t know of anyone who has used 1
Thank You
 

Pro439

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My truck does the lock unlock thing at 50 mph. I don’t know if it’s because my engine is very tired or it needs to be changed in the computer. I don’t know anyone around here who can do that. And I have 4:10’s so changing the gears may only change where it does it. My truck originally had 3:73’s but I swapped to the 4:10’s as soon as I had the truck
 

kennythewelder

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Hey Kenny
I’m looking at diff’s and am not happy with the posi replacement from Eaton. I was looking at the grizzly cone style but I don’t find much information on how good they work. Do you know anything about them and this is for 400hp bbc in a 8’ box crew cab. I personally don’t know of anyone who has used 1
Thank You
Eaton, make several different carriers. I haven't looked at all, at grizzly. The 8 inch, 10 bolt gets a bad rapp. It all depends on how hard you are on it. If you are looking for something to do some serious off roading, yeah, you want a clutch style limited slip carrier. Also, as mentioned above, what ever you do to the rear differential, you have to do the same thing to the front, at least where gearing is concerned, anyway. And, you will need to flash the ECM, with the new gear ratios. This will effect shift points, somewhat. I looked hard, at the lunchbox lockers, before I got the truetrac. I'm always on the street, so the truetrac was perfect for me. Keep in mind that limited slip, is what you want, not positive traction. Limited slip, will let you turn corners without dragging the outside tire, around the turns. Positive traction, is always engaged, so you will drag the outside tire as you turn. You can weld the spider gears, and achieve this effect, or install a locking spool. Only good for straight line driving, EG, drag racing only.
 

Pro439

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Yeah the spools and welded gears are definitely not the answer for the street. I was thinking that the cone style would lock up when you get it where as the posi doesn’t unless it’s really greasy and I know the newer posi have a governor
 
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