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01-22-2015, 10:14 PM | #1 |
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Rear end conversion question
Hello guys, I have just finished my serp swap and am looking for my next project for my 70 c10. I have a 383 stroker in it and a th350 transmission in it. When I get up around 65 or so, the motor seems like is is about to explode from the rpms. I don't have a tach, so I don't know exactly how many rpms I am at, but seems really high. I don't know what rear end gears I have in my truck, and I am pretty sure it is not the original axel for the truck. My question is what would be a good gear ratio to go with? I don't do any towing in the truck and mostly cruise around in it. The next quest is where is a good place to get said gears? Thanks guys.
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01-22-2015, 10:30 PM | #2 |
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Re: Rear end conversion question
It sounds like you may have 3:73 or 4:11 gears. I have 3:08 ratio in my 69 with a TH400 and at 65 MPH it's turning around 2300 rpm. I usually buy my gear sets from JEGS because of the reasonable prices and free shipping.
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01-22-2015, 11:56 PM | #3 |
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Re: Rear end conversion question
Do you have a brand you have had success with?
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01-23-2015, 05:19 AM | #4 |
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Re: Rear end conversion question
Be prepared for a reduction in acceration. Switching from 4:11 to 3:08 is dramatic. Your truck will feel sluggish. No free lunch with gearing.
I have used Richmond gears successfully in 2 diffrent applications. Installation and setup of the gears is probably more critical than the brand. |
01-23-2015, 10:19 AM | #5 |
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Re: Rear end conversion question
Buy a tach or pull the diff cover and see what gear you have. Then make some dicisions. I just installed a rebuilt eaton posi with Richmond 3.73 gears. I have 295/50/15 tires on the rear the are 26.5 inches tall and a th400. 55 pmh is 2600 , 2850 is 60. If you go up 2 inches in tire dia it will put you at 59 mph at 2600 rpm
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01-23-2015, 10:45 AM | #6 |
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Re: Rear end conversion question
Rear end rebuild with all new parts about $750. Overdrive transmission about $1750 with a new driveshaft. And every bit of that extra $1000 worth it if you drive the truck all the time.
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01-23-2015, 10:58 AM | #7 |
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Re: Rear end conversion question
At richmondgear.com there is a gear ratio calculator. Its pretty awsome, type in your trans, and what rpm you want at a givin speed and it will tell you what rear end gear you need to get it. That's what I would check first.
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01-23-2015, 11:23 AM | #8 |
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Re: Rear end conversion question
Why not use an overdrive? 200 4R or Richmond would let you have take off and cruise.
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01-23-2015, 11:26 AM | #9 |
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Re: Rear end conversion question
I run 3.08 gears in my 70 with a BB 462, Turbo350 with lock up converter. Turn around 2200 RPMs at 55 mph, around 2600 at 65 mph. That's with a 26.5" tall tire.
Tire height will make a differance, but the best thing is to I stall an overdrive tranny. Best of low gears with your rear end (assuming you have 3.73 or 4.11) and better highway lower RPMs.
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MyToys: Goldilocks the "Ol School Survivor" 1968 C10, SWB Stepside, 08/15 TOTM, 250 CI 6 cylinder, 3 on the tree, 3.73 rear, 3/5 static drop, 23,500 original miles. Samson the 1970 CST10, LWB, 462Ci, Turbo 350 tranny, 3.08 rear gear, PB, PS, A/C, AM/FM, 2/4 Drop. Brutus the 1998 Camaro Z28, 33,500 original miles, LS1, 519 RWHP/497 RWTQ. Member of the Louisiana Classic Truck Club, LCTC Member of the Louisiana C10 Club Member of the Baton Rouge Drifters Car Club |
01-23-2015, 11:39 AM | #10 | |
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Re: Rear end conversion question
Quote:
I would check what gears you have first. All it will cost you is fluid, gasket and some time. Next add a tach... No need to spend money on a new rearend if you already have a gear that is useable. I run 3.73's in any truck I own.
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My Trucks: 1967 Chevrolet Short Wide Box 327 TH350 9" w/3.90 gears paint will be White - Current Project 1967 Chevrolet Custom LWB 283 TH400 3.73 Posi, no-AC, no-PS, no-PB, bench-seat, small-window - mostly orig driver 1967 Chevrolet CST LWB originally a 327 TH400 3.73 Posi AC PS PB, had Buddy Buckets, Small Window - parts truck 1967 Chevrolet CST LWB, 283 MT 3.73 had Buddy Buckets, Panoramic Window - parts truck 2001 Chevrolet 3500 2WD Crew Cab Dually 8.1L Allison White |
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01-23-2015, 12:18 PM | #11 |
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Re: Rear end conversion question
I agree with all the above comments. Especially the ones about finding out what gears you actually have first. One thing to consider if you are thinking about going to an overdrive is how much power your 383 is putting down. A stock 200r4 or 7004R may not live very long behind a strong stroker, and it can be pretty expensive to upgrade them to take the extra torque.
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01-23-2015, 01:30 PM | #12 | ||
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Re: Rear end conversion question
A small block Chevy even in stock form can spin to 4,500 RPM's safely. You aren't going to hurt the engine. Just your wallet as it eats gas at those RPM's.
Most people nowadays are used to low RPM overdrive and fuel injected rigs. It was very common back when these trucks were built to cruise at 3,000 plus RPM's on the highway. Gary
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01-23-2015, 01:52 PM | #13 |
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Re: Rear end conversion question
Thank you all for the replies. I was an idiot, and didn't check what gears where in the rear end when I changed the gasket on it a few months back. I guess that will be my next step. I always seem to do things twice on that old truck.
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01-23-2015, 01:53 PM | #14 |
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Re: Rear end conversion question
My 250 always sounded like it was revving very high on the highway. Then I got a tach and realized my old truck is noisier compared to newer vehicles and only sounds like it's revving high.
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