Changing gears questions

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txbullets

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so I picked up a 489 case with sure grip out of a 2nd generation camero my dad bought. The car was a drag project that had a mopar rear end. Best part is I got it for free 90 free. Sadly it has 4.56 gears in it. The gears look to be new or close to it. I have 2 questions

1. How hard is it to change the gears out on my own?
2. Assuming everything is good inside, will I need to buy any kits as well or just the ring and pinion? Need to get this ordered soon.

Debating between 3.55 and 3.73 gears.
 
Well it really depends on what kind of driving as well as your setup.
If you're mainly street driving 3.55 or 3.73 will both work.
What transmission do you have? A904 or A727?
If you have the close ratio A904 (or A999's). 3.55's will be an excellent choice.
3.73's are good too but keep in mind it'll be buzzy on the freeways
 
Has a 904 in it now but putting a 727 with small stall in.

Building the car now. Car info
72 dart
68 340 10.5/1 comp.
X heads
Xe268 cam
Air Gapper intake
Have not bought a carb yet but 750 dp most likely
Dougs headers

Would like to run mid to high 12s but not stressing that. Mostly a street car with occasional trip to the track for fun.
 
If you're going for the A727, personally I would go for 3.73, maybe even 3.91's. Especially since your're trying to hit the 12's.
However, if you can I would look for a close ratio A904's and beef it up or better yet an A999. And then stick a 3.55 gear, that should get you close. Or you can rebuild your A904 with a TF2 kit and beefier internals, not sure about this but I think you can also put a close ratio setup in your A904.
A close ratio with 3.55 gears will act like you have 3.91's in the first 2 gears.

That is what I have, I have a 360 with 9.7:1 compression with rollerized valvetrain and camshaft. Mated to a close ratio A999 with TF2 kit. I have 3.23 gears in it for now and this thing still can book-it if it wants to.
 
txbullets said:
1. How hard is it to change the gears out on my own?
2. Assuming everything is good inside, will I need to buy any kits as well or just the ring and pinion? Need to get this ordered soon.
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1. Not easy. You need special tools that most amateur mechanics don't have and/or don't know how to use. The gears have to set up to mesh properly, otherwise they will be noisy and/or wear out quickly.
2. Yes, no matter what you'll need an installation kit.
 
69_340_GTS said:
1. Not easy. You need special tools that most amateur mechanics don't have and/or don't know how to use. The gears have to set up to mesh properly, otherwise they will be noisy and/or wear out quickly.
2. Yes, no matter what you'll need an installation kit.
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What should I expect to pay for all this.
 
Not to discourage you but setting up gears is a difficult task even with vast experience you need to know exactly what you are doing and have the correct tools. By time you get install kit, new ring and pinion and pay the machine shop or hot rod builder to setup your gears you can find a bolt in unit ready to go for cheaper just shop around and then simply sell your 4.56's and break even or trade somebody even up.
 
dragondan64 said:
Not to discourage you but setting up gears is a difficult task even with vast experience you need to know exactly what you are doing and have the correct tools. By time you get install kit, new ring and pinion and pay the machine shop or hot rod builder to setup your gears you can find a bolt in unit ready to go for cheaper just shop around and then simply sell your 4.56's and break even or trade somebody even up.
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Kind of what I was thinking.
 
69_340_GTS said:
1. Not easy. You need special tools that most amateur mechanics don't have and/or don't know how to use. The gears have to set up to mesh properly, otherwise they will be noisy and/or wear out quickly.
2. Yes, no matter what you'll need an installation kit.
Click to expand...

x2
 
It is a bit of a task, and there are certain steps to take. BUT, I certainly wouldn't shy away from it if you have a dial indicator, a spanner wrench to adjust the side bearings and something to hold the yoke.

The two biggest things that can hang you up is a torsional torque wrench, and a regular torque wrench that will go to at least 250 ft lbs.

If you can cover all of that, I say study up and have at er.

But that's just me, I like to do things myself if at all possible.
 
I have 3.55's on my hot street 360 Dart Sport. I had anemic 2.45's and were no go! The 3.55 are so much more fun in the sun!:burnout: So consider 3.55's you will like them. 3.73 is getting closer to 3.91 or even 4.10 and are not so much fun on the freeway. I guess it is a matter of preference or what you are willing to tolerate (RPM's).
 
dragondan64 said:
Not to discourage you but setting up gears is a difficult task even with vast experience you need to know exactly what you are doing and have the correct tools. By time you get install kit, new ring and pinion and pay the machine shop or hot rod builder to setup your gears you can find a bolt in unit ready to go for cheaper just shop around and then simply sell your 4.56's and break even or trade somebody even up.
Click to expand...

I agree.

TXBullets if you really want to learn to set up differentials go for it but I'd just about bet you can sell the chunk you have now for most of the cost of a replacement with the gears you want and you won't have to do the labor of setting it up, which isn't for the faint of heart even if you have the tools
 
txbullets said:
Has a 904 in it now but putting a 727 with small stall in.

Building the car now. Car info
72 dart
68 340 10.5/1 comp.
X heads
Xe268 cam
Air Gapper intake
Have not bought a carb yet but 750 dp most likely
Dougs headers

Would like to run mid to high 12s but not stressing that. Mostly a street car with occasional trip to the track for fun.
Click to expand...

Why are you changing the trans to something that'll make it slower and use more fuel? Don't get me wrong I love the 727 but it's a power hog and generally not needed with a stock stroke small block. 12's should be no problem as long as you get it to hook good.

As for gears keep this in mind. The rear tire ht has an effect on the final drive ratio. If your running short tires (26-1/2" or less) run the 3.55 gear. If your running taller tires (27" and up) run the 3.73's
 
Thank you all for all the help. You all have me really reconsidering the 727. The 727 was suposibly rebuilt with a "small" stall but I have no idea what shape the 727 is actually in and was gonna have someone open it up and look it over. Now I am thinking sell the 727 and just use the 904.
 
Don't get me wrong the A727 is a very good trans. But for a small block the beefed up A904,A998 and A999 would suffice very nicely (the folks here at FABO convinced me about that). And I never regretted it.
The guy at my transmission shop told me that A727 takes about 45 hp to run, While A904 series only takes about around 24 hp.
 
txbullets said:
If I go with the 904 will I still need a mini starter to have room for my dougs headers?
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I would use the mini starter anyways, lighter and more torque. However you might have to do a little grinding (like I did, but its nothing major) to make it fit.
 
So you all have convincede to go with my 904. What all needs to be done to it to hold up to 350-400hp?
 
txbullets said:
So you all have convincede to go with my 904. What all needs to be done to it to hold up to 350-400hp?
Click to expand...

It'll take that with a good basic rebuild. A shift improver kit is a great addition that will make it more fun to drive and last longer. I generally use the Trans-go TF2 kit for street and strip cars.
 
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