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Old 08-13-2020, 07:56 PM   #1
Woodnears
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Rear differential help please

I am asking for your help or basically telling me what I need to do to get the most out of this truck. 68 C10, currently has a 4.8 ls engine backed with a 4l60e. The rear axle is stock with 373 gears. I am running 22x9 wheels and Iím curious if I need to consider changing gear ratios but have no experience with this area.
Anyone else running a similar setup that could give some advice? Itís obviously not a speed demon but I do want a quality built rearend that will handle any future upgrades. Am I asking too much?
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Old 08-13-2020, 08:45 PM   #2
kwmech
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Re: Rear differential help please

I wouldn't bother with the 3.73s and the overdrive
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Old 08-13-2020, 08:50 PM   #3
Woodnears
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Re: Rear differential help please

It seems a little bogged down. What would you bother with?
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Old 08-13-2020, 08:58 PM   #4
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Re: Rear differential help please

What size tires are you running?
The 4.8 is no powerhouse, but you may need a good tune...did you run it on a chassis dyno after your swap?
The cost to swap gears isnt gonna be cheap, but 373s should be fine with a 4l60e..unless you have really tall tires
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Old 08-13-2020, 09:15 PM   #5
Woodnears
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Re: Rear differential help please

Tire and wheel combo are roughly 31Ē
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Old 08-13-2020, 09:22 PM   #6
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Re: Rear differential help please

You’re running about 2 grand at 70 mph.
Are you carbed or injected?
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Old 08-13-2020, 09:38 PM   #7
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Re: Rear differential help please

Heres a rpm calc to help you out...
http://www.csgnetwork.com/multirpmcalc.html

Your turning a little over 1800rpm at 65mph..with a 31in tire and a .7 od with 3.73s
I try to set mine up to turn 2k at 65mph..seems to be the sweet spot for me.
If you were starting from scratch I'd say 4.10s...since your already 3.73s I wouldnt waste the money to swap it
But your 3.73s should be fine if you have a good tune..
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Last edited by mongocanfly; 08-13-2020 at 09:43 PM.
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Old 08-13-2020, 11:33 PM   #8
Woodnears
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Re: Rear differential help please

Thanks for the calculator link, thatís handy. This rearend is leaking anyway and needs new seals, bearings, axle. The Way I see it needs rebuilt anyway. Is it worth going to limited slip?
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Old 08-14-2020, 08:40 AM   #9
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Re: Rear differential help please

In my book,It's always beneficial to add a locker...the Eaton trutrac is one of the best....
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Old 08-14-2020, 10:51 AM   #10
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Re: Rear differential help please

Trutrac is a great unit
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Old 08-14-2020, 06:20 PM   #11
Ziegelsteinfaust
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Re: Rear differential help please

On my 07 gmc with a 4.8 I ran 4.56, but if I had it to do over 4.11's or 4.33's would of been my choice. I had stock steel 17's though.

The 4.56's were not bad, and suited the truck well. Just ceuising over 75, a.d it was always wanting to down shift.
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Old 08-14-2020, 07:40 PM   #12
b454rat
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Re: Rear differential help please

Plus those wheels ain't helping any. I have 20s on my tundra and are HEAVY.
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Old 08-15-2020, 12:16 PM   #13
gmc684x4
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Re: Rear differential help please

Why such a tall tire on a c10 i can see taller tires on a k10 ?
C10 tire hits the range of 28.5 inchs tall usually
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Old 08-15-2020, 01:22 PM   #14
Woodnears
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Re: Rear differential help please

Hereís a pic of the truck! Think Iím gonna try a trutrac, Iíve heard a lot of good things about them.
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