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Discussion Starter · #1 ·
I would like to change the rear end and transmission on my 57 Bel air Hardtop. I want to put in a 5 speed transmission and want to change the rear end from a non-posi to a posi 373. Can anyone suggest what rear end from what year and make of gm car will be a good fit without a lot of modifications. I have found that Tremmic Transmission makes a 5 speed for the specs I need but the rear end I have is terrible and needs changing. I am also looking to change the bucket seats that I have as well. What year and make car seats could I use to put in my 57? I am looking to find seats that will be comfortable, but not with a tall seat back. Right now I have bucket seats from a Chevy pickup truck, they are electric, comfortable but too tall. Some one told me to look at Cadillac seats... Any suggestions?
 

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To get a meaningful answer I think you need to state the particulars on your engine and also what you want to achieve with your transmission and rear change. IE, what type of driving do you do with the car.
 

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Discussion Starter · #3 ·
Tranny and rear end question

Thank you for your reply. I have a small block 350 with an Edelbrock performance package. I want to put in a posi and the transmission change is to be able to drive on the highway with lower rpms.
 

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Thank you for your reply. I have a small block 350 with an Edelbrock performance package. I want to put in a posi and the transmission change is to be able to drive on the highway with lower rpms.
That helps.
One more question.
Which 5-speed transmission do you have your eye on?
 

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Discussion Starter · #5 ·
I have found a company that has a Tremmic 5 speed specially modified to fit in my tunnel. It comes complete.
 

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The TKO-500 has a 3.27 first and a .68 5th.
The TKO-600 has a 2.87 first and a ..64 (or.82) 5th.

Another question I forgot to ask is what tire size you are running in the rear. That would help us tweak the recommendation for a rear gear choice.

For the highway, a 3.73 rear is not going to be the best choice for the 500 or 600 transmission. You are going to want a higher gear (numerically lower). For a good highway cruiser, you want to get a combination that will keep your rpm around 2000 at about 65 mph.

Let me know your rear tire size and I'll come some choices I would recommend.

Also, what are the speed limits on the highways you will be traveling on over there?
 

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Discussion Starter · #8 ·
Tranny and rear end question

I have 15" tires all the way around and the speed limits here are 65 70 but most folks do 70 to 75.
 

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Give me the model and size of the rear tires.
 

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That's a 28" diameter tire. In my formula, I'm using 13" for the loaded radius instead of 14" to account for an inch of tire squish.

Unless you are needing the extra torque capacity of the TKO-600, the 500 gives you a better first gear ratio for a combination street and highway driven car. If you choose the TKO-600, absolutely go with the .64 5th and not the .82.

With the TKO-600 and a 3.73 gear, you would be turning 2005 rpm at 65.

With the TKO-500 and a 3.36 gear, you would be turning 1919 rpm at 65.

If it were me, I'd choose a 3.55 or 3.73 for the TKO-600 and either a 3.08 or 3.36 for the TKO-500.

If you want the best mileage possible while still keeping a pretty good off-the-line feel, go with the TKO-500 and a 3.08 rear.
For relativity sake, a TKO-500 with a 3.08 rear will have a little better off-the-line performance than a wide Muncie 4-speed with a 3.73 rear.
 

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Discussion Starter · #13 ·
Tranny and rear end question

Thank you for the information, but I will have to purchase a rear end and could you tell me which rear end would make the swap easiest...from what model car i.e. '81 Camaro... Olds Cutlass...what car rear end should I be searching for.
 

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Discussion Starter · #14 ·
Tranny and rear end question

Thank you for the information, but I will have to purchase a rear end and could you tell me which rear end would make the swap easiest...from what model car i.e. '81 Camaro... Olds Cutlass...what car rear end should I be searching for.
 

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Thank you for the information, but I will have to purchase a rear end and could you tell me which rear end would make the swap easiest...from what model car i.e. '81 Camaro... Olds Cutlass...what car rear end should I be searching for.
Why not just rebuild the one you've got?

They hold up fine unless you do hard launches with sticky compound tires.
 

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Discussion Starter · #16 ·
Tranny and rear end question

Thank you for all the information you have given me so far. I have learned a lot.

The rear end that's in there we think is a 200 from God knows where, and it is not a posi. The car was a mongrel when we got it and we have been straightening things out. Now that the engine is done right I want to do the tranny and rear end right... The Tranny needs to be rebuilt so that is why I want to go with something that will give power on the line and greater highway cruising capability. What should I look for as far as markings on the outside of the rear end that could tell me about the one I have because I don't trust that it is even a Chevy rear end. And is there a website that where I could input these markings and get information on it. Thank you again.
 

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Discussion Starter · #18 ·
Tranny and rear end question

I have been reading the sites you posted and that totally answers my questions. Thank you again.:shakehands:
 

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I am doing a 55 build also and have done a bunch of research on Tremac transmissions. American Power Train has one they say will not require tunnel modifications. Silver Sport transmissions has Termac's also. My research notes the stock Tremac's shift hard from 2nd to 3rd and can be a problem when powering through the gears. Liberty Gears offer a upgraded Termac that I read good things about and is billed as the best shifting Tremac on the market.
I am about to find out......
I had my rear end custom built by J & D Gear in California.
 

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trans/rear end

I have a 8 1/2 ten bolt 3.73 posi from J&d also with munci 4sd. I am wanting to go to a Tremec. The top square shifter box is about 1/2" shorter that they say makes it fit. I am getting one local and hope no problems installing.
 
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