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10 bolt rear end


ChrisM

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So I know this question has been asked I am sure.

 

I have the 10 bolt open diff I'm my 70 MC, and what I am wondering, is there anything out there that will give me posi with still keeping a good street/highway car.

 

Or am I into finding another diff?

 

Parts here in Ontario are somewhat difficult to come by and shipping/buying from the states right now is sort of pricey.

 

Any ideas or info is much appreciated!

 

Thanks, Chris

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Hey Chris,

 

A few questions to ask yourself?

 

- What gears are in it now?

- What do you consider a good gear for a street/highway car?

- Do you have a Chevy or BOP rear?

 

Most folks will say a "2" series gear ratio is for highway driving but it really depends on what engine you have and what RPM range you like to run.

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No idea what gears are in it now, how could I tell?

 

To be honest I am not sure what gears, I always hear 3.73's are usually a good gear

 

In terms of bop or Chevy, how do I find that out?

 

The motor I am running, is a 396 bored 30 over, so 402, as far as rpm, I'll have to wait for it to get on the engine Dyno.

 

I need some education, what is a 2 series gear?

 

Thanks mike

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2 series is a 2.56 up to a 2.73 (a lot of the montes had 2.73). A 3 series is 3.08-3.73 (if it's a stock carrier 3.73 is the max on it, aftermarket carrier might support 4.10). 4 series 4.10- 4.56. If you want to keep the gear ratio u have now look into a powertrax unit, it replaces the spider gears in the carrier. My 70 was a peg leg 2.73 but I added the powertrax and kept the 2.73. Car moves good with my 402 and the 700r4 trans.

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There is two ways one is the sufix code on the rear end it self, but if someone has made any changes to the car the best way is to count how many times the rear tire turns  divided by the drive shaft (or pinon yoke if there is no drive shaft). You can also pull the rear cover and count the teeth on both the ring and pinon and divide that. Some times the ring or the pinon will have the number of teeth stamp on them.

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I used an auburn gear locking unit with 3.73 gears in my 10 bolt. I don't know about all that carrier stuff because my stock unit was the 2.73 and I made the conversion without any issues. I am also running a 200-4R automatic, which is why I selected the 3.73 ratio. If you have a th350 you may want to consider a different gear to make the car more streetable.

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So it looks like I have the 8.2 inch 10 bolt with the 11 inch cover. The motor I am running is a big block 396 bored 30 over (402) with a th350.

 

The engine has a very mild cam and hats about all that's done to it. Other then just up grading push rods, lifters and rockers.

 

What are the options for using this rear end housing but different gear? Who has this style, what's your drive line setup and gear setup?

 

Thanks everyone

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The question is, what kind of driving are you planning to do primarily? That will determine which gear ratio will be best for you. If you are planning on highway cruising a 3.08 would be a good choice. If you plan on hitting the strip now and again you would likely want at least a 3.73. Since you are running a TH350 behind a 396 you may want to consider the 3.08's if you want to drive the car any distance on the highway. The 3.55's may be a better choice for around town red light to red light cruising...... The point is you should choose a gear based on how you plan to drive the car. Just my .02

 

I should answer your question. I have a mild 350/265-ish hp, a TH200-4R lockup trans, and 3.73 gears. My goal is 20+ mpg at 70+ mph..... I am really close. Looking back, I should have chosen the 3.55's... I would be well over 20mpg with that set up.

 

Yes, its a 8.2" 10 bolt as well.

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Well cbolt I appreciate the input!!!

 

I for sure will be cruising to different meet spots, and once in a while take it up north with me, so I think with all your info, 3.55 will probably give me the fun I want but also the ability to hit the highway an cruise!

 

My next question, is who do you guys buy through for these parts, I am not to sure of a place in Ontario that deals with diff gears. I will do my research for sure though!

 

Thanks a lot

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I got most of my stuff through JEGS, but Summit is good as well. I don't know how easy either place is to deal with from Canada though.

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Thanks guys, yea it's not to bad really it's just the dollar right now that makes it difficult.

 

Also making sure I get the right stuff so I don't have to ship something back lol.

 

Thanks for the input everyone, when I get to that step I'll let you know how it goes!

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  • 2 months later...

Not to hijack a thread but it is a rear end question.

I found a '69 Chevelle 10-bolt with 3.07(?) gears in it. Can I get 3.55 or 3.73 gears into this carrier?

From what I've read, I'd say 'yes', but I'd like to verify.

 

I have a 12 bolt with 2.73 gears. To my understanding, I can't change to any 3.xx gears - correct?

 

Thanks.

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keep an aye on kajiji and I am sure there are gear and differential shops that have used sets that could further your information hunt that also sell and install because it sounds like you will not be doing the work..sot sure where you live..unless you are waaaay up north there are plenty of shops around

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...with 3.07(?) gears in it. Can I get 3.55 or 3.73 gears into this carrier?

 

I have a 12 bolt with 2.73 gears. To my understanding, I can't change to any 3.xx gears - correct?

 

 

 

  Droff,  both should work for you.

 

   The 3-series starts with 2.73's.  So, any 3.xx ratio is available for your carrier.  And likewise, any 3.xx ratio is available to swap for your 3.07.

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  Droff,  both should work for you.

 

   The 3-series starts with 2.73's.  So, any 3.xx ratio is available for your carrier.  And likewise, any 3.xx ratio is available to swap for your 3.07.

 

So my 12 bolt with the stock 2.73 gears can be changed over to 3.55 gears?

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  • 9 months later...

Ok so I have to ring this thread back to life haha.

 

I have found a 70 monte carlo 12 bolt rear end for sale near me in ontario. Question is, are the rear drum brakes the same from my 10 bolt to the new 12 bolt? Thanks

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  • 2 weeks later...

Sorry that no one has answered this. Yes the brakes will switch over. Hopefully you snagged that rear end and didn't wait for an answer. lol David

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