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Discussion Starter · #1 ·
Im having my 283 rebuilt and while its in the shop im considering having the stock gear ratio changed. It has a 3.36 but i would like to go much lower if i could. How low of a ratio could i get? I refuse to change out the powerglide, and it sees a good amount of highway use so those RPMS are killing me. And how much would it cost?
 

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A 200-4R with 0.67 4th gear will cut your rpms down as if you had a 2.25 rear gear. A 700-R4 with a 0.70 4th gear will cut your rpms down as if you had a 2.35 rear gear ratio. A ratio of 3.08 could be alright but if you numerically lower the rear gear ratio too much you could have troubles. Do you know your 283 power ban? If you get that from who is building your motor a trans shop could match a trans to the motor. You could buy a 700r4 from Summit Racing but here are some trans people to call and discuss your situation with. Check out your options :anim_25:


http://www.monstertransmission.com/

https://www.gearvendors.com/hrgm3s.html
 

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Discussion Starter · #5 ·
O yea, the transmissions wpuld be much better but, i just wont let go of the iron glide. It was rebuilt right before i got the car so its pretty new. I have no idea about the powerbamd, but im having the engine rebuilt right now so itll be fresh as can be
 

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How much wpuld that be? And would that fit an iron glide?
Any Gear Vendor over drive unit i looked at for a turbo 350 or a turbo 400 was twice the amount you can buy a 700R4 for. Not sure if they make them for a power glide though....

Gear Vendors Overdrive if you can afford it.Best of both worlds .
:sign0020: if you can afford it :sign0020:
 

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But, getting back to the original post, how low of a ratio can a stock rear end go? Is 3.08 the limit?
3.08 is higher than 3.36 Lower would be 4.11 or 4.56 You must want higher gears.
Factory was 3.36 for autos and 3.70 for manual, unless you ordered 4.11 or 4.56.
Not sure what gear sets are available for stock housing, or if you want to swap the whole differential unit. 3.08 is pretty common, but they make higher - my Vette has a 2.87 rear - and still gets 13 MPG.
 

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Discussion Starter · #14 ·
O yea i forgot the naming convention, yea id like a higher gear like a 2.76 or something. Ill go as far as the stock differential will let me. Only 13 mpg? What else do you have in your car?
 

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You might want to call someone like Yukon Gear https://www.yukongear.com/ and see if they have a distributor near you that can rebuild your center section with the appropriate gear. Or Quick Performance a sponsor on here. http://www.quickperformance.com/
You don't want to go too high because the car will lug off the line. You want to be able to pull onto a street with the ability to get up to speed. The problem with the 2 speed power glide is it is not versatile in a daily driver. They can be set up for racing but I'm not sure you'll be happy with it and a real high rear gear. Simply put a 2 speed transmission is not set up for highway driving.
 

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Ive got a 308 center section. That's the tallest gear ive ever seen for the 55 thru 64 rearends. You can install taller (larger diameter) tires and increase speed and drop RPM. My dad bought a new 64 chevy Pk. 283 three speed and it had 410 gears. He put really tall 16 inch rims & tires on the rear. He traveled back and forth between Indiana and Arkansas a lot back then. Made the speedometer off by about 10 MPH. He got a few tickets in Ill back then because of it. The car speed limit on I 57 was 70 and trucks 60. and they would give a PK truck a ticket for going above 60 MPH. Dad would be going less than 60 by the speedometer and was still speeding.:sign0020:
 

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I'll suggest a G body differential. Some of those had like 2.76 gears in them. They're 58" wide which makes it a little easier to put on 8" rims. Those would be out of mid-80's cars like Monte Carlos, Cutlass and Regals.
You'd need to weld on spring perches.
Bad thing would be your low end power. These cars are heavy and even a 3.08 will be a dog without a low 1st.
Ultimately, take your lumps on the powerglide and get a 200R4 or 700R4 and leave the differential alone. Low 1st and overdrive, solves all problems.
 
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