New to Bronco - 1976 Manual to Automatic

[Raneycat]

Hi All,

I am Looking to convert my 1976 Ford Bronco from a 3 speed manual to an automatic. I'd be grateful for any insight from those out there who have done this and recommendations on where to source all of the necessary elements to complete it. I've got a family member that's a certified Ford mechanic, so he's willing to do the labor piece for me need to know all of the parts to secure for him!

Many thanks,

CRN

 

[1969]

What automatic transmission do you want? There are a few popular choices for them. Is your bronco stock? Lifted? Big tires? What axles gears do you have?

 

[thegreatjustino]

C4 Automatic Transmission Conversion Kit ($1495+$150 refundable core), Subject to Availability - TOMS OFFROAD

Good Used Rebuildable C4 Automatic Conversion Kit for converting 66-77 Early Broncos with Manual Transmission to the C-4 Auto Tranny. Kit includes the foll

tomsoffroad.com

 

[Raneycat]

What automatic transmission do you want? There are a few popular choices for them. Is your bronco stock? Lifted? Big tires? What axles gears do you have?

It's a 3-speed manual on the floor. Bronco is slightly lifted with a 2-inch lift and has 33-inch tires. No clue on the axels/gears. Original 302 engine

Looking for recommendations from others on what they have used for an automatic transmission. No need for extreme performance with the car.

Thank you in advance for your help!

 

[Timmy390]

It's a 3-speed manual on the floor. Bronco is slightly lifted with a 2-inch lift and has 35-inch tires. No clue on the axels/gears. Original 302 engine

Looking for recommendations from others on what they have used for an automatic transmission. No need for extreme performance with the car.

Thank you in advance for your help!

You need to get the axle gearing right first.....else you will kill the automatic with heat due to slippage.......

Do a Driveshaft Turn Test.

Before you can begin identifying the gear ratio, you will also need to know if the rear end is a “posi” or open differential.
This is required because identifying gear ratios is a little different for each unit.

---

To begin with, raise the rear of the car with a floor jack and place a good set of jack stands under the car on the frame or rear-axle housing.
Once supported, place the transmission in Neutral and turn one of the rear wheels.

• If the opposing wheel spins in the same direction, you have a posi – or limited-slip – differential.
  If this is the case, you can leave both jack stands under the car.
• If you spin one of the rear wheels and the other one rotates in the opposite direction, you have an open differential.
  In this case, you will need to remove one of the jack stands and put one tire back on the ground.
  
  

While doing this test, some guys like to use soapstone, chalk, or tape to put a mark on the tire and driveshaft to make counting the total revolutions easier. If you also want to do that, a modeler’s paint marker also works well. I typically focus on an already supplied marking of some sort on the tire (like a certain letter of the tire’s name) and one of the universal-joint bolts and use those as your reference. If using a paint marker, make a large, visible dot on both the inside of the tire and on the driveshaft.
(we used tape)

When you have your marks applied, if the car has a posi unit, both tires will be in the air.
Rotate the marked tire one revolution while counting how many times the driveshaft rotates.

eg, If your driveshaft made 3 3/4 revolutions, that would determine a 3.73 gear ratio.
If you get approximately 2 3/4 revolutions, you have a 2.76 gear ratio.

Tim

 

[DirtDonk]

Bronco is slightly lifted with a 2-inch lift and has 35-inch tires. No clue on the axels/gears.

Well, then, forget the transmission for now. Deal entirely with finding out what gear ratios you have currently. Then choose your transmission.

Certainly the original three speed was not the most appropriate for a Bronco, with its poorly spaced gear ratios, but you’ve got 35 inch tires now! Of course, it’s under powered and a drag to drive.
Well, it literally had like 145 hp, so yes, it’s under powered literally. But it doesn’t matter how much power you add, or that swapping to an automatic will make it slightly easier to get rolling, you’re still dealing with 35 inch tires with what is most likely 3.50 gears in the differential.
That’s a horrible combination with any engine. Spend your money on getting the proper gear ratios first.
Then worry about the trans, and maybe eventually the engine.
Even if you’re just changing to an automatic, because someone else in the family would find it easier to drive.

As for which transmission, the most straightforward swap should be to an original bronco C4 transmission.
It fits without a body lift, has all the right hardware, and is what Ford installed in your year bronco to begin with.
They worked very well, but still needed to have the gear ratios matched to the tire size.

If you do end up changing your gear ratios, you could actually plan for an overdrive transmission which has the best of both worlds.
Both lower first gear, and a taller fourth gear.
A lot of us are doing it, but it does take more work. Sometimes a lot more work!
Still, all depends on what you’re ultimately looking for.

 

[Raneycat]

My mistake it's running on 33's

Mickey Thompson Classic III 15”x12” wheels with BF Goodrich Mud-Terrain T/A 33” tires

 

[DirtDonk]

Still a lot of tire for a stock 302 engine, presumably with those 3.50 gears. It would still be a bit of a dog off the line.
Very hard on a clutch.

But a basic 3-speed Bronco C4 transmission is looking better.

 

[sprdv1]

Hi All,

I am Looking to convert my 1976 Ford Bronco from a 3 speed manual to an automatic. I'd be grateful for any insight from those out there who have done this and recommendations on where to source all of the necessary elements to complete it. I've got a family member that's a certified Ford mechanic, so he's willing to do the labor piece for me need to know all of the parts to secure for him!

Many thanks,

CRN

Welcome aboard!!

 

[sprdv1]

Still a lot of tire for a stock 302 engine, presumably with those 3.50 gears. It would still be a bit of a dog off the line.
Very hard on a clutch.

But a basic 3-speed Bronco C4 transmission is looking better.

for sure...