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Diff gear ratio suggestions

davo727 said:
Hey midniteplowboyy: I didnt even know they made 3.21 sets for a 14 bolt full floater, So I just looked it up on randys ring and pinion. U got a high speed cruiser there!
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Hmnn how much pulling power loss 3:21, my burb is a people mover not load mover, but occasionally pull a light trailer with it, looks like me & Randy are gonna have a chat, so Veg there may be a 3;42 set available soon.
 
midniteplowboyy said:
3.73's or 3.42's would work for what your doing.

This is what I suggest for cruising speeds in OD,
70mph-3.21's
65mph-3.42's
60mph-3.73's
55mph-4.10's
keeping the engine in its sweet spot.
For highway towing I like the 4.10's, then the 3.42's. For back road cruising I like the 3.73's. For highway cruising I love my 3.21's.

For best milage, if you drive 65mph, I'd put the factory size tire back on and some 3.42's.

Where is Overton? I'm up by Texarkana.
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Overton is south of Longview and east of Tyler. Take 59 south to I20, then go west to the Liberty City/FM3053 exit. Head south 16 miles and you'll be in beautiful downtown Overton, pop 2310.

Thanks for the cruise info. Sounds like the 'sweet spot' for the 6.5 is around 2100rpm. That's sure better/quieter than the 2700 I see now at 70mph! I had never considered anything lower than 3.73, because of the weight of my truck. Which gear ratio are you using in your dually? How has it affected mpg and acceleration? I'd like to get as close to 18mpg as possible, but "I don't want to create a slug that can't get out of its own way.
 
Turbine Doc said:
with ATT my sweet spot is closer to 2300 rpm which is knocking on door of 20 mpg & 3:73
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That sounds mighty attractive! I might hafta reorganize my priorities and apply the No-Slip diff $$$ towards an ATT! ):h

I realize that your results won't directly transfer over to my setup - I've probably got easily 1000# on you. Even so, it's still be worth trying. I think the first step will be to change out the gear set over Christmas and see what effect that has.

The No-Slip unit was the one I first looked at and liked the most. Part #92-0705-3000 fits the 10.5" corporate axle. After reading your writeup, I figured that was the best choice.
 
Dave Barbieri said:
Sounds like the 'sweet spot' for the 6.5 is around 2100rpm. That's sure better/quieter than the 2700 I see now at 70mph! I had never considered anything lower than 3.73, because of the weight of my truck. Which gear ratio are you using in your dually? How has it affected mpg and acceleration? I'd like to get as close to 18mpg as possible, but "I don't want to create a slug that can't get out of its own way.
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I think the sweet spot is closer to 1700-1800rpm.

Well, my 93 is far from stock, so its hard to say, but I dont regret the switch. It still accelerates pretty good, even though I'm wasting some power through the two speed(thinking about taking it off, never needed it), plus the added rotational weight of the 22's(atleast 350lbs)(same height as a your 235/85's) and my truck prolly weighs atleast 750lbs more than yours.

It hurt accelleration to about 10mph, after that I dont notice it, its by far my quickest 6.5 truck, though my other two are closer to stock, my D-max is not much quicker.

The 93 gets around 15mpg driving locally 30 miles to work(usually running late), but I dont baby it at all, usually run 75-80(when traffic permits) and hit 85-90 on a daily basis(passing ect.) and jackrabbit starts. I dont have an accurate highway mpg yet under decent driving conditions.

I plan on taking it on a road trip this Thanksgiving, so I may have you some mpg's figures next week.

I need to get my IP timed, its just set line to line right now(DB2), I think its retarded or the advance is not working right, as the EGT's get hot quicker and builds boost alot easier than the old pump. Any one know what the timing specs are for a 92-93 db2, @idle and say 3krpm to check advance, I bought a timing light but havent played with it yet.

For your truck, I recomend 3.42's and stock size tires for best mpg's for the way you drive, next I would suggest 3.73's and 235/85's(like you have).

My 92 has 3.42's, but its a 5sp, it gets 18-20mpg's running around here local and 22 highway, I have put over 700 miles on a tank several times highway driving.
 
Turbine Doc said:
Hmnn how much pulling power loss 3:21, my burb is a people mover not load mover, but occasionally pull a light trailer with it, looks like me & Randy are gonna have a chat, so Veg there may be a 3;42 set available soon.
Click to expand...

I'll need front's and rear! Thanks. I wonder if I'll need to reflash my Heath tune for the 3.42's?

Can I have them installed tomorrow? Big road trip for Thanksgiving.
 
Veg_Out said:
I'll need front's and rear! Thanks. I wonder if I'll need to reflash my Heath tune for the 3.42's?
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Nope, just recalibrate your VSSB/DRAC or what ever you call it.

The PCM will just think your truck is loaded heavier than before, its no wiser to the gear change, It just sees X output shaft speed vs throttle position, not that the tires are turning 30% faster than before.
 
Veg_Out said:
Tim,

That does get me half way there. If you end up with a spare rear set of 3.42's, perhaps we can make a deal. Then I'll only have to chase the fronts.

Thanks.
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What rear diff do you have,9.5" or 10.5 14bolt? I think Tim was trying to tell you his was a 9.5" and is asuming yours is a heavy duty 2500 with a 10.5" diff.

Look at where the pinion shaft goes into the diff housing, if there is six bolts surrounding the pinion behind the driveshaft yoke, it is a 10.5" ring gear. The 9.5" has no bolts in that area.
 
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