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Old 05-21-2009, 06:25 PM
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Changing My Rear End gears ...chevy truck

Hi I just got 1972 C20 Chevy and it has a 250 Ci V6 with a 4 speed manual transmision and 4.11 rear end gearing. I was going about 65 on the interstate and was almost redlineing it and as wondering what ratio of rear end gearing would I need to get alot more speed I am probably going to put a 350 V8 in it. Thanks
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Old 05-21-2009, 08:23 PM
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Quote:
Originally Posted by bosco200
Hi I just got 1972 C20 Chevy and it has a 250 Ci V6 with a 4 speed manual transmision and 4.11 rear end gearing. I was going about 65 on the interstate and was almost redlineing it and as wondering what ratio of rear end gearing would I need to get alot more speed I am probably going to put a 350 V8 in it. Thanks
3.07 gear is good for freeway cruising & MPG, 3.55 is good all around gear, towing etc...
BTW there's tons of good Info here. > http://67-72chevytrucks.com/vboard/forumdisplay.php?f=3

Quick links here. > http://67-72chevytrucks.com/vboard/f...splay.php?f=92

Last edited by SSedan64; 05-21-2009 at 08:46 PM.
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Old 05-23-2009, 03:02 PM
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Just a thought.....

My bro -inlaw had a 69 Chevy Truck same type as yours and It had a 283 engine with same rear end as yours and he claims it liked the high rpms
and ran like a Champ (Burnrubber and Fast)
without using alot of fuel
What is your fuel mileage now and you can put dual exhaust and headers on the 250-6 engine if u dont have already
or put a 700r4 Tranny in it and overdrive will drop down some of your rpms
Or put tall tires on it

Last edited by BigDawgsEatFirst; 05-23-2009 at 03:08 PM. Reason: add more to post
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Old 05-23-2009, 03:09 PM
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Straight 6 or v6

Do u have a str 6 or V6 ?????
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Old 05-23-2009, 03:40 PM
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Quote:
Originally Posted by bosco200
Hi I just got 1972 C20 Chevy and it has a 250 Ci V6 with a 4 speed manual transmision and 4.11 rear end gearing.
That 4.11 gear would have that 250 straight 6 humming pretty good! I only mention this because in case you need parts, the parts counter guy isn't confused.

BTW, the Chevy V6's (90 degree-type) are the '78-'79 3.3L 200 cid (3/4 of a 267), the '80-'84 3.8L 229 cid (3/4 of a 305) and the '85-up 4.3L 262 cid (3/4 of a 350). As I type this, I thought there were years that overlapped, but I guess not- at least not by the Wiki info I'm looking at...
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Old 05-23-2009, 03:48 PM
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I had a straight 6 in a Nova

I had a 1973 Nova and It liked the hi rpm
The 250 str 6 is a good motor
IMO
I was 18 and could not kill it
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Old 05-23-2009, 05:44 PM
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the engines in these era of trucks were known as the hi-torque as per GM information.

car version engines were turbo-fire

they had lots of low end torque but low horsepower ratings.

they need the higher RPM to put out said torque, to perform the truck duties.

if yours has a leaf spring rear suspension(G70 on the RPo sticker in the glovebox) then you could fit a 3.31 ratio axle under it if you can find one.... 3.31 ratio started in 1969 and carried over from the old eaton HO52 and HO72 axles to the 14 bolts in 73.

these had the same 42" spring pack distance since '63 or '64. the only difference is the shock mounts changed to staggered in '73..
unlike '72-older where they were both on the same side of the axle tubes,.


3.31 is the least common 3/4 and 1 ton ratio however

3.73 and 4.10 were the most common.

another option would be to go with a 2004r or 700r4 trans, but would be more difficult to convert from the 465 trans, than most others, and certainly more difficult than swapping axles if its leaf type rear

good luck!
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Old 05-24-2009, 10:38 AM
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Well I just need a gearing to where I get more speed.
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Old 05-24-2009, 10:43 AM
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Quote:
Originally Posted by bosco200
Well I just need a gearing to where I get more speed.
Until you get different gears, put the tallest tires on it that'll safely fit. That will help- some.
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Old 05-24-2009, 10:53 PM
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So what have u got from the advice
Speed limit is 60 in most places anyway
If ur going 60-65 ,and thats too slow for someone else then they will pass u
plus if it starts,steers and stops leave it alone
Putting a highway friendly gear in it will kill your city driving MPG and Peppy ness
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Old 06-28-2009, 04:30 PM
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1972 C20 Transmision or Rearend gearing?

I have a 1972 C20 and I have 4.11 geairng in my rear end and the transmision is a 4 speed manual and the numbers are CH465. When I go on the interstate I go 65 and I am redling my truck already and was wondering if I would have to change the transmision gearing or the rear end gearing? It has a straight 6 in it but I have going to put a 350 V8 in it.
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Old 06-28-2009, 05:03 PM
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Quote:
Originally Posted by bosco200
I have a 1972 C20 and I have 4.11 geairng in my rear end and the transmision is a 4 speed manual and the numbers are CH465. When I go on the interstate I go 65 and I am redling my truck already and was wondering if I would have to change the transmision gearing or the rear end gearing? It has a straight 6 in it but I have going to put a 350 V8 in it.
4th gear will always be 1 to 1 ratio in that trans, so nothing you can change with that.

Just change the gear ratio in the Differential.
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Old 06-28-2009, 05:06 PM
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Is changing the rear end hard.
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Old 06-28-2009, 06:20 PM
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Bosco200

I merged your threads since you have asked the same basic question twice
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Old 06-28-2009, 07:37 PM
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Swap the whole rearend, then when you do your V8 swap and put an overdrive in it you can put the original rearend back in. This would probably be easier/cheaper than setting up the rear with a new ring and pinion. A 3.07 rear shouldn't be hard to find especially if your truck has leaf springs.
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