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Old 02/12/18, 05:30 PM   #1
Robster
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C4 to AOD swap question

Will I need to add a body lift kit to help clear the AOD transmission or can I keep the factory body mounts. I have a 2.5" suspension lift but don't really want to do a body lift if I can avoid it. Thanks guys
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Old 02/12/18, 05:37 PM   #2
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You don't need a body lift for an AOD. A 1" helps but is not needed. You will need to modify the crossmember and move it back a little bit, but that's really a 15 minute job with a cut off wheel and a welder. You will need to re-gear your axles and you 'might' need to shorten your driveshaft? I did a 3.5" lift and an AOD at the same time and I didn't need to change my drive shaft out.

1971 Mall Crawler- Resto mod. http://classicbroncos.com/forums/sho...dabronco+frame

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Old 02/12/18, 09:22 PM   #3
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Do u have a picture of what needs to be done to the cross member? Is there any frame modification that need to be made? Thanks
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Old 02/12/18, 10:18 PM   #4
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Robster what size tires you going with? What gears were u thinking
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Old 02/12/18, 10:21 PM   #5
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35" tires and 4:56
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Old 02/13/18, 04:37 PM   #6
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That’s exactly what I am doing I have a 302wiyh an aod and have been wanting to get my gears changed that’s what I’m going with
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Old 02/13/18, 06:23 PM   #7
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You will probably want a lot more gear with those tires and the overdrive in the AOD. 5.13s come to mind. Still have a 302?

This advise comes from someone who has run 4.88s with 33s and a 4R70W behind a 351W built for torque. Your planned 4.56 gears you can expect gear hunting on every hill, and gear hunting in and out of OD is what kills an AOD.

"She's built like a steakhouse but she handles like a bistro"-Zapp Brannigan
“How hard can it be?”-Clarksonius 4th century BC.
Full throttle, it either solves the problem or ends the suspense.
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Old 02/13/18, 07:15 PM   #8
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In my situation I will just be riding it around town and an occasional highway 98%of the time
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Old 02/13/18, 08:36 PM   #9
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Quote:
Originally Posted by Tulsa76bronco View Post
In my situation I will just be riding it around town and an occasional highway 98%of the time
Yea, that is where the 5.13s would be really good. Strange to think of 5.13 as a good highway gear, but they would be. Comes to an effective 3.42 gear with the AOD. And the AOD has a locked convertor in OD, so no fudging a little slip, its locked like a stick shift would be. Now 3.42 gears and 35" tires, that's still pretty tall geared. I can remember my first bronco running around with only 31s on it and 3.50 gears. And I know I was pushing a lot less air then you will be, you have a lift and taller tires I didn't have.

If you have 3.50 gears and a C4 already, 5.13s will be even less RPM. Geared a little taller, and a locked convertor.

You need enough gear that at cruising speed you are still pulling some manifold vacuum. If you are not pulling vacuum at cruise the engine is running a peak torque (at that RPM), you have no reserve capacity to pull a grade or accelerate, fuel and timing will be in "power" delivery and not "economy" mode.

"She's built like a steakhouse but she handles like a bistro"-Zapp Brannigan
“How hard can it be?”-Clarksonius 4th century BC.
Full throttle, it either solves the problem or ends the suspense.
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Old 02/13/18, 10:02 PM   #10
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I mis spoke my bronco with the AOD has 33inch tires and I am putting in the 4.56 gears what’s ur thought on that

that’s what happens when u have two EBs can’t keep them straight othe is 302 w C4 but was still going with 4.56....thoughts
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Old 02/13/18, 10:05 PM   #11
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both have 302 engines
C4 had 35 tires 3.5 lift 1 inch body
AOD has 33 tires 2.5 lift 1 inch body
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Old 02/14/18, 02:57 PM   #12
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4.88s minimum or 5.13s and be done. I run 4.88s and 34"s, really wishing I went to 5.13s

1971 Mall Crawler- Resto mod. http://classicbroncos.com/forums/sho...dabronco+frame

1970 Basket case

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Old 02/14/18, 04:10 PM   #13
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I'll represent the other view. For a while I had an AOD with a manual valve body and a non-lock-up torque converter (yes I know now that was a bad idea) with 4.10 gears and 33" tires. I actually really liked the gearing. (I still have the 4.10 / 33s but now with an NV3550). Yes it needed to be downshifted to pull hills, but the flat cruising was great for what I want anyway. With the manual valve body mine didn't hunt obviously, but manually taking it out of overdrive when needed works too.

But yes, if you want to stick it in "OD" and not think about it, the 4.10s were way too tall.

Bob
'71 Bronco, 302, NV3550 5 spd, Atlas 4.3:1, 4.10:1, Detroit rear, 33" BFG AT Build Thread
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Old 02/14/18, 04:20 PM   #14
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Not trying to highjack the tread, I plan on running 37's, AOD, 302. which gear ratio would work best for me, its just gonna be a highway driver.
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Old 02/14/18, 04:48 PM   #15
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Quote:
Originally Posted by chriskent85 View Post
Not trying to highjack the tread, I plan on running 37's, AOD, 302. which gear ratio would work best for me, its just gonna be a highway driver.
5.38s
Only because that is as low as you can pratically go

"She's built like a steakhouse but she handles like a bistro"-Zapp Brannigan
“How hard can it be?”-Clarksonius 4th century BC.
Full throttle, it either solves the problem or ends the suspense.
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