Rearend Gear for my 71 LWB

[big.l.a]

I am currently run 3.07 single peeler on
my 71 C10 350; with a 350 3 speed tranny.I just purchased a Gov-Loc Posi of ebay. I was
told gear range was 2.73-3.42 or I could get a Thick 3.73 or I could run the current 3.07 I have in now. What gear will give the
best mileage and performance for my truck?Also got some 186 heads (202 1:6) what's the best valves and spring should I get. I am running the stock cam for now. Though I would
wait until it's time to rebuild the engine to can out the cam. She's run very well now
so it may be years to come unless I feel the need for more power again.

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71 C10 LWB
79 Monte C

[Fast68Chevy]

well its hard to have performance and mileage both, you ll have to find middle ground, IMO 3.40 to 4.11 is middle ground, 4.11 is pretty high rpm at 65 mph, and 3.40 isnt so bad, randysring and pinion.com has an rmp calculator to determine engine rpm at certain speed with certain tranny and certain tire height, all three affect rpm, 3,000 and over is pretty fast for running constantly on long trips, so you owuld want to choose tires and tranny and axle ratio to keep you below that unless you wont take it on freeway much

29.5" tires(237/75/15") and 3 speed auto or manual tranny and 3.73 gears run you right about 2850rpm in which i think is good and and isnt working engine hard IE it doesnt seem to resist running at that rpm down the road, but more rpm sucks more fuel than lower does on a trip, but makes you launch alot quicker than say 3.08 or 3.27 or 3.36, etc etc, but 3.08 or 3.76 is harder ot get going with, and you need more pedal action to get it going off a dead stop, IE more fuel. so bad on gas in town, but not on highway

thick ring gear is a cheap trick and is not as strong as thin due to longer retaining bolts needed, and lower gear ratio sets are weaker than higher ratio sets due to less tooth contact between gears of lower ratios because of smaller diameter pinion gear head.
3.40 and numerically lower sets have alot larger ring gear, the gears are closer to same size and stronger due to more teeth intermesh contact area, truck 12 bolt are weaker anywas due to smaller diameter pinon gear stem, compared to most all other axles of all manufacturers and models, even of GM

all just my $.02

tradeoffs tradeoffs

I like 67-69 Z28 302 and 350 valve springs and unbrella type valve stem seals, those springs will handle a pretty good lobe lift

good luck


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Randy- Lincoln, IL
217 735 3230
r68c30@hotmail.com
-71 C-10 350/CH465/3.07, assemble it, yeah right, that'll happen in this world,(not)
-84 Z28 Camaro 5.0L 700R4, 3.73, beater, paid way too much for it like an idiot,,
-84 Firebird SE 2.8L T-5, rod knocking, dammit,,
-82 Firebird 350 4bolt (TBL)/TH350, not running, dammit...
buy/sell/hoard/trade most any GM vehicle parts of any kind
-parting out: '81 Cutlass Supreme Brougham
*Paint is overrated
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[This message has been edited by Fast68Chevy (edited April 18, 2002).]