Rear end conversion question

[Kaptain Kadian]

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.

[Eddie H.]

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.

[Kaptain Kadian]

Do you have a brand you have had success with?

[Norcal72]

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.

[70CHEVYBB]

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

[Mike C]

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.

[Custom/Ten]

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.

[Longhorn 70]

Why not use an overdrive? 200 4R or Richmond would let you have take off and cruise.

[CST10]

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.

[67 cst swb]

Originally Posted by 70CHEVYBB

Buy a tach or pull the diff cover and see what gear you have. Then make some dicisions.

I agree.. who knows you may be having a trans issue. Such as its not shifting into drive. So, example being, if you're still in second gear, even with 3.08's your motor will be screaming at 65 mph.
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.

[Eddie H.]

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.

[GASoline71]

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

[Kaptain Kadian]

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.

[EARNHARDT#3]

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.