Axle ratio 2.56 to 3.73 - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #1 of 32 (permalink) Old Mar 24th, 20, 3:26 PM Thread Starter
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Axle ratio 2.56 to 3.73

Hi all,

I already know that if i want to change my 10 bolt 8.5" from 2.56 to 3.55 or 3.73 i need a series 3 carrier instead of my current series 2 carrier.

My question... does the 3 series fit in my diff housing?
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post #2 of 32 (permalink) Old Mar 24th, 20, 3:33 PM
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Re: Axle ratio 2.56 to 3.73

Yes.
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post #3 of 32 (permalink) Old Mar 24th, 20, 4:23 PM Thread Starter
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Yes.
Do i need to modify anything with spacers or will it just fit in
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post #4 of 32 (permalink) Old Mar 24th, 20, 6:21 PM
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Re: Axle ratio 2.56 to 3.73

You will need the pinion and differential shims to set the pinion depth, bearing preload and backlash, but if you use a 3 series differential you will not need any other spacers.


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post #5 of 32 (permalink) Old Mar 25th, 20, 5:54 AM Thread Starter
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Ok i think i understand. But to be more sure.
What is exactly a carrier
What is exactly a differential


I would like to sketch a scenario.
My car has the 10 bolt 8.5" with carrier type 2 and 2.56 ratio.

If i find any gm axle 10 bolt 8.5" maybe from 1977 or so with a carrier 3 and 3.73 ratio can i take out the guts of this axle and put it in my axle?
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post #6 of 32 (permalink) Old Mar 25th, 20, 6:41 AM
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Freddie
 
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Re: Axle ratio 2.56 to 3.73

Yes. Just be sure that it has the same axle splines as what you have now. You have 28 spline axles. In '89 or '90 the 8.5 rear ends were upgraded to 30 spline axles.

The carrier and differential are the same thing. I don't understand why it's called a carrier. I guess because the ring gear bolts to it, but it's actually a differential.


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post #7 of 32 (permalink) Old Mar 25th, 20, 7:45 AM Thread Starter
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Yes. Just be sure that it has the same axle splines as what you have now. You have 28 spline axles. In '89 or '90 the 8.5 rear ends were upgraded to 30 spline axles.

The carrier and differential are the same thing. I don't understand why it's called a carrier. I guess because the ring gear bolts to it, but it's actually a differential.
Oke I see, and my 28 spline shafts will not fit a series 3 carrier for a 30 spline.

Perfect
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post #8 of 32 (permalink) Old Mar 25th, 20, 10:44 AM
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Re: Axle ratio 2.56 to 3.73

You can also change the first gear ratios to something lower.. The 2.56 with a 1:1 high gear is an excellent highway combo.. I like it better then overdrive since the driveshaft isn't spinning so fast..
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post #9 of 32 (permalink) Old Mar 25th, 20, 11:57 AM Thread Starter
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You can also change the first gear ratios to something lower.. The 2.56 with a 1:1 high gear is an excellent highway combo.. I like it better then overdrive since the driveshaft isn't spinning so fast..
Last year i put in a 700r4 with lockup iy runs around 2000rpm or so at 65 mph.

Since this year in the netherlands the max speed went down to 55mph.

And i like to gain some pulling force in stead of fuel economy.
I run a 400sbc with minor upgrades. I think max 250hp or so
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post #10 of 32 (permalink) Old Mar 25th, 20, 1:12 PM
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Re: Axle ratio 2.56 to 3.73

Quote:
Originally Posted by Bart Fransen View Post
Ok i think i understand. But to be more sure.
What is exactly a carrier
What is exactly a differential


I would like to sketch a scenario.
My car has the 10 bolt 8.5" with carrier type 2 and 2.56 ratio.

If i find any gm axle 10 bolt 8.5" maybe from 1977 or so with a carrier 3 and 3.73 ratio can i take out the guts of this axle and put it in my axle?
I mean this in the nicest way possible: are you having a professional do this?

I ask b/c you don't just pull one set of gears out and then put a new set in. There is a LOT more work/time involved.....and professionals are way better at it then shade tree mechanics.
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post #11 of 32 (permalink) Old Mar 25th, 20, 1:33 PM Thread Starter
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Quote:
Originally Posted by Bart Fransen View Post
Ok i think i understand. But to be more sure.
What is exactly a carrier
What is exactly a differential


I would like to sketch a scenario.
My car has the 10 bolt 8.5" with carrier type 2 and 2.56 ratio

If i find any gm axle 10 bolt 8.5" maybe from 1977 or so with a carrier 3 and 3.73 ratio can i take out the guts of this axle and put it in my axle?
I mean this in the nicest way possible: are you having a professional do this?

I ask b/c you don't just pull one set of gears out and then put a new set in. There is a LOT more work/time involved.....and professionals are way better at it then shade tree mechanics.
I really appriciate you tell me this before it would have give it a go.

However indeed a specialist would do this job and not myself.

The specialist i talked with, already had doubts about second hand parts.

Whats are your opinions regarding second hand parts swapping
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post #12 of 32 (permalink) Old Mar 25th, 20, 2:28 PM
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Re: Axle ratio 2.56 to 3.73

It's much more difficult to set up a used set of gears than it is a new set. Used gears don't give a clear contact pattern and it's very hard to tell when you have the pinion depth set correctly. New gears are much easier to read. A used differential is not as much of a problem, and if it's in good condition then there isn't any problem with using one. Bearings should always be replaced.
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post #13 of 32 (permalink) Old Mar 25th, 20, 2:31 PM
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Re: Axle ratio 2.56 to 3.73

I buy the best, NEW, hecho en USA, rear-end parts that I can afford...and then let a pro do it.

Other than wanting everything in the rear end to work right, you want to avoid having the gears whine.

What you're up against is that the potential cost savings from saving used parts is much, much less than having to go back to a pro should this rear end fail....and then buy more used/new parts.

You also don't know how many miles are on used rear end parts and what kind of life they led.
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'69 Malibu 383/TCI TH350/8.2 3.36 Eaton Posi. Street Edge 10" 2800, E-Tec 170s, Custom Mike Jones HR Cam, RPM Air-Gap, StreetAvenger 770, Pertronix HEI, Hedman 1 5/8" Headers, Moser Axles, PMT 1320R Kit. [email protected] 111 MPH, 1.6865 60 ft, Nitto 555
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post #14 of 32 (permalink) Old Mar 25th, 20, 3:23 PM
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I just had my 12 bolt done they removed the 4.33 and installed US Gear pinion and gear 3.73 also new axles and bearings thruout better safe than sorry buying new and not having to do again next season
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post #15 of 32 (permalink) Old Mar 27th, 20, 7:52 AM
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Re: Axle ratio 2.56 to 3.73

Quote:
Originally Posted by Bart Fransen View Post
Hi all,

I already know that if i want to change my 10 bolt 8.5" from 2.56 to 3.55 or 3.73 i need a series 3 carrier instead of my current series 2 carrier.

My question... does the 3 series fit in my diff housing?
They also sell a thick ring gear set, that allows you to mount 3 series gears on a 2 series carrier. They sell a spacer as well, but those aren't really that durable.
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