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Old 07-21-2017, 06:28 AM
AugustDiesel AugustDiesel is offline
Join Date: Jul 2014
Location: Jacksonville, FL
Posts: 74
Default Down the Road Planning: Gearing and Exhaust Options

Seems like I'm flooding the board with different posts, to which I apologize, just have a lot to figure out and figure maybe I'll help some others in the process. Fortunately this post is more for a future state planning, so here goes...

Picked up a Dana 60 front end last night to ultimately replace my blown up 10 bolt once the 60 is rebuilt. It's geared to 3.54 and my 14 bolt is geared to 4.10. My question is which axle should be regeared? See my signature, I have a 6.5L NA, 700R4, and 305/75R16s. I'd like to find the happy medium between fuel economy and towing capability.

Then, I need to do something about my exhaust. PO put in a hacked up single 4" pipe all the way back, no muffler. This thing is LOUD. Too loud for hauling family on road trips. I'd like to quiet it down but still maintain a high flow for performance. Should I go back to dual exhaust? Maintain single exhaust? What mufflers would you recommend?

One step at a time ...
1988 K10 Suburban. 6.5L NA Goodwrench Engine: 506 block cast on August 12, 1996. Heavy Duty built 700R4. Full-floating 14 bolt rear axle. 3/4ton 10 bolt front. Brand new 305/75R16 Procomp AT Sport tires on brand new 16x8 steel wheels.
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Old 07-21-2017, 08:19 AM
Yukon6.2 Yukon6.2 is online now
Join Date: Dec 2003
Location: Yukon Canada
Posts: 949

Hi August
You will have to get the matching rear differential.
The Dana 60 will have 8 lug wheels where your existing rear diff will have 6 hole wheels.
No sense having a uber tough front diff and a weak little rear diff.
Sorry just read your sig and seen you had changed your rear already.I was faced with a similar decision,my sig truck has 4:10's and is slow,i have since picked up a set of diffs with 3:73 i believe.I was going to swap diffs,but now have a Gearvendors overdrive so i might go with the Gearvendor instead.
You have a bit of an overdrive with the 700,my choice would be to regear the rear unless you plan on towing a lot.
90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews
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Old 07-21-2017, 09:12 AM
DmaxMaverick's Avatar
DmaxMaverick DmaxMaverick is offline
Join Date: Apr 2001
Location: CA
Posts: 11,882

3.54 is too tall for a N/A engine and tall tires. I recommend 4.10+ for any tire over 33" (yours are ~34"), especially for the 700R4, even if "heavy duty built". The 700 has a low enough 1st gear, but the upshifts will be too tall, and OD will fall flat on all but the tamest highway (downhill). 4.10 gearing with your tires will allow a ratio similar to 32" (stock-width) tires with 3.73 gears, which is near ideal for your rig without a turbo. Your axles and tires have quite a bit more rotational mass than stock, which really saps power past the edge of marginal with near-stock gears.

Straight-piped N/A's are really loud. Louder than their gasser counterparts. A 4" chambered muffler will go a long way to tame the noise, while retaining the throaty sound tone and minimize drone (make sure the tail pipe exits outside the body). If going to a dual, you'll need 2.5" pipes to retain the cross-sectional flow area of the 4", and a tuned crossover (H pipe) will promote scavenging, as well as tame droning.
1985 Blazer 6.2
2001 GMC 2500HD D/A
2014 Chevy Cruze Diesel - Fabulous car, no problems at all, but sold Nov. 2016 @ 55K miles.
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Old 07-24-2017, 06:16 AM
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arveetek arveetek is offline
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Join Date: Oct 2001
Location: Granby, Missouri, USA
Posts: 2,642

I had a built 6.2L turbo with a 700R4, 4.10 gears, and 31" (245/75R16) tires in my old C20, and loved that combo. I would recommend at least 4.10's, if not lower, for your larger tires.

1995 K1500 Tahoe 2 door, 6.5LTD, NP241, 4L80E, 3.42's, 285/75R16 BFG K02's, Kennedy OPS harness, gauges, and TD-Max chip, Dtech FSD on FSD Cooler, vacuum pump deleted, Turbo Master, 3.5" Kennedy exhaust, F code intake, '97 air box, dual t/stats, HO water pump, Racor fuel filter, 330K miles and running strong!
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