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Gear Options for Dummies (see post #7)

ObscureMachine

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Focusing on Chassis and running gear since I have to wait 6 months on my FG body from Bronco Design. ;D ;D ;D ;D

1.Thinking about overdrive while I can get to everything. 4R70W Pros and Cons? Better Options? Least amount of fab?

2. Does anyone have an install and parts thread? The one in the tech section reads like an airport novel (sorry). I'm a simple man and need a simple plan.

3. I have a 302, C4, Dana 20 (I guess) and I believe I have 3.50 gears (not sure) and 33" tires. What would an overdrive do for me?

Yes, I used the search button but couldn't find what I was looking for.

THANKS! - jim
 
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Broncobowsher

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Since I wrote the novel I guess I don't have anything to add.

3) 3.50 gears and 33s won't use the overdrive. You will need better axle gearing for the overdrive to work right. I wouldn't even recommend 3.50 and 33s, 4.10s and 33s are a well known great gear ratio in Broncos without overdrive.
 

suckerpunched

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The simplest plan in to leave the C4 in it and like Bowsher said, 4.10 gears would be nice with the 33's. Really probably ideally with the 4r70w you want 4.56 or 4.88 gears and RPM at highway speed ends up about the same. you end up with a little better ratio from a dead stop, but if you are not doing a lot of highway driving, and just want to enjoy it around town and light offroad. I think the C4 is fine and will save you a few grand over buying a transmission, controller and adapter kit. paying trans shop to take it apart to install kit. (Might as well freshen up the trans too at this point) drive shafts shift linkage etc. etc
Don't get me wrong, the OD is nice, I am running an AOD and like it, would probably have gone with a 4r70w knowing what I know now. also I am running 35's 5.38 gears and heavy duty axle shafts front and rear. It all just keeps adding up.
 

Rustytruck

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Your planning a 351 conversion. Are you planning a fuel injection conversion. Going explorer fuel system you get the tranny controller too. The rabbit is running far in this build. Gotta start with motor dreams and tire size so you can figure the rest of the system.
 
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ObscureMachine

ObscureMachine

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The simplest plan in to leave the C4 in it and like Bowsher said, 4.10 gears would be nice with the 33's. Really probably ideally with the 4r70w you want 4.56 or 4.88 gears and RPM at highway speed ends up about the same. you end up with a little better ratio from a dead stop, but if you are not doing a lot of highway driving, and just want to enjoy it around town and light offroad. I think the C4 is fine and will save you a few grand over buying a transmission, controller and adapter kit. paying trans shop to take it apart to install kit. (Might as well freshen up the trans too at this point) drive shafts shift linkage etc. etc
Don't get me wrong, the OD is nice, I am running an AOD and like it, would probably have gone with a 4r70w knowing what I know now. also I am running 35's 5.38 gears and heavy duty axle shafts front and rear. It all just keeps adding up.

Nothing personal about the novel quote. I'm just easily lost and need a list, bullet points and pictures. I'll start checking out gearing. That seems like a better option for what I'm planning.
 

Boss Hugg

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The 4th gear is nice, but if you don't get over 50 or 60 much, it's not necessary. Better gearing will be tremendous on take-off alone. Later, you can switch to the 4R70W if you get the itch. But I wouldn't stop at 4.10 if you have a hunch you want OD. You'll end up regearing again. With 33's and OD you'll need 4.56.
 
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ObscureMachine

ObscureMachine

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The 4th gear is nice, but if you don't get over 50 or 60 much, it's not necessary. Better gearing will be tremendous on take-off alone. Later, you can switch to the 4R70W if you get the itch. But I wouldn't stop at 4.10 if you have a hunch you want OD. You'll end up regearing again. With 33's and OD you'll need 4.56.

No highway speeds. Just up and down Hwy 90 on the Gulf Coast.

So, looks like 4.11s are the way to go.

Any suggestions on brand or vendor?
How much does it cost to have a pro replace them?

Thanks! - jim
 

Rustytruck

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4:11 with 33" tire and keeping the C-4. with the 351 you may pull 35" depending on what you do with the 351 still keeping the C-4 if going with overdrive all bets are off and you need more gear than the 4:11
 

Bronco Junkie

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Just for reference I have a 289, NP 435, 35" tires and 4:11 gears.

I am around 2500 rpm at 65 on the freeway.
 

Boss Hugg

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Just for reference I have a 289, NP 435, 35" tires and 4:11 gears.

But you also have a 6:69 first gear or a 3:1 second gear for take off. The c4 is something around 2.46 in low and depends on the torque converter to apply the power to take off.

and for the record, I also ran a 289, but with c4 and 3.50. I was happy with my explorer stuff power train and 3.50. But I wanted more gear for crawling which allowed me to use OD in my 4R70W.
 
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